Touch Question

[RossJ]

I'm looking for input on this. When I open the squelch up and get max background static, I notice that it makes a difference if I'm touching the microphone and/or the radio. With the mic in the bracket and hands off the radio, the static is loud, I can hear distant skip and would have to turn the squelch up quite a bit to cancel it out. If I pick up the mic or touch the radio, the background drops away significantly and just a little squelch will be enough to cancel. It doesn't matter what mic I use or whether I'm running AM or SSB. This is a mobile radio (Uniden Bearcat 980) set up as a base. Strong and local stations come in well with no attenuation regardless if I'm touching or not. It seems to effect background noise (RF sensitivity?) more than anything. My gut says it's a ground issue, but input from those more knowledgeable would be nice... thanks.

[MDYoungblood]

Your gut is right and it doesn't help using a magnet mount antenna. Try adding a wire from a case screw to a good ground close to the radio. Also check the antenna's SWR,, that could be another problem.

3's

Greg

[Gunner357]

My radio was doing the same I have a tri mag mount under a Predator 10k and I tried grounding the radio chassis to frame it didn't help but after I got the SWR down it went away?? go figure

[Scrambler82]

What antenna are you using ?

Where is it mounted ?

Does the antenna have a ground plane ?

I too think it could be grounding issue, but it could also be a miss match in the antenna, which could be caused by a ground place issue.

[MDYoungblood]

It is called "Common Mode Current" , CMC for short. The thing about a magnet mount is they are a capacitance ground and depend on the coax's shield to do this, and then the coax is depending on the negative power lead. The reason it stopped after adjusting the antenna was there was less RF dancing on the coax shield. The Wilson "Little Wil" is a short antenna, 32" total so the SWR curve is narrow, if you can get a good SWR (1.1:1) on channel 19 the ends of the band, 1 and 40 are above 2.5, just the nature of the beast. a longer antenna is going to give you more usable bandwidth, hence less CMC.
Look through the forum at grounding, bonding a vehicle, you'll find some interesting stuff there.

3's

Greg

[RossJ]

Thanks for the responses. Let me give you a little more information.

The radio is set up in the house and powered by a 13.8 VDC power supply. The antenna is on top of a 20’ steel pole, swivel mounted on a cement pier in the side yard. The antenna is a Workman 100B (no ground plain) and no doubt the weak part of the setup (limited budget and all). The cable is 60’ of RG8X run down the pole and in through a first floor window. I intend to upgrade to a Solarcon A-99 when I get a few more pennies saved up.

I’ve been wondering if running a copper ground wire from the antenna base clamp at the top of the pole to a ground rod would improve the situation I’m experiencing. A ground wire needs to be installed anyway, but I hate to take the money out of my antenna upgrade fund unnecessarily.

[MDYoungblood]

Is the steel mast grounded? If so then the wire would be unnecessary. That antenna was called a "Saturn" back in the day, look it up and you will find the spec's for it if you don't have them. The coax is length specific if you read the instructions and the cap on top can pop off to adjust the antenna's SWR.

3's

Greg

[jessejamesdallas]

Problem does sound like a ground problem...If I'm thinking this right, it sounds like your mast isn't grounded and mounted to a concrete pole?

First thing I would do is run a ground strap off that pole, to a 9' copper ground rod that's been hammered into the ground...maybe have a couple two or three of them all connected together...If nothing else, this will help if lightning ever strikes the antenna...

I would double check the SWR too...high SWR can cause weird problems...might even try a different radio if you have one just to see if the problem go's away or not when switching radios.

I never had this problem with my base set-up, but have with mobile installs, and those usually were just bad, or not good enough ground to the antenna mount...mounting to mirror brackets was the worst.

[RossJ]

Thanks Greg. I cut the coax to one of the specified lengths in the instructions (59'). The SWR is hovering around 1.6. The steel pole is not intentionally grounded. It's bolted to a steel bracket at the bottom end and that's held in place by a couple threaded rods embedded in an 8" diameter cement pier. The 20' steel pole is painted, so there is no metal-to-metal contact between the aluminum base of the antenna and the top of the steel pole. I haven't checked continuity, but I doubt there's any electrical path.
I've done some searching on the Saturn Twinpoint antenna, other than playing with the length of the coax, I haven't found any discussion about tweaking the SWR.

[Bluerunner]

Sounds like CMC problem. Put a choke in the coax. 5 turns of the coax feed line close wound on a piece of 4" pvc pipe. Keep it away from the mast or other metal. I think that choke is like "antenna 101" It works so well to avoid problems.

[RossJ]

I appreciate all of your responses and well considered input. I just bit the bullet and ordered a Solarcon A-99... supposed to be here by Wednesday. Surprise of the century... wife just nodded and said, "sounds good". Anyway, with improved grounding and a more substantial antenna, I'm hope the issues become a thing of the past. Again, thanks everyone.

[RossJ]

I put up a Solarcon A-99 yesterday. Mounted it at the top of a 20’ steel pole, running a ground wire from the ‘U’ bolts at the base of the antenna, to a self-tapping screw in the top of the steel pole and then down the pole to an 8’ copper-clad rod in the ground. My SWR is now essentially flat from channel 1 to 40. There’s no sign of the problem I was having when touching the mic or radio. I did have to drop the RF sensitivity down to “local” because there was so much skip and static, (I think some neighbors are still running generators following the storm that came through).

I’m anxious to start making contacts on side band now and would hope to enjoy some improved reach over the previous antenna. D/M output of the radio running AM is only about 2.5 watts, out of the box. I’m undecided whether to tweak it or leave it alone. At present, though I’m pretty happy with the upgrade to the A-99 antenna.

[Gunner357]

I put up a Solarcon A-99 yesterday. Mounted it at the top of a 20’ steel pole, running a ground wire from the ‘U’ bolts at the base of the antenna, to a self-tapping screw in the top of the steel pole and then down the pole to an 8’ copper-clad rod in the ground. My SWR is now essentially flat from channel 1 to 40. There’s no sign of the problem I was having when touching the mic or radio. I did have to drop the RF sensitivity down to “local” because there was so much skip and static, (I think some neighbors are still running generators following the storm that came through).

I’m anxious to start making contacts on side band now and would hope to enjoy some improved reach over the previous antenna. D/M output of the radio running AM is only about 2.5 watts, out of the box. I’m undecided whether to tweak it or leave it alone. At present, though I’m pretty happy with the upgrade to the A-99 antenna.

Please keep me informed on your A99 Im in the market for a new antenna was considering the A99 or The Imax 2000