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
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