[TenTec] 566 v3.028

[Jim Brown]

On 4/4/2012 6:16 PM, Ron Castro wrote:
> The biggest RFI problem I found with the Orion II was RF getting back in via
> the headphone jack.  There is a small mod board that the factory can supply
> if that's the source of your problem.  I would also check for RF getting in
> at the key jack.

Hmmm -- RF getting in via headphone and speaker cables is quite common 
in audio gear, and there are two common ways it happens. First is via 
the feedback network, which simply requires ordinary low-pass filtering. 
Second is a Pin One Problem, whereby the connector shell goes to the 
circuit board rather than the chassis. Another Pin One Problem is also a 
likely cause of RFI via the key jack.  The last Ten Tec transceiver I 
owned, an Omni V, was built with Pin One problems at all the RCA 
connectors at the back.

The band-aid (that is, without going inside to actually FIX the Pin One 
Problem) is to add a ferrite choke with enough turns through the core to 
put the resonance in the frequency range where there is RFI.

73, Jim Brown K9YC