Valcom transmit issues

[dlsmith]

Hello all, brand new POA member!

I also happen to be the proud new owner of a 1947 Luscombe 8E. Currently, it has a Val 760, Garmin GMA340, and a Garmin GTX327.

Im having a slight issue. My Val seems to be having an intermittent transmit problem. I've gotten reports that sometimes I'm clear as a bell, while at others my calls are a garbled mess. I was wondering if anybody had any ideas as to what the cause could be. The radio powers up and seems to operate fine. It has a relatively short range receiving, but is always fairly clear, regardless of how others hear me. I have some fairly limited electrical knowledge, and the only thing that crosses my mind is a grounding issue.

Granted, I'm at a uncontrolled airport in a VFR only airplane, but we have such a high volume of training that goes on here that I would really like to get this fixed. Plus, taking the luscombe into Nashville Class C on a slow day sounds like fun

Thanks in advance

 

[weirdjim]

My Val seems to be having an intermittent transmit problem. I've gotten reports that sometimes I'm clear as a bell, while at others my calls are a garbled mess.

Describe (or post a photo) of what the Val's antenna looks like.

Thanks,

Jim

 

[flyingron]

In addition to Jim's antenna guesses, I'd check the feedline.

 

[weirdjim]

In addition to Jim's antenna guesses, I'd check the feedline.

Yeah, once I got past whether he is using a limp piece of spaghetti in a copper septic tank or a real antenna, there is a pretty easy test using a handlheld on the antenna and the old wiggle the stick test.

Jim

 

[dlsmith]

Well the antenna is a thin rigid metal type, I see them all the time on these older planes. The connection at the antenna looks rather suspect to me, being two nuts on poles rather than a single spliced on connector. All of these were installed in 2004. I can't post pics from my phone, but i will snap some and run by campus to the computer lab and post some there.

 

[dlsmith]

Here's a pic of the antenna



This connection doesn't look right to me, thoughts?

 

[weirdjim]

OK, what you have is commonly referred to as a stainless steel whip. They were all the rage back in the '50s when a radio that went all the way from 118 to 124 MHz. was state of the art. They aren't particularly "good" (a purely subjective term) above 124 or 125 MHz.

The installation is just fine. I'd probably remove the braid wire connected to the airframe and wipe it clean with contact cleaner, lightly sand the area where it connects, then use something like a thin coat of WD-40 and bolt it back. Some folks have had great success with a lockwasher BETWEEN the ground lug and the airframe as it forms a gas-tight seal between the lug and the frame.

Do the same kind of "cleaner" trick on the lug that connects to the base lug of the antenna. Then try a frequency between, say, 120 and 124 MHz. and see if you are good and clear. THen go up above 130 and see if things go to scoop in a pooper.

Bottom line is that you've got a 2010 radio with a 1955 antenna.

Jim