[TenTec] RF and Ten Tec Rigs

[Jim Brown]

On Thu, 30 Sep 2004 18:05:58 EDT, ARDUJENSKI at aol.com wrote:

>As you aptly pointed  out in most cases RF problems are 
>generally site specific relating to type of  antenna/feed system, station 
>grounding, etc.

RFI problems have two parts. Both have to be present for there to be problems. 

1) Something has to cause the RF to be in the shack. This is entirely related to the 
antenna system -- the antenna itself, the tuner, any counterpoise, etc. If you have use a 
long wire antenna that ends in the shack, there WILL be RF in the shack. Various forms 
of mismatch can also put it there. When there is RF in your shack, it will induce current 
onto the wiring in your shack by antenna action (for example, your mic cable, the cable 
connecting to to your computer, etc.) Repeat after me -- "we say "mic cable," mother 
nature says "antenna." 

2) Something has to couple it into parts of the radio where it doesn't belong. The most 
common way this happens is incorrectly terminated shield wiring on mic inputs, 
loudspeaker outputs, serial control lines, etc.  The correct place to connect the shield is 
the chassis. Connecting it anywhere else (like the circuit board) couples any current 
flowing on the shield into the radio. Every TenTec radio I have owned does it wrong, and 
so does most other ham gear. If you don't believe me, open up you radio and look at the 
RCA connectors -- they go to the circuit board, not the chassis. TILT!   

In the pro audio world, this is known as "the pin 1 problem" because pin 1 of the XLR 
connector used for pro audio is the designated shield contact. Lots of pro gear, 
including nearly all everything manufactured before about 1999, has pin 1 problems. 
We've been fixing our problems. It's time for the ham radio manufacturers to do the 
same. 


Jim Brown  K9YC