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Author Topic: Exact G5RV configuration???  (Read 4125 times)
KC7HUX
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« on: August 05, 2006, 02:28:14 PM »

Since I have gotten my G5RV I have had some problems, so I am asking for descriptions and hopefully pictures of EXACT G5RV configurations that work. Mine is 204' long and I have NO! space restrictions, I live on 25,000 acres, yes Twenty Five Thousand acres. I have trees and telephone poles available.

Apex height, end height, feed line layout and where you're grounded and how. How much coax you have between antenna and tranceiver.

I have 140' of 213.

Experience is what I am looking for, not theory. I have theory, yada, yada.... Pictures can be sent to bowhuntelk@netzero.com  

Thanks
Craig
KC7HUX
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K8GU
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« Reply #1 on: August 05, 2006, 07:53:44 PM »

I had a G5RV when I was getting started.  It was the 102-ft Van Gordon model.  I had the apex at 25 feet on a rusty TV tower.  One end was tied to a garage and the other end sloped along the roof of our 1-story ranch-style home.  The transmitting twinlead came down the tower on stand-offs and along the foundation of the house until it got to the balun.  I had about 30 feet of RG-8X on the other side going to my shack.  I had a ground rod right at the shack that the gear was all grounded to.  The system worked great and loaded on all bands 80-10 as advertised using an MFJ-941 tuner.  I did have tremendous RFI problems with everything electronic in the house, though.
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WB2WIK
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« Reply #2 on: August 05, 2006, 09:08:41 PM »

Mine for years had been as follows:

One end up 90' above ground, rope tied to tower.

Other end up 60' above ground, rope tied to another tower.

Center about 75' above ground, unsupported other than by the 204' G5RV antenna wire (#12 AWG copperweld).

450 Ohm ladder line drops straight towards ground from feedpoint.  About 15' above ground level it splices to the coaxial feedline (RG213/U).  There is a 1:1 coaxial choke balun at this junction, made of 60 turns of RG213/U on a 6" diameter form and taped to hold its form.

Coax drops to ground and travels on ground for about 120 feet, to station.

Not quite "level," but it worked about as well as it modeled for a "level" (flattop) antenna.

Very good results on 160-80-40.  Not great above 40m, but never expected it to be.

What kind of problem do you have with yours?

WB2WIK/6
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WB2WIK
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« Reply #3 on: August 05, 2006, 09:11:07 PM »

Forgot to comment on "where you're grounded and how."

My answer: Not grounded in any way, to anything.

A coaxial lightning arrestor grounds the coax just outside the shack wall, at ground level.  Connecting or disconnecting the arrestor makes absolutely no difference in the way the antenna works, or the way it loads.  (It's a gas discharge tube type arrestor.)

WB2WIK/6

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KC7HUX
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« Reply #4 on: August 06, 2006, 11:26:13 AM »

Well, you might have answered my problem with your answer. When I first got mine I buried a telephone pole putting the center about 35' above ground on top of a knoll that allowed the ends to slope away and down a bit yet remain more than 30' off the grouund on each end. I then moved the antenna closer to the house and made it to span the draw that my house is in. This has the center about 60' off the ground and each end 40' or so. but it is in the kind of configuration that yours is. Higher on one end sloping down through the feed point to the other end. All was ok till we had a 70 mile an hour wind blow through. It took my ladder line and snapped the balun off like a whip never to be found again. I mean I have been looking for a month! I bought a new balun. I called AES and told them I needed a new balun and they sold me a "4:1" balun. Now I can't tune on nearly any band, I can tune on 17, 15, and 12 meters. But it just sucks everywhere else. It had tuned on nearly the entire hf spectrum except 20 and 40. Now it's just junky throughout and the balun is the only difference.

The reason I had posted to begin with was that from all I could tell from researching online the 4:1 balun is the component for a 204' G5RV with 65' of ladder line fed with 140' of coax.

Well there it is and thanks for your response
Craig
KC7HUX
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WB2WIK
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« Reply #5 on: August 06, 2006, 01:57:37 PM »

It should *not* be a 4:1 balun!  The matching device on a G5RV is the ladder line section.  That provides a direct interface point with no impedance transformation required, to 50 Ohm coax.

With a 4:1 balun, you should have a serious mismatch on most bands.

If you refer to the original Varney articles on the G5RV antenna (in PW, c. 1973 or so), you'll see no 4:1 balun is used.  In fact, he didn't use any kind of balun at all; he just connected the coax directly to the ladder line.

WB2WIK/6
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KC7HUX
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« Reply #6 on: August 06, 2006, 06:51:52 PM »

Thanks Steve,
It took me a while to research that out. I firstly and wrongly took it for granted that an AES salesman would know what was needed. Secondly, I just didnt know, I need to purchase a few books for refernce material.

I do appreciate your input.

I also have either worked you, but I dont think so or I have monitored you during QSO at sometime. I had your call scribbled and recognized your picture with your family on QRZ. It is a great photo and notes about your family. I see you are a \6 now so I will have to listen for you on the lower bands, I'll talk to you someday.

Craig
KC7HUX
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K8AG
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Posts: 352




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« Reply #7 on: August 11, 2006, 09:21:02 AM »

Hi,

I have used G5RV and variants for years.  The G5RV is 102 feet across the top with a specific length of parallel line (twin lead, laddrer line etc) before the coax.  The parallel line needs to be a specific length as should the top.  I suppose you could try to double everything, but what you have to make sure that you also double the length of the parallel line feed.  If you run the parallel line all the way back to the tuner, all bets are off as its not a G5RV anymore.

My ladderline is soldered directly to RG-8X at about 100'.  I have 10 or 12 turns of coax immediately after the ladder line on a 2-liter pop bottle to choke currents on the shield.

I have 1 8' ground rod roughly 4' from my rig connected with 1" wide braid..

Right now I am using a ZS6BKW up about 45 feet straight across between 2 trees.  The ZS6BKW is a computer optimized (for SWR) version of a G5RV with different lengths.  Lowers the SWR on the coax feed.

I use an FT-920 with an internal tuner that only does 3:1 or better. It seems to have no problems except 75 (80 is OK), 30 and parts of 15M.  Everything else (including WARC bands seems to tune through 6M).

Hope this helps.

73, JP, K8AG
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KL7YK
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« Reply #8 on: August 29, 2007, 12:07:29 PM »

G5RV mounted on the roof, literally on the roof. Lying right on the shingles.  Roof is non-conductive. Have antenna restrictions and the antenna is invisable.  Not that you need worry about that.

102' model not grounded other than by the coax.  Operates 10-80m daily with 100 watts.  Have worked into Eastern Europe, New Zealand, Mexico and even some of the Pacific DXpeditions.  Overall above ground is 30 feet, space between shingles and antenna nadda.

RFI? Only if I run over 100 watts and then only on 20m.

Main point, G5RV will work about anywhere.  No not the greatest DX antenna but it will work DX.  Best compromise antenna I have seen.  Get it 25-35 feet off the ground, bend it whatever way you need to and go for it!

Ron, KL7YK
Anchorage


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