[TenTec] Oll & RF @mic input.

[Jim Brown]

On 1/31/2012 2:36 PM, Carter wrote:
>   there was finally
> talk here on the reflector about the cause of the problem, ultimately
> named the "pin 1" problem.

The Pin One Problem is the likely culprit. Two easy fixes, take your 
pick.  It is NOT Pin One of a HAM mic connector that is the problem, it 
is Pin One of PRO AUDIO mic connectors, which carry the shield.  A Pin 
One Problem exists when the CABLE SHIELD does not go directly to the 
chassis at the point of entry.

To fix it, first verify that the shell of the connector on the radio is 
actually screwed down to the chassis (and that there is no paint acting 
as an insulator). If that shell does not make contact, do what you must 
do to MAKE that contact -- scrape the paint, etc.).  If the connector is 
not screwed down to the chassis but is mounted to the circuit board and 
sticking through a hole in the chassis, do what you must do to force the 
shell to make contact with the chassis.

Step #2 is simple. Open the cable-mounted connector and find out where 
the cable shield is connected, and either MOVE it to the shell, OR go 
inside the radio and BREAK the connection of that pin to the circuit 
board, and ADD a connection between that pin and the cable shell. This 
simple procedure eliminates the Pin One Problem.

The other solution is to stick a Band Aid on the Pin One Problem by 
killing the RF current that flows on the cable shield. To do this, you 
need a MULTI-TURN FERRITE CHOKE.  A simple bead or clamp-on will NOT 
block the current.

All of this goes on the assumption that the MIC input is where the Pin 
One Problem is.  The Ten Tec transceivers I have owned ALSO had Pin One 
Problems on RCA jacks on the back panel.  The solutions are exactly the 
same -- either add a choke or connect the cable shield to the chassis 
and not to the circuit board or other internal wiring.

For more details, study http://audiosystemsgroup.com/RFI-Ham.pdf

73, Jim Brown K9YC