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Re: [TenTec] Oll & RF @mic input.

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] Oll & RF @mic input.
From: Stuart Rohre <rohre@arlut.utexas.edu>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Tue, 31 Jan 2012 20:24:52 -0600
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
A search of the internet with key words "pin 1 Audio connector problem" 
should bring up discussions of the pin 1 grounding for XLR audio 
connectors.  Perhaps the TT fix was for a floating mic shield wire and 
this type of grounding problem.  And maybe Ten Tec's connector also used 
pin 1 for shield?

Sometimes if you have hot coax or other transmission line in the shack 
(hot with RF) you can alter the RF in the shack condition by adding or 
subtracting a length of line.  Another issue  is, are all rig and 
accessory chassis well grounded for RF (short flat and wide strap), to 
the outside earth ground and everything on the same ground bus).

Other known RF fixes include blocking introduction of RF into a rig via 
the mic cable by placing a ferrite choke on the cable just before it 
enters the rig enclosure. Or beads on connector wires.

It is likely the specific VI model audio RF issue was discussed in 
detail in the reflector of past years and a search of the postings by 
keywords should help find it.

Hint for keeping up with rig notes:  Upon receiving mods or updates, 
place original manual in a folder with any revision papers, or staple 
those papers to the appropriate pages of the manual, for later use.

Ideal, is reserving one of those two drawer file cabinets for tabbed 
folders for each piece of ham equipment.  That eases the task of finding 
notes when time to repair or sell.

Thanks to those with a better memory, that TT may have had a lack of 
grounding the mic connector shell to the mic cable shield and to the 
chassis.  The mic shield should be an extension of the chassis shielding 
the radio innards from RF.  See how your mic is wired, see if there is a 
connection to mic connector shell,and see if that shell connects to the 
chassis.  If the shell connects to the board ground, you need to change 
that to alter the RF induced path.  Make sure your mic PTT ground goes 
where it needs to on the transceiver circuit board.
(IE, someone did not double up shield and PTT ground as a short cut.)

-Stuart Rohre
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