Radio help please

I have a microair radio installed(no I'm not a fan of them either), my transmission is so garbled it cannot be understood, reception is excellent. I have tried 3 different headsets, both pilot and co pilot sides, bypassed installed coax on antenna, checked all connections and earth terminals to no avail. I have side tone and seperate intercom works fine, no sidetone when I transmit though which used to be there. I have connected another like radio which was working fine in another aircraft but this too has not fixed my problem.

To add to my frustration microair don't have any techs on site for quite a few months as they are focusing on another project, so much for the after sales service for those of us that have dished out a fair bit of money to purchase one of their products which they don't seem to want to know about now.

Any help from those knowledgeable techos out there would be very much appreciated, I am at a loss at this point.

Hi Biggles , give Mark Kyle a pm he is a whiz with radio stuff ,i am sure he would help out

Cheers gareth

One of our guys had the same problem. He was ready to throw it in the rubbish bin.

Jake Jansen happened to fly in to do work on a new installation.

Fixed in less than two minutes.

He commented Magic fingers.

PM him, he maybe helpful.

PHIL.

Four or five years ago I had a similar problem with mine ie (garbled transmissions), I sent it back to Microair for repair after I got a loaner radio from Jabiru to use while mine was away being fixed. There was a problem with a component "in the front end" of the radio which was a known failure with them at times. All good now.

Biggles:

If you've swapped ou the radio, headsets and antenna cable there is not much else.

This could be a simple case of too much mic gain. If there is a setting in the radio for mic gain, try adjusting that to see if it improves things. If you are using non-ANR headsets, you will get noisier transmissions than using ANR headsets. However, ANR headsets sometimes have powered mics which might overwhelm the input to the radio.

Also, you didn't mention if your aircraft has a separate intercom system. If it does, try adjusting the mic gain and output levels to the radio on that.

You listed several aircraft on your profile, but I'm guessing the Jab is the only one with a microair radio. Was the radio always this bad or has it just started? (Or have you just found out that you probably always were transmitting garbled?)

Another possibility is a poor ground connection to the radio. This will be a bit harder to check as you will have to dig into the wiring and visually inspect the wiring to the radio. I've forgotten how the Microair radios are connected, but I think it is with a computer style DB25 connector. That being the case, there will probably be 2 or more pins used for ground connections into the plug. They should ALL have good solid wires on them and the wires should be connected to the main aircraft ground bus bar or common grounding point. When airband radios are transmitting they draw more current than when receiving, so they need good solid power connections with plenty of current capability.

If my battery is low and I have turned on everything (I have a Dynon sky view as well), idling can cause my radio to be incoherent on transmit so I turn off the transponder and what ever I can or I guess which I haven't tried, rev the engine a bit.

Thanks for the replies, have pulled the panel out and checked for good earth and power connections, the radio I believe has worked fine in the past, in and out of CTA. This problem just started when I realized that I had no green light on receive and no squelch, hence the reason I put another radio in from another aircraft.

Thanks again for your replys now if someone could direct me on how to PM another member that would be awesome

Just on the good connection issue, I took the plug apart and all seemed ok, as each wire was heat shrinked I didn't remove this. Would it be fair to assume that as transmission takes more power and if a connection was only just, I would lose power to the set during transmission ?

Biggles, you need to call into a computer shop, and buy about 4 of I think they are ferrite resistors, basically they are the clamp around white magnet things you see on every computer lead, I had the same problem for ages, could not work it out, swapped about 4 radios, bigger ground plane ect ect.

All you need to do is put one of them on each lead, aerial, power , and any other wires in the area, they stop feed back into the radio that is basically all that is doing it. Well from my experience it was anyway.

Another thing it maybe I found once, make sure the aerial lead is not near any power sources, ie strobe wires, light wires, I had one radio worked perfectly until the light was turned on, went digging and the aerial wire was tied to the power wire once, shift it and fine then.

Biggles,

Probably easier to send you Jake Janens phone number.

He supplied it to a forum member with a radio problem so guess it is ok.

0412624723

Mention I gave it to you if you like. Nice guy with heaps of experience in avionics.

He will remember the incident at YLOX a few months ago with Chis' problem

Cheers.

Cheers for that Phil. Bones thanks but I have tried the ferrites, still no change. I will get the answer one day I'm sure.

Biggles,Probably easier to send you Jake Janens phone number.

He supplied it to a forum member with a radio problem so guess it is ok.

 

0412624723

 

Mention I gave it to you if you like. Nice guy with heaps of experience in avionics.

 

He will remember the incident at YLOX a few months ago with Chis' problem

 

Cheers.

I have a microair radio installed(no I'm not a fan of them either), my transmission is so garbled it cannot be understood, reception is excellent. I have tried 3 different headsets, both pilot and co pilot sides, bypassed installed coax on antenna, checked all connections and earth terminals to no avail. I have side tone and seperate intercom works fine, no sidetone when I transmit though which used to be there. I have connected another like radio which was working fine in another aircraft but this too has not fixed my problem.To add to my frustration microair don't have any techs on site for quite a few months as they are focusing on another project, so much for the after sales service for those of us that have dished out a fair bit of money to purchase one of their products which they don't seem to want to know about now.

Any help from those knowledgeable techos out there would be very much appreciated, I am at a loss at this point.

I have heard of a problem like yours when battery voltage is on the low side ie 12.0v - 12.3v or you have heaps of avionics draining battery power on a battery that is no longer up to par. Try swapping out your battery leaving unnessesary avionics of during testing. Having the same problem with two different radios would point to it being something else in the plane.

Just on the good connection issue, I took the plug apart and all seemed ok, as each wire was heat shrinked I didn't remove this. Would it be fair to assume that as transmission takes more power and if a connection was only just, I would lose power to the set during transmission ?

Nope, that would not be fair to assume. The reason being that radios sometime have multiple power and ground pins in the connector, for the purposes of carrying the extra current requirements during transmission. If one of the power or ground pins was broken or had strands broken, this reduces the current input capability, but wouldn't necessarily completely de-power the radio when you transmit.

Also, heat shrink can be useful stuff, but it can hide a lot of nasties too. If the pins are heat shrinked, I'm betting the connections are soldered rather than crimped. While you have the connector out, it might be a good time to re-do it with a crimped pin connector. Unfortunately, they are not as cheap nor as readily available as soldered connectors, and they require the used of specialist crimping tools.

Thanks again for all the advice, keep it coming I will eventually sort this thing out. Had a good yarn with Jake, appreciate he took the time, however without him being able to examine the aircraft I imagine difficult to diagnose. I have connected a fully charged battery pack to external jump point to rule out the voltage issue, no change. I have not changed out the multi pin plug that fits into the radio as CS suggested at this point, I have again checked them and they do feel secure, I imagine the crimping tool for this multi pin plug must be minute to fit between each pin.

It's back to the drawing board.

Cheers

Thanks again for all the advice, keep it coming I will eventually sort this thing out. Had a good yarn with Jake, appreciate he took the time, however without him being able to examine the aircraft I imagine difficult to diagnose. I have connected a fully charged battery pack to external jump point to rule out the voltage issue, no change. I have not changed out the multi pin plug that fits into the radio as CS suggested at this point, I have again checked them and they do feel secure, I imagine the crimping tool for this multi pin plug must be minute to fit between each pin.It's back to the drawing board.

Cheers

LOL, the crimper is not really tiny, but it's understandable that someone might guess that it is. The crimper crimps the pins on the wire before they are inserted into the plug. There is also a special plastic tool for removing the pins from the plug.

This is what the crimper looks like

It has 4 pins inside that close on the socket of the pin and secure the stripped wire end into the socket of the pin.

These are what the pins look like

Male and female pins

And this is what the connector looks like

And here's the pin removal tool

WARNING, the crimper is very expensive (around $300.00US) so it's best to borrow one or get someone to do the crimping for you.

Great info thanks. One other symptom is when I press the mic and not speak there is a hum coming into my headset, not the usual pre speak hollow sound??

Hi Biggles,

There's something no one has touched on. You mention hum in the headset. Is the aircraft antenna ok? I know you said you changed the coax to the antenna but it might be worth getting a SWR meter on the antenna. If for some reason it's poorly matched, you can get RF feeding back into the radio which can distort the audio. If you've changed the radio, it's obviously the installation at some point. Just a thought.......

Paul

Thanks Paul, one thing I haven't done is checked the SWR, due to not having a meter. Should have access to one next week all being well and that will be one more thing to check off the list. One of the drawbacks of living where I do I don't have easy access to technical people close by, hence I greatly appreciate the input here.

Cheers Danny

FWIW,

Those borrowing a known "good" radio should be aware that there could be a wiring, or other, issue in their aircraft causing a fault. If that is the case you may damage the 'borrowed' radio, IMO it's better to try the suspect radio in another aircraft first otherwise you may have to pay for 2 X repairs.

I had this issue, drove me nuts. Turned out in my case, the mic was overdriving the transmitter input. Some radios have a MIC GAIN control which is usually a screwdriver adjust potentiometer that you can access after pulling the radio out of the panel. My Icom radio has an AGC (automatic gain control) on the mic input so no joy there. I finally found the mic on my headset had a tiny gain adjust screw under the muff on the mic where you couldn't see it. I turned the gain on that all the way down and that fixed it. Later on, I replaced the ANR headset that came with the airplane with a David Clark passive headset..... wouldn't fly without it. Good luck with your problem!

I have a microair radio installed(no I'm not a fan of them either), my transmission is so garbled it cannot be understood, reception is excellent. I have tried 3 different headsets, both pilot and co pilot sides, bypassed installed coax on antenna, checked all connections and earth terminals to no avail. I have side tone and seperate intercom works fine, no sidetone when I transmit though which used to be there. I have connected another like radio which was working fine in another aircraft but this too has not fixed my problem.To add to my frustration microair don't have any techs on site for quite a few months as they are focusing on another project, so much for the after sales service for those of us that have dished out a fair bit of money to purchase one of their products which they don't seem to want to know about now.

Any help from those knowledgeable techos out there would be very much appreciated, I am at a loss at this point.

Since symptoms are the same with two radios, it all points to the aircraft side.

The most likely problem is RF feedback from the antenna into the mic. input during transmit. This is usually results from radiation from the outside of the coaxial cable during transmit The ferrite filters mentioned earlier are a good precautionary measure but do not address the cause which is usually the antenna and ground plane and particularly the quality of the electrical bonding between the two. An SWR check would rule out the antenna/ground plane (but probably rule it in) but it is easier to routinely remove the antenna and clean the connection to the ground plane.

Remember that the antenna mast is only half of the antenna. The ground plane is the other half and the connection between the two is extremely vulnerable to any added resistance due to even mild corrosion.

The other common problem area of vulnerability to RF feedback is the MIC input circuit and, in particular, the outer shield running from the headset to the inside of the radio via the MIC ground input (which is not the same as the other grounds such as power and should not be connected to any other grounds). In extreme cases it is therefore necessary to insulate the MIC jack mounting to achieve this and stepped plastic washers are available for the purpose.

Plastic and rag aeroplanes are particularly vulnerable to RF feedback.

Good luck!

Thanks again to all, another full day yesterday without result.

This is what I do know:

I connected base station aerial from hangar into aircraft radio no change, I have sidetone on intercom on borrowed radio but no sidetone on transmit, I connect original radio and have sidetone on intercom and sidetone when I transmit however nothing is being transmitted. This is the faulty radio that does not receive or transmit and needs to go back for repair. Very little voltage drop on transmit when measured. I am reluctant to adjust the mic gain on the borrowed radio, I am using pretty new DC headset but have tried two others as well. At least the issue is constant and not intermittent as this would add to my level of frustration at this point.