Noisy radio advice

[Mazda]

My aircraft had an old Narco Com11A which had occasional problems at towered airports - the other aircraft could hear the radio but sometimes the controller couldn't. So I had the radio tested and it was moving slightly off frequency. The tower receivers are apparently a very narrow band which explains why the controllers were the only ones that couldn't hear! It was time to upgrade.

 

I bought a nice shiny new TSOd ICOM A-200. While receiving transmissions the new radio is as clear as anything but while monitoring the frequency there is quite a lot of background noise. It sounds like it needs a squelch adjustment but the squelch on this radio is an automatic type. The book says to pull out the knob, set the audio volume, then push in. There doesn't seem a way to adjust the squelch itself.

 

The aircraft has no intercom but I've tried going through a portable intercom with a squelch control and the noise seems worse.

 

Has anyone had a similar problem? Is there a way of adjusting the squelch or could the radio be faulty? Could it be something in the electrical system of the aircraft making noise? (The generator perhaps?)

 

 

[Guest brentc]

There's a screw on the side of the A-200 for squelch adjustment. You may also be hearing the non-vox intercom. These units are often paired with a VOX intercom. If the squelch was 'open' as such, then there would be no noticeable difference when pulling out the volume knob.

 

 

[Guest ozzie]

Are you using you old coax and aerial? if so may be time to check al the components for corrosion ect. sounds like a a shielding or arial location problem.

 

ozzie

 

 

[PaulN]

Just a couple of thoughts Mazda.

 

1. Ian had comms problems in his ex CTsw recently which proved allusive until someone put him onto a very simple fix. Over to you Ian ...

 

2. Do you have a good earth strap on your engine mount frame as well as the engine block? I've heard that if this is missing our inefficient you can get radio noise.

 

Paul

 

 

[Mazda]

Thanks all.

 

Brent when the volume knob is pulled out there is no difference in the squelch sound.

 

 

[Guest Nelson Smith]

Hi Mazda,

 

The squelch adj. is on the top of the radio,along with mic gain and side tone.To adj.any of these the radio needs to be out of the cradle.From memory to reduce the squ cut in the tiny trim pot needs to be turned CW.A very small screwdriver is required and just the slightest movement on the trimpot is necessary.

 

Nelson

 

 

[Admin]

The problem in the CT came down to simply the BNC connector - see this thread http://www.recreationalflying.com/forum/showthread.php?t=4449

 

It took a radio man months to try and find the problem - even replaced the radio until JetBoy here made the BNC suggestion

 

 

[Guest brentc]

Thanks all. ... when the volume knob is pulled out there is no difference in the squelch sound.

Problem solved by the sounds of it. A small squelch adjustment based on Nelsons post above should solve things for you.

 

 

[Mazda]

Thanks very much everyone! I knew people on here would know! I'll let you know how it goes when I've made the adjustment.

 

 

[Knighty]

I had the same problem with the Icom A 200 in my Quicksilver, NEW COAX, NEW BNC's and NEW GROUND (6mm) wires starting from the battery along the frame right up to the motor. I wish this forum was about when I was working on my radios, would have saved a lot of colourful words coming from the workshop and hanger!!!

 

Good luck

 

Knighty

 

PS, I tried the squelch on the trimpot but that was not the problem, the radio is tested and set at the factory so it should be right or one would assume anyhow.

 

 

[Guest Perry]

Mazda,

 

The fixes above are all fundamental when considering comms - noise from all quarters needs to be suppressed and connectors are the biggest culprit. I have found, however, with recent installations, another substantial source of RF noise that requires careful thought. Your trusty GPS has now become a noise generator and the newer mob of GPS are particularly noisy - for example the Garmin 296.

 

I have effected many installations of radios and intercoms to find that the resonant noise generated through the GPS and VHF Antenna is significant. The quickest fix is to place the VHF antenna as far from the GPS Antenna/unit as possible - this is not always practical.

 

So far the results I have been able to acheive have been quite unexpected - I have had to trim the output of the Icoms and Vertex units to less than 1Watt for a range of over 100NM receive and transmit. Clarity of comms has certainly improved.

 

Furthermore, I have found a significant number of issues related to the quality of the DC supply afforded to the radio by the aircraft electrical system. Without doubt most supplies are incredibly noisy and these can affect comms quite significantly. My first advice to all is to possibly run the comms independent of the aircraft supply on a stand-alone battery. This is not always practical and hence one should spare no expense on purchasing a self-contained active noise filter setup for your comms.

 

I hope this helps further?

 

Regards

 

Perry

 

 

[Mazda]

Thanks Perry, but the aircraft does not have a GPS.

 

It only has an ADF which has just been serviced and the radio noise is no different with the ADF on or off. The ADF doesn't even have a proper external antenna as it is just a bit of wire in the back of the canopy.

 

The noise is still there. The radio is nice and clear during transmissions but the background noise when monitoring is unbearable.

 

Maybe I shouldn't have spent the $2,000+ to replace the radio and just stuck with the old out of tune Narco.

 

 

[Guest brentc]

Mazda, how did you go with adjusting the squelch? Something isn't right if it's still not working! Warranty?

 

 

[Guest Nelson Smith]

A good check if squelch is a problem is to position aircraft on the ground where the radio will receive then switch off engine. switch radio on.If radio is still full of shooshing then it is undoubtably the squelch adjustment.If the shooshing stops, then one could assume it is coming from the regulator/alternator.Please post an update.

 

Nelson

 

 

[Mazda]

Thanks all. I haven't tried the radio after shutting down the engine but it is quite clear before the engine starts. It even seemed OK on my first taxi after adjusting the squelch but it seemed noisier after run ups. Why would that happen?

 

I'm flying tomorrow so I'll see how it goes then.

 

 

[Knighty]

Also in addition to my last post a fellow by the name of Clauss Grimm in Qld makes an alternative regulator/rectifier for Jabiru and Rotax, he has sorted out power spikes and electrical noise generated by the stator. FANTASTIC invention and has worked well in my plane for 350 hours without a problem. You should look at http://www.powermate.com.au/prod03why%20powermate.htm

 

Cheers

 

Knighty

 

 

[slartibartfast]

I have a Powermate in mine, and I still have terrible engine noise on the radio.

 

I am going to try someone's suggestion of running the radio off a separate battery. If there's no noise then, is it probably being induced in the wiring and I'll try relocating the mag switch wires away from all the other wires to the panel.

 

Everything is new in mine, so it should be something simple.

 

</end optimist mode>

 

 

[Guest brentc]

If it's a noisy engine (electrically speaking) it may still affect the radio even if it is on a battery. I tested this recently when another local pilot with Sonerai and VW engine parked really close to my aerial on the rear of my aircraft and it upset my radio quite badly, moreso than my own engine.

 

 

[Guest Perry]

Folks,

 

I am using an Airmagic Power Box Active filter - about the size of an oversize matchbox and the results have been fantastic. So far I have found little that will compare with this little box when it comes to filtering noise. I first tried it on an Xcom in a trike and it had excellent results restoring audible comms - I was not aware how much dirt made its way into your headset.

 

I have just finished installing the first Airmagic Chatterbox ANR Intercom on a Microair in a trike with a Rotax 912S motor - what a difference, crisp 5/5 comms for 100NM with the transceiver turned down to 1.5Watts transmit - and thats without a visor in the open!! I am sure this will make open cockpits and Jabirus a quiet place when it comes to comms...

 

Regards

 

Perry

 

 

[Mazda]

Well, I flew today and the radio noise was terrible. My pax kept taking her headset off to see if it was quieter! That gives you an idea of the level of noise. At one point I turned the volume right down but it was still noisy. On the return trip once I was clear of any airports/airspace I couldn't stand it any more and turned the radio off completely. I turned it on again as I got close to my destination.

 

Perhaps I do need a filter. Is anyone flying anything with a generator? I might need to find some sort of condensor/filter to go across the generator. Perry do you have any information on the Airmagic one?

 

 

[Guest Baphomet]

Perry,

 

Can you give us some dealer/web? contact details for the Airmagic product

 

 

[vk3auu]

Mazda, it sounds like your squelch is open all the time.

 

I had a similar problem with a noisy switch mode power supply. The set was OK running off its own battery, but with the power adapter plugged into the cigarette lighter, all sorts of crap got into the receiver via the antenna, which at the time was just the rubber ducky mounted to the set. The cure was to place an external antenna half way back along the fuselage.

 

David

 

 

[Mazda]

Thanks David. This one is panel mounted with an external antenna.

 

I might have to pull it out and re-adjust the squelch again this weekend. The weather looks pretty dismal so I might not be able to test it in flight.

 

 

[Mazda]

It is fixed!

 

I met with the avionics guy this morning as I'd arranged to take him for a fly. No need, the noise was obvious on the ground. He tried with the generator off, the noise was still there. Definitely not the generator. Tried magnetos, tried different power settings. Then he borrowed another Icom radio and tried that. The noise was still there.

 

A few things were done to resolve the problem. Yes, the squelch wasn't set correctly. From the factory it had no squelch setting at all and I don't think this was correctly set on installation. An adjustment was made after fitting but this was not sufficient, so it was re-adjusted today.

 

The antenna was also removed, cleaned and re-earthed. The radio itself was also re-earthed to the starter relay on the firewall.

 

I took it for a fly today and it is great. Not perfect, probably 9 out of 10. Considering the age of the wiring and the fact that there is no panel mounted aircraft intercom, that is a great result. It was well worth the effort.

 

Thanks everyone for all your advice. I thought you'd like to know what happened.

 

 

[Kev]

I first tried it on an Xcom in a trike and it had excellent results restoring audible comms

Perry,

I am currently running an Xcom with Lynx comms and a 912S engine. I have the required (by Xcom) 22,000 mf capacitor on the radio power supply, and a locally purchased noise suppression filter on the power supply to the Lynx and am suffering with noise on reception. Apparently my transmissions are clear.

 

On the ground and with engine at idle, reception is clear.

 

Do you think the Airmagic power box would help, and would I be better connecting it to the radio or comms?

 

Any help appreciated.

 

Safe flying

 

Kev