More Radio Noise

[Screw]

Screw-In

Ok. I still have alot of radio noise and according to my hanger buddy, a serious humm when transmitting.

Equiptment:

Sporty's JD-200 Nav comm radio. 8 AA batteries
Comtronics helmet with ear phones and mic.
Comtronics patch cord
Comtronics intercom. One 9 volt battery.

Helmet worked fine while training with Steve, but then again, I never transmitted on his radio, I was just comunicating with Steve via intercom.
When I transitioned to "DaScrew-Driver" I had the radio strapped to my leg usings it's own battery and my helmet. I was getting alot of RF interferance from my engine. The noise would increase in pulse with the increase of engine RPM.

I replaced the ground wire with shielded ground wire and all instruments are wired with shielded wire. Someone told me that by using an intercom would cut out some of the noise, so I bought one. Mounted all to the aircraft and began testing.

Keep in mind that I have no power source other than the equiptments built in batteries.

First test was on the ground with the engine off and using the radio only. All worked well. Plugged in the helmet and the intercom and I got a serious hummmm when transmitting. I don't know whether this means I have a bad mike (Worked fine with Steve on the intercom) or I need to run the radio and intercom off another power source.

Started the engine and went flying. Powered up the radio and the intercom only to have the same noise as before increasing and decreasing with engine RPM.

I don't have a clue what to do, but as long as I have no radio, I'm limited to where I can fly. Can anyone help?

Screw-Out

[KenSandyEggo]

I've posted this several times (like a million), but here goes again. On some radios with a plugged in headset, when you key the mic, the mic in the radio and the headset mic both open simultaneously. The radio mic picks up wind, engine and every other noise. Take the cover off and snip one of the wires on the built in mic of the radio. A similar problem drove me nuts for quite awhile (about 42 years, I think), but snipping the built in mic wire solved it and the hand-held worked great after that. If that doesn't solve your problem.........never mind.

[Chuck Irby]

Hey Screw, are you using resistor plugs in the VW? If not, add an R to the required plug number. It sure wouldn't hurt to try it.

PS, if nothing seems to help, email me for a guys name and # to call.

[Screw]

Screw-In

Thanks Ken, I do remember you making a post like that before. I just didn't remember it until I read it. Thanks.

Chuck, I don't think I have "R" plugs. I'm not sure if the noise is comming from the plugs, that big magnito, or the plug wires. But in any case, I got to find a way to stop it.

Screw-Out

[Chuck Irby]

Screw, it can't hurt to try the resistor plugs. What have you got to loose? Try em!

[Screw]

Screw-In

Ok, Ok, I'll try them. Yur right, I have nothing to lose but noise. Can you tell me how to gap new plugs? :D

BTW- I've cut one of the wires to the mic speaker on the hand held, and hopefully that'll get rid of the hummmmmm when I key up using the patch cord.

I couldn't tell if Ken was talking about the Mic switch or the microphone itself, and I took a guess and cut the microphone itself. I didn't mess with the side switch at all.

Screw-Out

[Udi]

John - What did you ground the wire sheathing to? Ungrounded sheathing does nothing. Since you don't have a battery, see if you can wire all the grounds to the engine block. Some people ground the wires to the airframe, but gyro airframes are not always electrically continuous (mine isn’t).

To test Ken's hypothesis, connect the helmet to the radio and transmit with your push button. Instead of talking into the helmet mic, talk into the radio mic. If you can hear yourself than Ken is right. But I don't think this is the problem. The new radios disconnect the built in mics when you plug in the external mic.

I agree with Chuck’s advice to use resistor plugs.

Udi

[Udi]

Sorry. I was too late to tell you not to cut the internal mic... Do you get the hummm with and without the intercom?

[KenSandyEggo]

John, cut the internal mic wire, not the speaker wire. It's very small and usually tucked in a corner somewhere. You can always solder it back if that's not the problem. Wait....I'm not sure what you cut. First you said speaker and then mic. Udi's test sounds correct also. Speak into the handheld mic and see if you hear yourself through the headset. If you don't.....never mind again. If you do, snip a mic wire.......you already did that, I think. Just test it out with one mic wire cut. Where's Samuel Wartzel? Who turned out the lights? Scram gravy ain't wavy. Notary Sojac, Straight Arrow. :confused:

[Caribean_gyro]

comtronic helmet mic amplifier is in the intercom box. going straight to the radio you will loose gain. Now in the ground with engine reving at 4,000 let say RPM. standing still does the hum is transmited. Also is not the first time I have replace the battery even testing it good.

Let me know more data I have gyros's here flying with your set up with no problem. I will check with a friend of mine
ChuckP

[Caribean_gyro]

CORRECTION the cable adapter from comtronis carries the mic amplification. The box is just for intercome. Now in The RAD brand the box(intercom) carries the amplification. I prefer RAD for noise reduction. But I will check with my friend locally
ChuckP.

ps. I had a nosie on my lycoming and I add a alternator capacitor and it took a lot of incoming nosie

[chuter]

I have a comtronics headset/mic and just bought a patch cable to plug into a Icom A3. The mic didn't work, and I called CPS (where I bought the patch cable); they said they are just discovering that some Comtronics microphones need a different preamp in the patch cable, and those are on back order. :mad:

Sorry for getting off sort of off topic.

[steveb]

I had a very similar problem, and cured it last weekend by replacing the spark plug leads. The old ones were only 3 years / 100 hours old, but I tried it anyway and it worked.

I also spotted that the internal mike on the ICOM wasn't cutting out (thanks, Ken) because I could hear myself tapping on the mike when I was transmitting (my intercom comes with sidetone, ie you get to hear your own voice through the headset when you transmit).

For an ICOM the answer is to get it to a repair man and have the mike socket replaced.

[Screw]

Screw-In

What I did was cut one of the small wires that went into the microphone. I haven't tested it yet, but I think it will work. This keeps the microphone from picking up any more noises.

As a matter of fact, when I depress the PPT switch on the side of the radio, it still displays "TX" as if I'm transmitting, but of course with the microphone disabled, nothing is transmitted.

Hopefully this will get rid of the HUMMMMM when I transmitt with my helmet and patchcord.

I still need to get wqith GreatPlanes and see if they have any Resistor type plugs for this engine. Hiopefull, that'll get rid of the other noises.

Do you think I should try to replace the spark plug wires as well? Does anyone make "Resistor" type spark plug wires?

Screw-OUt