Google Groups no longer supports new Usenet posts or subscriptions. Historical content remains viewable.
Dismiss
Antenna for channel 36
139 views
Skip to first unread message
Peabody
Nov 28, 2012, 12:34:36āÆAM11/28/12
to
I need to bring in a distant TV station, and would like to build an
antenna specifically for that channel. It's physically channel 36,
which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm.
I just told you everything I know about antennas, and haven't had
much luck on Google. I need it to be about 3-4 feet long, and it
will be indoors. If anyone knows of a fairly simple design that
might work, I would appreciate a link.
I have a $10 indoor antenna, and it gets all the local channels,
but not the distant one. The tuner shows the channel is there, but
at low strength, and I'm hoping an antenna with the
elements optimized for channel 36 will be enough to bring it in.
antenna specifically for that channel. It's physically channel 36,
which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm.
I just told you everything I know about antennas, and haven't had
much luck on Google. I need it to be about 3-4 feet long, and it
will be indoors. If anyone knows of a fairly simple design that
might work, I would appreciate a link.
I have a $10 indoor antenna, and it gets all the local channels,
but not the distant one. The tuner shows the channel is there, but
at low strength, and I'm hoping an antenna with the
elements optimized for channel 36 will be enough to bring it in.
Michael A. Terrell
Nov 28, 2012, 1:06:03āÆAM11/28/12
to
about $200, wholesale.
Sylvia Else
Nov 28, 2012, 1:10:30āÆAM11/28/12
to
http://tf.nist.gov/timefreq/general/pdf/451.pdf
indicating that the design is far from straightforward.
I'd just get a normal rooftop UHF (band IV/V) wideband antenna, and see
how well it works indoors.
Sylvia.
miso
Nov 28, 2012, 2:56:06āÆAM11/28/12
to
The Blonder Tongue BTY-10-U is a high gain UHF antenna that spans a few
channels. It is not cut for one channel, but you would get the one that
spans channels 57 through 69. I have my doubt how well this will work
indoors.
Unless your time is 100% free, I'd get an antenna off the shelf. When
you roll your own antennas, it is an exercise in material science. You
can build out of aluminum, but there is always that nasty connection to
copper. If you build out of copper, the thing is heavy. Plus copper
isn't cheap.
channels. It is not cut for one channel, but you would get the one that
spans channels 57 through 69. I have my doubt how well this will work
indoors.
Unless your time is 100% free, I'd get an antenna off the shelf. When
you roll your own antennas, it is an exercise in material science. You
can build out of aluminum, but there is always that nasty connection to
copper. If you build out of copper, the thing is heavy. Plus copper
isn't cheap.
Jeff Liebermann
Nov 28, 2012, 3:05:56āÆAM11/28/12
to
On Tue, 27 Nov 2012 23:34:36 -0600, Peabody
<waybackNO...@yahoo.com> wrote:
>I need to bring in a distant TV station, and would like to build an
>antenna specifically for that channel. It's physically channel 36,
>which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm.
There are plenty of stand alone and online yagi antenna designers.
<waybackNO...@yahoo.com> wrote:
>I need to bring in a distant TV station, and would like to build an
>antenna specifically for that channel. It's physically channel 36,
>which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm.
Google for "yagi designer" and "yagi calculator". If you want it
online, add the word "online". The calculator will give you the basic
dimensions, the gain, bandwidth, and VSWR. Use the longest boom you
consider practical. Bigger is better.
If you want to see whether you have a chance, plug your address into:
<http://www.tvfool.com>
and check if you will have enough signal from the station of interest.
All the antenna gain on the planet will do you no good if there's no
signal to receive.
For a starter, build the antenna out of #12 copper electrical wire, or
thicker aluminum rod. Use a length of kiln dried wood for the boom
(green wood doesn't work well). Attach with U shaped staples.
The key part is the driven element. Design for a 300 ohm, folded
dipole, driven element and use a commonly available 300-75 ohm
transformer balun. That will eliminate any complicated matching
networks.
The lengths closest to the driven element are critical. The one's
further away are somewhat less important. Element spacing is not
hugely critical. Since you probably don't have any test equipment, do
your best to cut the lengths accurately.
For an antenna amplifier, just go to Radio Shack and buy something
that installs at the antenna, but it's it's power through the coax
cable. Use common RG-6/u coax, not twinlead.
The wooden boom and electrical wire prototype will be a quick test to
see if the exercise is worthwhile. If you get a good signal, then
either clean it up so that it will survive outdoors, or build a real
Yagi antenna out of aluminum tubing. Also have a local ham or RF
expert put the antenna on an antenna analyzer to check if it's
properly cut and tuned. If it doesn't work well, and you can't find
any obvious faults in the construction, it's likely that an aluminum
tubing version will work no better.
--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Jon Elson
Nov 28, 2012, 12:46:58āÆPM11/28/12
to
Peabody wrote:
> I need to bring in a distant TV station, and would like to build an
> antenna specifically for that channel. It's physically channel 36,
> which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm.
HOW distant is the station? That is the most important parameter, and
> I need to bring in a distant TV station, and would like to build an
> antenna specifically for that channel. It's physically channel 36,
> which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm.
then maybe if there are any big hills between you and them.
Many years ago, I built a very simple 3-element Yagi to pick up a distant
FM radio station, and it worked surprisingly well. Distance was
about 90 miles. Much of the path was over the Chesapeake Bay, which
probably helped some.
The front 2 elements were just straight coat hanger wire. The
back element was a folded dipole, also coat hanger wire, feeding
300 Ohm twinlead. I got the design out of "Reference Data for
the Radio Engineer" and scaled appropriately. I hung it from the
ceiling, and tilted it up into the sky about 10 degrees.
Your frequencies sound suspect, I don't think broadcast TV has
a 96 MHz bandwidth.
Jon
Peabody
Nov 28, 2012, 12:59:31āÆPM11/28/12
to
Jeff Liebermann says...
> If you want to see whether you have a chance, plug your
> address into:
> <http://www.tvfool.com>
> and check if you will have enough signal from the
> station of interest. All the antenna gain on the planet
> will do you no good if there's no signal to receive.
Yes, I've done that, and also confirmed with the station
engineer that under normal conditions people in my area
do get the channel. But in my particular case, I'm on the
backside of a large hill with respect to the station's
antenna, so I may just be blocked no matter what I do.
I'm 35 miles from the antenna, but a friend of mine 10 miles
farther out can get it ok. But he's out on the flat plains,
and has a rooftop antenna.
Remember the analog-to-digital transition? Well I got one
of those voucher-paid converters, just in case, which I
haven't used until now. It's a Zenith DTT901, and it can
display a little signal-strength meter in real time. The
local channels that I get just fine come it at about 70% on
the meter, or close to that. It does detect channel 36, but
at about 35%, and the tuner just can't make sense of it at
that point - it doesn't even display the nominal channel
number.
But that's with a RCA ANT111, with just the basic single
loop for UHF. So I thought with maybe a little better
antenna, I might be able to receive the channel.
I appreciate all the suggestions. I think I have enough
information now to build a yagi. And with the wavelength
being only about 1.6 feet, it shouldn't be that expensive.
I have some twinlead, and a balun, and maybe even some
copper wire that would work. It turns out that there is the
right Blonder Tongue antenna on Ebay for $100 plus shipping,
but, you know, I may learn something about antennas doing it
myself.
> The wooden boom and electrical wire prototype will be a
> quick test to see if the exercise is worthwhile. If you
> get a good signal, then either clean it up so that it
> will survive outdoors, or build a real Yagi antenna out
> of aluminum tubing. Also have a local ham or RF expert
> put the antenna on an antenna analyzer to check if it's
> properly cut and tuned. If it doesn't work well, and
> you can't find any obvious faults in the construction,
> it's likely that an aluminum tubing version will work no
> better.
That was my thinking. If I build one for cheap, and the
signal strengh is only marginally better, then it's unlikely
even a good antenna would do the trick. But if I get major
improvement, even if not quite good enough, then it may be
worthwhile to build, or buy, something better performing.
Just to clarify a couple things - it appears that the
reflector and the directors are continuous elements - not
cut in the middle, whereas the driven element is cut. Is
that right? And does it matter where the twinlead is
attached to the driven element - does it have to be at the
inside ends?
Thanks for all the comments and suggestions.
> If you want to see whether you have a chance, plug your
> address into:
> <http://www.tvfool.com>
> and check if you will have enough signal from the
> station of interest. All the antenna gain on the planet
> will do you no good if there's no signal to receive.
engineer that under normal conditions people in my area
do get the channel. But in my particular case, I'm on the
backside of a large hill with respect to the station's
antenna, so I may just be blocked no matter what I do.
I'm 35 miles from the antenna, but a friend of mine 10 miles
farther out can get it ok. But he's out on the flat plains,
and has a rooftop antenna.
Remember the analog-to-digital transition? Well I got one
of those voucher-paid converters, just in case, which I
haven't used until now. It's a Zenith DTT901, and it can
display a little signal-strength meter in real time. The
local channels that I get just fine come it at about 70% on
the meter, or close to that. It does detect channel 36, but
at about 35%, and the tuner just can't make sense of it at
that point - it doesn't even display the nominal channel
number.
But that's with a RCA ANT111, with just the basic single
loop for UHF. So I thought with maybe a little better
antenna, I might be able to receive the channel.
I appreciate all the suggestions. I think I have enough
information now to build a yagi. And with the wavelength
being only about 1.6 feet, it shouldn't be that expensive.
I have some twinlead, and a balun, and maybe even some
copper wire that would work. It turns out that there is the
right Blonder Tongue antenna on Ebay for $100 plus shipping,
but, you know, I may learn something about antennas doing it
myself.
> The wooden boom and electrical wire prototype will be a
> quick test to see if the exercise is worthwhile. If you
> get a good signal, then either clean it up so that it
> will survive outdoors, or build a real Yagi antenna out
> of aluminum tubing. Also have a local ham or RF expert
> put the antenna on an antenna analyzer to check if it's
> properly cut and tuned. If it doesn't work well, and
> you can't find any obvious faults in the construction,
> it's likely that an aluminum tubing version will work no
> better.
signal strengh is only marginally better, then it's unlikely
even a good antenna would do the trick. But if I get major
improvement, even if not quite good enough, then it may be
worthwhile to build, or buy, something better performing.
Just to clarify a couple things - it appears that the
reflector and the directors are continuous elements - not
cut in the middle, whereas the driven element is cut. Is
that right? And does it matter where the twinlead is
attached to the driven element - does it have to be at the
inside ends?
Thanks for all the comments and suggestions.
amdx
Nov 28, 2012, 1:23:59āÆPM11/28/12
to
http://www.csgnetwork.com/tvfreqtable.html
> http://www.csgnetwork.com/tvfreqtable.html
Mikek
Dave Platt
Nov 28, 2012, 2:36:36āÆPM11/28/12
to
>> I need to bring in a distant TV station, and would like to build an
>> antenna specifically for that channel. It's physically channel 36,
>> which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm.
>>
>> I just told you everything I know about antennas, and haven't had
>> much luck on Google. I need it to be about 3-4 feet long, and it
>> will be indoors. If anyone knows of a fairly simple design that
>> might work, I would appreciate a link.
>>
>> I have a $10 indoor antenna, and it gets all the local channels,
>> but not the distant one. The tuner shows the channel is there, but
>> at low strength, and I'm hoping an antenna with the
>> elements optimized for channel 36 will be enough to bring it in.
>>
>
>The Wikipedia article on Yagi antennas points to this document
>
>http://tf.nist.gov/timefreq/general/pdf/451.pdf
>
>indicating that the design is far from straightforward.
If you want the ultimate gain (or front/back ratio) for a given boom
>> antenna specifically for that channel. It's physically channel 36,
>> which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm.
>>
>> I just told you everything I know about antennas, and haven't had
>> much luck on Google. I need it to be about 3-4 feet long, and it
>> will be indoors. If anyone knows of a fairly simple design that
>> might work, I would appreciate a link.
>>
>> I have a $10 indoor antenna, and it gets all the local channels,
>> but not the distant one. The tuner shows the channel is there, but
>> at low strength, and I'm hoping an antenna with the
>> elements optimized for channel 36 will be enough to bring it in.
>>
>
>The Wikipedia article on Yagi antennas points to this document
>
>http://tf.nist.gov/timefreq/general/pdf/451.pdf
>
>indicating that the design is far from straightforward.
length for a given frequency... yes, the design can be pretty
involved. There are software packages which will generate a good Yagi
for you, though, based on certain reference designs.
However, you don't need to push for the ultimate. Good enough, will
probably be good enough.
One approach you might look into is the "cheap Yagi" design, by Kent
Britain. Kent came up with this design in an effort in support of a
fellow amateur-radio operator who resides in a relatively impoverished
country, where both money and supplies are scarce... it's intended to
be something that you can throw together easily, out of commonly
available materials.
It's not the ultimate Yagi design, by any means, but it works very
well. The basic supplies: something to use as a boom (wood, or white
PVC plumbing pipe) and stiff wire (14-gauge copper wire stripped out
of ordinary Romex cable works fine; solid aluminum "grounding" wire
works equally well for all of the elements other than the one to which
you solder the connecting coax) and coaxial able.
Kent has a design document at
http://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf
This document shows designs for a bunch of ham-radio frequencies, and
there is a set on page 5, for 421 MHz, that are designed for a 75-ohm
coax feed such as you would use with a television (it's designed for
amateur-radio TV).
If you take one of the 421 MHz designs (the longer ones have more
elements and more gain), and scale all of the dimensions down in size
by the ratio of (421/603), and wire it up, it should work quite
decently. Even if it doesn't have as much gain as an "ultimate" Yagi,
you probably won't notice the difference.
The biggest factor in whether it's successful or not, is probably
where you mount it. Higher is better. Up on the roof, on a mast at
least a few feet above the roof (with proper static and lightning
protection) is best. Hanging it indoors in an attic will probably
work unless your roof and walls are too full of metal. Hanging it
under your viewing-room ceiling... ditto but moreso.
The longest 421 MHz version is under 5 feet long... scale it down for
603 MHz and it'll be right around a yard long.
Or, take a look at
http://www.wa5vjb.com/references/CheapYagi4HDTV.pdf
and you'll see a more broadly-tuned Yagi which is designed to give
compromise gain across a wide span of the television band.
I made one of Kent's designs a few years ago, tuned for around 445 MHz
(the middle of the amateur-radio UHF repeater sub-band) out of PVC
pipe and scrap wire. Works like a charm, and I think my total
expenses were under $10 (even including a 6' PVC mast).
I made a slightly different homebrew Yagi about 15 years ago, tuned
for TV channel 11 (VHF high band)... wood, and copper-plated steel
welding-rod elements. Worked very nicely indeed.
--
Dave Platt <dpl...@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
Joerg
Nov 28, 2012, 2:56:13āÆPM11/28/12
to
Peabody wrote:
> Jeff Liebermann says...
>
> > If you want to see whether you have a chance, plug your
> > address into:
> > <http://www.tvfool.com>
> > and check if you will have enough signal from the
> > station of interest. All the antenna gain on the planet
> > will do you no good if there's no signal to receive.
>
> Yes, I've done that, and also confirmed with the station
> engineer that under normal conditions people in my area
> do get the channel. But in my particular case, I'm on the
> backside of a large hill with respect to the station's
> antenna, so I may just be blocked no matter what I do.
>
Once you get a Yagi going try pointing it in the opposite direction if
> Jeff Liebermann says...
>
> > If you want to see whether you have a chance, plug your
> > address into:
> > <http://www.tvfool.com>
> > and check if you will have enough signal from the
> > station of interest. All the antenna gain on the planet
> > will do you no good if there's no signal to receive.
>
> Yes, I've done that, and also confirmed with the station
> engineer that under normal conditions people in my area
> do get the channel. But in my particular case, I'm on the
> backside of a large hill with respect to the station's
> antenna, so I may just be blocked no matter what I do.
>
you can't catch enough signal. May sound weird but sometimes it can pick
up a station via reflection from a gutter or metal roof far away, from a
house that can "see" the station.
> I'm 35 miles from the antenna, but a friend of mine 10 miles
> farther out can get it ok. But he's out on the flat plains,
> and has a rooftop antenna.
>
That <censored> transition was a major loss for us. Many evenings we can
barely receive a single station, on account of multipath reception.
[...]
> Just to clarify a couple things - it appears that the
> reflector and the directors are continuous elements - not
> cut in the middle, whereas the driven element is cut. Is
Correct.
> ... And does it matter where the twinlead is
> attached to the driven element - does it have to be at the
> inside ends?
>
Yes, it has to be connected in the center.
> inside ends?
>
[...]
--
Regards, Joerg
http://www.analogconsultants.com/
Jon Elson
Nov 28, 2012, 3:23:21āÆPM11/28/12
to
Jon Elson wrote:
>
> Many years ago, I built a very simple 3-element Yagi to pick up a distant
> FM radio station, and it worked surprisingly well. Distance was
> about 90 miles. Much of the path was over the Chesapeake Bay, which
> probably helped some.
>
Oh, forgot to mention, the "beam" of the antenna was a broken-off
>
> Many years ago, I built a very simple 3-element Yagi to pick up a distant
> FM radio station, and it worked surprisingly well. Distance was
> about 90 miles. Much of the path was over the Chesapeake Bay, which
> probably helped some.
>
broomstick!
Jon
Jon Elson
Nov 28, 2012, 3:27:16āÆPM11/28/12
to
Peabody wrote:
But in my particular case, I'm on the
> backside of a large hill with respect to the station's
> antenna, so I may just be blocked no matter what I do.
>
> I'm 35 miles from the antenna, but a friend of mine 10 miles
> farther out can get it ok. But he's out on the flat plains,
> and has a rooftop antenna.
OK, there are a couple ways to deal with this. If there is a
But in my particular case, I'm on the
> backside of a large hill with respect to the station's
> antenna, so I may just be blocked no matter what I do.
>
> I'm 35 miles from the antenna, but a friend of mine 10 miles
> farther out can get it ok. But he's out on the flat plains,
> and has a rooftop antenna.
big building that is in direct line of sight to the transmitter,
you may be able to receive the signal bouncing off that
building, or water tower, or whatever. One trick that has
been used is a pair of back-to-back antennas at the
top of the hill or other good location, to retransmit the signal
in your direction.
35 miles should not be a big problem at all, so you just need a way
to get around that hill.
Jon
Joerg
Nov 28, 2012, 3:18:47āÆPM11/28/12
to
because you had already mentally repurposed the broomstick piece :-)
whit3rd
Nov 28, 2012, 3:29:28āÆPM11/28/12
to
On Wednesday, November 28, 2012 11:36:36 AM UTC-8, Dave Platt wrote:
> >> I need to bring in a distant TV station, and would like to build an
> >> antenna specifically for that channel. It's physically channel 36,
> >> which is [602 - 608 MHz}
> >> I need to bring in a distant TV station, and would like to build an
> >> antenna specifically for that channel. It's physically channel 36,
> ... designs for a bunch of ham-radio frequencies...
> If you take one of the 421 MHz designs (the longer ones have more
> elements and more gain), and scale all of the dimensions down in size
> by the ratio of (421/603), and wire it up, it should work quite
> decently.
I did this very thing a few decades ago, and would offer three more bits
> elements and more gain), and scale all of the dimensions down in size
> by the ratio of (421/603), and wire it up, it should work quite
> decently.
of info.
First, the yagi design is very directional; find the correct bearing to your
transmitter with (for instance) info from antennaweb.org.
Second, long range transmission is limited by line-of-sight, and the curvature of the
earth. Higher antennae see farther. If you can't get your antenna high, look for
high items that act as reflectors (my best reception was with the antenna
aimed at a nearby ham operator's high antenna mast).
Third, lots of folk will suggest amplifiers; they do NOT GENERALLY HELP
because your signal-strength limit is on signal/noise ratio, which is
not improved by any addon amplifiers. Amplifiers amplify noise just like
they amplify signal.
tm
Nov 28, 2012, 4:07:31āÆPM11/28/12
to
"whit3rd" <whi...@gmail.com> wrote in message
news:47b4f110-b94a-4ef4...@googlegroups.com...
> On Wednesday, November 28, 2012 11:36:36 AM UTC-8, Dave Platt wrote:
>> >> I need to bring in a distant TV station, and would like to build an
>> >> antenna specifically for that channel. It's physically channel 36,
>> >> which is [602 - 608 MHz}
>
>
>> >> I need to bring in a distant TV station, and would like to build an
>> >> antenna specifically for that channel. It's physically channel 36,
>> >> which is [602 - 608 MHz}
>
>
> Third, lots of folk will suggest amplifiers; they do NOT GENERALLY HELP
> because your signal-strength limit is on signal/noise ratio, which is
> not improved by any addon amplifiers. Amplifiers amplify noise just like
> they amplify signal.
This is certainly not correct. The loss in the feed line adds directly to
> because your signal-strength limit is on signal/noise ratio, which is
> not improved by any addon amplifiers. Amplifiers amplify noise just like
> they amplify signal.
the noise figure. Put a LNA right at the antenna and you establish the
system NF to that of the LNA.
upsid...@downunder.com
Nov 28, 2012, 4:18:26āÆPM11/28/12
to
>I need to bring in a distant TV station, and would like to build an
>antenna specifically for that channel. It's physically channel 36,
>which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm.
Where are you living ? In Americas or the rest of the world ?
>antenna specifically for that channel. It's physically channel 36,
>which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm.
Channel 36 with 602-608 MHz might suggest this is about America.
>I just told you everything I know about antennas, and haven't had
>much luck on Google. I need it to be about 3-4 feet long, and it
>will be indoors.
antenna, you _must_ be able to use an outdoor antenna !!
>If anyone knows of a fairly simple design that
>might work, I would appreciate a link.
(directional) yagis, _unless_ you have a direct view from your window
towards the transmission station.
Michael A. Terrell
Nov 28, 2012, 4:19:45āÆPM11/28/12
to
second set.
upsid...@downunder.com
Nov 28, 2012, 4:24:11āÆPM11/28/12
to
On Wed, 28 Nov 2012 16:07:31 -0500, "tm" <No_on...@white-house.gov>
wrote:
Since the OP was not able to use an outdoor antenna, the issue of
antenna amplifier gain or feeder losses are quite irrelevant.
wrote:
antenna amplifier gain or feeder losses are quite irrelevant.
Jon Elson
Nov 28, 2012, 5:15:22āÆPM11/28/12
to
handle lasts about 2 weeks around here, the threaded end gets broken off.
Of course, most of that crap is now tinfoil rolled into a tube with a
plastic threaded piece crimped to the end. You can crumple the
handle just by rough handling. Sometimes you still see a wood handle,
though.
Jon
Joerg
Nov 28, 2012, 5:08:48āÆPM11/28/12
to
playing hockey :-)
k...@att.bizzz
Nov 28, 2012, 5:24:05āÆPM11/28/12
to
On Wed, 28 Nov 2012 11:56:13 -0800, Joerg <inv...@invalid.invalid>
wrote:
>Peabody wrote:
>> Jeff Liebermann says...
>>
>> > If you want to see whether you have a chance, plug your
>> > address into:
>> > <http://www.tvfool.com>
>> > and check if you will have enough signal from the
>> > station of interest. All the antenna gain on the planet
>> > will do you no good if there's no signal to receive.
>>
>> Yes, I've done that, and also confirmed with the station
>> engineer that under normal conditions people in my area
>> do get the channel. But in my particular case, I'm on the
>> backside of a large hill with respect to the station's
>> antenna, so I may just be blocked no matter what I do.
>>
>
>Once you get a Yagi going try pointing it in the opposite direction if
>you can't catch enough signal. May sound weird but sometimes it can pick
>up a station via reflection from a gutter or metal roof far away, from a
>house that can "see" the station.
Or point the null to eliminate one source of multi-path.
>> I'm 35 miles from the antenna, but a friend of mine 10 miles
>> farther out can get it ok. But he's out on the flat plains,
>> and has a rooftop antenna.
>>
>> Remember the analog-to-digital transition? ...
>
>
>That <censored> transition was a major loss for us. Many evenings we can
>barely receive a single station, on account of multipath reception.
>
I probably should try OTA where I am now but there was no hope where I
was before.
>> ... And does it matter where the twinlead is
>> attached to the driven element - does it have to be at the
>> inside ends?
>>
>
>Yes, it has to be connected in the center.
It is a dipole. ;-)
wrote:
>Peabody wrote:
>> Jeff Liebermann says...
>>
>> > If you want to see whether you have a chance, plug your
>> > address into:
>> > <http://www.tvfool.com>
>> > and check if you will have enough signal from the
>> > station of interest. All the antenna gain on the planet
>> > will do you no good if there's no signal to receive.
>>
>> Yes, I've done that, and also confirmed with the station
>> engineer that under normal conditions people in my area
>> do get the channel. But in my particular case, I'm on the
>> backside of a large hill with respect to the station's
>> antenna, so I may just be blocked no matter what I do.
>>
>
>Once you get a Yagi going try pointing it in the opposite direction if
>you can't catch enough signal. May sound weird but sometimes it can pick
>up a station via reflection from a gutter or metal roof far away, from a
>house that can "see" the station.
>> I'm 35 miles from the antenna, but a friend of mine 10 miles
>> farther out can get it ok. But he's out on the flat plains,
>> and has a rooftop antenna.
>>
>> Remember the analog-to-digital transition? ...
>
>
>That <censored> transition was a major loss for us. Many evenings we can
>barely receive a single station, on account of multipath reception.
>
was before.
>
>
>> Just to clarify a couple things - it appears that the
>> reflector and the directors are continuous elements - not
>> cut in the middle, whereas the driven element is cut. Is
>> that right? ...
>
>
>Correct.
Yes, the driven element of a yagi is a dipole.
>
>> Just to clarify a couple things - it appears that the
>> reflector and the directors are continuous elements - not
>> cut in the middle, whereas the driven element is cut. Is
>> that right? ...
>
>
>Correct.
>> ... And does it matter where the twinlead is
>> attached to the driven element - does it have to be at the
>> inside ends?
>>
>
>Yes, it has to be connected in the center.
Joerg
Nov 28, 2012, 5:52:06āÆPM11/28/12
to
k...@att.bizzz wrote:
> On Wed, 28 Nov 2012 11:56:13 -0800, Joerg <inv...@invalid.invalid>
> wrote:
>
>> Peabody wrote:
>>> Jeff Liebermann says...
>>>
>>> > If you want to see whether you have a chance, plug your
>>> > address into:
>>> > <http://www.tvfool.com>
>>> > and check if you will have enough signal from the
>>> > station of interest. All the antenna gain on the planet
>>> > will do you no good if there's no signal to receive.
>>>
>>> Yes, I've done that, and also confirmed with the station
>>> engineer that under normal conditions people in my area
>>> do get the channel. But in my particular case, I'm on the
>>> backside of a large hill with respect to the station's
>>> antenna, so I may just be blocked no matter what I do.
>>>
>> Once you get a Yagi going try pointing it in the opposite direction if
>> you can't catch enough signal. May sound weird but sometimes it can pick
>> up a station via reflection from a gutter or metal roof far away, from a
>> house that can "see" the station.
>
> Or point the null to eliminate one source of multi-path.
>
In our case there are many stations such as Fox-40 where there is no
> On Wed, 28 Nov 2012 11:56:13 -0800, Joerg <inv...@invalid.invalid>
> wrote:
>
>> Peabody wrote:
>>> Jeff Liebermann says...
>>>
>>> > If you want to see whether you have a chance, plug your
>>> > address into:
>>> > <http://www.tvfool.com>
>>> > and check if you will have enough signal from the
>>> > station of interest. All the antenna gain on the planet
>>> > will do you no good if there's no signal to receive.
>>>
>>> Yes, I've done that, and also confirmed with the station
>>> engineer that under normal conditions people in my area
>>> do get the channel. But in my particular case, I'm on the
>>> backside of a large hill with respect to the station's
>>> antenna, so I may just be blocked no matter what I do.
>>>
>> Once you get a Yagi going try pointing it in the opposite direction if
>> you can't catch enough signal. May sound weird but sometimes it can pick
>> up a station via reflection from a gutter or metal roof far away, from a
>> house that can "see" the station.
>
> Or point the null to eliminate one source of multi-path.
>
null. You always have tons of signal but sometimes the TV can't decipher
any of it, other times it sorta works. 80-90% of the time, at the most.
That was our "digital dividend" :-(
DTV, what a joke. I think it means "disrupted television" or something.
>>> I'm 35 miles from the antenna, but a friend of mine 10 miles
>>> farther out can get it ok. But he's out on the flat plains,
>>> and has a rooftop antenna.
>>>
>>> Remember the analog-to-digital transition? ...
>>
>> That <censored> transition was a major loss for us. Many evenings we can
>> barely receive a single station, on account of multipath reception.
>>
> I probably should try OTA where I am now but there was no hope where I
> was before.
(if you are lucky and the signal path holds for 2h) and Dancing with the
Stars it's hardly worth it. In contrast to the election our favorite
candidate won yesterday on Dancing with the Stars.
>>
>>> Just to clarify a couple things - it appears that the
>>> reflector and the directors are continuous elements - not
>>> cut in the middle, whereas the driven element is cut. Is
>>> that right? ...
>>
>> Correct.
>
> Yes, the driven element of a yagi is a dipole.
>
>>> ... And does it matter where the twinlead is
>>> attached to the driven element - does it have to be at the
>>> inside ends?
>>>
>> Yes, it has to be connected in the center.
>
> It is a dipole. ;-)
portable EMC antenna is like that.
miso
Nov 28, 2012, 6:11:02āÆPM11/28/12
to
If you found the BTY-10-U cut for your channel for $100, I'd get it.
Worse comes to worse, you put it back on ebay. That price is about half
of what Solid Signal charges.
I only build antennas for what I can't buy. It is way more work than you
think.
If you don't want to buy the BT antenna, I would suggest building a
biquad. They don't take long to build. You would probably have to scale
a biquad designed for wifi.
> http://martybugs.net/wireless/biquad/
Your reflector would be Al screen rather than PCB at these dimensions.
The thing with yagis or log periodics is that you need to align a lot of
things for the magic to happen. The biquad doesn't have many critical
dimensions.
Worse comes to worse, you put it back on ebay. That price is about half
of what Solid Signal charges.
I only build antennas for what I can't buy. It is way more work than you
think.
If you don't want to buy the BT antenna, I would suggest building a
biquad. They don't take long to build. You would probably have to scale
a biquad designed for wifi.
> http://martybugs.net/wireless/biquad/
Your reflector would be Al screen rather than PCB at these dimensions.
The thing with yagis or log periodics is that you need to align a lot of
things for the magic to happen. The biquad doesn't have many critical
dimensions.
Jim Thompson
Nov 28, 2012, 6:34:33āÆPM11/28/12
to
On Wed, 28 Nov 2012 14:52:06 -0800, Joerg <inv...@invalid.invalid>
wrote:
[snip]
it not ?>:-}
>
>>>> I'm 35 miles from the antenna, but a friend of mine 10 miles
>>>> farther out can get it ok. But he's out on the flat plains,
>>>> and has a rooftop antenna.
>>>>
>>>> Remember the analog-to-digital transition? ...
>>>
>>> That <censored> transition was a major loss for us. Many evenings we can
>>> barely receive a single station, on account of multipath reception.
>>>
>> I probably should try OTA where I am now but there was no hope where I
>> was before.
>
>
>Other than evening news (which you can get on the web), some old movies
>(if you are lucky and the signal path holds for 2h) and Dancing with the
>Stars it's hardly worth it. In contrast to the election our favorite
>candidate won yesterday on Dancing with the Stars.
You mean you're still watching "Dancing with the Has-been Stars ?:-)
[snip]
I get 1000's of Channels with beautiful picture quality and useless
content :-(
...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
wrote:
[snip]
>>
>
>In our case there are many stations such as Fox-40 where there is no
>null. You always have tons of signal but sometimes the TV can't decipher
>any of it, other times it sorta works. 80-90% of the time, at the most.
>That was our "digital dividend" :-(
>
>DTV, what a joke. I think it means "disrupted television" or something.
>
Well! It _is_ successful. It's breaking you of relying on OTA TV, is
>
>In our case there are many stations such as Fox-40 where there is no
>null. You always have tons of signal but sometimes the TV can't decipher
>any of it, other times it sorta works. 80-90% of the time, at the most.
>That was our "digital dividend" :-(
>
>DTV, what a joke. I think it means "disrupted television" or something.
>
it not ?>:-}
>
>>>> I'm 35 miles from the antenna, but a friend of mine 10 miles
>>>> farther out can get it ok. But he's out on the flat plains,
>>>> and has a rooftop antenna.
>>>>
>>>> Remember the analog-to-digital transition? ...
>>>
>>> That <censored> transition was a major loss for us. Many evenings we can
>>> barely receive a single station, on account of multipath reception.
>>>
>> I probably should try OTA where I am now but there was no hope where I
>> was before.
>
>
>Other than evening news (which you can get on the web), some old movies
>(if you are lucky and the signal path holds for 2h) and Dancing with the
>Stars it's hardly worth it. In contrast to the election our favorite
>candidate won yesterday on Dancing with the Stars.
[snip]
I get 1000's of Channels with beautiful picture quality and useless
content :-(
...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Joerg
Nov 28, 2012, 6:56:26āÆPM11/28/12
to
Jim Thompson wrote:
> On Wed, 28 Nov 2012 14:52:06 -0800, Joerg <inv...@invalid.invalid>
> wrote:
>
> [snip]
>> In our case there are many stations such as Fox-40 where there is no
>> null. You always have tons of signal but sometimes the TV can't decipher
>> any of it, other times it sorta works. 80-90% of the time, at the most.
>> That was our "digital dividend" :-(
>>
>> DTV, what a joke. I think it means "disrupted television" or something.
>>
>
> Well! It _is_ successful. It's breaking you of relying on OTA TV, is
> it not ?>:-}
>
Yup. But it backfired on the stations. This is a fairly affluent
> On Wed, 28 Nov 2012 14:52:06 -0800, Joerg <inv...@invalid.invalid>
> wrote:
>
> [snip]
>> In our case there are many stations such as Fox-40 where there is no
>> null. You always have tons of signal but sometimes the TV can't decipher
>> any of it, other times it sorta works. 80-90% of the time, at the most.
>> That was our "digital dividend" :-(
>>
>> DTV, what a joke. I think it means "disrupted television" or something.
>>
>
> Well! It _is_ successful. It's breaking you of relying on OTA TV, is
> it not ?>:-}
>
middle-class neighborhood and many people can't see much OTA TV anymore.
Got miffed, pulled the plug. Now they get the news via Internet and the
movies via Netflix. Guess what that does to the ad revenue of the stations.
>>>>> I'm 35 miles from the antenna, but a friend of mine 10 miles
>>>>> farther out can get it ok. But he's out on the flat plains,
>>>>> and has a rooftop antenna.
>>>>>
>>>>> Remember the analog-to-digital transition? ...
>>>> That <censored> transition was a major loss for us. Many evenings we can
>>>> barely receive a single station, on account of multipath reception.
>>>>
>>> I probably should try OTA where I am now but there was no hope where I
>>> was before.
>>
>> Other than evening news (which you can get on the web), some old movies
>> (if you are lucky and the signal path holds for 2h) and Dancing with the
>> Stars it's hardly worth it. In contrast to the election our favorite
>> candidate won yesterday on Dancing with the Stars.
>
> You mean you're still watching "Dancing with the Has-been Stars ?:-)
>
ballroom dancing so we always thoroughly enjoy that. And ok, the hi-res
is nice for such events. If the signal holds, that is.
> [snip]
>
> I get 1000's of Channels with beautiful picture quality and useless
> content :-(
>
Peabody
Nov 28, 2012, 8:36:14āÆPM11/28/12
to
k...@att.bizzz says...
> Yes, the driven element of a yagi is a dipole.
>>> ... And does it matter where the twinlead is attached
>>> to the driven element - does it have to be at the
>>> inside ends?
>> Yes, it has to be connected in the center.
> It is a dipole. ;-)
Well, that brings up the issue of what kind of dipole. From
what I've read, using a folded dipole as the driven element
has two advantages - it provides a broader bandwidth (which
isn't really important in my case because I only need one
channel), and it provides a better match to a standard
300/75 balun. Apparently a simple dipole presents matching
problems, although to tell you the truth I don't understand
why.
I found a video on Youtube which looks like a good example
for me to duplicate - adjusted a bit for the difference in
frequency. It's a 6-element Yagi which uses a folded
dipole:
http://www.youtube.com/watch?v=43JZBCGDJkU
Of course this is an Aussie design, so I'll probably have to
turn it upside down.
> Yes, the driven element of a yagi is a dipole.
>>> ... And does it matter where the twinlead is attached
>>> to the driven element - does it have to be at the
>>> inside ends?
>> Yes, it has to be connected in the center.
> It is a dipole. ;-)
what I've read, using a folded dipole as the driven element
has two advantages - it provides a broader bandwidth (which
isn't really important in my case because I only need one
channel), and it provides a better match to a standard
300/75 balun. Apparently a simple dipole presents matching
problems, although to tell you the truth I don't understand
why.
I found a video on Youtube which looks like a good example
for me to duplicate - adjusted a bit for the difference in
frequency. It's a 6-element Yagi which uses a folded
dipole:
http://www.youtube.com/watch?v=43JZBCGDJkU
Of course this is an Aussie design, so I'll probably have to
turn it upside down.
amdx
Nov 28, 2012, 9:16:44āÆPM11/28/12
to
find a couple of happy directions to cancel a portion of multi-path of
the Fox-40 signal.
Just a thought.
Mikek
Jeff Liebermann
Nov 28, 2012, 9:37:18āÆPM11/28/12
to
On Wed, 28 Nov 2012 11:59:31 -0600, Peabody
<waybackNO...@yahoo.com> wrote:
>I'm 35 miles from the antenna, but a friend of mine 10 miles
>farther out can get it ok. But he's out on the flat plains,
>and has a rooftop antenna.
Line of sight is very important. If the hill is big enough, it can
<waybackNO...@yahoo.com> wrote:
>I'm 35 miles from the antenna, but a friend of mine 10 miles
>farther out can get it ok. But he's out on the flat plains,
>and has a rooftop antenna.
completely block the signal. As I mentioned, a big high gain antenna
does nothing if there's no signal to receive. I can run the numbers
for you if you send me the station call sign, your EXACT lat-long, and
the proposed height above the ground. Something like this:
<http://802.11junk.com/jeffl/coverage/RST/>
The catch is that I'm rather busy during the holiday madness month and
may not have much time to do it right. If you want to try it
yourself, you can do a fair job with Google Earth.
Reading between the lines, are you proposing to build an indoor TV
antenna? If so, that will limit the size of the antenna boom. It
would still be worthwhile, but not as much as simply putting the
antenna on the roof. Think of devious ways you can install a rooftop
antenna. I recently built a yagi out of sheet mylar and aluminum duct
tape. It worked.
Also, if you do it indoors, you will not have much feed line. The
purpose of the antenna mounted amplifier is mostly to compensate for
the losses of the coax cable between the antenna and receiver.
However, if the coax cable is short (less than 10m) don't bother with
the amplifier.
Indoor antennas through glass has another problem. The IR reflective
coating found on all new construction windows is quite effective at
blocking RF signals. That's another reason for a roof mounted
antenna.
>Remember the analog-to-digital transition?
I'm trying to forget. There was more garbage sold as converters than
>Remember the analog-to-digital transition?
I ever saw in my worst nightmare. Fortunately, most of those were
either trashed, recycled, or sold on eBay.
>It's a Zenith DTT901, and it can
>display a little signal-strength meter in real time. The
>local channels that I get just fine come it at about 70% on
>the meter, or close to that. It does detect channel 36, but
>at about 35%, and the tuner just can't make sense of it at
>that point - it doesn't even display the nominal channel
>number.
user confusion. Of course, it did quite the opposite. At this time,
the channel number has NOTHING to do with the actual transmit
frequency. Various frequency lists will have both the indicated
channel and the real transmit channel.
The Zenith DTT901 is actually one of the better converters. The
limiting factor on almost all of them is receive sensitivity but the
Zenith box was better than most.
>But that's with a RCA ANT111, with just the basic single
>loop for UHF. So I thought with maybe a little better
>antenna, I might be able to receive the channel.
>I have some twinlead, and a balun, and maybe even some
>copper wire that would work.
into a proper constructed version. If the rabbit ears are as bad as I
suspect, anything will gain will make a substantial improvement.
However, there's nothing sacred about building a yagi. It just
happens to be fairly easy to build and delivers lots of gain. There
are plenty of other designs that work. Try a Gray Hoverman antenna:
<https://www.google.com/search?q=gray+hoverman+antenna&tbm=isch>
<http://www.digitalhome.ca/ota/superantenna/design.htm>
>It turns out that there is the
>right Blonder Tongue antenna on Ebay for $100 plus shipping,
>but, you know, I may learn something about antennas doing it
>myself.
those. I just was forced to buy a 10ft 1.25" mast at Radio Shock. $32
each. OUCH!
<http://www.radioshack.com/product/index.jsp?productId=3739599>
Oh swell. The price went up for Christmas.
Incidentally, you can compare many commercial antennas at:
<http://www.hdtvprimer.com/antennas/comparing.html>
>That was my thinking. If I build one for cheap, and the
>signal strengh is only marginally better, then it's unlikely
>even a good antenna would do the trick. But if I get major
>improvement, even if not quite good enough, then it may be
>worthwhile to build, or buy, something better performing.
>Just to clarify a couple things - it appears that the
>reflector and the directors are continuous elements - not
>cut in the middle, whereas the driven element is cut. Is
>that right?
not going to be building it like the typical yagi calculator shows.
It's not going to be a simple dipole. Build a folded dipole instead.
The feed point will (hopefully) be about 300 ohms. At the feed point
attach a 300 ohm to 75 ohm balun, and then the coax cable to the TV.
One of these things:
<http://mycoffeelounge.net/pixup/38612-6404.jpg>
There are better matching networks, but this is the easiest.
>And does it matter where the twinlead is
>attached to the driven element - does it have to be at the
>inside ends?
folded dipole, the 300 ohm feed point is at the wire ends.
A few more details... I suggested building a single channel yagi
instead of a broadband antenna because it's easier and because it
delivers more gain. If you build the yagi from any of the online
calculators, you'll end up with a fairly narrow band antenna. The
more elements, the narrower the bandwidth. When the bandwidth starts
to approach that of the TV channel (6MHZ) you're going to run into
critical design parameters and cut dimensions that can't be worked out
by trial and error. So, don't make it with too many elements and you
should be ok. Otherwise, borrow an antenna analyzer that covers the
frequency range, a reflection coefficient bridge with sweep generator,
a network analyzer, or some manner of RF test equipment that can
determine if you've hit the correct tuning frequency.
A rough guess as to bandwidth for the single channel yagi would be
about 15% or about 90MHz (see bottom graph) so you should be ok.
<http://www.supernec.com/yagi.htm>
Here's an antenna a friend built:
<http://802.11junk.com/jeffl/antennas/DTV-jw/slides/P1010012.html>
It should work, but doesn't. Note the creative use of hardware store
materials.
Jeff Liebermann
Nov 28, 2012, 10:00:39āÆPM11/28/12
to
On Wed, 28 Nov 2012 15:11:02 -0800, miso <mi...@sushi.com> wrote:
>If you found the BTY-10-U cut for your channel for $100, I'd get it.
>Worse comes to worse, you put it back on ebay. That price is about half
>of what Solid Signal charges.
List prices is $215.
>If you found the BTY-10-U cut for your channel for $100, I'd get it.
>Worse comes to worse, you put it back on ebay. That price is about half
>of what Solid Signal charges.
It comes in several mutations by channel range:
A (14-19), B (20-26), C (27-34), D (35-44),
E (45-56), F (57-69)
Gain is about 12-14dBi.
>I only build antennas for what I can't buy. It is way more work than you
>think.
design is fairly easy depending on complexity. The initial prototypes
are also fairly easy. Shoving it into production is difficult.
Dealing with customer illusions, deranged marketing executives,
creative applications, and impossible installations are my nightmares.
>If you don't want to buy the BT antenna, I would suggest building a
>biquad. They don't take long to build. You would probably have to scale
>a biquad designed for wifi.
>> http://martybugs.net/wireless/biquad/
>Your reflector would be Al screen rather than PCB at these dimensions.
<https://www.google.com/search?q=loop+yagi&tbm=isch>
However, that gives me an idea. I designed a 2.4GHz patch antenna
made from foam board building construction insulation panels. It's
basically polystyrene foam sandwiched between two layers of aluminum
foil. It comes in various thicknesses. The same design would work
for 600MHz. Gain was about 8dBi.
>The thing with yagis or log periodics is that you need to align a lot of
>things for the magic to happen.
many parts and pieces make it difficult to build and optimize. Fewer
parts are easier.
>The biquad doesn't have many critical dimensions.
one wavelength long instead of 1/2 wave. The same dimensional
tolerances apply to both antennas. The reason yours were not critical
was that they probably didn't have much gain. At 2.4Ghz, anything
less than 10dBi gain can be thrown together with little concern for
tolerances. However, above about 14dBi, things get rather critical.
At 24dBi and up, you're looking at about 80MHz bandwidth, which is the
entire 2.4GHz band. Miss a little on the dimensions, and you could
easily chop off the upper or lower ends of the band.
tm
Nov 28, 2012, 10:05:13āÆPM11/28/12
to
"Jeff Liebermann" <je...@cruzio.com> wrote in message
news:o1gdb8lfss7btaaoo...@4ax.com...
over.
k...@att.bizzz
Nov 28, 2012, 10:16:52āÆPM11/28/12
to
On Wed, 28 Nov 2012 19:36:14 -0600, Peabody
<waybackNO...@yahoo.com> wrote:
>k...@att.bizzz says...
>
> > Yes, the driven element of a yagi is a dipole.
>
> >>> ... And does it matter where the twinlead is attached
> >>> to the driven element - does it have to be at the
> >>> inside ends?
>
> >> Yes, it has to be connected in the center.
>
> > It is a dipole. ;-)
>
>Well, that brings up the issue of what kind of dipole.
One without a modifier. ;-)
<waybackNO...@yahoo.com> wrote:
>k...@att.bizzz says...
>
> > Yes, the driven element of a yagi is a dipole.
>
> >>> ... And does it matter where the twinlead is attached
> >>> to the driven element - does it have to be at the
> >>> inside ends?
>
> >> Yes, it has to be connected in the center.
>
> > It is a dipole. ;-)
>
>Well, that brings up the issue of what kind of dipole.
>From
>what I've read, using a folded dipole as the driven element
>has two advantages - it provides a broader bandwidth (which
>isn't really important in my case because I only need one
>channel), and it provides a better match to a standard
>300/75 balun. Apparently a simple dipole presents matching
>problems, although to tell you the truth I don't understand
>why.
least somewhat. If you need more, a Yagi isn't the right topology. A
log-periodic is a better choice.
I don't understand the 300/75 balun thing. Isn't a 1/2 wave dipole 75
ohms directly? It's been a long time...
>I found a video on Youtube which looks like a good example
>for me to duplicate - adjusted a bit for the difference in
>frequency. It's a 6-element Yagi which uses a folded
>dipole:
>
>http://www.youtube.com/watch?v=43JZBCGDJkU
>
>Of course this is an Aussie design, so I'll probably have to
>turn it upside down.
Jeff Liebermann
Nov 28, 2012, 10:27:00āÆPM11/28/12
to
On Wed, 28 Nov 2012 22:05:13 -0500, "tm" <No_on...@white-house.gov>
wrote:
>> Here's an antenna a friend built:
>> <http://802.11junk.com/jeffl/antennas/DTV-jw/slides/P1010012.html>
>> It should work, but doesn't. Note the creative use of hardware store
>> materials.
<http://www.thehulltruth.com/attachments/marine-electronics-forum/223929d1330300345-digital-tv-antennas-cm-4149.jpg>
<http://www.hdtvprimer.com/antennas/doublebow.html>
<http://www.newegg.com/Product/Product.aspx?Item=N82E16882557016>
Note the feed point in the middle of the phasing lines instead of at
the ends, which I think was the major problem. When it's built
correctly it's actually a very good indoor antenna.
The bow tie elements really should be a solid sheet of copper or
aluminium in order to get a broad bandwidth. It will work using "fan"
type wire dipoles, but solid is better.
"The uglier the antenna, the better it works"
Me about 1989
wrote:
>> Here's an antenna a friend built:
>> <http://802.11junk.com/jeffl/antennas/DTV-jw/slides/P1010012.html>
>> It should work, but doesn't. Note the creative use of hardware store
>> materials.
>I think the connections between the top and bottom dipoles need to cross
>over.
Nope. See:
>over.
<http://www.thehulltruth.com/attachments/marine-electronics-forum/223929d1330300345-digital-tv-antennas-cm-4149.jpg>
<http://www.hdtvprimer.com/antennas/doublebow.html>
<http://www.newegg.com/Product/Product.aspx?Item=N82E16882557016>
Note the feed point in the middle of the phasing lines instead of at
the ends, which I think was the major problem. When it's built
correctly it's actually a very good indoor antenna.
The bow tie elements really should be a solid sheet of copper or
aluminium in order to get a broad bandwidth. It will work using "fan"
type wire dipoles, but solid is better.
"The uglier the antenna, the better it works"
Me about 1989
tm
Nov 28, 2012, 10:44:35āÆPM11/28/12
to
news:njkdb89js88ljgsc4...@4ax.com...
The spacing from the rear reflector could also be a factor if not correct.
Years ago I built up a ten foot yagi from 1/2 inch copper pipe on Ch-22 and
put it in the attic. It really worked well. I used a pre-amp that went from
300 ohms balanced to 75 coax to the basement distribution system. Used it
for when the cable (often) went out (Comcast).
Regards,
tm
> On Wed, 28 Nov 2012 22:05:13 -0500, "tm" <No_on...@white-house.gov>
> wrote:
>
>>> Here's an antenna a friend built:
>>> <http://802.11junk.com/jeffl/antennas/DTV-jw/slides/P1010012.html>
>>> It should work, but doesn't. Note the creative use of hardware store
>>> materials.
>
>>I think the connections between the top and bottom dipoles need to cross
>>over.
>
> Nope. See:
> <http://www.thehulltruth.com/attachments/marine-electronics-forum/223929d1330300345-digital-tv-antennas-cm-4149.jpg>
> <http://www.hdtvprimer.com/antennas/doublebow.html>
> <http://www.newegg.com/Product/Product.aspx?Item=N82E16882557016>
> Note the feed point in the middle of the phasing lines instead of at
> the ends, which I think was the major problem. When it's built
> correctly it's actually a very good indoor antenna.
>
> The bow tie elements really should be a solid sheet of copper or
> aluminium in order to get a broad bandwidth. It will work using "fan"
> type wire dipoles, but solid is better.
>
> "The uglier the antenna, the better it works"
> Me about 1989
>
> --
Oh, good info. Thanks. And I agree, the elements would be better if solid.
> wrote:
>
>>> Here's an antenna a friend built:
>>> <http://802.11junk.com/jeffl/antennas/DTV-jw/slides/P1010012.html>
>>> It should work, but doesn't. Note the creative use of hardware store
>>> materials.
>
>>I think the connections between the top and bottom dipoles need to cross
>>over.
>
> Nope. See:
> <http://www.thehulltruth.com/attachments/marine-electronics-forum/223929d1330300345-digital-tv-antennas-cm-4149.jpg>
> <http://www.hdtvprimer.com/antennas/doublebow.html>
> <http://www.newegg.com/Product/Product.aspx?Item=N82E16882557016>
> Note the feed point in the middle of the phasing lines instead of at
> the ends, which I think was the major problem. When it's built
> correctly it's actually a very good indoor antenna.
>
> The bow tie elements really should be a solid sheet of copper or
> aluminium in order to get a broad bandwidth. It will work using "fan"
> type wire dipoles, but solid is better.
>
> "The uglier the antenna, the better it works"
> Me about 1989
>
> --
The spacing from the rear reflector could also be a factor if not correct.
Years ago I built up a ten foot yagi from 1/2 inch copper pipe on Ch-22 and
put it in the attic. It really worked well. I used a pre-amp that went from
300 ohms balanced to 75 coax to the basement distribution system. Used it
for when the cable (often) went out (Comcast).
Regards,
tm
Jeff Liebermann
Nov 28, 2012, 10:47:00āÆPM11/28/12
to
On Wed, 28 Nov 2012 22:16:52 -0500, k...@att.bizzz wrote:
>I don't understand the 300/75 balun thing. Isn't a 1/2 wave dipole 75
>ohms directly? It's been a long time...
Yes in free space, but nowhere else. The easiest way to explain it is
>I don't understand the 300/75 balun thing. Isn't a 1/2 wave dipole 75
>ohms directly? It's been a long time...
that the impedance of a horizontal dipole changes with the height
above ground. Near (perfect) ground, the impedance is nearly zero. As
the antenna gets higher, so does the impendance. It goes up and down
like in a damped wave and eventually settles down to 75 ohms when the
height above ground is many wavelengths.
<http://www.svgkablo.com.tr/ta1dx/amator/impedance.htm>
<http://hamchatforum.lefora.com/2009/11/12/center-fed-half-wave-dipole/#post7>
It's the same with a yagi antenna. As the driven element gets closer
and farther from the reflector and director, the impedance also
changes. By juggling the antenna spacing, a fairly modest range of
impedances can be produced at the drive point. The problem is that an
ideal 75+j0 ohm impedance does not guarantee that the other antenna
parameters are also optimized or ideal. Perfect VSWR does not
necessarily occur at the same point as maximim gain, optimum
bandwidth, or best efficiency.
Jeff Liebermann
Nov 28, 2012, 11:15:23āÆPM11/28/12
to
On Wed, 28 Nov 2012 22:44:35 -0500, "tm" <No_on...@white-house.gov>
wrote:
>Oh, good info. Thanks. And I agree, the elements would be better if solid.
Just connecting the ends together will make a big improvement. Some
creativity as to what is a solid bow tie dipole is also interesting:
<http://esl.eng.ohio-state.edu/~rmarhefka/antennas/illustrations.htm>
See the artistic fractal antennas. Stranger antennas have been built.
<http://www.instructables.com/id/How-to-make-a-fractal-antenna-for-HDTV-DTV-plus-/>
>The spacing from the rear reflector could also be a factor if not correct.
Nope. The spacing only affects the feed point impedance and the
pattern. The wrong spacing might cause a loss of gain or directivity,
but it won't cause the antenna to totally fail to function. Feeding
the antenna at the wrong point will do that nicely.
>Years ago I built up a ten foot yagi from 1/2 inch copper pipe on Ch-22 and
>put it in the attic. It really worked well. I used a pre-amp that went from
>300 ohms balanced to 75 coax to the basement distribution system. Used it
>for when the cable (often) went out (Comcast).
Nice, until you have to rotate it. I've done a few attic antennas for
CC&R infested homes. However, that's becoming a challenge as more
homes are insulating the roof with aluminum coated foam board. The
white rocks which are now required on most industrial flat roofs (for
energy efficiency) also seem to block RF. I'm also finding roll
roofing and shingles which are held together with wire mesh.
I've done a few "emergency" antennas for various applications. Copper
pipe booms are expen$ive. I prefer wooden booms (boiled in wax or KD
pine covered with Varathane. However, my favorite emergency antenna
is a rope yagi. No boom at all. Just rope, wire or tubing elements,
and hopefully plenty of room to deploy. I built one monster 30 meter
long 144Mhz rope yagi with about 20dBi gain. I think there were 48
elements. That's a power gain of 100 turning a common 44 watt 2 meter
ham radio into 4,400 watts EIRP, enough to cook your dinner. Ummm...
don't stand in front of it or aim it at your neighbors.
A variation on the same idea is the roll out mylar yagi. I had a roll
of mylar left over from my tape and donut black tape PCB layout days.
I cut strips of aluminum duct tape forming a yagi pattern on the
mylar. Dealing with the asymmetrical cross section of the elements
was a bit of a modeling challenge, but worked after some guesswork. I
haven't tried to apply too much power as I'm somewhat afraid it might
melt. Four poles in the corners, some guy rope, and it's on the air.
It could probably be turned into a TV yagi antenna, if a suitable
place could be found to mount it.
wrote:
>Oh, good info. Thanks. And I agree, the elements would be better if solid.
creativity as to what is a solid bow tie dipole is also interesting:
<http://esl.eng.ohio-state.edu/~rmarhefka/antennas/illustrations.htm>
See the artistic fractal antennas. Stranger antennas have been built.
<http://www.instructables.com/id/How-to-make-a-fractal-antenna-for-HDTV-DTV-plus-/>
>The spacing from the rear reflector could also be a factor if not correct.
pattern. The wrong spacing might cause a loss of gain or directivity,
but it won't cause the antenna to totally fail to function. Feeding
the antenna at the wrong point will do that nicely.
>Years ago I built up a ten foot yagi from 1/2 inch copper pipe on Ch-22 and
>put it in the attic. It really worked well. I used a pre-amp that went from
>300 ohms balanced to 75 coax to the basement distribution system. Used it
>for when the cable (often) went out (Comcast).
CC&R infested homes. However, that's becoming a challenge as more
homes are insulating the roof with aluminum coated foam board. The
white rocks which are now required on most industrial flat roofs (for
energy efficiency) also seem to block RF. I'm also finding roll
roofing and shingles which are held together with wire mesh.
I've done a few "emergency" antennas for various applications. Copper
pipe booms are expen$ive. I prefer wooden booms (boiled in wax or KD
pine covered with Varathane. However, my favorite emergency antenna
is a rope yagi. No boom at all. Just rope, wire or tubing elements,
and hopefully plenty of room to deploy. I built one monster 30 meter
long 144Mhz rope yagi with about 20dBi gain. I think there were 48
elements. That's a power gain of 100 turning a common 44 watt 2 meter
ham radio into 4,400 watts EIRP, enough to cook your dinner. Ummm...
don't stand in front of it or aim it at your neighbors.
A variation on the same idea is the roll out mylar yagi. I had a roll
of mylar left over from my tape and donut black tape PCB layout days.
I cut strips of aluminum duct tape forming a yagi pattern on the
mylar. Dealing with the asymmetrical cross section of the elements
was a bit of a modeling challenge, but worked after some guesswork. I
haven't tried to apply too much power as I'm somewhat afraid it might
melt. Four poles in the corners, some guy rope, and it's on the air.
It could probably be turned into a TV yagi antenna, if a suitable
place could be found to mount it.
Jasen Betts
Nov 29, 2012, 3:30:50āÆAM11/29/12
to
On 2012-11-28, Peabody <waybackNO...@yahoo.com> wrote:
>
> Yes, I've done that, and also confirmed with the station
> engineer that under normal conditions people in my area
> do get the channel. But in my particular case, I'm on the
> backside of a large hill with respect to the station's
> antenna, so I may just be blocked no matter what I do.
>
>
> Yes, I've done that, and also confirmed with the station
> engineer that under normal conditions people in my area
> do get the channel. But in my particular case, I'm on the
> backside of a large hill with respect to the station's
> antenna, so I may just be blocked no matter what I do.
>
> I'm 35 miles from the antenna, but a friend of mine 10 miles
> farther out can get it ok. But he's out on the flat plains,
> and has a rooftop antenna.
If you put up a huge mast you may get a usable signal,
> farther out can get it ok. But he's out on the flat plains,
> and has a rooftop antenna.
but it's probably beyond hope. do any of your neighbours
get a good signal from that station.
We get marginal analogue UHF here and no usable digital UHF.
and all the digital is UHF here.
I put up a satellite dish and tht works well except in high
winds, I need to put some stay bars on it or move it to a less
aesthetic, more sheltered location.
> That was my thinking. If I build one for cheap, and the
> signal strengh is only marginally better, then it's unlikely
> even a good antenna would do the trick. But if I get major
> improvement, even if not quite good enough, then it may be
> worthwhile to build, or buy, something better performing.
but there's no saying what it might do to the signal quality.
> Just to clarify a couple things - it appears that the
> reflector and the directors are continuous elements - not
> cut in the middle, whereas the driven element is cut. Is
> that right?
> And does it matter where the twinlead is
> attached to the driven element - does it have to be at the
> inside ends?
--
āā 100% natural
Jasen Betts
Nov 29, 2012, 3:48:28āÆAM11/29/12
to
On 2012-11-29, Jeff Liebermann <je...@cruzio.com> wrote:
> Here's an antenna a friend built:
><http://802.11junk.com/jeffl/antennas/DTV-jw/slides/P1010012.html>
> It should work, but doesn't. Note the creative use of hardware store
> materials.
It looks like a bowtie phased array done wrong.
> Here's an antenna a friend built:
><http://802.11junk.com/jeffl/antennas/DTV-jw/slides/P1010012.html>
> It should work, but doesn't. Note the creative use of hardware store
> materials.
The feedpoint should be in the centre, or the vertical wires should
cross. I guestimate it to be about 150 ohms, so it may need a
custom balun.
That reflector may be too close too, or is that to change the
impedance?
--
āā 100% natural
--- news://freenews.netfront.net/ - complaints: ne...@netfront.net ---
Mark Zenier
Nov 28, 2012, 2:23:33āÆPM11/28/12
to
In article <20121128-0...@news.astraweb.com>,
>but not the distant one. The tuner shows the channel is there, but
>at low strength, and I'm hoping an antenna with the
>elements optimized for channel 36 will be enough to bring it in.
There were plans for an easy to build four bay Hoverman on a website
back a few years ago. This is a broadside array, not a boom antenna.
But it's basically just some sticks, a couple lengths of bent wire,
(and an optional screen if you want it to be unidirectional, instead
of bidirectional). It will probably have as much gain as you can get
with a convenient Yagi. This would be a low effort try just to see
if more antenna will help.
Somebody here in the newsgroup built it, try and see if google groups has
the traffic (with the URL) from around the time of the digital conversion.
Or google for terms like "UHF", "Four Bay", "Hoverman". I vaguely
remember it as being on a Canadian web site.
Mark Zenier mze...@eskimo.com
Googleproofaddress(account:mzenier provider:eskimo domain:com)
Peabody <waybackNO...@yahoo.com> wrote:
>I need to bring in a distant TV station, and would like to build an
>antenna specifically for that channel. It's physically channel 36,
>I need to bring in a distant TV station, and would like to build an
>antenna specifically for that channel. It's physically channel 36,
>which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm.
>
>
>I just told you everything I know about antennas, and haven't had
>much luck on Google. I need it to be about 3-4 feet long, and it
>will be indoors. If anyone knows of a fairly simple design that
>much luck on Google. I need it to be about 3-4 feet long, and it
>might work, I would appreciate a link.
>
>I have a $10 indoor antenna, and it gets all the local channels,
>
>but not the distant one. The tuner shows the channel is there, but
>at low strength, and I'm hoping an antenna with the
>elements optimized for channel 36 will be enough to bring it in.
There were plans for an easy to build four bay Hoverman on a website
back a few years ago. This is a broadside array, not a boom antenna.
But it's basically just some sticks, a couple lengths of bent wire,
(and an optional screen if you want it to be unidirectional, instead
of bidirectional). It will probably have as much gain as you can get
with a convenient Yagi. This would be a low effort try just to see
if more antenna will help.
Somebody here in the newsgroup built it, try and see if google groups has
the traffic (with the URL) from around the time of the digital conversion.
Or google for terms like "UHF", "Four Bay", "Hoverman". I vaguely
remember it as being on a Canadian web site.
Mark Zenier mze...@eskimo.com
Googleproofaddress(account:mzenier provider:eskimo domain:com)
Peabody
Nov 29, 2012, 1:04:32āÆPM11/29/12
to
Here's the link to the TVfool.com analysis of my location:
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3dcc49cef0
f10fd5
The channel I'm trying to get is real 36 (virtual 35) KRSC, which
is 29.5 miles away on a magnetic heading of 35 degrees. And going
out in the back yard with my Boy Scout compass, I find that the
hill situation isn't what I thought. The hill is actually more to
the North. So based on the TVfool analysis and what the station
engineer told me, a rooftop antenna should definitely work. But,
you know, it's only one channel, and I don't think I want to got to
that expense for one channel. So I'm going to try the Yagi and see
what happens.
Oddly, there is one local channel that I can't get, and that's
KTUL, real channel 10 (virtual 8). And that's despite the fact
that real 11, within 10 degrees of 10, comes in fine. Very
strange.
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3dcc49cef0
f10fd5
The channel I'm trying to get is real 36 (virtual 35) KRSC, which
is 29.5 miles away on a magnetic heading of 35 degrees. And going
out in the back yard with my Boy Scout compass, I find that the
hill situation isn't what I thought. The hill is actually more to
the North. So based on the TVfool analysis and what the station
engineer told me, a rooftop antenna should definitely work. But,
you know, it's only one channel, and I don't think I want to got to
that expense for one channel. So I'm going to try the Yagi and see
what happens.
Oddly, there is one local channel that I can't get, and that's
KTUL, real channel 10 (virtual 8). And that's despite the fact
that real 11, within 10 degrees of 10, comes in fine. Very
strange.
Joerg
Nov 29, 2012, 1:09:22āÆPM11/29/12
to
four locations and the respective channels are all over the map. So this
would get old really fast.
Jeff Liebermann
Nov 29, 2012, 6:37:47āÆPM11/29/12
to
On Wed, 28 Nov 2012 19:23:33 GMT, mze...@eskimo.com (Mark Zenier)
wrote:
>There were plans for an easy to build four bay Hoverman on a website
>back a few years ago.
<http://www.digitalhome.ca/ota/superantenna/index.htm>
<http://www.digitalhome.ca/ota/superantenna/performance.htm>
<http://www.digitalhome.ca/ota/superantenna/design.htm>
NEC2 models:
<http://www.jedsoft.org/fun/antennas/dtv/gh.html#toc-3>
wrote:
>There were plans for an easy to build four bay Hoverman on a website
>back a few years ago.
<http://www.digitalhome.ca/ota/superantenna/performance.htm>
<http://www.digitalhome.ca/ota/superantenna/design.htm>
NEC2 models:
<http://www.jedsoft.org/fun/antennas/dtv/gh.html#toc-3>
Jeff Liebermann
Nov 29, 2012, 7:09:45āÆPM11/29/12
to
On Thu, 29 Nov 2012 12:04:32 -0600, Peabody
<waybackNO...@yahoo.com> wrote:
>Here's the link to the TVfool.com analysis of my location:
>
>http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3dcc49cef0f10fd5
>
>The channel I'm trying to get is real 36 (virtual 35) KRSC, which
>is 29.5 miles away on a magnetic heading of 35 degrees.
<http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3dcc49cef0f10fd5%26t%3dALLTV%26n%3d24>
<waybackNO...@yahoo.com> wrote:
>Here's the link to the TVfool.com analysis of my location:
>
>http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3dcc49cef0f10fd5
>
>The channel I'm trying to get is real 36 (virtual 35) KRSC, which
>is 29.5 miles away on a magnetic heading of 35 degrees.
>And going
>out in the back yard with my Boy Scout compass, I find that the
>hill situation isn't what I thought. The hill is actually more to
>the North. So based on the TVfool analysis and what the station
>engineer told me, a rooftop antenna should definitely work.
<http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3dcc49cef0f10fd5%26t%3dALLTV%26n%3d24>
Noise margin is 6.6dB with 2 knife edge diffraction problems somewhere
along the path. You should be able to make it work with a rooftop
antenna.
You don't need much accuracy for aiming the antenna. A compass is
good enough. However, if you ever want more accuracy, build a
plotting board. Take a common road map and thumb tack it to the
board. Find yourself on the map and insert a push pin or nail. Find
a distant mountain top on the map that you can also see. Insert a 2nd
push pin or nail at it's location. Sighting along the two push pins,
rotate the plotting board and aim it at the distant mountain top. Your
map should now be properly aligned. You can find the direction of a
distant transmitter by just locating it on the map, and inserting
sticks into the ground around the map with the same orientation. No
compass or magnetic declination calculation required.
>But,
>you know, it's only one channel, and I don't think I want to got to
>that expense for one channel. So I'm going to try the Yagi and see
>what happens.
fiberglass telescoping window washing pole. I have one of those that
is 25 ft long that I use for wireless site survey tests. Things work
better when the antenna is clear of obstructions.
>Oddly, there is one local channel that I can't get, and that's
>KTUL, real channel 10 (virtual 8). And that's despite the fact
>that real 11, within 10 degrees of 10, comes in fine. Very
>strange.
<http://en.wikipedia.org/wiki/KTUL>
Are you sure your converter is properly setup to deal with virtual
channels? It could be listening to a different real channel. Check
the virtual channel 8 status display on your Zenith or just rescan and
start over.
<http://www.dtv.gov/rescan.html>
Incidentally, if you want a clue as to what type and size of TV
antenna is required to get decent TV reception in your area, just look
around at the rooftops of your neighbors. What works for them, should
work for you.
Peabody
Nov 30, 2012, 12:56:41āÆAM11/30/12
to
Jeff Liebermann says...
> Are you sure your converter is properly setup to deal
> with virtual channels? It could be listening to a
> different real channel. Check the virtual channel 8
> status display on your Zenith or just rescan and start
> over.
Yes, I'm sure. The Zenith picks up nothing as virtual
channel 8 even on repeated auto-scans at different antenna
positions, or when I try to go to virtual 8 on the remote.
And it also has a menu function where you can go to a real
channel number (i.e. - 10) manually. It shows something is
there, about like it does on channel 36, but too low a
signal strength to bring it in. Turning the antenna doesn't
have much effect. Well, there must be something in the
way, I guess, but it's still surprising since it's a VHF
channel, which should come through pretty readily.
> Are you sure your converter is properly setup to deal
> with virtual channels? It could be listening to a
> different real channel. Check the virtual channel 8
> status display on your Zenith or just rescan and start
> over.
channel 8 even on repeated auto-scans at different antenna
positions, or when I try to go to virtual 8 on the remote.
And it also has a menu function where you can go to a real
channel number (i.e. - 10) manually. It shows something is
there, about like it does on channel 36, but too low a
signal strength to bring it in. Turning the antenna doesn't
have much effect. Well, there must be something in the
way, I guess, but it's still surprising since it's a VHF
channel, which should come through pretty readily.
miso
Nov 30, 2012, 3:13:46āÆAM11/30/12
to
But with a yagi, you have many more dimensions to get right. Driven
element, space to next element, first direction, space, second director,
blah blah blah. That was my point. The "Loop yagi" doesn't have many
things to cut, while a multi-element yagi does.
element, space to next element, first direction, space, second director,
blah blah blah. That was my point. The "Loop yagi" doesn't have many
things to cut, while a multi-element yagi does.
miso
Nov 30, 2012, 3:21:55āÆAM11/30/12
to
I prefer SPLAT!, though you need a bit of linux knowledge to run it.
Radio Mobile is OK, but you need to set up some options at sufficient
tolerance to get a decent profile. The advantage to Radio Mobile is it
runs in windows, while SPLAT! needs to be compiled.
Both programs are free.
> http://www.ve2dbe.com/english1.html
> http://www.qsl.net/kd2bd/splat.html
I've also done LOS analysis in GRASS, but that is really tough to use.
> http://grass.osgeo.org/
There is a paper by some high school students doing wifi analysis with
GRASS and I seriously doubt they did it without some adult help. Just
loading GRASS itself is a bear since the order of compilation is critical.
Radio Mobile is OK, but you need to set up some options at sufficient
tolerance to get a decent profile. The advantage to Radio Mobile is it
runs in windows, while SPLAT! needs to be compiled.
Both programs are free.
> http://www.ve2dbe.com/english1.html
> http://www.qsl.net/kd2bd/splat.html
I've also done LOS analysis in GRASS, but that is really tough to use.
> http://grass.osgeo.org/
There is a paper by some high school students doing wifi analysis with
GRASS and I seriously doubt they did it without some adult help. Just
loading GRASS itself is a bear since the order of compilation is critical.
Jeff Liebermann
Nov 30, 2012, 12:09:34āÆPM11/30/12
to
elements except perhaps the driven element. You can even round the
ends of the yagi elements to add additional bandwidth. With a loop
yagi, you have to get the circumference correct the first time, with
no easy way to adjust the circumference. I've tried cutting the loops
by pretuning with a grid dip meter and couldn't get sufficient
precision. It's also easier to build things in 2D than in 3D.
What's nice about the loop yagi and cubical quad antennas is that they
have approximately a theoretical 2dB more gain than a yagi with the
same boom length and better f/b ratio. Also nice is the ability to
build a quad using insulating spreaders and wires instead of tubing.
You can also build a loop yagi that works with circular polarization
(which is of no benefit for a TV antenna). Quads and Loop Yagis also
meet my criteria for the ugliest antenna working better. So why are
we not all using quads and loop yagi's for TV antennas? Because
they're difficult and more expensive to build than yagis and they
don't broadband very nicely. Visualize one of the more elaborate TV
yagi antennas with loops replacing all the dipole elements. I don't
think it would sell, and would certainly be a mess to build.
Bandwidth for a yagi is also affected by the diameter of the element
rods. Large diameter tubing has a wider bandwidth. It's easy to use
large diameter tubing (with rounded ends) for a flat yagi, but almost
impossible to bend such tubing into a loop or quad arrangement.
Typically, loop yagis are made from thin strips of sheet metal with
the overlapping ends connected by a pop rivet or spot weld. While
this results in an antenna that's a bit more broadband than one made
from wire loops, it not even close to a fat element yagi.
wand...@dialup4less.com
Nov 30, 2012, 4:52:24āÆPM11/30/12
to
On Wednesday, November 28, 2012 12:34:36 AM UTC-5, Peabody wrote:
> I need to bring in a distant TV station, and would like to build an
>
> antenna specifically for that channel. It's physically channel 36,
>
> which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm.
>
>
>
> I just told you everything I know about antennas, and haven't had
>
> much luck on Google. I need it to be about 3-4 feet long, and it
>
> will be indoors. If anyone knows of a fairly simple design that
>
> might work, I would appreciate a link.
>
>
>
> I have a $10 indoor antenna, and it gets all the local channels,
>
> but not the distant one. The tuner shows the channel is there, but
>
> at low strength, and I'm hoping an antenna with the
>
> elements optimized for channel 36 will be enough to bring it in.
You might want to try a Fractal Antenna. Though they are not designed for a specific frequency, they seem easy to make.
> I need to bring in a distant TV station, and would like to build an
>
> antenna specifically for that channel. It's physically channel 36,
>
> which is 602-698 MHz, wavelengths of 49.8 - 49.3 cm.
>
>
>
> I just told you everything I know about antennas, and haven't had
>
> much luck on Google. I need it to be about 3-4 feet long, and it
>
> will be indoors. If anyone knows of a fairly simple design that
>
> might work, I would appreciate a link.
>
>
>
> I have a $10 indoor antenna, and it gets all the local channels,
>
> but not the distant one. The tuner shows the channel is there, but
>
> at low strength, and I'm hoping an antenna with the
>
> elements optimized for channel 36 will be enough to bring it in.
http://www.instructables.com/id/How-to-make-a-fractal-antenna-for-HDTV-DTV-plus-/
Mark Zenier
Nov 30, 2012, 12:40:04āÆPM11/30/12
to
In article <v3sfb8tc3v5270klh...@4ax.com>,
Jeff Liebermann <je...@cruzio.com> wrote:
>On Wed, 28 Nov 2012 19:23:33 GMT, mze...@eskimo.com (Mark Zenier)
>wrote:
>
>>There were plans for an easy to build four bay Hoverman on a website
>>back a few years ago.
>
><http://www.digitalhome.ca/ota/superantenna/index.htm>
><http://www.digitalhome.ca/ota/superantenna/performance.htm>
><http://www.digitalhome.ca/ota/superantenna/design.htm>
That's it. Thanks.
>On Wed, 28 Nov 2012 19:23:33 GMT, mze...@eskimo.com (Mark Zenier)
>wrote:
>
>>There were plans for an easy to build four bay Hoverman on a website
>>back a few years ago.
>
><http://www.digitalhome.ca/ota/superantenna/index.htm>
><http://www.digitalhome.ca/ota/superantenna/performance.htm>
><http://www.digitalhome.ca/ota/superantenna/design.htm>
Paul Hovnanian P.E.
Dec 1, 2012, 11:10:12āÆPM12/1/12
to
--
Paul Hovnanian mailto:Pa...@Hovnanian.com
------------------------------------------------------------------
"Nothing Important Happened Today"
-- King George III, diary entry July 4, 1776
Clifford Heath
Dec 5, 2012, 6:32:00āÆPM12/5/12
to
On 12/01/12 04:09, Jeff Liebermann wrote:
> With a loop
> yagi, you have to get the circumference correct the first time, with
> no easy way to adjust the circumference.
Incorporate a screw-driven hose-clamp perhaps?
> With a loop
> yagi, you have to get the circumference correct the first time, with
> no easy way to adjust the circumference.
> Bandwidth for a yagi is also affected by the diameter of the element
> rods. Large diameter tubing has a wider bandwidth.
A DF antenna doesn't necessarily want maximum gain or even F/B ratio,
what it wants is to minimize lobing, across the band. Difficult.
It's a five-element Yagi that has two short-long pairs. We believe it
works like a 3-element yagi but with the pairs coupling to broaden the
response. It took a lot of optimising - using a custom build of 4NEC
with a multi-dimensional slope optimiser.
Clifford Heath.
Jeff Liebermann
Dec 5, 2012, 11:19:08āÆPM12/5/12
to
On Thu, 06 Dec 2012 10:32:00 +1100, Clifford Heath
<c...@no.spam.please.net> wrote:
>On 12/01/12 04:09, Jeff Liebermann wrote:
>> With a loop
>> yagi, you have to get the circumference correct the first time, with
>> no easy way to adjust the circumference.
>
>Incorporate a screw-driven hose-clamp perhaps?
Good idea, but probably too critical on the tuning. It certainly
<c...@no.spam.please.net> wrote:
>On 12/01/12 04:09, Jeff Liebermann wrote:
>> With a loop
>> yagi, you have to get the circumference correct the first time, with
>> no easy way to adjust the circumference.
>
>Incorporate a screw-driven hose-clamp perhaps?
would be difficult to preset the circumference to a specific length.
For example, at 600MHz, we're looking at a wavelength of:
3*10^8 meters/sec / 600*10^6 cycles/sec = 0.5 meters
for a full wave loop. In terms of loop cut length, that's approx:
0.5 meters / 600 MHz = 0.83mm/MHz
In other words, if your cut length is 0.83mm off, you're 1 MHz off
frequency. Since the channel is 6MHz wide, you can probably be about
+/- 2.5mm off, and still have the peak within the 6MHz channel. You
could probably get it that close if you lay the hose clamp on a flat
surface, and mark the target value, but I wouldn't want to bet on its
accuracy or stability.
>> Bandwidth for a yagi is also affected by the diameter of the element
>> rods. Large diameter tubing has a wider bandwidth.
>
>VK3BLN has an interesting and extremely effective DF antenna for 70cm.
>A DF antenna doesn't necessarily want maximum gain or even F/B ratio,
>what it wants is to minimize lobing, across the band.
Homing In column that cover the requirements for rotating antenna
computerized direction finding which emphasizes the same point. If
you happen to have a perfectly clear signal source, and you spin the
antenna, the pattern you'll see on a PPI scope will be the antenna
pattern. Add a logarithmic signal strength magnitude indication, it
should look exactly like the advertisers data sheet or the NEC2 plot.
However, that's not an important requirement for a TV antenna. Having
side lobes are not a good thing due to multipath distortion, frequency
selective fading, and digital "ghosting" effects, but can be
tolerated.
>Difficult.
If it were easy, it would not be fun.
>It's a five-element Yagi that has two short-long pairs. We believe it
>works like a 3-element yagi but with the pairs coupling to broaden the
>response. It took a lot of optimising - using a custom build of 4NEC
>with a multi-dimensional slope optimiser.
antenna VHF/UHF DF (i.e. T-Hunt) systems using quad antennas. I'm
always interested in something better. I found some fox hunting
references for VK3BLN but no antenna or NEC deck. Any links?
>Clifford Heath.
Clifford Heath
Dec 5, 2012, 11:41:27āÆPM12/5/12
to
On 12/06/12 15:19, Jeff Liebermann wrote:
> In other words, if your cut length is 0.83mm off, you're 1 MHz off
> frequency. Since the channel is 6MHz wide, you can probably be about
> +/- 2.5mm off, and still have the peak within the 6MHz channel. You
> could probably get it that close if you lay the hose clamp on a flat
> surface, and mark the target value, but I wouldn't want to bet on its
> accuracy or stability.
You can get hose-clamps with inches of adjustability. I'm certain you
> In other words, if your cut length is 0.83mm off, you're 1 MHz off
> frequency. Since the channel is 6MHz wide, you can probably be about
> +/- 2.5mm off, and still have the peak within the 6MHz channel. You
> could probably get it that close if you lay the hose clamp on a flat
> surface, and mark the target value, but I wouldn't want to bet on its
> accuracy or stability.
could adjust to within 1mm and have it stay there too. The ones I'm
thinking of have a screw as a worm-drive on the ribbon.
>> A DF antenna doesn't necessarily want maximum gain or even F/B ratio,
>> what it wants is to minimize lobing, across the band.
> Add a logarithmic signal strength magnitude indication, it
> should look exactly like the advertisers data sheet or the NEC2 plot.
It does. The BLN foxhunt team has that all in-car with custom SDR
> should look exactly like the advertisers data sheet or the NEC2 plot.
with spectrum display (user-settable brick-wall filters to eliminate
adjacent-channel interference) and automated lobe analysis that sends
bearings to display on the GPS maps. Motorised antenna with motorised
polarization adjustment too. They're very hard to beat!
>> It's a five-element Yagi that has two short-long pairs. We believe it
>> works like a 3-element yagi but with the pairs coupling to broaden the
>> response. It took a lot of optimising - using a custom build of 4NEC
>> with a multi-dimensional slope optimiser.
>
> I'll give it a look. Sounds interesting. I've built a few rotating
> antenna VHF/UHF DF (i.e. T-Hunt) systems using quad antennas. I'm
> always interested in something better. I found some fox hunting
> references for VK3BLN but no antenna or NEC deck. Any links?
NEC, but contact me privately and I can at least send you the dimensions.
first...@gmail.com
Clifford.
0 new messages