Long Wire direction question
ma...@pplant.usask.ca
At home I use a long wire about 150feet from my house to a tree, it runs
east/west in a straight line.
At work I can run one using trees again, but I can only go about 30 feet
in one direction before I have to turn 90 degrees.
My question is - am I better to stop at 30 feet in one straight line, or
will additional length turned at 90 degrees add to reception?
Terry Maton - University of Saskatchewan, Saskatoon, Canada
INTERNET: terry...@usask.ca
FREENET: ap...@cleveland.freenet.edu | TRI_STATE ONLINE:
usr6...@tso.uc.edu
Jerry Bransford
The longer and higher the antenna, the better it works for receiving. A 90
degree change in direction is fine (the antenna will look like an 'L' on
it's side). You will receive at a 90 degree angle from the direction of
the antenna's two legs, so if your antenna runs N-S, turns 90 degrees in
the middle to run E-W, you're covered in all directions for good SWL.
You may try a 'L' shaped orientation for your home antenna, too. The way
it's running now (East-West), you will not receive stations from Europe or
the far East very well. The way it's presently situated, you'll do well
receiving North and South America (and the long path to Europe), but
stations from the East or West will be much weaker. Long wire antennas
don't receive well off their ends.
Good Luck, 73
Jerry, KC6TAY
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry Bransford
Silicon Graphics
(619) 546-0409
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Chris Brewster
You may try a 'L' shaped orientation for your home antenna, too. The
way it's running now (East-West), you will not receive stations from
Europe or the far East very well. The way it's presently situated,
you'll do well receiving North and South America (and the long path
to Europe), but stations from the East or West will be much weaker.
Long wire antennas don't receive well off their ends.
I've taken a good look at great-circle directions on my globe, and I
don't think it's quite this simple, because Europe is relatively far
north (considering its moderate climate). This is why ships and planes
going to England from New York travel NE, keeping fairly close to, for
example, Newfoundland. (I think people confuse the true directions due
to planar thinking, which has been encouraged by the use of world maps.)
Anyway, from my position in the middle of North America, I decided that
the best orientation for receiving Europe, Russia, and the Middle East
would be WNW-ESE. That is, the angle is generally NW-SE, but closer to
E-W than to N-S.
Chris Brewster E-MAIL ADDRESS: c...@cray.com
Kevin W. Plaxco
>Jerry Bransford writes:
> Long wire antennas don't receive well off their ends.
I'm sure some kind soul will correct me if I'm mistaken, but
I respectfully submit that this is wrong. Antennas are directional
*off the ends* for wavelengths that are shorter than the antenna.
Random wire antennas (defined, I believe as shorter than 1/2 wave
length) recieve poorly off of thier ends.
I use a 40 m antenna pointed directly at Europe (and the south
pacific) and 90 degrees to all of the radio noise that LA
(south of me) generates. I have reasonably good results with this
setup.
-Kevin
Jerry Bransford
First, a random length long-wire antenna is just that....random in length,
not necessarily 1/2 wave length. A 75' long-wire antenna is the
'stereotypical' random length antenna and is not much less than 1/2
wavelength for most frequencies listened to by shortwave listeners.
It's also not necessary in a RECEIVING ONLY situation to have an antenna
cut specifically for a certain band. Within reason, any 50-100' antenna is
going to produce EXCELLENT results in the HF band. If you are
TRANSMITTING, then yes, you want the antenna cut for 1/2 (1/4, 5/8, etc.)
wavelength. But to receive in the 40M band, etc., you don't need it to be
cut specifically for that frequency.
The age-old adage is, the longer and higher up the antenna, the better it
will work (for receiving). Not my thoughts, just an old basic fact.
Let me clarify my earlier comment: Long wire antennas don't receive WELL
off their ends.
ANY antenna is going to be less sensitive off it's ends. After all, how do
radio direction finder antennas work? By rotating the antenna until you
get a 'null' on the desired signal's strength. Therefore, it MUST be
receiving 'less well' off it's ends.
area 1
area 2 ------------(antenna)-------------- area 3
area 4
The above antenna will receive stations from areas 1 and 4 very well, and
not as well from stations in areas 2 and 3.
Why are 'beam' antennas so directional? Because, in addition to director
and reflector elements providing additional gain in a 'forward' direction,
they don't receive well off the ends of the antenna's elements.
Finally, think about vertically polarized antennas. If they didn't receive
and transmit much better off their sides than their end points, vertical
antennas wouldn't exist. Or at least, all vertical antennas would have to
be repositioned to a horizontall position if this weren't true.
Regards,
Jerry
Dave Pierson
>off their ends.
>ANY antenna is going to be less sensitive off it's ends.
As the antennan becomes electrically longer, the directivity becomes
endfire. For most practical antenna lengths, for MW work, for practical
budgets they can't get that long. However, for fixed path, cost is no
object, circuits. long (multiples of wavelengths) antennas provide
directionality off the end, and work well.
For references, the ARRL handbook, the ARRL Antenna Handbook and Jasik,,
et al, Antenna Engineering.
>After all, how do radio direction finder antennas work?
In a variety of ways.
> By rotating the antenna until you get a 'null' on the desired signal's
>strength. Therefore, it MUST be receiving 'less well' off it's ends.
Thats one of them. For electrical lengths around a half wave, this
is accurate, say from .1 wavelength to 3/4:
> area 1
>
> area 2 ------------(antenna)-------------- area 3
>
> area 4
>
>The above antenna will receive stations from areas 1 and 4 very well, and
>not as well from stations in areas 2 and 3.
As the antenna becomes electrically long (as the applied frequency
goes up), the pattern becomes endfire. In between, a variety of lobes
develop.
thanks
dave pierson |the facts, as accurately as i can manage,
Digital Equipment Corporation |the opinions, my own.
40 Old Bolton Rd |I am the NRA
Stow, Mass 01775 USA |pie...@msd26.enet.dec.com
"He has read everything, and, to his credit, written nothing." A J Raffles
e...@ham.almanac.bc.ca
> In article <1qnae2...@gap.caltech.edu>, k...@wag.caltech.edu (Kevin W.
> Plaxco) writes:
> |> In article <CB.93Apr...@tamarack13.timbuk> c...@tamarack13.timbuk
> |> (Chris Brewster) writes:
> |> >Jerry Bransford writes:
> |>
> |> > Long wire antennas don't receive well off their ends.
> |>
> |> I'm sure some kind soul will correct me if I'm mistaken, but
> |> I respectfully submit that this is wrong. Antennas are directional
> |> *off the ends* for wavelengths that are shorter than the antenna.
> |>
> |> Random wire antennas (defined, I believe as shorter than 1/2 wave
> |> length) recieve poorly off of thier ends.
> |>
> |> I use a 40 m antenna pointed directly at Europe (and the south
> |> pacific) and 90 degrees to all of the radio noise that LA
> |> (south of me) generates. I have reasonably good results with this
> |> setup.
> |>
> |> -Kevin
>
> First, a random length long-wire antenna is just that....random in length,
> not necessarily 1/2 wave length. A 75' long-wire antenna is the
> 'stereotypical' random length antenna and is not much less than 1/2
> wavelength for most frequencies listened to by shortwave listeners.
>
You're confusing the terms. A "long wire" antenna is at least several
wavelengths long. A 75' wire antenna is only a "long wire" for
frequencies higher than about 25MHz. It's a half wave at 6.24 MHz.
A "long wire" antenna is indeed directive off the ends, while your
"typical 75'" wire antenna is NOT. Please remember that while it may seem
like a "long piece of wire" to you, it's not a "long wire" antenna unless
it's at least several wavelengths long. A 10 MHz "long wire" antenna thus
needs to be about 187 feet long or longer.
>
> Let me clarify my earlier comment: Long wire antennas don't receive WELL
> off their ends.
>
> ANY antenna is going to be less sensitive off it's ends. After all, how do
> radio direction finder antennas work? By rotating the antenna until you
> get a 'null' on the desired signal's strength. Therefore, it MUST be
> receiving 'less well' off it's ends.
>
> area 1
>
> area 2 ------------(antenna)-------------- area 3
>
> area 4
>
> The above antenna will receive stations from areas 1 and 4 very well, and
> not as well from stations in areas 2 and 3.
>
> Why are 'beam' antennas so directional? Because, in addition to director
> and reflector elements providing additional gain in a 'forward' direction,
> they don't receive well off the ends of the antenna's elements.
>
> Finally, think about vertically polarized antennas. If they didn't receive
> and transmit much better off their sides than their end points, vertical
> antennas wouldn't exist. Or at least, all vertical antennas would have to
> be repositioned to a horizontall position if this weren't true.
>
You're wrong. Long wires produce quite complex multi-lobe radiation
patterns. The longer the wire is in terms of wavelength, the more likely
is the radiation to be from its ends.
For example, a two wavelength antenna, has four main lobes, each at about
36 degrees from the axial direction, and four minor lobes about 5 db down
at 75 degrees from the axial direction. In contrast, a five wavelength
antenna still has four main lobes, but at 22 degrees from the axis of the
antenna. There are 16 minor lobes, the weakest of which is down about 10
db from the major lobes. In both these examples, there are deep nulls at
right angles to the wire.
A 10 wavelength antenna, for example, has a gain of 7.4 db over a dipole,
and has lobes at 16 degrees from the axis of the wire. At 14.15 MHz,
however, a 10 wavelength "long wire" would be 693 feet long. In addition,
they should be at least a 1/2 wavelength above ground for decent low
angle radiation.
I think at least part of the confusion comes from the common but
erroneous description of any end fed wire antenna as a "long wire"
antenna. In actual fact, it's only a "long wire" when it's at least two
wavelengths long, and to have really signifigant power gain, needs to be
8 wavelengths or longer.
I suggest further reading in the book "Practical Wire Antennas" by John D
Heys, G3BDQ, published by the RSGB.
>
> Regards,
> Jerry
>
>
Robert Smits There is *no* idiotproof filter.
VE7EMD Idiots are proof against anything!
Ladysmith B.C. - Richard Chycoski, VE7CVS
e-mail: e...@ham.almanac.bc.ca
Cliff Shivcharan
questions on long-wire antenna use.
1. If I have a "long wire" antenna, say 60ft. (I have a DX440 as well), and
I want to use it for regular SW listening (9 - 21 MHz, say), what is the
best way to use it? Should I connect the lead-in wire close to the centre
or towards one end (I have NO signal strength meter etc. to guide me)?
2. Can this antenna be used for MW listening? If so, do I have to position
in a particular direction?
Thanks a lot.
Cliff.
*********************************************************
Cliff B. Shivcharan
Bell Northern Research Inc.
R & D Subsidiary of Northern Telecom Ltd.
Richardson TX 75083.
Any opinions expressed are mine and do not reflect those
of my employer.
**********************************************************
Jerry Bransford
You are making a mountain out of a molehill. This was a reply to someone
who is strictly a 'listener' and was not interested in someone complicating
his answer by expounding on theories of 'radiation from the ends' and
'quite complex multi-lobe radiation'.
Also, I assume not everyone cared or noticed that my reply was to a
listener, not someone who would be transmitting.
For example one comment was, "You're wrong. Long wires produce quite
complex multi-lobe radiation patterns. The longer the wire is in terms of
wavelength, the more likely is the radiation to be from its ends.
The above problem isn't important to a listener. What listener cares about
'radiation to be from its ends.', which illustrates my point. My answer
that he was commenting on was addressed to a listener, not a transmitter.
To those who read this net and ask simple questions typical of a beginning
shortwave listner, I would hope not everyone tries to give them answers
that are so complex as to make SWL seem as though it's a science, not a
hobby.
As an EE who's been involved in radio communications and amateur radio
since 1966, I understand antenna theory as well as most, not as well as
some. But I'm not in the business of giving beginners answers that are
complex and too theoretical.
A simple 75' to 125' long-wire antenna is, for all practical purposes,
bi-directional and is an ideal antenna for beginners. For those people
interested in getting into shortwave listening, I stand by my guns that
that type antenna is hard to beat...peformance-wise, cost-wise, and
installation-wise.
You simply don't need elaborate antennas to listen to short wave. My God,
why do some people have to pick everything apart they see on this net!
For those that care to argue more, be my guest. But what's the point,
unless you just want to prove what an in depth knowledge of antennas you
may have. I'm not here to prove anything, maybe answer as few questions
once in a while in a simple, easily understood manner. Lets keep this net
friendly, and keep the answers and suggestions practical for the average
SWL, not the theoretical antenna guru.
--
Regards,
Jerry
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Bob Myers
> off their ends.
>
> ANY antenna is going to be less sensitive off it's ends. After all, how do
> radio direction finder antennas work? By rotating the antenna until you
> get a 'null' on the desired signal's strength. Therefore, it MUST be
> receiving 'less well' off it's ends.
>
> area 1
>
> area 2 ------------(antenna)-------------- area 3
>
> area 4
The above is simply incorrect. It is NOT true that all antennas are less
sensitive off their ends. The earlier poster was correct in noting that
"long-wire" antennas show directivity IN LINE WITH the antenna element.
The transition from the normal "broadside" directivity to "end" directivity
happens as the antenna (the long wire) exceeds about 4 half-wavelengths at
the frequency in question. The directivity is not especially pronounced
at this point, but it IS better "off the end." The "gain" of such an
antenna also varies with the *vertical* angle (the angle of the antenna
wire w.r.t the incoming signal in the vertical plane, assuming that the
horizontal direction of the signal is on-axis with the antenna), which should
give some clue as to what's going on here. William Orr's _Radio_Handbook_
includes a graph of long-wire gain (along the axis of the antenna) vs.
a broadside dipole; it gets up to 10 dB gain over the dipole at 15 wavelengths!
(Of course, few of us have the room for a 15-wavelength antenna at any
reasonable SW frequency!)
The example of DF antennas given above is not relevant, as these do not fall
into the class of long-wire antennas. Another interesting class, though, is
the "V beam" in which the directivity is along the axis of a "V" formed from
two long-wires; again, it is *not* broadside to either element of the antenna.
> Why are 'beam' antennas so directional? Because, in addition to director
> and reflector elements providing additional gain in a 'forward' direction,
> they don't receive well off the ends of the antenna's elements.
>
> Finally, think about vertically polarized antennas. If they didn't receive
> and transmit much better off their sides than their end points, vertical
> antennas wouldn't exist. Or at least, all vertical antennas would have to
> be repositioned to a horizontall position if this weren't true.
Again, neither of these belong to the class of long-wire antennas. Beams and
verticals are both resonant antennas, derived originally from the good ol'
half-wave dipole.
Bob Myers KC0EW Hewlett-Packard Co. |Opinions expressed here are not
Systems Technology Div. |those of my employer or any other
my...@fc.hp.com Fort Collins, Colorado |sentient life-form on this planet.
Dave Pierson
(Jerry Bransford) writes, in part:
>You are making a mountain out of a molehill. This was a reply to someone
>who is strictly a 'listener' and was not interested in someone complicating
>his answer by expounding on theories of 'radiation from the ends' and
>'quite complex multi-lobe radiation'.
Reception is the "dual" of transmission. Strictly. If it transmits
poorly off the end, it receives poorly off the end.
>Also, I assume not everyone cared or noticed that my reply was to a
>listener, not someone who would be transmitting.
Reception is the "dual" of transmission. One would assume a listener
was interested in potential weak apots in the pattern.
>The above problem isn't important to a listener. What listener cares about
>'radiation to be from its ends.', which illustrates my point.
They may well be interested in resption from the ends. Or lack of
reception. Reception is the dual of transmission.
>To those who read this net and ask simple questions typical of a beginning
>shortwave listner, I would hope not everyone tries to give them answers
>that are so complex as to make SWL seem as though it's a science, not a
>hobby.
Agreed. But it is possible to over simplify, also. IMO, providing the
info and assuming the reader has the ability to sort it out is
preferable.
>A simple 75' to 125' long-wire antenna is, for all practical purposes,
>bi-directional and is an ideal antenna for beginners. For those people
>interested in getting into shortwave listening, I stand by my guns that
>that type antenna is hard to beat...peformance-wise, cost-wise, and
>installation-wise.
>You simply don't need elaborate antennas to listen to short wave. My God,
>why do some people have to pick everything apart they see on this net!
Only, in my case, if its "wrong in fact". Unfortuantely, the term
"long wire" and its application antennas, is commonly abused.
>For those that care to argue more, be my guest. But what's the point,
>unless you just want to prove what an in depth knowledge of antennas you
>may have.
And, perhaps, pass on some referneces, and some knowledge to those
intereted.
Dave Pierson
(Cliff Shivcharan) write
>After all this discussion, I am a little lost. Guys, here are a couple simple
>questions on long-wire antenna use.
>1. If I have a "long wire" antenna, say 60ft.
A 60 ft antenna is not a long wire, in antenna terms, on any SW band.
It is a random wire. I believe the pattern will be essentially
omnidirectional anywhere in the MW bands, without digging out refernces.
>(I have a DX440 as well), and I want to use it for regular SW listening
>(9 - 21 MHz, say), what is the best way to use it?
IMO, use whatever is easiest to implement. Reception is less critical
than transmission in many regards. With some effort, particular
directionality might be achieved, but that means _loss_ of signal
from other directions.
>Should I connect the lead-in wire close to the centre or towards one end
I believe moderately offset from center helps. But do what is
simplest.
>2. Can this antenna be used for MW listening?
Yes.
> If so, do I have to position in a particular dirtection?
I wouldn't bother. ASSuming that MW==500-1600KHz, there will not
be much directionality. In any case, in any directional antenna, "gain"
in one direction is paid for by "loss" in another. (moderately over
simplified...)
andy gardner
## Let me clarify my earlier comment: Long wire antennas don't receive WELL
## off their ends.
##
## ANY antenna is going to be less sensitive off it's ends. After all, how do
## radio direction finder antennas work? By rotating the antenna until you
## get a 'null' on the desired signal's strength. Therefore, it MUST be
## receiving 'less well' off it's ends.
#
#
#The above is simply incorrect. It is NOT true that all antennas are less
#sensitive off their ends. The earlier poster was correct in noting that
#"long-wire" antennas show directivity IN LINE WITH the antenna element.
#The transition from the normal "broadside" directivity to "end" directivity
#happens as the antenna (the long wire) exceeds about 4 half-wavelengths at
#the frequency in question. The directivity is not especially pronounced
#at this point, but it IS better "off the end." The "gain" of such an
#antenna also varies with the *vertical* angle (the angle of the antenna
#wire w.r.t the incoming signal in the vertical plane, assuming that the
#horizontal direction of the signal is on-axis with the antenna), which should
#give some clue as to what's going on here. William Orr's _Radio_Handbook_
#includes a graph of long-wire gain (along the axis of the antenna) vs.
#a broadside dipole; it gets up to 10 dB gain over the dipole at 15 wavelengths!
#(Of course, few of us have the room for a 15-wavelength antenna at any
#reasonable SW frequency!)
#
#Bob Myers KC0EW Hewlett-Packard Co. |Opinions expressed here are not
# Systems Technology Div. |those of my employer or any other
#my...@fc.hp.com Fort Collins, Colorado |sentient life-form on this planet.
Yep, the directionality of a longwire (ie a antenna of a length >1
wavelength) depends entirely on how many wavelengths long it is.
There are a number of points that should be noted. I talk from a
Mediumwave DXers point of view here.
1. A beverage antenna of a length of 600 metres (whatever that is
in feet) is 2 wavelengths long at 1MHz (the middle of the MW band).
This antenna, however, is 3.2 wavelengths long at 1.6MHz and only
1.06 wavelengths long at 530kHz. So directionality will differ
depending what frequency you are listening to. This can explain
the phenomenon when a certain station from a distant location
comes in well when another station from the same location but
on a different frequency can hardly be heard. The antenna lobes
are different!
2. A beverage antenna can have very strong lobes near the two
ends of the antenna and receive very poorly off the sides. A
beverage antenna can be made to be directional in only one
direction by correctly terminating the end furthest away from
the receiver. A beverage antenna has a measureable impedance
(which will vary over frequency). If a resistor of a resistance
equal to the impedance is placed at the opposite end of the
antenna and connected to ground, all signals travelling along the
wire in the wrong direction will be obsorbed by the resistor. Signals
travelling along wire wire from the correct direction will be absorbed
by the receivers impedance (which should be matched to the antenna!)
and thus produce a listenable signal.
3. You need a lot of real estate to put up a decent beverage and you
need to picj the direction correctly. I once erected a 1,200 metre long
beverage here in New Zealand pointing towards Peru. It was terminated
correctly. During good conditions this aerial was a beauty! I heard
a large number of South American stations, many who would swamp out
stations here in New Zealand on the same frequency. A number of
European stations were also heard (including Radio Albania 1215kHz
longpath!).
And now the bad news. When conditions to Latin America were bad (ie
the Summer & Winter months), this aerial was useless. Stations from
the US, Caribbean and Canada were inaudible. The antenna (which
required wading through frog infested swaps to erect) was only
useable for around 4 months of the year!
Good luck!
Andy Gardner
Andy Gardner,
Wellington, New Zealand
Te Whanga-nui-a-Tara, Aotearoa
Jim Kearman
>After all this discussion, I am a little lost. Guys, here are a couple simple
>questions on long-wire antenna use.
>
>I want to use it for regular SW listening (9 - 21 MHz, say), what is the
>or towards one end (I have NO signal strength meter etc. to guide me)?
>
>2. Can this antenna be used for MW listening? If so, do I have to position
>in a particular direction?
>
>Thanks a lot.
>
>Cliff.
>
>*********************************************************
>
>Cliff B. Shivcharan
>Bell Northern Research Inc.
>R & D Subsidiary of Northern Telecom Ltd.
>Richardson TX 75083.
>
>Any opinions expressed are mine and do not reflect those
>of my employer.
>**********************************************************
>
>
1. After 35 years of playing with radios, I can only say there is
no one correct answer to this question. So much of an antenna's
performance depends on its environment. Nearby objects will
definitely affect how it works in different directions and wave
angles. When you're dealing with antennas in space, with no objects
nearby (pretty hard to do unless you build the radio into the
antenna itself!), you can work up reproducible theories. Otherwise,
it's just cut and try.
Antenna experimenting is one of the most rewarding sidelines of
shortwave listening. It helps to have one baseline antenna that
you can use for comparison, but by all means, experiment with
what you have. Wire is not that expensive and is reusable. Keep
a notebook (with your log) and soon you'll be answering questions
like this based on your experiences.
2. My experience with MW antennas in the real world is that loops
work better than random wires, mainly because loops tend to pick
up less electrical noise and are steerable to null out undesired
stations. You might have better signal strength on your wire, but
you might also pick up more noise and be unable to hear what you
want because other stations are splattering over the desired
signal. On the other hand, I don't live where you do. Put up the
antenna and give it a shot. Then, be sure to let us know how you
made out. We want to know. There's no one on this group who's so
knowledgeable he or she can't benefit from the experience of others.
Radio is more art than science. The best advice about antennas is:
1. Generally, the higher and more in the clear the better.
2. Install an antenna where it or you cannot possibly come in
contact with other wiring, whether power, phone or what have you.
3. Use large doses of common sense when climbing, and securing wires.
If it can fall and hurt someone, it will.
4. Disconnect the antenna from your station when you aren't using it.
Good listening.
Jim
Chris Brewster
... My experience with MW antennas in the real world is that loops
work better than random wires, mainly because loops tend to pick
up less electrical noise and are steerable to null out undesired
stations. ...
The latest WRTH (is it called '92 or'93?) has an interesting article
about an antenna setup that, as I remember, uses two loops in what
amounts to a miniature diversity setup. I posted about this last month
but got no responses. I'm wondering if anyone has tried it, because I
have a few questions about details in their plans. It looked like a
really good setup.
e...@ham.almanac.bc.ca
> After all this discussion, I am a little lost. Guys, here are a couple simple
> questions on long-wire antenna use.
>
> 1. If I have a "long wire" antenna, say 60ft. (I have a DX440 as well), and
> I want to use it for regular SW listening (9 - 21 MHz, say), what is the
> best way to use it? Should I connect the lead-in wire close to the centre
> or towards one end (I have NO signal strength meter etc. to guide me)?
>
First, let's get the terminology straight. I know it may sound confusing,
but you have a wire antenna, NOT a "long wire" antenna. To be a long wire
antenna, it needs to be several wavelengths long at the frequency of
interest, and is often 8 or 10 times the wavelength.
However, that doesn't matter. Get your antenna as high up and in the
clear as you can. It doesn't matter if you have to turn a corner with it,
either. Attach the leadin to the antenna the most convenient spot.
Getting your antenna high and in the clear (away from metal objects,
especially) is far more important than where you attach the leadin wire.
> 2. Can this antenna be used for MW listening? If so, do I have to position
> in a particular direction?
>
You sure can. The short length of your antenna compared to medium waves,
however, means it won't have much directionality, although the signal
will probably be strongest off the sides of the antenna.
Be careful, too, that your antenna is placed so that if a supporting rope
or wire breaks, it won't fall onto power lines, etc, and that it is high
enough that people don't walk into it. Antennas can be quite invisible,
especially under poor lighting conditions.
Have fun.
Bob.
> Thanks a lot.
>
> Cliff.
e...@ham.almanac.bc.ca
>
> You are making a mountain out of a molehill. This was a reply to someone
> who is strictly a 'listener' and was not interested in someone complicating
> his answer by expounding on theories of 'radiation from the ends' and
> 'quite complex multi-lobe radiation'.
>
> Also, I assume not everyone cared or noticed that my reply was to a
> listener, not someone who would be transmitting.
>
> For example one comment was, "You're wrong. Long wires produce quite
> complex multi-lobe radiation patterns. The longer the wire is in terms of
> wavelength, the more likely is the radiation to be from its ends.
>
> The above problem isn't important to a listener. What listener cares about
> 'radiation to be from its ends.', which illustrates my point. My answer
> that he was commenting on was addressed to a listener, not a transmitter.
>
I'm sorry that you've misunderstood my reason for posting, Jerry. I
agree, by and large with your comments about keeping replies simple and
not adding extra detail, but you have repeatedly failed to distinguish
between a "long wire" antenna and a random wire 75 feet long.
There's a tremendous difference between a "long wire antenna" and a wire
antenna. As an EE, you should appreciate the difference.
> To those who read this net and ask simple questions typical of a beginning
> shortwave listner, I would hope not everyone tries to give them answers
> that are so complex as to make SWL seem as though it's a science, not a
> hobby.
>
> As an EE who's been involved in radio communications and amateur radio
> since 1966, I understand antenna theory as well as most, not as well as
> some. But I'm not in the business of giving beginners answers that are
> complex and too theoretical.
>
Fine. I agree completely with that approach. But only when your facts are
correct to begin with.
> A simple 75' to 125' long-wire antenna is, for all practical purposes,
> bi-directional and is an ideal antenna for beginners. For those people
> interested in getting into shortwave listening, I stand by my guns that
> that type antenna is hard to beat...peformance-wise, cost-wise, and
> installation-wise.
>
On this, we completely agree. As you may have seen elsewhere, I DO
recommend this very setup to others interested in short-wave listening.
> You simply don't need elaborate antennas to listen to short wave. My God,
> why do some people have to pick everything apart they see on this net!
>
> For those that care to argue more, be my guest. But what's the point,
> unless you just want to prove what an in depth knowledge of antennas you
> may have. I'm not here to prove anything, maybe answer as few questions
> once in a while in a simple, easily understood manner. Lets keep this net
> friendly, and keep the answers and suggestions practical for the average
> SWL, not the theoretical antenna guru.
> --
> Regards,
> Jerry
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I do hope we can keep it friendly, Jerry. And practical. And accurate.
The only place I quarrel with you at all is your description of a 75 foot
antenna as a long wire. It simply is not.
73, Bob.
Ralph Brandi
>once in a while in a simple, easily understood manner. Lets keep this net
>friendly, and keep the answers and suggestions practical for the average
>SWL, not the theoretical antenna guru.
I don't know, I kind of like reading postings from theoretical
antenna gurus and other assorted experts in their fields. I think
there's room for both kinds of postings here. It does help to keep
the knowledge base of a poster in mind when you reply so that you
don't "scare people off," but I would hate to see the newsfroup
descend into a kind of lowest common denominator drivel.
--
Ralph Brandi ra...@mtunp.att.com att!mtunp!ralph "You're bound to be
stuck in no time at all in the midst of the Great Bazaar, surrounded by rich
and exotic foods in reckless abundance, screaming 'Where the hell are the Cheez
Doodles? I'll starve if I cannot find any Cheez Doodles!'" -gtaylor
Ralph Brandi
>the US, Caribbean and Canada were inaudible. The antenna (which
>required wading through frog infested swaps to erect) was only
>useable for around 4 months of the year!
I have a question here. I seem to recall reading that the Beverage
works better over less-conductive soil. How does this relate to
that land's status as a swamp?
The reason I ask is that I've got about 350 feet pointing east-west
in which I'm thinking of stringing a so-called "mini-Beverage". The
land is pretty damp, so to speak. Would this be considered a plus,
a minus, or a wash?
Will Martin
I realize these are intended to be medium-wave or low-frequency-HF
(tropical bands) types of antennas. If you have one, and hook it
up to a regular HF receiver and tune the higher HF frequencies,
how well does it work? Is it worse than, or better than, or no
different from, a much shorter and higher-mounted random-wire?
Is there a difference here between a properly-terminated Beverage
and an unterminated one? Is there any directionality at the higher
frequencies, or does it act like a random wire with the max
sensitivity to the sides, or what?
Since this would be many wavelengths long at these higher frequencies,
one might guess that it would gather in a much stronger signal from
the amount of RF it intercepts. But then it is mounted much lower
than an HF antenna should be, so maybe these two factors cancel
each other out?
Basically, I'm wondering if an all-band listener lucky enough to
have one or more Beverages needs anything else, too...
Will
Julian Smith
Dear Readers:
It is probably impossible to determine theoretically what a given
long-wire antenna will do...whether it will receive better off the
ends, or the sides, or whatever. I've been a Ham Radio Operator
(VE5JFS) for about 15 years now, and have used lots of antennas, of
all types, and I hate to say it, but in my opinion the three most
important things about an antenna are just like those of real estate:
(1) location, (2) location and (3) location!
In other words, what really counts is where your antenna is located;
its orientation is only of secondary importance. I used a longwire
antenna on salty flats just off the Carribean coast (near Bonaire,
Netherlands Antilles; on the Colombian coast; in Venezuela; etc). I
found that propagation there was absolutely incredible! The same
antennas in an electrically noisy area like Toronto, far inland, gave
me indifferent results. The best advice I could give you is:
experiment! What works in one environment may not work in another,
and, antenna design is far from being an exact science (despite all
those pretty technical blueprints in the ARRL Antenna Manuals).
Yours Sincerely
Julian Smith
Ryerson Polytechnical University/
Jim Kearman
long distances (over 2500 miles) have different incident angles
depending on frequency. From _The ARRL Antenna Book_:
Measured Vertical Angles of Arrival of Signals from England
at Receiving Location in New Jersey
Freq MHz Angle below which signals arrived 99% of the time
7 35 deg
10 26
14 17
18 12
21 11
28 9
The Beverage antenna takes advantage of the wave tilt to
induce currents in the wire and the ground beneath it. The optimum
height of a Beverage is determined by the frequency band it's
used for (see "The Antenna Book" for details). Because the
frequencies are higher and the wave angles are lower (less tilt),
the Beverage doesn't perform as well at higher frequencies.
The height of an antenna above ground or other reflective
surface determines where it's main lobe (the range of angles over
which it has the best response) appears. A higher antenna generally
has a lower main lobe, which is useful at higher frequencies, as
you can see from the table.
Low antennas are less prone to picking up noise. If you lived in
a noisy area, the low wire might give much lower signal strength,
but the ratio of signal to noise might be improved enough to
allow reception not possible on a textbook antenna.
Some advice for those planning Beverages. Other antennas and
metallic objects nearby will reradiate signals and noise into
your Beverage. Keep them as far away as possible. For example,
terminating one end of the antenna at your house or onto a
metal tower is not as good as terminating farther away and
running coaxial cable into the house.
Peter Somlo
short antenna. It will radiate like a point source, launching a
quasi-spherical wave. To be a dual receiver antenna, `to play the film
backwards', the received wave would have to be a shrinking spherical wave.
In practice, the received field is more like a plane wave (far from the
source), so antennas can be quite different in transmitting and receiving.
--
Dr Peter I. Somlo FIEEE | CSIRO Div. Appl.Phys. | "Every coin has three
Head RF/Microwave Proj. | Natl. Meast. Lab. | sides - at least"
FAX: 61-2-413-7383 | POB 218 Lindfield 2070| (Somlo, cca. 1985)
TEL: 61-2-413-7505 | NSW AUSTRALIA |
Dan Schein
>
>However, that doesn't matter. Get your antenna as high up and in the
>clear as you can. It doesn't matter if you have to turn a corner with it,
>either. Attach the leadin to the antenna the most convenient spot.
>Getting your antenna high and in the clear (away from metal objects,
>especially) is far more important than where you attach the leadin wire.
>
They are based on a dipole (wire) using a dipole insulator and coax
cable for the feedline.
1) If the feed is attached in the middle of an antenna will the
performance be the same as if it was connected to the end?
2) Does it hurt/help to ground the shield side of a feedline?
A) Is the shield side actually conected to the antenna?
3) When using something like a "Budwig" center/dipole insulator. Are the
two parts of the dipole feed 1 via center and the other via sheild?
Or are both feed via the center conductor?
Sorry if these are novice questions, but I just recently decided to start
building (and stop buying) antennas.
-Dan
--
Host of Motor Racing Review -=- seen on 4 cable systems in Pennsylvania
--
Reading Rehabilitation Hospital _/\_ Parenting, Firefighting,
Dan Schein - Information Systems \ / Programming, Rappelling,
RD 1 Box 250 /_ _\ and Network Scapegoat.
Reading, PA 19607 \/
dans%reh...@canal.org -OR- uunet!mimsy!widener!gvls1!lock60!rehab1!dans
Jerry Bransford
|> In article <VuyD3B...@ham.almanac.bc.ca> e...@ham.almanac.bc.ca
|> writes:
|> >
|> >However, that doesn't matter. Get your antenna as high up and in the
|> >clear as you can. It doesn't matter if you have to turn a corner with
|> it,
|> >either. Attach the leadin to the antenna the most convenient spot.
|> >Getting your antenna high and in the clear (away from metal objects,
|> >especially) is far more important than where you attach the leadin
|> wire.
|> >
|> Heres an area (attaching the feed) where I have had a few questions.
|> They are based on a dipole (wire) using a dipole insulator and coax
|> cable for the feedline.
|>
|> 1) If the feed is attached in the middle of an antenna will the
|> performance be the same as if it was connected to the end?
Not really, but it's better to connect at the end.
|>
|> 2) Does it hurt/help to ground the shield side of a feedline?
|> A) Is the shield side actually conected to the antenna?
In this type antenna, the shield isn't connected to the antenna. It won't
hurt to ground the shield at the 'radio end'.
|>
|> 3) When using something like a "Budwig" center/dipole insulator. Are
|> the
|> two parts of the dipole feed 1 via center and the other via
|> sheild?
|> Or are both feed via the center conductor?
|>
When connected to a dipole, the center conductor goes to one 'leg', and the
shield goes to the dipole's other 'leg. However, a dipole is really
overkill for receiving. Dipoles are more commonly needed for transmitters
and are usually cut to an exact length to allow the transmitter to operate
efficiently at the desired frequency.
|> Sorry if these are novice questions, but I just recently decided to
|> start
|> building (and stop buying) antennas.
|>
|> -Dan
|>
|> --
|> Host of Motor Racing Review -=- seen on 4 cable systems in
|> Pennsylvania
|> --
|> Reading Rehabilitation Hospital _/\_ Parenting,
|> Firefighting,
|> Dan Schein - Information Systems \ / Programming,
|> Rappelling,
|> RD 1 Box 250 /_ _\ and Network
|> Scapegoat.
|> Reading, PA 19607 \/
|>
|> dans%reh...@canal.org -OR-
|> uunet!mimsy!widener!gvls1!lock60!rehab1!dans
--
e...@ham.almanac.bc.ca
> In article <VuyD3B...@ham.almanac.bc.ca> e...@ham.almanac.bc.ca writes:
> >
> >However, that doesn't matter. Get your antenna as high up and in the
> >clear as you can. It doesn't matter if you have to turn a corner with it,
> >either. Attach the leadin to the antenna the most convenient spot.
> >Getting your antenna high and in the clear (away from metal objects,
> >especially) is far more important than where you attach the leadin wire.
> >
> Heres an area (attaching the feed) where I have had a few questions.
> They are based on a dipole (wire) using a dipole insulator and coax
> cable for the feedline.
>
> 1) If the feed is attached in the middle of an antenna will the
> performance be the same as if it was connected to the end?
>
If it's a dipole, it's supposed to be fed at the centre. A dipole
antenna has two "legs", each a quarter wave length long at the frequency
of interest. Assuming you are using it for reception, the overall length
should be approximately (in feet) 468 / frequency (in MHz).
For example, a dipole for 9.5 MHZ would be about 50 feet long, with two
25 ft. sections.
> 2) Does it hurt/help to ground the shield side of a feedline?
> A) Is the shield side actually conected to the antenna?
>
If you are using a dipole and coaxial cable (cable with an outer shield
and an inner conductor, like RG-58) it is unnecessary to ground the
shield side of the feedline, although I suggest you use a lightning
protective device near the point where the cable enters the house. This
kind of suppressor connects in line with the antenna cable - that is, you
screw the antenna connector to it, then another cable from the suppressor
to your radio, and a heavy ground strap from the suppressor to ground.
This won't protect you from a direct hit on your antenna, but will likely
save your radio from a near miss.
When feeding a dipole with coaxial cable, yes, the shielded side DOES go
to one half of the antenna. The antenna has one quarter wave section
separated from the other quarterwave section by the insulator in the
middle. The shield (braid) goes to one side, the centre conductor goes to
the other side. The copper in the centre conductor should NOT touch the
braid or shield of the cable, nor should there be any electrical
connection from one half of the antenna to the other.
> 3) When using something like a "Budwig" center/dipole insulator. Are the
> two parts of the dipole feed 1 via center and the other via sheild?
> Or are both feed via the center conductor?
>
See above.
> Sorry if these are novice questions, but I just recently decided to start
> building (and stop buying) antennas.
>
> -Dan
Don't sweat it. Everybody's got to start sometime. Building your own
antennas is fun, inexpensive, and a great way to learn about radio.
And I strongly recommend you consider purchasing the ARRL Antenna Book,
usually available at ham radio stores everywhere. It is probably one of
the best all around books on antennas you can find.
Other books you might consider include Practical Wire Antennas, by John
Heys, an excellent book on wire antennas from the Radio Society of Great
Britain, and W1FB's Antenna Notebook, both of which are available from
the ARRL.
Have fun.
Nikolaus Pollak
: da...@rehab1.UUCP (Dan Schein) writes:
:
: > In article <VuyD3B...@ham.almanac.bc.ca> e...@ham.almanac.bc.ca writes:
: > >
: > >However, that doesn't matter. Get your antenna as high up and in the
: > >clear as you can. It doesn't matter if you have to turn a corner with it,
: > >either. Attach the leadin to the antenna the most convenient spot.
: > >Getting your antenna high and in the clear (away from metal objects,
: > >especially) is far more important than where you attach the leadin wire.
: > >
: > Heres an area (attaching the feed) where I have had a few questions.
: > They are based on a dipole (wire) using a dipole insulator and coax
: > cable for the feedline.
: >
: > 1) If the feed is attached in the middle of an antenna will the
: > performance be the same as if it was connected to the end?
: >
: If it's a dipole, it's supposed to be fed at the centre. A dipole
: antenna has two "legs", each a quarter wave length long at the frequency
Do dipoles generally perform better than simple long wires ?
+---------------------------------------+-------------------------------+
| Nikolaus Pollak | SIEMENS Austria Corp. |
| Email: po...@siemens.co.at | PSE 2354 |
| Phone: +43-1-60171-5719 | Gudrunstr. 11. |
| Fax: +43-1-60171-5712 | A-1100 Wien |
+---------------------------------------+-------------------------------+
Jerry Bransford
Providing the simple long wire is 'long enough' to be at least 1/2
wavelength long at the desired frequency, a dipole has no significant
advantage when you are receiving and not transmitting. A dipole is usually
cut to a specific length which allows a transmitter to operate (into the
dipole antenna) efficently.
By efficiently, I mean the antenna needs to present a proper 'load' or
'impedance' to the transmitter, similar to your stereo amplifier's need for
a proper 4/8/16 ohm impedance from the speaker(s). The antenna is like a
speaker...if it's impedance (as seen by the transmitter) is incorrect, the
transmitter doesn't like it and can either be damaged or be forced to
reduce it's power output in an attempt to reduce the possibility of
damage.
For receiving duties, dipoles are USUALLY (not ALWAYS) not desireable.
Since a dipole is usually cut to a specific length for a specific
frequency, it is optimized for that frequency alone. Trap-dipole antennas
are good at multiple specific frequencys (bands), but again, don't do well
at the other frequencies that fall between the frequencies or bands the
dipole was designed for. Again, that type antenna are used primarily for
transmitters.
A simple long wire antenna, as long as you can make it and as high as you
can get it works very well. Technically, a long-wire antenna is at least
1/2 wavelength of the lowest frequecies you will listen to, but my
experience has been that a 20 to 40 meter length antenna is VERY good for
the entire HF band.
Solder your lead-in wire to the end of the antenna wire, and use insulated
or non-insulated stranded copper wire for the antenna itself. .
|>
|>
|>
+---------------------------------------+-------------------------------+
|> | Nikolaus Pollak | SIEMENS Austria Corp. |
|> | Email: po...@siemens.co.at | PSE 2354 |
|> | Phone: +43-1-60171-5719 | Gudrunstr. 11. |
|> | Fax: +43-1-60171-5712 | A-1100 Wien |
|>
+---------------------------------------+-------------------------------+
Hope this helps!
--
Regards,
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry Bransford
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
e...@ham.almanac.bc.ca
>
> Do dipoles generally perform better than simple long wires ?
>
>
It's kind of like asking, "Are apples better than oranges?"
The answer is that it all depends on what you are using the antenna for.
And where it is located. And how wide a spectrum you're listening to.
Each antenna has its own advantages and disadvantages.
Dipoles, for example, are resonant antennas designed for a particular
frequency. They are easy to feed with coaxial cable, and will match
impedance reasonably well with either 50 or 75 ohm cable. Being able to
feed the antenna with coaxial cable is an advantage, because coaxial
cable is easy to run, can be taped or tied to metal pipes, masts, etc,
without ill effect. In addition, the presence of a station ground, while
desirable at the lightning arrestor (fitted in series with the coax cable
at the point of entry to the building), is not necessary for good
reception.
If you want to cover several bands with your dipole, there are ways to do
this, either by adding traps (tuned circuits in the antenna itself) or by
tying together 2 or 3 dipoles at the feed point, all resonant on
different frequencies, and fanning them out at the ends.
A random wire antenna, which is usually fed at one end, is sometimes the
only antenna we can fit on our property. Good results depend on antenna
height, wire length, proper impedance matching, the quality of ground
below the antenna and whether or not you have a lot of metallic objects
near the antenna or lead in wire.
For the ground, for example, I would suggest not only 3 or 4 long ground
rods tied together with braid from the outside of a piece of coax cable,
but also a piece of wire one quarter wave long for each band the antenna
is operated on. For optimum results, I'd use an antenna tuner as well, to
match the impedance of the antenna to the radio.
You also need to keep the feed wire away from metal pipes, masts,
aluminum siding - basically anything metal and conductive.
As you can see, there are advantages and disadvantages for each kind of
antenna. Both types of antennas will work - how well is highly variable,
and depends a lot on the physical location you have to deal with. The
real nice part about it, though, is that both types are relatively cheap,
easy to construct, and that it can be very enjoyable building them, and
learning about antennas in the process.
I'm afraid I haven't given you a direct yes/no answer, but I don't think
it's a yes/no kind of question. I'll be glad to answer other questions,
though.
Bob Myers
Define "better." They can be a better match to a given line, etc., but
a real longwire (as opposed to a random wire) will show directivity and
gain superior to that of a dipole.
Bob Myers KC0EW Hewlett-Packard Co. |Opinions expressed here are not
Systems Technology Div. |those of my employer or any other
mj
:>> Do dipoles generally perform better than simple long wires ?
:>Define "better." They can be a better match to a given line, etc., but
:>a real longwire (as opposed to a random wire) will show directivity and
:>gain superior to that of a dipole.
Probably, though directionality (if there is such a word), I have found
that sloping, Ls and Ts work quite well if you stick to the 1/4, 1/2 wave
rules.
--
Mark Jones - The man who thinks the R-209 is a brand new receiver
(and Marconi is 20years old this year ).
*Disclaimer* My views are my own invention.
eigh...@gmail.com
2e0sir. 73s.
J.B. Wood
> Why do all hams fall for the same old bait of random length wire V x amount of wavelengths wire. Does it really matter, it's a wire antenna fed from the end. Why try and justify its length, name and how many wave lengths long the bloody thing is.
Why? Because a lot of hams are hobbyists, not theoreticians. That's
not particularly a problem except when hams provide theoretical
explanations that are inconsistent with electromagnetic theory, such as
the notion that one can transmit/receive an "E-field" as if it's
independent from the "H" field component of an electromagnetic wave (I'm
assuming far-field here.). And then there's that constant reference to
a "magnetic loop" antenna as if to imply there must also be an "electric
loop" antenna. Sincerely, and 73s from N4GGO,
--
J. B. Wood e-mail: arl_1...@hotmail.com