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Old 09-17-2019, 07:18 AM
dpansier's Avatar
dpansier dpansier is offline
Join Date: Jan 2006
Location: Green Bay, WI (GRB)
Posts: 390

Originally Posted by BobTurner View Post
You do need to be careful with ohmmeters around RF stuff. Some perfectly good antennas will show zero dc resistance to ground, or an open circuit to the antenna radiating element.
By all means, get rid of that handheld ‘adaptor’. It uses a phone plug instead of a real coax connector; and what you’re calling a relay is a mechanical contact activated by inserting the phone plug. No impedance matching of any sort. It belongs in the trash.
As Bob mentioned above, it depends on the antenna design, Comant and Rami VHF Com antennas will show an open when measured with a VOM across the BNC connector, D&M and Delta Pop will show a short across the BNC connector.
D. Pansier
Green Bay, WI (GRB)

Antennas for Experimental Aircraft
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Old 09-17-2019, 07:42 AM
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Jerry Fischer Jerry Fischer is offline
Join Date: May 2007
Location: Winder Ga
Posts: 899
Default Checking coax

In my experience the ONLY way to check coax for a short or an open for that matter is to ISOLATE it from any connection to an antenna or radio/relay. otherwise you may see a resistance from a component that he coax is connected to i.e. coupling transformer in the radio itself, etc.
Jerry Fischer KW4F
VAF# 1646
USS Randolph CVS-15 V-6 Div. AT2
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Old 09-26-2019, 12:16 AM
Mandy Mandy is offline
Join Date: Jun 2019
Location: Ridgecrest
Posts: 5
Default Resolved!

Hey guys -

So after a week of troubleshooting, I finally stumbled upon the answer. Loud cockpit noise. So I went to Walmart, bought a pair of $10 "leather" gloves, cut off the forefinger, punched a pin sized hole, put it over the mic, and zip-tied it down. Now ATC has no problem hearing me! Just flew down to LA tonight with no issues.

Things that were preventing me from diagnosing this sooner:

1) Better reception in close proximity to airfields.

-I would assume that every time I tried it with an airfield I was usually below 120 as opposed to 190 when cruising around. I guess that squared velocity term in dynamic pressure makes for a big difference.

2) No difference with headsets.

-Just thinking about it now, if the ambient cockpit noise is loud enough it will affect all mics equally.

I feel kind of dumb that it took me this long to figure out, but I appreciate all of your help! Now to figure out how to seal the cockpit better...

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Old 09-26-2019, 12:21 PM
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RV8JD RV8JD is offline
Join Date: Jan 2005
Posts: 338

Nice catch! Oregon Aero offers Mic Muffs for $14:

See this page to see which Mic Muff fits your headset:
Carl N.
Arlington, WA (KAWO)
RV-8, 600 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

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Last edited by RV8JD : 09-26-2019 at 12:27 PM.
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