Comm Radio Reception Issue

[DaveF]

The SL30 and 40 are well-designed and don't require forced cooling. I had my SL30 in a big rack with lots of other radios, some old and hot, and never had a heat problem. I know a few other guys with SL30/40s and haven't heard of any heat problems. So it could be heat related, but only if there's a failing component in the radio. Not that that would make you feel better!

Before spending money to bench check the radio I'd carefully inspect the installation; grounds, connectors, cables, circuit breaker, and antenna. Do a heat test with forced air, hot and cool. You could blast the radio with a hair dryer and do a radio check on the ground. Try the on/off test that Frank suggested. Try swapping the radio for a known-good one.

[Sixracer]

I'm having just the opposite problem. My old Narco is getting great reception, but transmission is a problem. Funny how it all started when I changed airports. I haven't had time to do a good check, but I would think all the info provided in these posts might apply to transmission, too. It started with the tower saying the transmissions were "Scratchy" sounding. It was that way when even cold & on different frequences. Everyone at the old unicom airport said my transmissions came in strong & clear. I'm leaning toward a bad connection or even the push to talk switch. With a little time I bet I get it figured out.

Bruce, I know it needs a shot of MMO, "The Great Cure All" LOL!

[FredMa]

It never hurts to check the easy simple things first like removing the radio to check the connections on the back and reinstall making sure it is fully seated in the rack. check headset plugs and clean tips with scotchbright to ensure good conductivity. You would be amazed at how many similar problems are something as simple as this or the volume control on your headset or radio either turned down or not working properly.

[c170b53]

If you have a new electronic equipment, that plastic bag that it came in has a funny symbol on it. Ignoring that symbol could be costly.

[fangzz]

Bad day by some metrics, but...I made the same number takeoffs as landings, so how bad can it have really been.

Radio bench checks GOOD! That was good news. Got a length of coax, known good, and put between pigtail and antenna. Took off. Worse than ever. Can you believe that?

Next is hook up to a known good antenna and see what happens. At the same time, gonna clean the headphone jack innerds. Keep chasing it. It'll be simple; it's just a matter of latching on to the simple thing.

[FredMa]

did the radio shop leave the radio powered up and test it repeatedly over an extended period to duplicate your (in aircraft) failure? If not you cannot completely rely on their standard test as a complete one. I have seen some bench tests fail to find a problem before. If you are going to temp install a different antenna make sure it's has a good ground to the airframe through the mounting screws. I see that you already removed the connector and checked where it grounds to the antenna. I had to change an ADF antenna last week because of corrosion. When I went to remove the connector it broke off in my hand from severe corrosion. the antenna receptacle still inside.

[fangzz]

No, Fred, it was a pretty quick checkout. But, this was a first-class facility. Never seen so many scopes. Guy knows his stuff. Don't think it's heat related anymore, but that was a good thought. What I now know is that no one can hear me and I can't hear anyone. Had a guy take my handheld and start walking away. At 50 paces, it was very quiet indeed. Back to basics.

[FredMa]

Your problem did change though when you used a "known good" coax. I don't think I would trust your known good coax. The antenna you are going to try next seems reasonable. let us know what you find, corrosion etc. Here is a picture of the corroded ADF antenna cannon plug with part of the antenna still inside.

[fangzz]

MAN! That is truly a corroded terminal! Looks like had been under water. Sea water. Amazing how well things will work even in conditions approaching that. As long as they aren't 'disrupted.' Which is why I've always thought over-maintaining is a big problem. Just me.

You make a great point on the 'known good' coax. Ran out of time to switch back to the old one (which is very clean and 'looks' good) yesterday, but that will be the next thing, to see if I can get back to that earlier baseline, albeit a stinky one.

[fangzz]

Problem would seem to be solved.

Coax.

Known good one - WHEN PROPERLY SEATED!!! - seems to have solved the problem. Haven't flown it, but it ground tested great. Loud and clear, as they say.

So, it appears the installed coax has a connector issue which I'll be isolating and fixing. Been that way since '09 and just getting worse and worse. Sometimes worked fine, sometimes not. Finally, it just quit. Something so simple.

It's amazing to me how we take for granted things that work just great -- til they don't.

Not much more to report on this one. Bless you guys for being interested enuf to suggest stuff. Adios for now.

[jwpalmer]

Would love to know if the problem was actually solved with coax replacement. Have an SL30 doing the same thing. Great reception and Xmittiing when sitting in front of the FBO.Then, FBO says I sound "far away" when sitting at the end of the runway, can't hear Approach, and they can't seem to hear me either. Can't get the AWOS until within 5 miles of airport. Garmin said to check coax, which was all new two years ago when I installed the radio. Ohm meter indicates good grounding and no resistance in the line from radio tray to antenna. New antenna didn't fix problem either. Thinking now I wasted 4K.

John

[fangzz]

Hi John,

The coax was fine. And ONE of the two connectors was good, one bad. The antenna connector was poorly done. Replaced it and it's been the way we want our radios ever since. Like you, I've been essentially NORDO since I bot the airplane and immediately installed the SL40. Have you tried the 'known good one trick' with the coax?

Good luck with yours!

[Sixracer]

I finally got some info back from the Radio shop about my Narco. Looks like it has had water or moisture in it at some time. (not while I had the plane) I was told the board material they had was subject to wick or absorb moisture over time. Looks like mine has done a good job of absorbing moisture. To the tune of about a grand. The radio shop told me a procedure to dry the radio out about once a year. back in Sept. I have moved to an airport closer to my home and the hanger I have does have a low spot by the door that pools water during rains. Might be an evaporative issue adding to the leaking windshield it might have had in its previous life... Just my luck. I think the airport Manager and I are going to have a talk.

[FredMa]

The coax could still be your problem. New doesn't always mean servicable. I would check for kinks or chaffing along it's entire length. Not clear on what you checked on the coax. Did you check the shielding from the rack to antenna or the center conductor? The shielding is there to capture the RF signal along the length of the coax and route it to ground to prevent interference with other instruments. Your likely problem is a shorting between the center conductor and the shielding of the coax. most likely at the connectors due to them being improperly terminated. You can confirm this by using a Mega-ohm meter and checking between the center conductor and shielding, with both ends disconnected or you will fry your radio. A regular meter will not always detect this type of higher resistance short but a Megger will. You can borrow a meter or simply take out your entire coax and take it to a radio shop and have them check it.

[FredMa]

If you are still wanting to check for proper bonding, antenna to fuselage, or radio rack etc, you should be using a milli-0hm meter and not just an ohm meter as you indicated earlier. Don't forget to check the simple, obvious things as well, like making sure the contacts between the radio and rack are clean (no bent pins) and the radio is properly seated in the rack and tight. I forgot to ask, where is your antenna located? Since radio frequencies transmit line of sight, that could be a factor as well. Even at the end of the runway, if there is a hill or building between you and the receiving radio, reports of weak radio may not indicate a malfunction. With clear line of sight though, that is a different story.