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Comm Radio Transmit Problem

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rmhou(at)yahoo.com
Guest

Posted: Wed Jun 04, 2014 3:24 pm Post subject: Comm Radio Transmit Problem

The Terra 760D comm radio in my Pazmany is getting harder for ATC to hear over time. Last weekend, my home field tower controller couldn't even hear me when I was only 5 miles away. 

So I formed a plan to find the issue relating to my comm radio or the antenna. My plan was to remove antenna coax cable from Terra comm and connect it to my Icom portable radio then go flying. If tower controller could hear me over the Icom without issue, the problem most likely is in the Terra comm.

Feeling good about my plan, I went ahead and made the needed connections, including connecting Icom to ship power. I also connected my headset directly to my Icom bypassing intercom. I tested it with ground and got a "loud and clear" reply. 

I  then started the engine, listened to ATIS, then called ground to taxi. This time the ground controller said he only received a transmit carrier. Thinking it maybe noise from ship power, I connected Icom to its battery pack then call ground, but the ground controller still could not hear me. I then turned the master switch off, called ground again and received a "loud and clear" reply. All of the above were done while the engine was still running.

I think the problem maybe in my charging system, most likely my alternator. But I have no idea what to do next  to locate the problem. Any suggestion?

Thanks in advance,

Robin Hou

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fherr(at)cfl.rr.com
Guest

Posted: Wed Jun 04, 2014 3:50 pm Post subject: Comm Radio Transmit Problem

Hi Robin,



Not sure about your specific system; but, how old is your main battery?

My radios had some issues until I replaced the four year old (Concorde) battery. Maybe the alternator could not keep the battery supplied with enough volts and enough amps to run the on board system?

Suggestion: swap in a new battery and see if it works.

Francis



On Jun 4, 2014, at 7:23 PM, Robin Hou wrote:

The Terra 760D comm radio in my Pazmany is getting harder for ATC to hear over time. Last weekend, my home field tower controller couldn't even hear me when I was only 5 miles away. 

So I formed a plan to find the issue relating to my comm radio or the antenna. My plan was to remove antenna coax cable from Terra comm and connect it to my Icom portable radio then go flying. If tower controller could hear me over the Icom without issue, the problem most likely is in the Terra comm.

Feeling good about my plan, I went ahead and made the needed connections, including connecting Icom to ship power. I also connected my headset directly to my Icom bypassing intercom. I tested it with ground and got a "loud and clear" reply. 

I  then started the engine, listened to ATIS, then called ground to taxi. This time the ground controller said he only received a transmit carrier. Thinking it maybe noise from ship power, I connected Icom to its battery pack then call ground, but the ground controller still could not hear me. I then turned the master switch off, called ground again and received a "loud and clear" reply. All of the above were done while the engine was still running.

I think the problem maybe in my charging system, most likely my alternator. But I have no idea what to do next  to locate the problem. Any suggestion?

Thanks in advance,

Robin Hou

 [quote]



href="http://www.matronics.com/Navigator?Avionics-List">http://www.matronics.com/Navigator?Avionics-List

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Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Wed Jun 04, 2014 4:44 pm Post subject: Comm Radio Transmit Problem

The other side of the coin could be either alternator diode failed or 

the alternator noise filter (capacitor/condenser) failed.



On 6/4/2014 4:49 PM, Francis Herr wrote:

 	  Quote: 	
		   Hi Robin,



 Not sure about your specific system; but, how old is your main battery?



 My radios had some issues until I replaced the four year old 

 (Concorde) battery. Maybe the alternator could not keep the battery 

 supplied with enough volts and enough amps to run _the on board _system?



 Suggestion: swap in a new battery and see if it works.



 Francis



 On Jun 4, 2014, at 7:23 PM, Robin Hou wrote:



 The Terra 760D comm radio in my Pazmany is getting harder for ATC to 

 hear over time. Last weekend, my home field tower controller couldn't 

 even hear me when I was only 5 miles away.



 So I formed a plan to find the issue relating to my comm radio or the 

 antenna. My plan was to remove antenna coax cable from Terra comm and 

 connect it to my Icom portable radio then go flying. If tower 

 controller could hear me over the Icom without issue, the problem most 

 likely is in the Terra comm.



 Feeling good about my plan, I went ahead and made the needed 

 connections, including connecting Icom to ship power. I also connected 

 my headset directly to my Icom bypassing intercom. I tested it with 

 ground and got a "loud and clear" reply.



 I then started the engine, listened to ATIS, then called ground to 

 taxi. This time the ground controller said he only received a transmit 

 carrier. Thinking it maybe noise from ship power, I connected Icom to 

 its battery pack then call ground, but the ground controller still 

 could not hear me. I then turned the master switch off, called ground 

 again and received a "loud and clear" reply. All of the above were 

 done while the engine was still running.



 I think the problem maybe in my charging system, most likely my 

 alternator. But I have no idea what to do next to locate the problem. 

 Any suggestion?



 Thanks in advance,



 Robin Hou

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