Altronics headset and Microair TX issues

[Guest Escadrille]

I have a new Microair Rev Q M760 transceiver and 2 Altronics headsets. When the old headst (C9073) is on transmit it is fine. When the new (C9075) is on transmit a loud high pitched tone drowns out the transmission. Has anyone had this problem and found a solution?

 

 

[Guest Andys@coffs]

sounds like RF induced feedback. Probably suggestive of poor shielding in the new headset cables. My suggestion buy a clip on RF Ferrite from an electronics store and wind the cable at least once around before clipping it closed. The ferrite should be as close to the plug as possible. If taht doesnt solve it and you want to test if it is the issue wrap the whole thing in caterers tin foil ( a bit thicker and tougher than cheap a$$ black and white brand) and earth it by wraping bare coper wire around the foil at a sensible location and then taking that wire to earth (yeah rough as I know) let it lie on the seat or whatever and with the working headset on trigger the mic on the wrapped in foil headset. If no feedback heard then tthat suggests its a shielding problem and you need to get the RF out of the mic in line somehow.

 

Andy

 

 

[Guest Escadrille]

Ok thanks Andy I will try that and see how it goes.

 

Interesting that the new headset does it and the old one doesn't...

 

 

[Herm]

Ok thanks Andy I will try that and see how it goes.Interesting that the new headset does it and the old one doesn't...

Sorry to butt in on this one Andy, but I have fixed this problem a number of times on this radio. On the side of the Microair radio is a small adjusting pot. You will need a plastic trim pot screwdriver to turn it anticlockwisevabout a 1/4 of a turn. It is caused when a headset overdrives the input of the radio. I help many people at the airfield with radio installs and this has come up lots of times. I also had the problem with my Icom A200 doing the same thing... I would almost put money on this one, and if I am wrong I will shout Andy a lunch next time we catch up..

 

Mardy

 

 

[ruffasguts]

I have a new Microair Rev Q M760 transceiver and 2 Altronics headsets. When the old headst (C9073) is on transmit it is fine. When the new (C9075) is on transmit a loud high pitched tone drowns out the transmission. Has anyone had this problem and found a solution?

the flex boom altronics were prone to this problem on different radios the wire booms did not suffer the problem we sent many back to altronics in my time as an avionics tech

 

never found the answer

 

 

[Guest Andys@coffs]

Sorry to butt in on this one Andy, but I have fixed this problem a number of times on this radio. On the side of the Microair radio is a small adjusting pot. You will need a plastic trim pot screwdriver to turn it anticlockwisevabout a 1/4 of a turn. It is caused when a headset overdrives the input of the radio. I help many people at the airfield with radio installs and this has come up lots of times. I also had the problem with my Icom A200 doing the same thing... I would almost put money on this one, and if I am wrong I will shout Andy a lunch next time we catch up..Mardy

Yeah, try this first. Either way the squeal is indicative of a feedback loop wether by overdriving the mic (Mic gain that Mardy is talking about beuing too high for the mic in question) or by RF induction. If its pure mic gain thats the problem then the brand or specs on the electret mic may be different between the 2 headsets.

 

P.S no ham fised adjustments, the pots are small and fragile... (just mark the starting position on the outer case so that you can return it to where it was if you still have a problem.

 

 

[Guest Escadrille]

Thanks to everyone for their replies as it's much appreciated. I will try out all suggestions this afternoon....Stay tuned ..if you will pardon the pun..

 

 

[Guest Escadrille]

As per Andy of Coffs initial suggestion .. I had a ferrite choke handy so I wrapped the lead (of the recalcitrant head set) in a loop and clamped the choke on, plugged in and pressed to transmit... and hey presto no drowning tone.. thanks Andy.

 

I had no time to try it in the air this afternoon. I will have to leave that until the weekend but until then thanks for all the suggestions...

 

Much appreciated ,

 

Cheers,

 

Andy

 

 

[Herm]

As per Andy of Coffs initial suggestion .. I had a ferrite choke handy so I wrapped the lead (of the recalcitrant head set) in a loop and clamped the choke on, plugged in and pressed to transmit... and hey presto no drowning tone.. thanks Andy.I had no time to try it in the air this afternoon. I will have to leave that until the weekend but until then thanks for all the suggestions...

Much appreciated ,

 

Cheers,

 

Andy

I am really happy you got the problem sorted. I went back and read your original post and I jumped in on this one as you mentioned a tone rather than a squeal... Hummm now I own Andy a lunch... Bugger! Oh well he never drops in to see us at the airfield so I guess I wont have too? A lunch might draw him in

 

Good news on the Radio as there is nothing worse than noise in the ears..

 

Mardy

 

 

[Guest Andys@coffs]

Mardy

 

Your option was just as valid as mine and may well have solved the same problem. Reduced Mic gain may well have prevented the feedback loop from self sustaining.

 

Mine had the advatge, already having the ferrite, of being a 30 second try without removing the radio from the panel.......

 

You owing me lunch.......I dont think so, Nonetheless I think I'm over in a week or so and I definately want to catch up with you Pete and Rob and check out your beast and get the low down on how you achieved the aviation bargain of the year!! I might laso hit rob up for a circuit or 2 of the foxbat....

 

Andy

 

 

[geoffreywh]

I had exactly the same problem 4 years ago, my solution was to put the Altronics in the shed and get David Clark's from the US. problem goes away...........

 

 

[Guest Escadrille]

Crikey Geoff... You are on to me!

 

Hopefully the final solution....

 

Andy

 

 

[bones]

Yep some head sets just dont work together, sometimes a expensive set dont work as good and or clear as a $150 set, it the dark art.

 

Ok how is this for a problem from far LEEEFFFTTT field.

 

Got a 760/uhf combo, now this was working perfectly in old A/C, when i removed them when i sold it, so i mounted it all in today, all seemed good after a quick test, so decided to take it for a fly to air test, after about 6 secs of transmitting the VHF turns off, WTF, turn it off and back on try it again same thing it shuts down. hmmm so i landed got multimeter(MM) out thinking i got a bad power drop causing it to shut down.

 

12.5v going to VHF, press PPT and the MM now reads 23v, WTF, thinking my MM is shagged, i go over and borrow a freshly calibrated MM off the Lame next door, and it tells me the same thing, press PPT goes to 23-24v.

 

on the UHF side it is normal about 12.5v, press PPT it drops to about 12.1v so it is something to do with the VHF.

 

This was with the motor not running either.

 

Rang Microair and you could hear the cogs turning, never heard of it before, nd swears there is nothing inside the radio that could double the voltage if it was playing up.

 

So any ideas??????? how the hell is it doubling the voltage, i should hook it up as a alternator i think :)

 

 

[frank marriott]

Bones

 

That is a strange one. I would first be checking you have good common earth points. Other then that it doesn't make sence to me either.

 

 

[goodcom]

I've had 2 Altronics headsets giving the exact same problem. Its in the head set them selves. The problem is not there with other headsets (tried david Clark, Bose, Lightspeed, and a couple of others) Have tried ferrites, caps, changing lead lenghts, earthing, isolation transformers, isolating and changing earths (all in conjunction with a RF test set). They all changed the amount of RF feed back thru the Altronics headset, some better, some worse, but none never fully fixed the high pitched tone on TX. It was definitely RF induced feedback (as tested on the testset and using various RF power levels and loads). The Altronic headsets are now like Geoff's, sitting under the bench in the hanger.

 

James

 

 

[bones]

Well this has got me absolutely stumped now, i have run new wires directly to the battery tried different aerials and removed possible cause from the dash, and now the bl**dy voltage spikes are going to 33-35 volts how and WTF is going on is beyound me, so tomorrow i am taking the whole lot out of the AC and going to try it all on the bench,all else fails its all going back to Microair to see if they can work it out.

 

 

[techie49]

Hi Bones,

 

Are you using an analogue MM or a digital?

 

If it's a digital it may not be giving a true reading. I'd bet your aerial is faulty and it's reflected RF which can get into the MM. Try an analogue MM first then get a SWR meter on your aerial lead if necessary.

 

Paul

 

 

[frank marriott]

Yes, it has got to be recterfied RF

 

 

[Kyle Communications]

digital multimeter is picking up the RF...best to use a older analogue meter the one with the moving needle. Your issue will be either a bad joint or fuse holder etc in the wiring harness or obviously a issue inside the radio...if the volts are stable on TX then its the radio more than likely.

 

 

[billwoodmason]

I have a problem with my Microair radio where my transmissions are unreadable ( breaking down). Microair say it is possibly mike volume and or side tone volume but first I should get a SWR test done to check the aerial. So my question is where in Victoria can I get a SWR meter or SWR test done?. Any help much appreciated.

 

 

[techie49]

Hi Bill (?),

 

I don't think you need to rush off and get someone with an SWR meter. Ask yourself some questions:

 

a) Has this problem suddenly developed?

 

b) Have I altered anything on the aircraft concerned or has anything been added around the antenna?

 

c) Have I changed the headset?

 

If the problem has suddenly developed and there's nothing to account for it, check the connector on the end of the coax at the radio end. If it's a crimped connector, is it properly connected to the braid of the coax? Pull the cable gently to see if the connector comes adrift. If all is well, check the antenna end of the cable. Again if there's a connector, check as before. If all's well get a multimeter and possibly with a friend, check the cable between inner and outer, if you can disconnect it from the antenna. It should measure no continuity , i.e. A resistance greater than 1 Megohm. Check the continuity of the inner conductor and of the outer braid. Both should be a few Ohms depending on the length. If all this is OK, connect the antenna cable to the radio and antenna.

 

If the answers to your questions don't give you a clue then perhaps it may be worth a test of the antenna, but problems such as this develop due to a cause. If all your investigations prove nothing, I'd suggest if possible connecting a borrowed handheld radio to the antenna if possible. Check transmission and reception from that and again it should give you a pointer to the problem.

 

You've not said what aircraft this is happening on. Is it a rag and tube job, composite or metal? Also what type of antenna is it? Is it a whip type or a dipole, perhaps on a rag and tube. These can all have a bearing on the problem. Hope this long reply gives you some help or clues.

 

Paul

 

 

[billwoodmason]

Thanks Paul, the aircraft is my J230 pictured in my avatar at left. As to your suggestions I intend to do all that you have mentioned tomorrow. When the radio was faulty 18 months ago with another problem ( warbled speech) I checked the continuity etc of the aerial and all was OK and finally sent the radio to Microair for repair after swapping it out to prove where the fault lay. This time the fault is described as "speach breaking" as in being over modulated or similar. If it proves to be a connector it will be an easy fix.

 

 

[techie49]

Hi Bill,

 

Must admit from your description it sounds like the radio again. If you haven't changed the headset especially, it's unlikely it's RF feedback. You sound like you're on top of it. Post what you find though. It could help someone else.

 

Regards,

 

Paul