Radio noise problem

cgmg

Senior Member
Joined
Oct 30, 2003
Messages
1,149
Location
El Paso, IL.
Aircraft
Empty hangar right now, have owned and flown Air Command & RAF
Total Flight Time
375
I have an Icom A4 handheld I'm using with my Sigtronics intercom. I'm using battery power, not engine power.

The rubber whip antenna is mounted on the nose of the cabin with a right angle adapter at the cabin wall. The extension cable is 3' long, and both ends have a plastic cover on them.

Sitting on the ground, nothing running, I can hear Chicago ATC, and the pilots talking to them, over 100 miles away. Loud and clear, no static.

Engine running, I can barely tell what they're saying, due to the static. The volume level also has dropped by about 80%. Adjusting the intercom volume or the headset volume does nothing to increase the sound level.

The static only appears while there are transmissions. I have isolated the static cause to the fuel pumps. For some reason, the aux fuel pump creates more static than the main pump.

If I shut off the pumps, the engine will run about another five seconds. I did so during a couple of transmissions, and while the engine is still running, but the pump is off, the voice clarity returns.

One thing I forgot to do this morning while troubleshooting was put the whip antenna directly on the radio, bypassing the extension setup. Will do that tomorrow.

One thing I have sourced is an RG400 cable, if the popular response favors that. Don't remember where I bought my current radio cable, but since both ends are covered, I'm assuming(and you know what that means) it's not a cheap cable.

I'm not concerned about long range transmitting. I know that this radio was transmitting about 5 miles out when I used it on my AC, which is more than adequate for where I fly.

OK, all you radio technophobes, what's my problem?
 
Mike,

Spent about an hour reviewing the various threads about this problem.

Also asked Icom tech support. They tell me it's RF interference from my fuel pumps, and that I need to shield the pumps, or move the antenna.

OK, I know it's interference from the fuel pumps, I told them that much. And if the antenna is on the nose of my cabin, the only place farther away would be at the end of a rotor. Thanks, Icom.
 
Keep me posted, Mike.

Thanks
 
Thanks Doug.

I have sourced an RG400 cable for about $15, and spending $10 for two chokes is worth a try.

Just need to double-check my cable setup tomorrow, and will order both these items.
 
Ferrite chokes certainly eased my Icom problems. Not all but improved it drastically.
 
Mark:
Has this been a successful installation that quit working?
If so, then you likely have something that's failed, e.g. power regulator coax cable, etc.

Or is it a new installation that you are debugging?
If so, I'd try a couple of things before spending money.
- If your antenna is a rubber duckie, try temporarily moving it to attach directly to the radio. They are not intended to be remotely mounted via coax as they rely on the radio ground as the counterpoise and having an unbalanced lad as with coax causes problems.
- Your antenna (rubber duck or purpose built antenna) should be more vertical than horizontal in orientation. I use a rubber duckie with a 90 deg BNC elbow (Radio Shack, $7).
- If you are using ship power, try going to radio battery power only. Icoms are picky about the input power they receive.
- If you are indeed using a rubber antenna designed to be remotely mounted, replacing with RG400 is unlikely to help assuming that you have an undamaged 50-ohm coax now. Note that water can get into coax and cause invisible failures.
- IMO, efforts to shield equipment that might be generating man-made electrical noise (QRM) are rarely successful, especially on an aircraft where you don't want shielding to hide things from inspection. Instead, try to understand what in your system is encouraging the reception of the QRM.
- Someone mentioned on another thread that it is possible that the radio's internal microphone may not be disabled when using the push to talk (PTT). This is certainly worth exploring.
My intent is to get you to go to the simplest possible configuration and see how it works. Then start adding back the whistles and bells until you find the culprit. Just like debugging other systems.
Best of luck.
 
Can i get a link to this "ferrite choke" thingy please?
 
Joe, the link is in Doug's post, #6.

Larry,

Although the radio system is 2 years installed, I haven't had a need to use it until last Sunday. I checked it out with a buddy after the initial install, but the rubber duckie antenna was still on the radio.

The current setup has the rubber duckie antenna mounted vertically next to my landing light, utilizing an RG58 A/U cable to get back to the radio.

I'm using battery power.

Today I took the antenna and put it back on the radio in the cabin. I was using scan to try to find an active air channel, but wasn't able to pick one up with enough traffic to test with the engine running.

I don't have anyone close with another radio to check my transmit function with the current setup, but it did work with the antenna on the radio the initial time.

If putting the antenna back on the radio eliminates the static, I will then make longer patch cords for the radio, and get it higher in the cabin. That's about the cheapest way to improve my range once I prove the cable is the problem.
 
I had an A4 on my machine. Spent more time and money trying to get it to work than anything else on the machine. Solved all the problems by buying a different handheld.
Graeme
 
Allow me to sum up my experiences with Icom. I test flew a borrowed Vertex Standard with my David Clark headset and was successful with transmissions being readable. Not so with the Two different Icons I own. My request for advice from Icom was met with a reply that my gyro or antenna was the problem; no suggestion that there was an issue with their product engineering. Yet I found in their own online website tech support FAQ a posting on my very complaint with an answer suggesting ferrite beads which they sell to add to the headset cables. It provides part # and photo of how to install same. Bottom line, Icom products work fine until you connect a headset; then who knows what my result.
 
Update on my radio problem. Flew around for almost two hours today, and fiddled some more with my setup.

Here's what I found: If I turn the squelch off on my intercom, I can hear the transmissions just fine. Can't talk to my passenger, but the radio does clear up. It sounds like I'm transmitting ok, but couldn't get anyone to give me a radio check, so not sure about that part yet.

With the squelch up, if I put my finger over my headset mike, I can still hear the transmissions, although there is still some background noise. With my finger over my mic, I can still hear myself in the headset.

So I was wrong about the fuel pumps creating the noise problem. It's actually caused by my headset mic being too sensitive. Last year I talked with Lightspeed about hearing too much engine noise through my headset. What they told me was that my headsets were not really meant for open cabin aircraft. They did suggest I play with the mic gain, which I did. That made the engine noise acceptable, but did not eliminate it. Evidently it's still enough to create background noise for the radio.

I've ordered a couple of leather mic guards and will wait to see if that helps the issue. If not, I will have a nice set of Lightspeed headsets that I will be looking to sell, or trade for headsets more suitable to an open cabin.

One other note: Found out where I bought the antenna extender cable. It was in Aircraft Spruce, and it's advertised as having been tested to improve the whip antenna reception for Icom radios. It does do what they say, as I hooked it back up today, and was getting transmissions from farther away than with the antenna on the radio itself.

Will post the results of the leather mic cover trial. If anyone has a good way to reduce the gain if the leather mic cover trial doesn't pan out, let me know.
 
A Vertex solved all my handheld probrems. It works good with my helmet or headset Icom just would not work on my gyro at all. They are good on the ground however.
 
Mark, Your problem sounds exactly like the one I had. I have the same radio too.

I had so much static and garbage sounds on my Icom I couldn't make out anything at all. I might as well have not had a radio. I would even get a thumping sound like it was picking up the rotors or something.

Before you spend any bucks on stuff, try what I did.

A radio master kinda guy down at Herbert Smart (Steve McGowan Land) told be to take a 6" dia. metal sheet and put it between the ant. and the cable and all my noise would stop.

I did and it did.
I had some chimney flashing in my shop so cut it out and drilled a hole in the center, slid it over where the cable connects to the ant. and problem is totally solved. I have no static or unwanted sounds at all anymore.

See attached photo. Not the best photo but you can kinda see what I did. I'm going to rework it so it looks better soon.

I'm going flying in a little while and will take a better photo and post it if you want.
 

Attachments

  • metal plate.jpg
    metal plate.jpg
    73.4 KB · Views: 1
Last edited:
Phil,

Thanks for the suggestion. I don't have room with my mount for a 6" diameter shield, but I may be able to get at least a 4" one on.

My antenna is on the nose of my RAF, right next to my single landing light. Next time I'm up at the hangar, I'll take a gander under the dash, and see what I can get in there.
 
OK, installed Phil's aluminum shield on my radio cable, and had a friend help me test the system again.

With the intercom off, I was transmitting with a so-so level of understandability, but reception was good. Interestingly, nothing improved if I took the whip antenna off the extension, and hooked it directly into the radio. Switched out my A4 for another buddy's A22, and Mike said my transmit was quite a bit better. There was some noise with my transmit, but Mike said it was a 100% improvement over the A4 transmissions.

With the intercom on, even with the intercom gain adjustment set at maximum, I was barely understandable while transmitting. We started with the gain at the lowest setting, and gradually increased it to the maximum. No discernible difference in my transmissions, even with the A22 radio. I could hear Mike's transmissions ok while the intercom was on. I used my Sigtronics headset and my Lightspeed headset, no difference in send or receive conditions between the two, so don't think it's a headset issue.

Tomorrow I'm going up to double-check the wiring to see if one of them is crossed. If nothing is out of place there, I'm going to buy a portable intercom, and see if eliminating the electrical system wiring and power fixes my problem.

For anyone out there using a portable two place intercom, especially with an Icom radio, what are you using?
 
I am about to try my Zulu headset and A-24 Icom combo soon. I'll let you know how they paired up OK?
 
Top