Radio interference

[frfly172]

Just recently I have been getting interference on my radios. Sounds like the squelch breaking. When listening to atis it comes in broken,untill I increase RPMs then I can hear it but there is a steady hum in the background. Interferes with transition also. Have a 430 and 530,can pick up the interference with my portable. Have changed the transmit button on the stick,tried isolTing the alternator,even changed the audio panel out to no avail. Any ideas or suggestions? Thanks Ron

 

[NoHeat]

Anything plugged into an accessory outlet? For example, a USB charger?

Did you try shedding various loads, while listening to your handheld?

 

[frfly172]

I have a fadec system,tried eliminating one mag at a time,also one power switch at a time unplugged the I pad power cord,all to no avail.

 

[Anticept]

Check ignition leads and make sure the ends are not fraying.

LED and flourescent systems can output a lot of noise on the aviation radio bands too as the ballasts go bad, so anything using these types of bulbs can throw off spurious emissions too.

To help isolate: take a piece of metal that is larger than the handheld antenna, and ground it to the airframe with an alligator clip. Now, run the plane and blank the handheld antenna like a shield, and move it around until you hear the noise decrease as much as possible. The source will be coming from the general direction if you draw a line from the antenna to a perpendicular angle of the metal plate. You might even have to run the ground to earth if it's real bad.

Symptoms sound like a bad voltage regulator, ignition system, or maybe a bad fadec system (i dont know much about the fadecs off hand). Basically something is putting off a lot of noise, and it's pretty characteristic of capacitors in a noise filtering circuit going bad, or ignition problems.

 

[weirdjim]

Just recently I have been getting interference on my radios. Sounds like the squelch breaking. When listening to atis it comes in broken,untill I increase RPMs then I can hear it but there is a steady hum in the background. Interferes with transition also. Have a 430 and 530,can pick up the interference with my portable. Have changed the transmit button on the stick,tried isolTing the alternator,even changed the audio panel out to no avail. Any ideas or suggestions? Thanks Ron

Slow up, slow up, slow up.

Let's get the problem description down a little better. You say you are getting "interference" on your radios. I'm presuming that you mean the 430 and 530 stack mount radios in the radio rack. And that you can hear the exact interference in a handheld not connected to the aircraft system in any way. So far so good?

The interference is "broken" at low RPM. I have absolutely no idea what "broken" means. A little better definition. And "hum" is generally considered a very low frequency audio, generally below 200 Hz. (120 Hz. "hum" is what you get from a radio plugged into the wall outlet when the power supply is poorly filtered.). So, is it truly hum, or whine, which is a frequency in the audio range 300-3000 Hz., sort of a muted screech. And does it change with engine rpm?

Unless your ISP charges by the word, give us a little more information and description of what is going on.

And why in the devil are you changing stuff in the airplane when your handheld is picking up the same interference?

Jim

 

[frfly172]

With the engine off and the radios on the atis is loud and clear.once you start the airplane both radios are full of stTic with the 530 showing transmit intermittently.as you raise RPM the atis becomes clearer,as at idle or low power the words are broken or not complete.

 

[Anticept]

Is the alternator running? If so, can you shut it down (pull the breaker or flip the switch, whatever). If the noise goes away, it's very likely the voltage regulator failing.

If the noise stays on, it's likely an ignition system throwing off RFI. You need to make sure the shielding on the harness, and for that matter the whole system, is being grounded properly. I am quite confident this is your issue since you pick up noise on a handheld (which, I assume, is NOT plugged in? Please test with the handheld completely isolated from the aircraft). It might be a bad spark plug, as there are resistors in them which greatly reduce radio interference and control spark plug wear. You could have a fadec system that is going bad, but I don't know enough about them, I'd say consider this the last check of your ignition system diagnostics, start with making sure the leads are grounded properly.

A third item to check, but very unlikely, is make sure all the grounds are secure in your avionics panel (again, this would not affect an isolated handheld).

 

[weirdjim]

With the engine off and the radios on the atis is loud and clear.once you start the airplane both radios are full of stTic with the 530 showing transmit intermittently.as you raise RPM the atis becomes clearer,as at idle or low power the words are broken or not complete.

And the same effect is noted on your handheld without the handheld being attached to ANYTHING in the airplane?

Jim

 

[biplanebob]

sounds like noise from the ignition system....... shielding on a bad spark plug lead ?

 

[frfly172]

Going out to the airport Monday will check the grounds and electric system,thanks for all the good info,will keep you all informed on progress Thanks Ron

 

[weirdjim]

Going out to the airport Monday will check the grounds and electric system,thanks for all the good info,will keep you all informed on progress

Don't bother. Jeezuz Murphy. Why ask for help if you aren't willing to take it?

Jim

 

[wilkersk]

And the same effect is noted on your handheld without the handheld being attached to ANYTHING in the airplane?

Jim

Don't bother. Jeezuz Murphy. Why ask for help if you aren't willing to take it?

Jim

Of all the guys on this board, Jim is for sure one guy I'd let help me with an avionics problem.

 

[Anticept]

Going out to the airport Monday will check the grounds and electric system,thanks for all the good info,will keep you all informed on progress Thanks Ron

As has been made a point here by many of us, it's very likely to be an ignition issue, which is easily picked up with an *isolated* handheld. It's very important that it not be connected to the aircraft in any way. I stated the voltage regulator bit because you didn't confirm that the handheld is isolated, and it's a super duper quick check while playing with the handheld, but I highly doubt this is your problem.

Don't bother with the grounds, that's a last resort.

 

[frfly172]

Don't bother. Jeezuz Murphy. Why ask for help if you aren't willing to take it?

Jim

I thought I already posted that the hand held was no attached to any device in the aircraft,sorry you are offended.

 

[weirdjim]

I thought I already posted that the hand held was no attached to any device in the aircraft,sorry you are offended.

Offended has nothing to do with it. Read back and you had SEVERAL questions asking whether or not the handheld was connected to the aircraft in any way. None of those questions got answered.

If you want good advice, answer good questions, even if it means you answer them several times. Sometimes the way we ask the question leads us down the correct path.

Now, please simply QUOTE this message and answer some simple questions. Yes or no is a perfectly good answer unless you see the need to elaborate.

1. Does the handheld have ANY physical connection to the aircraft. If we put you and your handheld in an isolation booth inside the cockpit would the setup remain the same?

2. So you are listening to your handheld on the ATIS. Everything is rosy until you start your engine. Turn EVERYTHING electrical in the airplane off ... radios, navs, lights, EVERYTHING. Is the ATIS still broken up? If not, turn electricals on one at a time until the handheld is broken up. Report which one made the handheld go bad.

3. If the handheld is still broken up in (2) with all the electricals off, what happens to the handheld audio when the engine revs up to, say, mag check speed?

4. If the handheld is still broken up or has interference after (3), then give the handheld to a friend and have them gradually walk away from your aircraft. How far away can they get before the ATIS is clear again?

​

Report back.

Jim

 

[frfly172]

Offended has nothing to do with it. Read back and you had SEVERAL questions asking whether or not the handheld was connected to the aircraft in any way. None of those questions got answered.

If you want good advice, answer good questions, even if it means you answer them several times. Sometimes the way we ask the question leads us down the correct path.

Now, please simply QUOTE this message and answer some simple questions. Yes or no is a perfectly good answer unless you see the need to elaborate.

1. Does the handheld have ANY physical connection to the aircraft. If we put you and your handheld in an isolation booth inside the cockpit would the setup remain the same?

2. So you are listening to your handheld on the ATIS. Everything is rosy until you start your engine. Turn EVERYTHING electrical in the airplane off ... radios, navs, lights, EVERYTHING. Is the ATIS still broken up? If not, turn electricals on one at a time until the handheld is broken up. Report which one made the handheld go bad.

3. If the handheld is still broken up in (2) with all the electricals off, what happens to the handheld audio when the engine revs up to, say, mag check speed?

4. If the handheld is still broken up or has interference after (3), then give the handheld to a friend and have them gradually walk away from your aircraft. How far away can they get before the ATIS is clear again?

​

Report back.

Jim

Point one the handheld has no connection to the aircraft.
Point two,I have isolated the alternator,also have switched off the mags one at a time also have shut down the mags and the power switches one at a time. The radios in the aircraft run without static,when the engine is off, when the engine is running at low rpm the radio comes in broken and partly readable,but gets more readable as you increase power.the handheld acts like the aircraft radio with engine running.
Will try your recommendation in 4 in the AM appreciate your help. Thanks Ron

 

[weirdjim]

Point one the handheld has no connection to the aircraft.
Point two,I have isolated the alternator,also have switched off the mags one at a time also have shut down the mags and the power switches one at a time. The radios in the aircraft run without static,when the engine is off, when the engine is running at low rpm the radio comes in broken and partly readable,but gets more readable as you increase power.the handheld acts like the aircraft radio with engine running.
Will try your recommendation in 4 in the AM appreciate your help. Thanks Ron

OK, sir, I mean no offense, but you don't seem to be able to follow simple step by step directions. I wish you the best of luck in finding your problem.

THanks,

Jim