Homemade quarter-wave ground plane base antenna

**222DBFL** · 10-16-2016, 12:37 PM

Leave it coiled up like JJD stated. It may be acting as a choke when you have it rolled up and this isn't necessarily a bad thing. As long as the radio is seeing a good match I would leave it be the way it is coiled up.
And yes JJD, they aren't swing monsters for sure but like you said add a nice 1x2 or even a 1x4 and watch out!! They are clean, clear sounding radios and clean in equals clean out. I've not noticed any channel rejection issues with the 980, but I haven't been close enough to anyone to see if it's an issue with that radio. I know my magnum 257HP and my optima MK3 do have this issue. Way over sensitive receivers. Nice thing about the Icom 746 I have is being able to use NR and the twin PBT as well as the notch filter. Man does it get rid of unwanted crap quick!! But it's an SSB radio and I know that. My cobra 29lx le is a nice radio as far as AM only and with the 1969 final mod does rather well. Someone in TN did the work and I picked it up from a trucker in Michigan while I was working there. Also got a nice predator 10k antenna as well. Use it with a 4 magnet mount on top of an old Nissan Pathfinder with my TNT 600hd from time to time. Gets the job done when I need it to. Anyhow. Enough BS.
Matt I truly hope that you get all your things right and have fun. That is what the hobby is all about man!!

**mattsowders1989** · 10-16-2016, 12:44 PM

Yeah. Thanks 222. Trying to just get everything working right.

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**JAF0** · 10-16-2016, 05:35 PM

Originally Posted by mattsowders1989

I know this is going to sound like a stupid question and I apologize for it before hand. I'm some what new to CB so bare with me. Why is it when I role up my excess coax, my SWR is 1:1 but when I stretch it out, it jumps up to a 1.9:1? Seems like I need something to fix that problem. Is it something I can make?

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Mind if I ask what type of coax you're using, and how many feet?

**mattsowders1989** · 10-16-2016, 05:38 PM

the coax i use is R & L Electronics RG 8/U .80 2015 Low Loss.

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**mattsowders1989** · 10-16-2016, 05:39 PM

About 50 feet

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**JAF0** · 10-16-2016, 06:01 PM

Originally Posted by mattsowders1989

the coax i use is R & L Electronics RG 8/U .80 2015 Low Loss.

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80% Velocity Factor RG-8? Usually RG-8 is 66%...???

**mattsowders1989** · 10-16-2016, 06:02 PM

That's how the cable is labeled.

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**JAF0** · 10-16-2016, 06:18 PM

OK, looks like it's their version of 9913 actually at 84% VF.
Try 7 turns around a 4" former like white or gray PVC right below the feed point of your antenna, (NEVER use black ABS, has a high carbon content, not invisible to RF)

...and if at all possible either elevate both the choke and antenna above the metal mast with several feet of fiberglass, wood, etc.,

or do like Booty did with his Homebrew Sigma-Vector, (which you can see in his picture) where he moved the coax & choke away from the metal of the mast and wrapped quite beautifully off to one side.

(MAJOR KUDOS, BOOTY, I LOVE that design, very clean & effective!)

Installing a CMC (Common Mode Choke) right on or around the metal of the mast defeats the purpose. The RF field continues to flow around the choke via the mast.

Notice how Booty's keeps the coax away from the mast and actually turns the RF field perpendicular (90°) to the mast. Perfect!

5.5T on a 4" former for 66%, 7T for 84% has worked well for me in the past.

Then you shouldn't have to coil your coax to fool the SWR.

**mattsowders1989** · 10-16-2016, 06:24 PM

Ah ok. Very useful info. Thank you so much!!!! I will post photos once I get everything lined out.

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**JAF0** · 10-16-2016, 06:50 PM

...and another thing people will sometimes do is carefully slice away 1/2" of the coax casing just outside of where it goes into the house and carefully solder a short-as-possible ground strap from there to a ground rod, taking care not to melt or deform the dielectric beneath the braided shield, then reseal with "Liquid Electrical Tape" in the can, or self amalgamating or vulcanizing tape.

This helps to shunt to ground any static or stray RF picked up by the shield of the coax, including any RF which may have leaked past the choke.