Icom ic-a200 transmit squealing help please

[Herm]

powed up the electrics in my Jab today for the very first time... Yay! it all worked!... Anyway I have an IC-A200 radio with a PS Engineering Intercom.. I am also using Lightspeed headsets... All seems to be working fine but I am getting Squealing when I transmit.. I have had this in the past with Microair and found it to be the input gain that was too high causing overdrive on the input.. The Microair has a small screw in the side to turn this down. However I am not able to find anything on the Icon or the PS intercom... Has anyone else had this problem as what was the fix?

 

The only other thing I can think of is that I was transmitting inside a low hangar and that may have caused the problem due to reflection?????

 

Any ideas would be a great help

 

Regards

 

Mardy

 

 

[goodcom]

Hi Mardy,

 

This squeal can be from all sorts of issues. First, try a different set of headsets. This is the most common problem as not all headsets are compatiable with all intercoms. If this dosn't work, try putting a RF dummy load onto the ant socket of the radio. This will confirm whether it is a RF feed back problem or not. This is only a start, as there that many things that can be the fault from bad earth or power, audio settings, ant trouble, or even where wiring has been placed against one another. It going to be a slow process of elimination. Icom do have mic gain control, but I can't remember whether it was a scew adjustment or software adjustment for that model. James

 

 

[kaz3g]

powed up the electrics in my Jab today for the very first time... Yay! it all worked!... Anyway I have an IC-A200 radio with a PS Engineering Intercom.. I am also using Lightspeed headsets... All seems to be working fine but I am getting Squealing when I transmit.. I have had this in the past with Microair and found it to be the input gain that was too high causing overdrive on the input.. The Microair has a small screw in the side to turn this down. However I am not able to find anything on the Icon or the PS intercom... Has anyone else had this problem as what was the fix?The only other thing I can think of is that I was transmitting inside a low hangar and that may have caused the problem due to reflection?????

 

Any ideas would be a great help

 

Regards

 

Mardy

Hi Mardy

 

I have the same radio {Voxcom intercom} and same squeal using the pilot's jacks and intercom button. If I plug my headst into the pax jacks and transmit on that button, no problem. Tad annoying but it disappears if I turn the intercom off.

 

kaz

 

 

[Guernsey]

Mick Wright may be able to help.

 

 

[Denny Fiedler]

Had some trouble with my Lightspeed Zulu in a Gazelle. Could hear loud squealing when transmitting, another pilot had the same problem.

 

Putting 2 loops in the headset cord solved the problem, put one loop next to the plug and one near the headset, someone in a forum wrote

 

that shielding in some plastic airplanes is not sufficient and the loops will help because they are RF chokes.

 

 

[djpacro]

In the past I have had similar problems with some headsets. Cleaning the mic and phone plugs helped. Problem cured for my headset by fitting Split Ring Clip-on EMI Suppression Ferrite Core Cat No R5120 from Dick Smith.

 

I have become much more fussy about wiring done in my aeroplane since.

 

 

[sfGnome]

Had this problem suddenly occur last week in a Tecnam (eg metal body), just as we joined the circuit. Luckily there was no one else around because we couldn't transmit any more. Tested with both headsets individually (one Zulu, one basic type) in both sockets with no improvement. Wound the mic gain down (quite a lot) and problem resolved. Subsequent radio checks still showed the voice to be quite loud, so it possibly could have gone down even further.

 

Yep, it could be many things, but if you have a gain control then it's a pretty good place to start.

 

 

[Guest Andys@coffs]

As an ex RAAF Radtech I see this question reasonably regularly. Most times its RF feedback into the mic circuitry and shielding or putting ferrites in place will help, as DJPACRO has identified. The trick is to get the ferrite aas close to the connector as you can as the ferrite effectively prevents RF from propegating down the headset lead up until the ferrite, any cable after that, depending on the length, can introduce some more rf that will be on the wrong side of the ferrite. Of course, if the cable that runs from the headset jacks back to the radio has poor or no shielding then this ferrite idea is unlikely to work unless the ferrite is located at, or very close to the connector going into the radio.

 

In the same way that oils aint oils, not all shielded cable is as good as other shielded cable, if in doubt get a qualified radio tech still in the business (Im not) to source you good quality shielded cable....

 

If trying the ferrite thing get a few of them and try and loop the cable around the ferrite ends at least once, preferrably twice so that you get a couple of loops going through the ferrite. clamping straight onto the cable without a loop is significantly less effective. use a few of them.

 

If at all possible the previous advise to plug the radio RF output into an RF dummy load (shielded load that will dissipate the power but NOT radiate it) can be used to prove if the squeal is RF induced...My experience tells me it likely is, and I would also try different brands of headsets before pulling the panel forward to chase up the mic signal in leads (which in most installations will be 2 signal/earth returns to cover pilot and co-pilot positions.) dont just try one to see if that fixes it, it may work but may not so isnt definitive.... Seperate ferrites for the signal line and the earth line, one ferrite for both if wound on the same way will be ineffective.

 

Andy

 

 

[Herm]

Well thanks all for your advice... this may be helpfull to others... My first thoughts were based on the same problem I have seen in the past with Microair radios.. I thought it may be that the input to the radio was being overdriven by either the intercom or the headset... I looked up to see if I could adjust gain and sidetone on the A200 Icom.. I found that it did not have a software or menu setting to do this, however if you remove the radio from the tray their are adjusters.. You will find 3 stickers (little round foil ones) that cover some adjustment pots.. They are marked and so I went for the Mic Gain and turned it down 1/4 of a turn... Put the radio back into the tray and the problem was gone. Good solid transmit with good modulation and did not have to touch the sidetone... My thoughts were correct.. The Microair radio has and adjustment on the back side of the radio and have used it in the past on Trike radio installs... Glad that the simple solution was the fix as all the other suggestions were next on the list if this did not work.. Thanks Andy for your advice,, I was going to use my meter that I used when testing my Black Widow TT2000 antenna's as that has a dummy load as well as the normal reflection and power readings...

 

Good stall recovery

 

Mardy