Great antennas
Billy Sarokin
Found a guy in Texas who makes custom built Yagi antennas. They're
inexpensive and he cuts them each to your exact frequency specs. He
also sells Log Periodics, but for our use Yagis are the way to go.
His name is Kent Britain, web site is WA5VJB.COM
Billy Sarokin
G. John Garrett, C.A.S
That depends. Yagis have better forward gain but if you have radios in blocks
that are not close together, the yagi is definitely bandwidth limited. But yagis
do work great.
John
clm...@comcast.net
who did not know
what a Yagi antenna was until 5 minutes ago? The Yagi would be plugged
into your
radio mic receiver and be custom-made to pull in just your frequency?
Does that mean it would substitute for the receiver's original antenna?
And what if you needed to change frequencies to avoid interference?
Would you need a different Yagi? How much does it improve reception?
And a Yagi is very directional, isn't it? On a movie set or a reality
show, if the talent is moving, could you lose reception? How would the
sound quality of a Yagi signal compare to a hard-wired connection?
Thanks much for any tips,
Jim
Billy Sarokin
Ok, Yagi class commences....
A Yagi is basically like the old fashioned tv antennas that used to
sprout on roof tops. They have one driver element which is essentially
a dipole cut to the operating freq. A rear 'reflector' element that is
slightly larger, and any number of forward elements that focus the
signal on the driver. The more forward elements the more gain and the
longer the antenna is. I use 4 element yagis, and as an example, the
whole rig is about 10" long and weighs maybe 5 ounces. The size of the
elements and the spacing between them determines both the frequency and
the bandwidth. Most are designed to cover approx 20 mHz (as opposed to
a log periodic which covers 500 mHz and more).
The fall off isn't that extreme. It's not like a receiver 2 mHz out of
the range wouldn't work. While the antennas are very directional
(again, depending on how many elements are used), I find that in fairly
close range (ie within 200'), the signal from the mic will be strong
enough from all sides that it is not critical to point the antenna
directly at the actors. Rather, I use the directional capabilities to
point AWAY from an offending signal source. Sometimes I can see it
(like the Empire State Building. Sometimes I just watch my receivers
rf meter and swing the antenna until the background rf noise drops.
For long range work you'll want to point directly at the actor.
I find (and Roberto mentioned it too) that in difficult circumstances,
the yagis are the difference between getting the dialog or not.
As for the sound quality... with digital radios there is no
difference. You either have 100% or zero. With analog radios the
stronger your rf signal the less noise and static.
Billy Sarokin
Billy Sarokin
Douglas Tourtelot
twith the 400s that I seem to be able to do almost everything with a
"shark-fin" at most. I do have a UHF yagi but it almost never even gets
built. Haven't uded it in years.
D.
"G. John Garrett, C.A.S" <j...@soundcartREMOVE.com> wrote in message
news:2Iqdnd0wjuHG7j3Z...@comcast.com...
Noah Timan
Douglas Tourtelot wrote:
> Who on the list is using yagis?
me
nvt
Billy Sarokin
anytime I needed more range I'd break out the PSC yagi (that weighs
like 5 lbs). There was no question that the range and rejection was
better, but the increased size and weight made them impractical. The
new light weight ones changed that. Nothing wrong with the paddles...
except when there is ....
Best,
Billy
gformicola
transmit applications. Senn recently introduced the A5000CP which is
supposed to be a better antenna for both xmt and rcv applications.
Also we use some of the Lectro SNA-600's in a couple of areas, and a
PWS helical for IFB/IEM transmit in studio made by James Stoffo and the
folks at www.professionalwirelesssystems.com.
Happy Reception or Transmission!
Gerry Formicola
Chicago, Illinois
TechnicalCrew
successfully using wireless near Orlando's theme parks can be a real
challenge. Fortunately, Orlando is the headquarters for Professional
Wireless Systems ( correct url: www.professionalwireless.com ) and we were
among the first to enjoy the benefits of using the PWS Helical Antenna (
http://www.professionalwireless.com/helical/index.htm ). Weighing almost 4
pounds, the spiral wound antenna housed inside a 14" plexiglass tube will
transmit and receive all UHF frequencies. It has become the industry
standard for remote audio production in Orlando as we have found that it
rejects off-axis signals extremely well and eliminates dropouts and weak
zones on-axis.
You can rent or buy the helical antenna thru PWS or their parent company,
Masque Sound ( http://www.masquesound.com ).
Cheers,
Frank Rohrer
www.TechnicalCrew.com
"gformicola" <gform...@yahoo.com> wrote in message
news:1151386187....@x69g2000cwx.googlegroups.com...
Douglas Tourtelot
Went to the site and saw some PC-style antennas. Is this "of what you
speak?" How are you mounting them?
D.
"Billy Sarokin" <big...@verizon.net> wrote in message
news:1151378994.0...@p79g2000cwp.googlegroups.com...
Jeff C
I am using a couple of the Log Periods, I simply soldered a 10' length
of fifty ohm coax directly to the traces on the board and screwed a
nylon block directly to the board for mounting. Works like a champ.
best 35 dollars I have ever spent
J
Charles Tomaras
http://www.bswusa.com/proditem.asp?item=HA8089
"TechnicalCrew" <techni...@hotmail.com> wrote in message
news:Oyaog.30396$Ui7....@tornado.tampabay.rr.com...
TechnicalCrew
"Charles Tomaras" <tom...@tomaras.com> wrote in message
news:ztOdnWIjJ_xr7TzZ...@comcast.com...
Douglas Tourtelot
D.
"Charles Tomaras" <tom...@tomaras.com> wrote in message
news:ztOdnWIjJ_xr7TzZ...@comcast.com...
Douglas Tourtelot
D.
"TechnicalCrew" <techni...@hotmail.com> wrote in message
news:Rzeog.30498$Ui7....@tornado.tampabay.rr.com...
parke...@gmail.com
success! In fact I just bought six more. I had a job a few weeks ago
with 22 wireless on a field about the size of a hockey rink. I did the
whole show with 2 WA5VJB Log's and two Lectro tuneable omni's ... it's
a nice combo when you run it through a PSC Multi Max.
One thing that seems to get over looked is transmission line.....too
many times I've seen 75 ohm cable and connectors thrown into a batch of
50ohm cable. A hundred feet of RG59 at 600 MHz will attenuate your
signal by more than the foward gain a log periodic or, in some cases a
yagi, will afford you. Always check the cable and connectors to make
sure your living in a 50 ohm world!
Kevin Parker
G. John Garrett, C.A.S
> Billy and John, would you indulge a few bonehead questions from someone
> who did not know
> what a Yagi antenna was until 5 minutes ago? The Yagi would be plugged
> into your
> radio mic receiver and be custom-made to pull in just your frequency?
Yes, more or less. The yagi at 500MHz would have [guessing] about 50-75MHz
bandwidth, so anything from ~470-540MHZ would give you gain over a dipole.
>
> Does that mean it would substitute for the receiver's original antenna?
Yes.
> And what if you needed to change frequencies to avoid interference?
See above. I think a yagi center cut for the block your receiver is on would
work OK from end to end.
> Would you need a different Yagi? How much does it improve reception?
It depends on how many elements are in the Yagi. There is a driven element which
is a dipole, a reflector behind it, and one or more directors in front. More
elements=more gain. The dipole alone is better than the supplied rubber duck by
almost 2dB.
> And a Yagi is very directional, isn't it? On a movie set or a reality
> show, if the talent is moving, could you lose reception?
Probably not. At close range the admittance off the sides of the antenna is
sufficient, and at long distance, the actor probaby can't move so far so fast.
One thing directional antennas are also good for is in noisy [RF wise] locations
you can point the null of the antenna at the noise source. That keeps it from
swamping your receiver.
How would the
> sound quality of a Yagi signal compare to a hard-wired connection?
What do you mean by hard-wired? They both connect to the BNC jack on the
reciever. Sound quality is no different, as this is about getting the RF into
the receiver, where it is then demodulated into audio.
>
> Thanks much for any tips,
No problemo.
John
Sergio Sanmiguel
anyone's interested contact me off list.
~
Sergio
G. John Garrett, C.A.S
G. John Garrett, C.A.S
> Even with the best electronics and proper frequency coordination,
> successfully using wireless near Orlando's theme parks can be a real
> challenge. Fortunately, Orlando is the headquarters for Professional
> Wireless Systems ( correct url: www.professionalwireless.com ) and we were
> among the first to enjoy the benefits of using the PWS Helical Antenna (
> http://www.professionalwireless.com/helical/index.htm ). Weighing almost 4
> pounds, the spiral wound antenna housed inside a 14" plexiglass tube will
> transmit and receive all UHF frequencies. It has become the industry
> standard for remote audio production in Orlando as we have found that it
> rejects off-axis signals extremely well and eliminates dropouts and weak
> zones on-axis.
>
> You can rent or buy the helical antenna thru PWS or their parent company,
> Masque Sound ( http://www.masquesound.com ).
>
> Cheers,
> Frank Rohrer
> www.TechnicalCrew.com
One of the nice things about helicals as opposed to linear polarized antennas is
the polarization null is much less...something like 6dB max. If your TX antenna
is oriented vertically and the RX antenna is horizontal, the difference in
polarization can be 20dB. Every time a transmitted signal bounces off something,
it changes polarity. Helicals pretty much eliminate this kind of RF dropout.
That's why commercial FM stations almost universally [there are a few special
cases if anybody is really interested...] use helically polarized transmit
antennas. If the antenna on your car were helical instead of a vertical, the FM
flutter would be even less. If the TX were vertical, you'd get about half the
coverage area for mobile receivers.
Now, are these left-hand polarization, or right-hand?
[What was that can-opening sound, and where did these worms come from?]
John
Brian Milliken A.M.P.S.
G. John Garrett, C.A.S
The difference between 50 and 75 ohm cable is not worth bothering over. The
length and type of transmission line, however, are. Keep the lengths as short as
practical [ie don't use 100' of anything for a 10' run] and as large as
manageable. RG 58 and 59 are marginally useful for UHF radios. At 700MHz RG58
gives 16.9dB/100' of loss [thats 1.69dB per ten feet], RG-8X is 11.0dB and
RG-213 is 6.6dB/100'. These are all 50 ohm transmission lines, btw.
John
Douglas Tourtelot
D.
"G. John Garrett, C.A.S" <j...@soundcartREMOVE.com> wrote in message
news:69ednVJ5g7F6NTzZ...@comcast.com...
G. John Garrett, C.A.S
It is. And the losses are about the same as 58.
John
parke...@gmail.com
Douglas Tourtelot wrote:
> I thought RG-59 was 75ohm.
. RG 58 and 59 are marginally useful for UHF radios. At
> > 700MHz RG58 gives 16.9dB/100' of loss [thats 1.69dB per ten feet], RG-8X
> > is 11.0dB and RG-213 is 6.6dB/100'. These are all 50 ohm transmission
> > lines, btw.
> >
> > John
Yep RG-59 is 75 ohm.
You have to be careful with cable ....not all RG 59 is the same. The
RG designation (Stands for "Radio Guide") dictates the outer diameter,
dielectric thickness and AWG of the inner conducter and impedance.
RG-58...one size...RG-8 ...another...etc Basically, it lets you know
which connector to buy! (ex...BNC for RG-58). The dB loss per hundred
feet is determined by the manufacturer. For example, Belden 9100 at
100 feet has 6.96 dB of loss at 750MHz and Belden 9231 has 7.4dB at the
same freq. They are both RG 59/U Not a big difference. RG 8x (Also
called Mini 8) gets worse...Belden makes two RG8x's with almost 4dB of
difference at 900MHz (per 100 feet) That kind of loss can add up. It's
one thing when you are on set and the actors are moving in a field of
action that's a 40 or 50 foot square...its another when its a sports
arena and "RF Land" is parked at one corner and you've got antennas
trying to cover the whole venue (Talent, Ref's.... etc) Hundreds of
feet of cable add up quick! It boils down to knowing your location,
job and client expectaions. Honestly, on a dramatic shoot, sometimes
it's a hell of a lot easier, quicker and effective to remote the
recievers on set than to lay out RG-8, antennas and stands.
Just my 2 cents...and hey.... as long as I'm workin'....I'm Happy!
Kevin
gformicola
That's what happens when I stay up to late!
As far as the helical in our application we found it a bit better than
what we were using for receive, but where it really shines for us is
transmit, so that's where it's living right now.
Also, to the 50 or 75 ohm discussion, I agree in short run applications
there is not a ton of difference. Although in coverage of a large
area, or in our case when you are wiring a whole plant with RF the
lower loss the better. Many of our runs are over 200 feet, so anything
that is going to bring down the signal level is critical to us. For
long runs we try to minimizie connections, not use adaptors and make
our cable runs as short and straight as possible.
At the moment we are using Times Microwave cable for our antenna runs,
for the long runs we use their LMR-600 which is about 3/4" thick, for
shorter runs the LMR-400 or 200 would be a good option. The 600 is
definetly a permananet install type of cable, where the 400 or 200
could be used in the field on a day to day basis.
Hope this helps,
Be Well,
Gerry Formicola
Chicago, Illinois
parke...@gmail.com
I've been considering buying this cable:
http://www.shakespeare-marine.com/antennas/mounts/cable-4080-50.htm
it specs out better than 8x, but not as good as 213. I have to travel
and ship my antenna cable so I try to find the most bang per pound!
Belden 7808r comes in at 40lbs per 1000' and 9 db of loss @ 100 feet.
You seem to have a lot of experience in this field .....any
recomendations???
Thanks!
Kevin Parker
PS Also, do you know of any broadband line driver/amps (about 10db @
450 to 900MHz)...similar to the Sennheiser AB-1?
wolf
longest refector) otherwise you screw up the low freq response. do not look at
our pictures for an example they are wrong too.
http://www.wolfvid.com/datasheets/Antenna_UHF_flat_panel.pdf
wolf