G5RV for 6 Meters and Other Bands:
MATTHEW C. PENTTILA (N1RWC)
on
July 29, 2003
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I was looking for a wire antenna to put up for 6 Meters one evening. As the hours of reading QST, CQ, 73, and other publications passed, (and it was 3AM) I found my epiphany. I read several articles for the G5RV in these publications and also how several fellows designed an antenna for one band and did the math to make one similar for different bands.
The next day (I think it was the next day) I looked at the basics of the G5RV. The G5RV was designed as a single band 3/4 Wave Dipole fed with Ladderline. Later in evolution, (my wife keeps asking why I am asking her how to spell these big words), Coax replaced Ladderline. And eventually it was adapted to the G5RV antenna.
So armed with this info I derived the following formulas to create the G5RV for any band, have gain over a dipole, and match up for direct connection without a tuner for the design frequency.
Formula 1 (Dipole Length)
1428/F MHz = Length in Feet
Formula 2 (Individual Wire Length)
1428/F MHz = Dipole Lenght/2 = Length Each Leg
Formula 3 (Ladder Line Matching Section)
468/F MHz = Length of Ladderline in Feet
Construction and notes:
Connect one end of each Wire Leg to an insulator to create Dipole, attach 450-Ohm Ladderline to center insulator and Legs of Dipole. Attach 70 Feet of RG6QS (72 Ohm preferred) or RG8X (52 Ohm) Coax to other end of the Ladderline, Center to one side of Ladderline, Braid/Shield to other side of Ladderline. Adjust length of Ladderline then Dipole ends for best match. When I first set this up, I centered for 50.110 MHz, with 28.5' Dipole and 9.3' Ladderline. I trimmed 1/4" off the Ladderline and ended up with a SWR of 1.2 to 1 at 50.1 and climbed to 2 to 1 at 52.525 MHz. I did build one for 80 Meters, 380 Feet Tip to tip and 125 Feet of Ladderline between the insulator and the coax.
One word of caution, do not exceed the power rating of the materials used, namely the coax or Ladderline, i.e. 100-200W PEP may be fine or max, but 1500-2000W PEP may destroy the antenna, coax, and finals.
I have used the 6 Meter version and worked several locals with 5 Watts with a FT-817 on 50.125. Also an added bonus was that I switched to 2 Meter FM and talked through a local repeater with low 1.5 to 1 SWR. Downfall was if the repeater was full scale on my end, I wasn't hitting the repeater. If the repeater was S-0, I was in Full Quieting. Strange but this happened only on 2 Meters, 6 Meters was not affected by this.
73 and good luck matt N1RWC
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G5RV for 6 Meters and Other Bands:
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by N1RWC on July 29, 2003
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Quick Clarification on this.... I wrote the G5RV is based on a 3/4 Wave Dipole. THIS IS INCORRECT. It is based on a 3/2 Wave Dipole. Each Leg is 3/4 of a wavelenght at Frequency of Design. Sorry about the mix up. 73 Matt N1RWC
PS If you go to get Ladderline, make sure it is STRANDED CONDUCTORS. HRO and Others sell 450 Ohm Ladderline that is SOLID Conductors, and over time and flexing will break the SOLID Conductors sooner than STRANDED Conductors.
And I am writing this at 1AM.. So I apologize for any type errors.
73 Matt N1RWC
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RE: G5RV for 6 Meters and Other Bands:
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by K0BG on July 29, 2003
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The G5RV is one of those enigmas which crop up in amateur radio now and then. As a single band antenna, it's fine. As a multiband antenna, it stinks.
On 6 meters, it is so easy to build a rotating dipole which will work just as well as the G5RV. And, in the old VHF handbook, there is a design for a 2 element 6 meter beam which uses twinlead attached to a wooden frame. I made one of those years ago and it was in the air for nearly 10 years before it finally weathered and broke. Total cost was less than $10 at the time.
Nonetheless, a nice how to. Thanks.
Alan, KØBG
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RE: G5RV for 6 Meters and Other Bands:
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by KA5N on July 29, 2003
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Consider the facts of antenna polarization. If you are using a horizontally polarized antenna on 2 meters and try using a repeater with vertical polarization you probably won't get very good results. One can build a small vertical co-linear array out of aluminum clothes line wire, adjust to low swr and get gain for practically nothing. A 2 meter beam of 3 or 4 elements is about the size of a small TV antennna and can be mounted for vertical or horizontal polarization.
A 6 meter array isn't that large. Wire beams for each of several directions is another possibility. Look at antenna books and see the host of VHF antennas that are better and easier to build than a G5RV.
Allen KA5N
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RE: G5RV for 6 Meters and Other Bands:
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by N2BR on July 29, 2003
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I used a G5RV with my Icom IC-746 on 6 meters and it work great for me over 100 grids worked,But it dont matter what kind of antenna you have up when the bands is open to work 6 meters.
Bob/N2BR
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RE: G5RV for 6 Meters and Other Bands:
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by KB1GMX on July 29, 2003
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G5RV for 6 is a nice exercize on an attempt toward multiband VHF. The problem is that at VHF the effort is less effective and more prone to failure.
I happen to have tried both dipole and an double extended zepp (basis for G5RV) and the Zepp does perform better IF the feed system doesn't have high losses. At 6m that may be less a problem but at 2m that is a real problem as is polarization (and a strange pattern). I prefer at VHF to avoid stranded wire feed at 2m and above meaning the ladder line can be lossier than expected though it gets by.
Wire on 6 and two will get you on the air fast and I've used it effectively but, even two element beam beats it and is easier to turn! With a three element beam it's no contest.
Allison
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G5RV for 6 Meters and Other Bands:
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by WB2WIK on July 29, 2003
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Any antenna is surely better than no antenna, but the 3/2-wave G5RV design seems fruitless for most, as it is typically too long to rotate and has a sharply defined radiation pattern with some rather steep nulls.
I think it would be better, for most, to build a simple 1/2-wave rotary dipole for 50 MHz, and rotate it. "Gain" is reduced about 3 dB, but at least one can aim the antenna in the desired direction, as opposed to hoping that stations happen to be in the favored directions for a fixed antenna. Then again, a "Hexbeam" (or Moxon) type design occupies considerably less horizontal space than a 1/2-wave dipole, costs perhaps $10 to build (including all materials) and can provide about 6 dB gain in its favored direction, being rotated by any lightweight "TV antenna" rotator.
The interesting phenomenon noted regarding two meter repeater operation is easy to explain, and I've seen this kind of thing many times. Phasing nulls can be very steep and very frequency sensitive at VHF-UHF. A null occurs every 90 degrees in the signal path, and a 90 degree phase shift at 146 MHz occurs every 20 inches in free space. With a cross-polarized antenna (using a horizontal doublet to contact a vertically polarized repeater, as they all are), one begins with a lot of cross-polarity loss, although the occasional reflection can rotate the signal, creating a phase boost in strength at certain frequencies, from certain directions.
Since repeater inputs and outputs are typically separated by 600 kHz on the two meter band, and since the frequency of a "boost" or a "null" can coincidentally be spaced about 600 kHz apart, one can achieve a very strong transmitted signal and a very weak received signal using a single repeater pair, antenna and feedline. Or vice-versa! (Meaning, a very weak transmitted signal report, with a very strong received signal.)
This phenomenon occurs more frequently at 222 MHz, where repeater input-outputs are separated by 1.6 MHz, and on 440 MHz, where the separation is so wide that it's possible to have a 40dB null on one frequency without impacting the other frequency at all.
WB2WIK/6
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RE: G5RV for 6 Meters and Other Bands:
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by KZ9G on July 29, 2003
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Steve's assessment is on target. I also suggest a unidirectional antenna such as a 3 element yagi. Easily mistaken as a TV antenna, it will give you gain and directivity. Obviously, it can be turned by the smallest of rotators out there.
While in the Air Force in the early nineties, I stacked two 50 MHz, 3 element yagis spaced 5/8 of a wavelength apart while living in USAF Sergeants housing at Keesler AFB, MS (Note: if I'm able to do that, I figure most organizations or neighbors won't object). With this small stack, I was able to work many stations in Australia two years in a row, the Pacific, the Caribbean, South America, and over 125 grids in less than 2 years of modest operation. By the way, the first year I ran 10 watts on SSB and CW. During the second year, I opted for the Mirage solid-state, 150 watt amplifier with I drove at the 7 to 8 watt level - the point where linearity started to suffer with the thing. Good Luck with your 6 mtr endeavors. 73!
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G5RV for 6 Meters and Other Bands:
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by W1JQ on July 29, 2003
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Well, you're talking about *designing* a g5rv for 6m. Not sure I'd recommend that.
I have a motley crew of HF wire antennas here, though, and I've tried just about all of them on 6 meters. Don't try this without an antenna tuner! Here's the results:
g5rv (full-size, 102'): Works OK
40m halfsquare: Sometimes outperforms the g5rv
3-el 15m dipole curtain: Don't bother
I'm not a real 6m operator, so I can't count my grids. In the past 2 years, though, I have worked the west coast, Europe, and central america from New England. And without spending any significant time on 6. (Every couple of months, I'll tune across the band, and if there's something going on, I'll work it.)
The bottom line is that, when 6 is open, it's very open., and if you're patient, you can work stations using the proverbial bed springs. I can also tell you that I have *never* felt like I have had a very good signal. Some time, I'll put up a real 6m antenna. In the meantime, I'm going under the "bad antenna has 1000 dB gain over no antenna" principle.
Mike
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RE: G5RV for 6 Meters and Other Bands:
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by N1RWC on July 29, 2003
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I think most of you missed the point of this article. It is how to make a G5RV for A Specific Frequency, not trying to use the G5RV cut for 14.1 MHz on 6 Meters.
By the way, it's got more gain than a regular Dipole at the Designed Frequency and can be put up in minutes, unlike a beam and rotator assembly. I will admit that a beam goes farther but a wire is easier to try and see if it's worth putting up a beam.
73 Matt N1RWC
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RE: G5RV for 6 Meters a better idea
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by K1MKF on July 30, 2003
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If you are making a new wire antenna for 6m then make a longwire. A wire several wavelengths long will present a feed point immediance of roughly 200 ohms. Install a 4:1 balun at the feed point then put a 2-1/4 wavelength of wire on the radiating side and a 1/4 wavelength of wire on the counterpoise side. Aim the wire with the end of the long portion at the general direction you wish to work. Several cones of radiation will be directed in that direction and you can raise and lower the feedpoint to alter the take-off angle. It's a great idea and one that can be done on a small lot with six meters.
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RE: G5RV for 6 Meters and Other Bands:
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by KB1GMX on July 30, 2003
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Matt, good point.
Though If I were doing the "just to see" test I'd do a wire dipole first, simpler and faster. Rotating a dipole for VHF is despite the wide pattern useful and does make a big difference. My first 6m dipole was a peice of pine strapping on 15ft of pipe with a 112" of wire dipole nailed to it and turned by armstrong, it worked and proved rotation helps.
At my place I have dipole, D-EDZepp, and beam and I can compare. They rank in that order but the difference level from dipole to D-edz is minimally with the effort where the difference from the d-EDZ (at 14ft) VS 3 element beam at 20ft significant as in 2 S-units on the stingy TenTec6n2 meter. What that says to me is while the HF G5RV is a useful multiband antenna it's design offers little as a single band antenna at VHF.
For 2m and up(222, 440 ect) 3-4 horizontal element beams are so small as to be a trivial effort. Wood
poles and simple stiff wire elements are easy to fabricate due to small size and easy aquisition. For Vertical polerized work there are a number of Jpole,
5/8ths and Colinear designs for omni gain that approaches or exceeds that of a 3 element beam. Up there using a less than effective antenna really can negatively distort the picture of what can be done in the upper reaches. Why, RG213(good stuff is around -3db/100ft and worse as you go up!) so you need the equivent of 2 element beam just to overcome your losses. Repeater work at VHF and Uhf is usually not representative of what weak signal work may (or may not) yeild.
I say go ahead and play with wire on VHF, however its results may surprize, disappoint or both. If anything else for the people that need to be stealth, VHF offers the possibility to conceal effective antennas in places where larger HF antennas could never hide.
Allison
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RE: G5RV for 6 Meters and Other Bands:
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by WB2WIK on July 30, 2003
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N1RWC, I fully understand the intent of your article and also your work, but I've gotta tell ya...
In my 38+ years on six meters, there is no way I'd ever recommend anyone install any sort of wire antenna "just to see" if it's worth being on the band from any particular location.
My 6 element yagi at 65' above ground on a rotator hears stations S9+ that cannot even be detected 1 dB above the noise with a tuned and resonant 6m dipole strung between a couple of trees at 25 feet. Nada, zero, nothing. (This isn't to say the beam has 54dB gain; of course it doesn't. But, it does have 54dB higher performance in many cases, partly due to its much greater height above ground, party due to favorable ground reflection gain that is most readily enjoyed by using horizontal, directional arrays, and partly due to it having an actual 11dB or so gain in free space.)
If I had to base my opinion of "what's on six?" by using a wire antenna (even providing the 3/2-wave G5RV-type might have 3dB gain in some favored directions over a 1/2 WL dipole), I'd have never gotten on the band at all.
That said, I recommend "antenna experimenting" on any band, for anyone! It's fun, it's cheap, it gets us outdoors in the fresh air and sunshine and I still do it all the time, myself.
WB2WIK/6
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G5RV for 6 Meters and Other Bands:
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by NJ6F on July 30, 2003
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2 meters is S 0 because your are horizontally polorized to a vertically polorized repeater.
Polorization is more pronounced on the higher frequencies 2 and up.
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G5RV for 6 Meters and Other Bands:
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by WB2AMU on July 30, 2003
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I just worked a ham today (7/30) in Tennessee via Sporadic-E on Six Meters that was using a G5RV. His signal strength was OK but he was reading me a lot better as I was using a two element Yagi. It is a compromise antenna if you have nothing else for Six, but as one reply said, a dipole is not difficult to cut and use.
I had made contacts using a 40 Meter dipole which loads up OK on the band, but one can imagine what the pattern must look like. I had to do this at the UN also as they had no Six Meter antennas. OK results, but the beam, dipole or vertical cut for Six will do better.
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RE: G5RV for 6 Meters and Other Bands:
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by K8DIT on August 2, 2003
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Antennas are such interesting commodities. We hams need them to play on our radios. Our wonderful world of wire takes on and takes off in a culture all its own. The g5rv answers alot of need due to the demands for simplicity erecting an antenna. If your needs are answered by a single wire antenna of any design for any band or multiple bands, don't be certain that it epitomizes the antenna art. Dont settle for and on any single design or theory as being optimum. Your understanding and enjoyment of wire antennas will evolve with your involvement in the hobby. Have fun.
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G5RV for 6 Meters and Other Bands:
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by KA7QOR on August 7, 2003
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I built a 6M collinear dipole using 4, 1/2 wave elements. My wife, BG7JBA, and I live in GuangZhou China. Last spring/early summer we worked many Japanese as well as Guam, Phillipines, Australian and Indian stations. We run only 5W QRP on 6M as we have a FT817. I agree that any yagi would be better, I have my doubts about a 6M G5RV, but I do not agree that it is impossibe to build an effective wire array for VHF. A note also that my 6M wire antenna is effective at 29.2 MHz as a 3/2 wave dipole.
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G5RV for 6 Meters and Other Bands:
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by KC8VWM on August 9, 2003
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Look out G5RV .....Now introducing the new
KC8VWM Dipole :) No ladderline or complicated baluns required !
A six meter dipole can be easily constructed using two 54" lengths of just about anything that will make a suitable radiator. Try a TV antenna!
Uses ordinary RG8 coax line.... easy.. versitile...
Converts easily to a high gain beam antenna too!
:)
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G5RV for 6 Meters and Other Bands:
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by KA5CVH on August 11, 2003
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I tend to agree that building a G5RV for 6 meters, outside of the knowledge learned and the satisfaction of the project, is not the best use of ones money if all they are looking for is a workable antenna. I know several people who are using KB6KQ loops and MFJ 9406's and having a blast. Now if you're looking to test your learning by building one ... kewl ... go for it.
Mike
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