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G5RV antenna guidance needed.

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elk2370bruce

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Going to install a G5RV 80 meter antenna (102 feet) running from a large pine tree in front yard to equally high hardwood tree in back yard. At least fifty feet above the ground. Reactive ladder line (31 feet long) will hang vertically about a two feet from back of house. Ladder line will terminate about 10 feet above the metal roof over the kitchen. Will this metal roof create a problem for SWR or power output. Lower end of ladder line terminates in a 4:1 balun and RG8 coax will run into the Shack (around 25 feet) into an MFJ 948 transmatch. Is this okay or should I remove the ladder line, insert the balun at the center of the two horizontal wires and just run in the coax without the ladder line. Different books give me different outcomes. Experience and knowledge would be appreciated before I try loading this puppy.

Thanks in advance.

73 de KC2PBJ
 

n4voxgill

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I would not modify it. The way you described putting it up should work OK. I had one
G5RV that had the balun about 6 inches above a chain link fence and I then ran the coax along the top of the fence to my shack. It was up for 10 years with no problem.
 

prcguy

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A G5RV is designed as a 20m antenna. It just happens to work fairly well from 40m on up, 80m is kind of lacking. A true G5RV does not have a balun and is intended to be extended (that rhymes!) directly with 50ohm coax if needed. I use one portable all the time with HF military manpack rigs and it works well for my use. Also had one 20-30ft above a 125ft X 200ft bonded steel roof and it worked as expected. It sounds like you have yours up high enough where the metal roof will not cause any problems. You have a tuner and you will need it for this antenna, regardless of the band, height or proximity to other stuff. What is your goal with this antenna? DX? Local stuff? At a height of 30-35ft it makes a good NVIS antenna for 80-60-40m and good low angle antenna for 20m. Around 65ft is a good height for 20 and 40m low angle but 80m will still be a cloud burner.
prcguy
 

jay427

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I'm thinking you will be fine, we use these on field day around the aluminum campers, seems to work.

Jay, n0mdf
 

elk2370bruce

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Thanks all for the help. Just getting ready to fire up the Yaesu FT-101E once I get that magical paper that lets me sign /AG in two weeks. Would love some 20m DX as well some general contacts. Want to trade up in the fall for 18 meter SSB along with digital displays. 40 and 80 meter CW is also on my list of activities so I can keep my speed at 20 wpm.
 

kb2vxa

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Hi guys,

Ah say WOAH HOSSIE! The G5RV has been modified over the years and comes in several flavors. Just put the darn thing up as it comes out of the plastic bag complete and don't worry about it. You shouldn't need a tuner, the SWR is acceptable unless you foul something up. By acceptable most rigs will tolerate anything up to 3:1 without appreciable power fold back and that's ALL need concern you. The fabled 1:1 match is a myth and back in the "boat anchor" days something called a pi network output would match anything from 25 to 600 ohms and the tubes didn't mind a bit. "SWR? Uh, well I don't know but you're hearing me, right?"
 

prcguy

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If you change the original G5RV to somehow work on all bands without a tuner, it’s not a G5RV anymore. With an actual G5RV you may not need a tuner on 20m but everywhere else a modern radio will not be happy. Except for some military rigs, every Yaesu, Kenwood and Icom I have used with a G5RV has needed a tuner or the radio folds back the power drastically. With a tuner, especially if you can connect directly to the balanced line or use a minimal length of coax, it will suit most people’s needs 80-10m and even 6m can be good of a lobe lands in the direction you need. The only differences I have seen from the way Louis Varney (G5RV) originally designed it is using 300ohm TV twinlead instead of 450ohm ladder line, and adding various chokes between the balanced line and coax if used. The feedline length is adjusted for TV twinlead to get back to the original ladder line design, but the choke has been deemed not needed and outright detrimental in some cases. Neither of these changes has made it work all bands without a tuner.
prcguy
 
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