Xcom troubles

I have an x-com 760. I have developed a problem. When my engine is off the radio works well. It transmits and receives well. With the engine on it transmits well, but does not receive weak signals well. When I listen to Awos at idle it is weak, but I can hear it. As I advance the rpm it breaks up and eventually I can not hear it at all. The ability to pick up signals diminishes with increases in rpm.

I have isolated the power source from the main battery, but that made no change. What else can I look for?

Any help is appreciated.

You did not mention your ignition set up. (Electronic, Mag, or both).

In any case, the first 3 things to isolate are:

alternator
left ignition
right ignition

Turn each off/on and determine which one is causing the RFI.

The other thing is you mention you "developed a problem". Does that mean it was working fine and just started doing it?

Sounds like you have a bad antenna connection to me. Please describe you're antenna wiring and the type/model of antenna you're using.

I'm a factory service rep for XCom, if you come to a dead end send it to me and I'd be happy to test the radio for you and install the latest firmware. This would be covered under your warranty.

Have you checked the filter cap?

Bob,
If it were the antenna connection wouldn't it affect the transmission even more than the receive?

The receiver's AGC will boost weak signals, but it becomes more difficult to do that if there's noise present in the signal, which is the case with the engine running.

There is also the possibility the radio could have been damaged by transmitting with no antenna, or from a bad antenna connection.

I'm just guessing here, but certainly I can test the radio with a service monitor to see if there's anything wrong with the radio.

Don't spend too much time on figuring it out before sending it back

I spent over a year off and on trying to get my radio to work with any 'range' to it. Replaced everything related but the internal software. Sometimes I thought it what I was doing was making a difference for the better. Finally I sent it back to Australia. After a Long wait, I got it back and believe me it now works so much better that I now know it never worked right to begin with. The difference is amazing. I don't know the component was they replaced which caused it to fail their bench test but I would not hesitate to put a handheld on to your existing system to test out the RF cable and antenna and if the handheld works fine, ship that sucker back to the factory and manage it's progress there.

I sent it in October and got it back in late Dec/early Jan.

Early Xcoms have had many known issues and some not widely acknowledged...... And I also know a brilliant electrical engineer who has been doing development work on the software for Xcom in recent times to improve a number of things.

Maybe a quick trip to Bob (see above) would help and yes..... Antennae are funny things!

DB

XCOM Problems Too

Sorry to say, but I have had the same problem. After sending the radio back to Michael in Australia, I eventually sent it to Great Planes Avionics in Tea, South Dakota that is an authorized XCOM repair shop (605) 498-1950. The radio checked out fine. The owner of the shop, Darrell, gave me the following to check out and correct if necessary.

1. Make sure to have a Comant antenna as it is the best antenna with this radio. (I have the C1-122 45 degree bent whip mounted on the belly of my RV4)
2. Make sure the antenna is installed correctly with a good ground (remove the cork gasket if necessary and rough up the mounting area on your fuselage to insure the ground).
3. Make sure the radio and transponder antenna wires are not touching each other and that they are at least 2" from each other.
4. The radio should have the "factory required" electrolytic capacitor (22,000 uF @ 25 Volts)
5. The radio should have the required grouding strap installed.
6. The grounds in the DIN plug should not be "ganged"(power and other grounds). They should separated and run the your common ground buss as separate wires.

I did all of the above one at a time with the addition of the capacitor as the last step. It seemed to be the real answer!!!
My transmissions and receptions are loud and clear now.... I'm very pleased with the radio .....now.

Hey guys,

I lost track of this thread. I am building an RV 12 and I have been hanging out in that section. I am still having problems as described above. I talked with Michal Coats at the Sebring FL Expo over the weekend. He said he thought I would really benefit from a better antenna as what was said above.

Bob you asked about me antenna. I am not sure about the brand, but it is not much. Basically the antenna is a wire with a BNC connector at the bottom. I can send you a pic if that would help.

I also have a problem with the LCD screen. Michael Coats said that if I sent him the radio, he would remove the front and clean or do something that would allow all the LCD bars to show up. He said there was a problem with some of the earlier units. Mine is number 604. He said he would fix the screen, update the firmware, and test the unit all under warranty. Is this something you can do? also making sure this unit does not have any of the problems that Bill described. I would rather keep it in the states.

I think a new antenna would make a world of difference. Would the AV-10 be a good antenna to use?


By the way Bob, you were recommended by Michael Coats.

Fl Mac said:

Hey guys,

I lost track of this thread. I am building an RV 12 and I have been hanging out in that section. I am still having problems as described above. I talked with Michal Coats at the Sebring FL Expo over the weekend. He said he thought I would really benefit from a better antenna as what was said above.

Bob you asked about me antenna. I am not sure about the brand, but it is not much. Basically the antenna is a wire with a BNC connector at the bottom. I can send you a pic if that would help.

I also have a problem with the LCD screen. Michael Coats said that if I sent him the radio, he would remove the front and clean or do something that would allow all the LCD bars to show up. He said there was a problem with some of the earlier units. Mine is number 604. He said he would fix the screen, update the firmware, and test the unit all under warranty. Is this something you can do? also making sure this unit does not have any of the problems that Bill described. I would rather keep it in the states.

I think a new antenna would make a world of difference. Would the AV-10 be a good antenna to use?


By the way Bob, you were recommended by Michael Coats.

Click to expand...

Yes I can do all of the above, install the latest firmware and can check the radio with a service monitor. At the very least if everything checks out ok you should have the latest firmware as it resolves a few annoyances with the radio.

A pic of the antenna would be a good start in resolving this. Also please describe the surface its mounted on.

Regarding the dim LCD, I've encountered that problem as well. It can be as simple as cleaning flux off the display board or fixed by changing a contrast resistor.

As others have mentioned the power supply cap can't do anything but help with noise issues.

Serial #604 is an early radio, with rev. 1 of the synthesizer board, but it should still work fine. If the radio cannot be easily fixed our standard practice has been to drop ship a new radio from Australia directly to you.

Email me, [email protected] for ship info.

rocketbob said:

Yes I can do all of the above, install the latest firmware and can check the radio with a service monitor. At the very least if everything checks out ok you should have the latest firmware as it resolves a few annoyances with the radio.

A pic of the antenna would be a good start in resolving this. Also please describe the surface its mounted on.

Regarding the dim LCD, I've encountered that problem as well. It can be as simple as cleaning flux off the display board or fixed by changing a contrast resistor.

As others have mentioned the power supply cap can't do anything but help with noise issues.

Serial #604 is an early radio, with rev. 1 of the synthesizer board, but it should still work fine. If the radio cannot be easily fixed our standard practice has been to drop ship a new radio from Australia directly to you.

Email me, [email protected] for ship info.

Click to expand...

Thank you, email is on the way.

I have a cap installed. I installed the cap and cleaned all connections. That did make a difference. I think the only problem I have left with noise is caused by my rectifier. Matt at Hirth said if I disscounnect the yellow wire on the rectifier, and the noise goes away, then he has a filter that I can install. Matt has seen this before. I hope to try this tonight or tommorow.

Bob took one look at the picture of my antenna and said that without a question my problem is with the antenna. He said I have no ground plane. I did a little research on what a ground plane is and what is required and I understand why my antenna was not getting the job done. What I read said you need about 9 square feet of metal under the antenna. Well my plane is cloth, so I have none. I am surprised it work as well as it did. I ordered the antenna that Bob recommended and that should make a world of difference.

When the antenna gets here in a few days I am going to install it and see what the difference is. After that I am going to send the radio out to Bob for updating.

I received the recommended antenna Friday and installed it yesterday. It made a world of difference. The x-com 760 performed well. I was able to receive signals I could not have before. I believe this antenna has solved many if not all my issues. Now I need to send my unit in for a software update and a LCD repair.

Thanks Bob

Got my radio back from Rocket Bob and installed it yesterday. It works great. Bob did the software upgrade and checked it out. This is a fantastic radio.

Xcom customer service is next to none. Bob actually hand delivered the radio from Indiana all the way back to me in Florida. If anyone has the need to do business with Bob I whole heartedly recommend him, but don't expect him to hand deliver your radio unless you live 30 minutes from Disney World and he already has a vacation planed there.

Thanks for all your help Bob.