[ccarter]

Been trouble shooting my SL-30 all weekend. Here's the problem.:

Com signals are in coming and out going but very weak. We used a hand held ICOM radio today to check that com is bi-directional. All intercom is good, mic gain good just very weak com traffic coming in and going out. The receptivity on the hand held is excellent but the SL-30 mounted in the bird right next to it is very poor. We thought it might be radio or wire harness but the work today proved the physical connections are good. We are looking closely at the coax and the antenna right now as the culprit. The antenna is a new Rami AV-17 bent whip. I checked the RF signal level on the radio and it ranges between 8 and 11. That seems very low to me but the manual did not state what the range should be? Anybody know from looking at your working SL-30? Also the COM noise level runs about 145 to 147. Again, not sure what the range "should" be but that sounded high???

Thanks guys,

 

[AltonD]

if you can lay your hands on a SWR meter you will be able to rule out/in theantenna.

 

[Bryan Wood]

Try this

Chris,

Here is a trick of the trade that can help you determine if your antenna system is good. Since you are using a metal antenna this will work. You are using a metal bent whip aren't you? If so, turn on your radio and select a frequency that is not being used and disable the squelch so that you hear static. Turn the volume up all the way so that you can clearly hear the static and take a screw driver and scrape the antenna with the side of the screw driver. You can clearly hear this if thru the radio if your antenna is good. Hope this helps. Then there is the obvious of borrowing a friends radio to plug in and try.

 

[Walt]

I've seen a shorted coax cause similar problems, with the radio removed use an ohmeter to check it, the antenna should read open (infinity).

 

[ccarter]

Great suggestions

Great suggestions guys, all of them.

I sort of ended up doing a "combo" of several of these, the simplest of which was to kiss it (keep it simple stupid... me being the stupid of course)

I had a portable antenna on a handheld with a BNC so I plugged that into the lead on the sl-30. The RF signal jumped to about 30 (carrier only). For the first time I then heard approach traffic going into BNA. The RF signal would jump to somewhere around 50 to 60 depending on the proximity of the aircraf overhead. Ah ha! Antenna problems. Prior to this I removed the antenna from the mount and clean/polished the aluminum skin where it mounted just to make sure ground plane conductivity was good. Quite a bit of crud came off including wash primer I forgot to clean before mounting... . Next I used a simple ohm meter to check continuity from the tip of the antenna to the lead into the radio... open circuit. Dang it! While tinkering with the BNC on the antenna end I happen to notice the center conductor pin did not seem to protrude as far through the connector as it should. I tugged gently on the pin with some needle nose pliers and it snapped the rest of the way into place. Problem solved.

That's one for the "Duh" file.

thanks guys....

 

[mikehoover]

Great suggestions guys, all of them.

I sort of ended up doing a "combo" of several of these, the simplest of which was to kiss it (keep it simple stupid... me being the stupid of course)

I had a portable antenna on a handheld with a BNC so I plugged that into the lead on the sl-30. The RF signal jumped to about 30 (carrier only). For the first time I then heard approach traffic going into BNA. The RF signal would jump to somewhere around 50 to 60 depending on the proximity of the aircraf overhead. Ah ha! Antenna problems. Prior to this I removed the antenna from the mount and clean/polished the aluminum skin where it mounted just to make sure ground plane conductivity was good. Quite a bit of crud came off including wash primer I forgot to clean before mounting... . Next I used a simple ohm meter to check continuity from the tip of the antenna to the lead into the radio... open circuit. Dang it! While tinkering with the BNC on the antenna end I happen to notice the center conductor pin did not seem to protrude as far through the connector as it should. I tugged gently on the pin with some needle nose pliers and it snapped the rest of the way into place. Problem solved.

That's one for the "Duh" file.

thanks guys....

I am having "weak" SL-30 problems myself. It transmits and received fine from the unicom at the FBO while taxiing out. As I get further away at some point around 10 NM out, I cannot hear and assume no one can hear me. ATIS can barely be heard with the squelch knob pulled out. I barely heard another aircraft call in 20 miles away with the squelch knob pulled out. He could not hear me.

I have had the antenna checked for SWR and the person that checked it with his box says it is fine. That was connected to the antenna cable where it would connect to the short SL-30 com cable with the tray connector that came with the SL-30.

My set up is a PS Engr PAR100EX as COM 2, with the SL-30 as COM 1. The PS Engr is working just fine.

How do you check the RF signal strength?

If I do a continuity check, can I test from the antenna itself to the BNC pin? It is a Comant CI-122 bent whip antenna.

Also, I have switched the COM antennas and the problem is the same. I am thinking it is not an antenna problem at this point, unless it has to do with the short run of antenna that came with the SL-30 that mounts to the tray.

Thanks for any help!

 

[mikehoover]

I found the problem!

I had check my two com antennas for continuity and isolation and had a SWR test to find that from the antennas through the RG-400 I installed that everything check out fine.

The one thing I overlooked was the brand new pig tail com antenna section that mounts to the back of the SL-30 tray. It comes with the SL-30 and is about 1.5 feet long and has special (expensive looking) 90 degree BNC connector that bolts to the tray. The problem turns out to be this poorly assembled pigtail.

I took the special BNC connector apart to find that a strand of the core wire was grounding. It had not been tinned with the rest of the core strands and was contacting the BNC housing.

I removed the solder from the BNC connector, re-tinned the core strands and reinstalled the cable into the BNC connector and solder it. Put it all back together and reinstalled in the aircraft and went flying.

The SL-30 seems to be working well at distances it had not previously. I can hear AWOS far away and I could be heard very well too. I did not have a long flight as weather was closing in, so I will test further, but I think the problem is solved.