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Author Topic: Attic G5RV Jr. assistance  (Read 6783 times)
K3BAK
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Posts: 37




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« on: September 17, 2011, 06:54:29 PM »

I installed an attic mounted G5RV Jr a few months back. It has performed better than i expected however not knowing much about antenna theory i am looking for some assistance. My attic is roughly 7-8 feet high in the peak. So on the exterior wall i hung the center and run the arms down along the peak almost to the edge and with the 8 feet or so that was left over i ran the arm at 90 degrees out to the exterior wall. So it basically looks like a wide v. The ladder line runs straight down the wall and then turns 90 degrees towards my coax access point.

My question is 1 is that a reasonable setup for the antenna or is there a better configuration? 2 should i run the ladder line in a different matter since it not exactly straight? Any help would be appreciated. I considered replacing the antenna with an Alpha Delta dx-EE but would really like to avoid taking the g5rv down as it has performed well on 20 meters. It also tunes 30 and 10 well, 12 and 17 are iffy and 15 is pretty much nonexistent. I know my setup is far from ideal but i hope someone has some ideas or similar experiences. Thanks in advanced!
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KI4SDY
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« Reply #1 on: September 18, 2011, 07:56:35 AM »

I don't think adding another indoor dipole attic antenna is going to improve anything much. I am glad to hear that your current set-up is performing as well as it is. I would work on finding a way to install it outside. That is where the real improvement would be. Dipole antennas are extremely easy to hide. If you have any trees outside that would be a good thing to look at.  Grin
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WX7G
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« Reply #2 on: September 21, 2011, 12:28:17 PM »

As long as the attic walls and roof are wood with no metalic insulation it is essentially transparent to HF RF. Moving the dipole outside may offer no performance improvement unless you raise the height.

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AA9ZY
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« Reply #3 on: September 22, 2011, 06:57:01 AM »

True! My attic (which peaks at 4 feet high!) has not hindered my 20 meter dipole fed with 450 Ohm ladderline. Wooden rafters and asphalt shingles are rf transparent. Enjoy that antenna!
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K8WTF
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Posts: 12




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« Reply #4 on: September 27, 2011, 01:57:14 PM »

I have very similar experience with my G5RV Jr - good on 20 meters, OK on 10, nearly impossible to tune on 15.  I originally had it installed in my attic as well, although I had less space than you it seems.  I did not have very good luck with it inside and I picked up a lot of noise, likely from the old knob and tube wiring that runs throughout the attic.

FWIW, moving it outside made a world of difference - noise floor dropped a lot, and getting it about 10 feet higher also seems to have been a big help.  I was also able to get more distance between the ladder line and the legs.

If you can't move it outside, you might want to experiment with moving the ladder line around.
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K0ECW
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Posts: 24




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« Reply #5 on: October 03, 2011, 11:23:27 AM »

Remember also that the ladder line on the G5RV Jr is part of the resonator on certain frequencies. The 90 degree turn you have in it may be causing some issues.
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K3BAK
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Posts: 37




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« Reply #6 on: October 11, 2011, 09:32:16 PM »

Im not sure what else to do with the ladder line. I didnt want to shorten it, but there is a lot of it compared to the space i have with it. Will shortening it hurt its effectiveness? Or should I just let it be since I've been doing ok on 20, 17, 15 and 10? I mean 52 countries thus far is a lot better than I expected.
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WB2JNA
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Posts: 92




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« Reply #7 on: October 12, 2011, 01:42:41 PM »

Could you just feed the antenna with ladder line and a tuner and leave the coax off altogether?
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K3BAK
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Posts: 37




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« Reply #8 on: October 13, 2011, 10:44:29 AM »

I think that would be possible. Not entirely sure. Im using a W8AMZ G5RV Jr. I would have to cut the connector off and splice the ladder line back together to get it thru the ceiling. Im not sure if the ladder line is long enough though to get from the attic to my shack. It would probably be close. I guess I could run it into the shack and if its short use coax from there.
« Last Edit: October 13, 2011, 10:55:05 AM by K3BAK » Logged
WB2JNA
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« Reply #9 on: October 13, 2011, 11:23:03 AM »

Coax is lossy but convenient. That may be it's only real benefit if you're using a tuner anyway. I'd try just using ladder line IF it's not too much of a hassle and won't be run too near metal or with any sharp turns. Of course also use a balun if your tuner requires one (lots of tuners have them built in.)
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N4HRA
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« Reply #10 on: October 13, 2011, 04:40:37 PM »

I have a G5RV Jr and I connected the ladder line to a SGC ATU and then DC and coax to the shack.

It works better that using coax feeding the G5RV Jr

my Grin 2 cents

Lew
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