Did a complete radio stack swap (not sure what was there before, got stuck on the job after a rip out.) The radios come on overhead and on headset. Just can’t get anything but static. I’ve exhaused all of my troubleshooting trees and the install manual. I believe it’s the antenna going bad or it may be the wrong ones for the radios. It’s a DM c70-4 tso its labeled as c37d, 38d, & DO160c standards. anyone with any experience with this stack would be greatly appreciated.
Do you have access to a VSWR tester to check the antenna installation? Ideally it should be less than 2.5:1 at end of frequency band (118 and 137Mhz) and hopefully less than 2:1 at mid-range of 126Mhz. If you can’t check this, at least do a continuity check on the co-ax cable and make sure the core and screen aren’t shorted together. Your antenna is a correct VHF version designed for bottom mount and they don’t often fail internally.
I have no experience at all on this kind of equipment – but surely you can localise the problem by connecting an alternative antenna? If only the rubber “ducky” that typically comes with hand-held transceivers? Even if the performance is not great, it will make a useful comparison.
Very sorry, that was pretty rude of me. I’m pretty one track minded when it comes to something being wrong with my avionics equipment. I’ll even dream about the issue. I’m new to civilian aviation and in school to get my A&P. My exp is 5 years avionics/military only so this is quite a change for me. I hate sloppy work and love my research! Anything else you want to know feel free to ask and I will answer the first chance I get.
I tried that to no avail. I did find however; that the 8 day clock was throwing 12v straight to ground on the same post as my comms. That has been fixed but the issue persists.
Not at the moment I don’t. I would like to get one, just not sure of the brand. I have done the continuity checks and everything comes up normal on the antenna and cables. So I’m back to square one.
Thank you to every one who has commented so far.
I hate sloppy work
You will see lot’s of that in old, GA aircraft, sigh. Seems most GA avionics after-market fits are of the “Dyke & Run” variety.
The KY196 is a very robust VHF and has no particular quirks or problems.
I would start by finding another acft with same and swapping units, then work from there.
Also: Are you SURE the squelch isn’t pulled ?
I’m afraid that I can’t help you at all, but would just like to welcome you to the forum
Presumably you are one of the many Peter says reads the the forum but doens’t post. Welcome to the other side!
I tried that to no avail.
Sorry but that is not a good answer. Either it made a difference, in which case the issue is with the antenna, or the antenna cable. Or it made no difference, in which case the issue is with the radio.
OK. So we have a reversed polarity, and the new systems are pulling to much power from the old alternator. Boss decided to have the people who first started this and wired some things backwards to fix it and fill out the form 337. Thank you very much for the assistance, and I don’t think I will allow myself in a situation of mid project solo tech again. Lesson learned!
And thank you so much for all the warm welcomes.