Engine noise on VOR radios

stevenhmiller

stevenhmiller

Pre-takeoff checklist
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Steve's Archer
I have a King KX155 radio coupled with a King KI209. I also have a Garmin GNS480 coupled with an Aspen Evolution 1000. When sitting on the ground without the engine running, I tune in a VOR frequency on both units (obviously I won't get anything) and listen to the frequencies. They are fairly quiet, with low hiss. When in the air and I tune in a VOR frequency on both units and listen for the morse code, I hear a lot of noise, which sounds like it may be engine noise. I have to be fairly close to the VOR to hear the morse code over all the noise on the frequency. Also, I need to be fairly close, about 20 miles or closer for the CDI to pick up.

Anyone have an idea if this is a bad filter? And if so, which one and where might I find it in my plane?

Also, anything else I might do to narrow the issue down, short of bringing it to the avionics shop (a good 1 hour flight, a day off from work, and sucking my wallet dry) which I'm trying to avoid for now, would be greatly appreciated!

Thanks!
 

All VOR frequencies, some, only a few? Any noise on the COM at all like this? Happens identically on both systems (I think you said yes)? I have no idea where you are, but is there a VOR ground station near an airport near you? Or a VOT? Happens on the localizer ident also?

Jim
 
It's prolly a bad ground....


(ducking and running really fast around a corner to hide from Jim):D
 
weirdjim said:
All VOR frequencies, some, only a few? Any noise on the COM at all like this? Happens identically on both systems (I think you said yes)? I have no idea where you are, but is there a VOR ground station near an airport near you? Or a VOT? Happens on the localizer ident also?

Jim
Click to expand...

Yes, all VOR frequencies. Com is fine, just the VOR. Yes, both the KX155 and GNS480 are full of noise.

I'm just north of Tampa, FL. St. Pete has a VOR test spot.
 
Clark1961 said:
It's prolly a bad ground....


(ducking and running really fast around a corner to hide from Jim):D
Click to expand...

Since the airplane resides on the east coast of Florida, I **might** agree with you, but I'm betting (until I get more information) on a salt corrosion problem in the VOR/LOC antenna connections.

Jim
 
stevenhmiller said:
Yes, all VOR frequencies. Com is fine, just the VOR. Yes, both the KX155 and GNS480 are full of noise.

I'm just north of Tampa, FL. St. Pete has a VOR test spot.
Click to expand...

Where the airplane resides, is there a place on the airport where you get even a wiggle of a VOR signal? Just enough to quiet the background hiss down just a little?

That's the best way, but perhaps the hiss itself may be enough. Engine on, engine off no difference. Takes two people and a ladder. One sits in the airplane tuned to the weak signal or the hiss, either one. The other one wiggles everything from the VOR antenna elements on the vertical fin to the coax coming down the fin (there is generally a BNC fitting right at the fin root where it attaches to the fuselage) past that connector and wiggle every inch of it right to where it splits into two parts near the firewall. My best bet is that you will find a corroded connector somewhere along that line.

You can replace the connector pair (a pain in the labonza) or take some good contact cleaner and clean the corrosion off of both the body AND the center pin(s). The best stuff for that used to be Radio Shack COLOR TV TUNER cleaner but I haven't seen a can of that stuff in years. WD-40 is OK, but dunk the cleaned connector in 95% isopropyl alcohol (or 190 proof corn likker like Everclear. Use 151 rum if you must but the voices will all have a Jamaican accent from then on) and let it dry before you mate it back together.

Jim
 
Last edited:
weirdjim said:
Since the airplane resides on the east coast of Florida, I **might** agree with you, but I'm betting (until I get more information) on a salt corrosion problem in the VOR/LOC antenna connections.

Jim
Click to expand...
West coast of Florida.
 
No, not on an airport that can get the VOR on the ground. Tomorrow, I'll listen to it with the engine off, then start it and see for sure that I get the loud chatter.

I looked in the tail section throught the hatch and can see some cables, but am not sure what is what. Also, I dont think I can climb back there without making the plane tail heavy and tipping it or messing up the control wires. As for under the dash, impossible to see under there. A lot of wiring and the radios are toward the top, out of reach.
 
stevenhmiller said:
No, not on an airport that can get the VOR on the ground. Tomorrow, I'll listen to it with the engine off, then start it and see for sure that I get the loud chatter.

Well, OK, I didn't know that the "chatter" could be heard with nothing but engine run. Do it at idle, and then high runup RPM and see if anywhere along the line it increases or decreases.

I looked in the tail section throught the hatch

More better we start using standard aviation nomenclature. Are you saying that you looked back into the tailcone through the aft bulkhead?

and can see some cables, but am not sure what is what.

You don't start in the tailcone. You start ON A LADDER (remember what I said in the first reply?) with a FRIEND (not yourself) and start wiggling parts. I believe that the aircraft has a fairing where the fin attaches to the fuselage. You need to remove that fairing to get to the coax that goes up to the catswhisker antenna on the top of the fin.

As to "what is what" if you don't know that antennas are connected with coaxial cable ("coax") to the radio then I'd suggest that you find somebody versed in electronics communication in your area and have them do the "wiggling".

Also, I dont think I can climb back there without making the plane tail heavy and tipping it or messing up the control wires.

You are correct. 5 gallon paint pails make a pretty nice tail stand. YOU don't climb back there. YOU are sitting in the front listening to the noises on the radio.

As for under the dash, impossible to see under there. A lot of wiring and the radios are toward the top, out of reach.

I take it you haven't done much work on your aircraft yourself? "Impossible" is not a word to be thrown around lightly. And bending yourself into a contortionist's pose is the price you pay for not taking it to a radio shop and have them trade you their knowledge for your pictures of old dead presidents.

It is NOT out of reach or somebody would never have been able to put them in there in the first place. But it seems to me that getting yourself greasy and dirty isn't on your list of things to do.

And there is no magic filter going to solve your problem.

Jim
Click to expand...
......
 
"Well, OK, I didn't know that the "chatter" could be heard with nothing but engine run. Do it at idle, and then high runup RPM and see if anywhere along the line it increases or decreases.

I looked in the tail section throught the hatch

More better we start using standard aviation nomenclature. Are you saying that you looked back into the tailcone through the aft bulkhead?

and can see some cables, but am not sure what is what.

You don't start in the tailcone. You start ON A LADDER (remember what I said in the first reply?) with a FRIEND (not yourself) and start wiggling parts. I believe that the aircraft has a fairing where the fin attaches to the fuselage. You need to remove that fairing to get to the coax that goes up to the catswhisker antenna on the top of the fin.

As to "what is what" if you don't know that antennas are connected with coaxial cable ("coax") to the radio then I'd suggest that you find somebody versed in electronics communication in your area and have them do the "wiggling".

Also, I dont think I can climb back there without making the plane tail heavy and tipping it or messing up the control wires.

You are correct. 5 gallon paint pails make a pretty nice tail stand. YOU don't climb back there. YOU are sitting in the front listening to the noises on the radio.

As for under the dash, impossible to see under there. A lot of wiring and the radios are toward the top, out of reach.

I take it you haven't done much work on your aircraft yourself? "Impossible" is not a word to be thrown around lightly. And bending yourself into a contortionist's pose is the price you pay for not taking it to a radio shop and have them trade you their knowledge for your pictures of old dead presidents.

It is NOT out of reach or somebody would never have been able to put them in there in the first place. But it seems to me that getting yourself greasy and dirty isn't on your list of things to do.

And there is no magic filter going to solve your problem.

Jim"

Directions? We don't need no stinkin' directions. More fun to use the shotgun approach. :mad2:
 
I'm very mechanical. Electronics are another story. As for the terminology, sorry. First airplane and one month away from my PPL.

Anyway, I need to change what I stated above. It's noise whether the engine is running or not. Here are the steps I've taken inside the cockpit.

I'm just going to outline the steps on the King radios. The same results occur for the Garmin GNS 480.

I have a KMA 24, a KX 155. I leave the identify switch pushed in. I turn on the speaker for the NAV2 on the KMA 24. There is a lot of static noise. I pull out the ident switch on the KX 155 with the same results, no change. Same results with the engine running.

Looks like I need to bring it into an avionics shop. This is beyond me.
 
stevenhmiller said:
I'm very mechanical. Electronics are another story. As for the terminology, sorry. First airplane and one month away from my PPL.

Anyway, I need to change what I stated above. It's noise whether the engine is running or not. Here are the steps I've taken inside the cockpit.

I'm just going to outline the steps on the King radios. The same results occur for the Garmin GNS 480.

I have a KMA 24, a KX 155. I leave the identify switch pushed in. I turn on the speaker for the NAV2 on the KMA 24. There is a lot of static noise. I pull out the ident switch on the KX 155 with the same results, no change. Same results with the engine running.
Click to expand...

Yesterday you said this:

I have a King KX155 radio coupled with a King KI209. I also have a Garmin GNS480 coupled with an Aspen Evolution 1000. When sitting on the ground without the engine running, I tune in a VOR frequency on both units (obviously I won't get anything) and listen to the frequencies. They are fairly quiet, with low hiss. When in the air and I tune in a VOR frequency on both units and listen for the morse code, I hear a lot of noise, which sounds like it may be engine noise. I have to be fairly close to the VOR to hear the morse code over all the noise on the frequency. Also, I need to be fairly close, about 20 miles or closer for the CDI to pick up.

​
And today you say you can get the noise on the ground with or without the engine running. Can't help you if we get different stories about what is happening less than 24 hours apart.

Jim
 
What I wrote is the latest. Sorry if I wasted your time. As stated, first plane and working on my PPL. Read between the lines. Newbie with the equipment and still learning how to use it.
 
stevenhmiller said:
What I wrote is the latest. Sorry if I wasted your time. As stated, first plane and working on my PPL. Read between the lines. Newbie with the equipment and still learning how to use it.
Click to expand...

No problem. Understand when you say "what I wrote above" it could refer to something in this post. Since a lot of us have the option set to "latest on top" that didn't make much sense since this WAS on top. Now I understand.

Best wishes on your upcoming checkride.

Jim
 
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