40M V Beam question

Discussion:

40M V Beam question

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Bob Wood

2004-06-23 00:41:12 UTC

V Beam antenna question

I want to put up a 40M V Beam antenna to enhance communication in one
direction only. From the limited design information that I have found, I am
thinking of 3/4 wavelength on each side with a horizontal separation angle
of either 72 degrees or 120 degrees. I have seen both separation angles
listed as optimum for maximum gain. I was wondering if anyone knew for sure
which angle would produce the best result. Also, and actually most
important, I need to have some idea of what the feed point impedance might
be. I can feed it with ladder line or good coax and a balun but I am not
sure what balun to use or would it be better to use ladder line? I sure
would appreciate any guidance on this antenna project.

Bob
W5QCP

Mark Keith

2004-06-23 06:26:41 UTC

Permalink

Post by Bob Wood
V Beam antenna question
I want to put up a 40M V Beam antenna to enhance communication in one
direction only. From the limited design information that I have found, I am
thinking of 3/4 wavelength on each side with a horizontal separation angle
of either 72 degrees or 120 degrees. I have seen both separation angles
listed as optimum for maximum gain. I was wondering if anyone knew for sure
which angle would produce the best result. Also, and actually most
important, I need to have some idea of what the feed point impedance might
be. I can feed it with ladder line or good coax and a balun but I am not
sure what balun to use or would it be better to use ladder line? I sure
would appreciate any guidance on this antenna project.
Bob
W5QCP

A true V beam is a minimum of one wave per side. And that minimum is not
much of a V beam...I'd have to double check, but with 3/4 wave per leg,
IE: about the same as an extended double zepp, I think you would have
the most gain with it straight like a normal EDZ. appx 5.1 dbi
bidirectional. I bet your gain will drop off if you try to set it up
like a V beam. As far as the feed impedance, it will vary per band. Not
really a major issue. Just treat it like any other balanced antenna fed
with ladder line. If if tunes, fine. If not, you might need to vary tyhe
feedline length a bit. You could feed with coax for a 3/4 wave per leg
antenna, "also 1/4 wave per leg on whatever band.." , but it would be
better to use a ladder line for all band use. MK

--
http://web.wt.net/~nm5k

Bob Wood

2004-06-23 17:17:07 UTC

Permalink

Thanks for the comments Mark. I do appreciate your taking time to give me
some advice. I only have a limited space around my home so can't put up a
one wave per side. I am currently using a sloping dipole and doing fairly
well but need to improve the reception to cover Texas, Arkansas, Oklahoma
and Louisiana for Navy MARS region nets. I saw an article somewhere that
indicated a V Beam 3/4 wave on a side would provide 3 dB gain over a dipole
in one direction. I will have to research it some more but it is really
difficult to find information on V Beams on the net. If you do discover any
more info I sure would appreciate you sharing it with me. Thanks again,
73, Bob

Post by Mark Keith

Bob Miller

2004-06-23 17:53:40 UTC

Permalink

Post by Bob Wood
Thanks for the comments Mark. I do appreciate your taking time to give me
some advice. I only have a limited space around my home so can't put up a
one wave per side. I am currently using a sloping dipole and doing fairly
well but need to improve the reception to cover Texas, Arkansas, Oklahoma
and Louisiana for Navy MARS region nets. I saw an article somewhere that
indicated a V Beam 3/4 wave on a side would provide 3 dB gain over a dipole
in one direction. I will have to research it some more but it is really
difficult to find information on V Beams on the net. If you do discover any
more info I sure would appreciate you sharing it with me.

Ten Tec sells a v-beam antenna. You can download the manual at
http://www.tentec.com/3402.PDF

It might be helpful as far as setup info goes.

Bob
k5qwg

Thanks again,

Post by Bob Wood
73, Bob

Post by Mark Keith

Post by Bob Wood
V Beam antenna question
I want to put up a 40M V Beam antenna to enhance communication in one
direction only. From the limited design information that I have found,

I am

Post by Mark Keith

Post by Bob Wood
thinking of 3/4 wavelength on each side with a horizontal separation

angle

Post by Mark Keith

Post by Bob Wood
of either 72 degrees or 120 degrees. I have seen both separation angles
listed as optimum for maximum gain. I was wondering if anyone knew for

sure

Post by Mark Keith

Post by Bob Wood
which angle would produce the best result. Also, and actually most
important, I need to have some idea of what the feed point impedance

might

Post by Mark Keith

Post by Bob Wood
be. I can feed it with ladder line or good coax and a balun but I am

not

Post by Mark Keith

Post by Bob Wood
sure what balun to use or would it be better to use ladder line? I sure
would appreciate any guidance on this antenna project.
Bob
W5QCP

Steve Nosko

2004-06-23 20:46:02 UTC

Permalink

Post by Bob Wood
Thanks for the comments Mark. I do appreciate your taking time to give me
some advice. I only have a limited space around my home so can't put up a
one wave per side. ...I saw an article somewhere that
indicated a V Beam 3/4 wave on a side would provide 3 dB gain over a dipole
in one direction.

While, classically, V beams have longer sides, I do know that a 3/4
vertical W/ground plane has a major lobe about 50 degrees above the horizon.
There was an antenna described by Inagaki (sp) some years back using this
characteristic to advantage with a corner reflector to obtain something like
18 dB gain and a nice 50 ohm Z. It also had a considerable minor lobe at
the horizon - obviously the main lobe remnant from "when it was a 1/4 wave",
so to speak.

If this can be generalized to a configuration where the "ground plane half"
of the antenna is supplied by another 3/4 wave element, then the V angle
would be about 100 degrees to get the two lobes to coincide. Modeling with
EZNEC should be easy...then there's the "how high is it" issue.

73, Steve

Mark Keith

2004-06-24 04:06:06 UTC

Permalink

Where are you now? Are they all in the same direction?

I saw an article somewhere that

Post by Bob Wood
indicated a V Beam 3/4 wave on a side would provide 3 dB gain over a dipole
in one direction.

Dunno about that. Sounds a bit fishy to me, but I'm not saying it's
impossible. But consider this...
An extended double zepp, which is .64 wave per side, has almost that
exact gain over a dipole in TWO directions. If you only need 3 db, that
would work, if f/b ratio is not a problem. If you need some f/b and
gain, I would use an array of two dipoles parallel.

I will have to research it some more but it is really

Post by Bob Wood
difficult to find information on V Beams on the net. If you do discover any
more info I sure would appreciate you sharing it with me. Thanks again,
73, Bob

I have some in books, but I don't know what you want to know
specifically..But I don't consider a 3/4 wave per leg antenna a V beam.
It has none of the properties of a true V beam, which is a form of
traveling wave antenna. To really act as a V beam, and have decent gain,
it must be a few waves long on each side.
A single long wire is the simpliest form of traveling wave antenna. It
must be at least one wave, and should be several. A V beam is two long
wires connected at one end. A rhombic is two V beams back to back. They
are all closely related. The longer the V beam or rhombic in WL, the
narrower the angle between the wires should be.
A 3/4 wave per leg antenna folded into a V, is just a 3/4 wave per leg
dipole in a horizontal V config...Having straight like a true EDZ, and
using only .64 wave per leg, instead of .75, should actually give you
the most gain you can get with that antenna size. Thats the way I see it
anyway...I'd forget about V beams. You probably don't have the room for
a real one. There are better options like the phased dipole array, or
the simple EDZ itself if f/b is not an issue.. I've run the phased
dipoles on 40m. It's almost like having a 2 el beam that can point in
two directions. More than that if you play with the different phase
options. That would give you your wanted gain easy, and about a 15-20 db
f/b ratio to boot.
MK

--
http://web.wt.net/~nm5k

Bob Wood

2004-06-24 12:28:40 UTC

Permalink

Thanks again Mark,

I am currently located in South Central New Mexico and all of the stations
on the net are East and North East of my location. Since FB ratio is not a
concern for me I think your suggestion of an Extended Double Zepp (EDZ)
would work just fine. 0.64 wave on a side would work perfectly since the
0.75 wave per side that I had been considering was really pushing the size
of my back yard. I will have to look into the EDZ but am assuming that the
max radiation pattern would be broadside to the wire which would work
perfectly for me. I have enough room on the property to run an EDZ
North-South which would provide the East-West broadside radiation and if it
has any gain over a dipole, I will be ahead for sure. I know that I do not
have enough room on the property to install two elements so I think we will
now shoot for the EDZ and see how it works. Thanks so much for the ideas as
they have been enlightening.

Bob
W5QCP

Mark Keith

2004-06-25 04:38:47 UTC

Permalink

Post by Bob Wood
Thanks again Mark,
I am currently located in South Central New Mexico and all of the stations
on the net are East and North East of my location. Since FB ratio is not a
concern for me I think your suggestion of an Extended Double Zepp (EDZ)
would work just fine. 0.64 wave on a side would work perfectly since the
0.75 wave per side that I had been considering was really pushing the size
of my back yard. I will have to look into the EDZ but am assuming that the
max radiation pattern would be broadside to the wire which would work
perfectly for me.

Yes. Appx 5.1 dbi in two directions broadside to the wires. Or almost
exactly 3 db over the 1/2 wave dipole.

Post by Bob Wood
North-South which would provide the East-West broadside radiation and if it
has any gain over a dipole, I will be ahead for sure. I know that I do not
have enough room on the property to install two elements so I think we will
now shoot for the EDZ and see how it works.

Should do pretty well. Will be appx 84 ft a side. Get it as high as you
can, and preferably set up as a flat top. It will work as as inv vee,
but the gain may drop off a bit. I ran one on 20m one time, and it did
well. One thing about the 40m EDZ.. If you feed with ladder line and a
tuner, it can be used on other bands also. Even 80m should work ok,
being it's longer than a 80m 1/2 dipole. Always use the minimum
inductance needed to get a usable match when tuning the tuner. MK

--
http://web.wt.net/~nm5k

Bob Wood

2004-07-01 03:39:20 UTC

Permalink

I want to thank all that replied to my request for information on the 40M
V-Beam. I certainly learned a tremendous amount of new things to consider
and to try. I did not realize that a V-Beam was numerous wavelengths and
that fact alone precludes the installation of such for my current residence.
I believe that I will try a better, higher, high quality dipole and then
experiment with a horizontal loop and perhaps a phased horizontal array if I
can squeeze these within the property lines.

Thanks again to all who shared their time and ideas with me and others
monitoring this thread.

Bob Wood
W5QCP
Alamogordo, NM

J. McLaughlin

2004-06-23 17:02:16 UTC

Permalink

Dear Bob Wood W5QCP:
Nice to see a name and call on a question.
Might you be asking about legs of 3 to 4 wavelengths on 40 meters?
Assuming that is the case, what is optimum depends on height and desired
take off angle (TOA) of the max. radiation.
Most often, three masts of a certain height are available and one
needs to deal with the limitations that result.
What are the expected heights of the masts? 73 Mac N8TT

Note that with one more mast, you will have a rhombic antenna, which is
a little better behaved and much more easy to terminate.
--
J. Mc Laughlin - Michigan USA

K9SQG

2004-06-24 01:40:10 UTC

Permalink

Bob,

Unless the antenna is up in the clear, the full gain, F/B, and F/S will not be
realized. You might be better off using 1/4 wavelength per side, rather than
3/4, and get the extra height instead. As to feeding it, open wire line will
work quite well, over a broad frequency range, and be virtually lossless at
even high SWRs negating the need for a balun and the associated problems. Just
one ham's opinion.

73s,

Evan

Jerry Martes

2004-06-25 05:48:08 UTC

Permalink

Bob

If you are still uncertain about what angle to use for a V with 1/4 waves
per side, you might get alot of insite from how good LPV antennas are
designed. The basic idea used for the LPV depends on the pattern from each
side of the V to combine to provide good directivity at that frequency where
the elements are 3/4 wave long.

Jerry

Richard Harrison

2004-06-25 17:25:14 UTC

Permalink

Bob Wood wrote:
"I want to put up a 40M V Beam antenna to enhance communication in one
direction only.---I am thinking of 3/4 wavelength on a side with a
horizontal separation angle of either 72 degrees or 120 fegrees."

Arnold B. Bailey catalogs a bidirectional horizontal unterminated Vee in
"TV and Other Receiving Antennas" Ends of the Vee must be terminated in
their surge impedance for unidirectional response. Bailey gives 800 ohms
as surge impedance of the wires in the Vee.

All antennas in Bailey`s catalog are "optimized" for a frequency of 200
MHz (1.5 meters).

The horizontal Vee is center-fed at its apex. So, it opens / closes
toward its best directions, since It is unterminated. It is
bidirectional.

Bailey`s Vee is several wavelengths per side. Its drivepoint resistance
is 160 ohms. Gain is 10 dB. 3-dB bandwidth is 3%. It still behaves as a
standing wave antenna without termination.

The Vee is made from two horizontal 35-foot #10 wires for 200 MHz,
forming an included angle of 35-degrees (21-feet between outer ends).

At 40m, the wavelength is about 27 times that at 1.5m. So, that`s the
scale factor. The wires become about 933 feet long.

The same wire formed into a rhombic is unidirectional if terminated. It
only takes one termination resistor, and the rhombic gives 3 or 4 more
dB gain than the same wires in a Vee. The rhombic is a little shorter
overall than the Vee, too. At 40 meters the rhombic requires about 567
feet overall length and is about half as wide as it is long.

If you can accept a total gain of about only 4 dB, you can have an
antenna with much less wire and space. Two parallel center-fed wires,
each about 1/2-wavelength, and 1/4-wave apart, elevated at about
1/2-wavelength, and connected together with parallel open-wire line in
the plane of the wires will give a drivepoint resistance of near 50 ohms
across either antenna.

Which direction is favored depends on which dipole is fed directly and
which acts as the directly connected reflector. 3 dB bandwidth is 60%,
which is much better than the 3% of the unterminated Vee.

Arnold B. Bailey gives data on page 521 of "TV and Other Receiving
Antennas" for the "Half-Wave Antenna and Connected Reflector". He
credits P.S. Carter, Proc. I.R.E.,vol. 20, p1032, June 1932.

Best regards, Richard Harrison, KB5WZI