[TenTec] RF Grounding

[Jim Brown]

On Tue, 15 Jun 2004 20:45:58 EDT, N0KHQ at aol.com wrote:

>You should have "One" single point for grounding.

Right.

>......and it aint to a bus 
>bar behind your station, it should be on the lug nut on the back of the Tuner 
>and thats it. Purchase from TT a TT-1251......put it together and use it.
>
>Any wires, straps or whatever you have going to that bus bar must be 
>disconnected and thrown away......including the bus bar. 

This is UTTER BS!  

>Inline with the coax leaving the Orion and going to your amp install a "T-4" 
>Line Isolator from Radio works. The linear keying line from the Orion to the 
>amp must be wound around a toroid, Radio Shack sells them. 

Sounds like a pin 1 problem!  Ten Tec gear is full of pin 1 problems.  Yes, 
winding the keying line around a ferrite can be a band-aid for pin 1 problems.  
The catch is that toroidal chokes can have fairly high Q, so you have a good 
choke on one or two bands but a not very good choke on others. 

>Your entire station, thats using 115vac, must be a dedicated circuit to the 
>service panel, other wise, that harmless little green wire thats running from 
>receptacle to receptacle is acting as an antenna and a ground loop. 

Huh?  A dedicated circuit is certainly a good idea, but grounding is NOT the 
reason. 

>Computer systems (Orion, Jupiter and Peg) require special power and 
grounding 
>techniques. And, dont let anyone tell you any different.

Well, they certainly do require single point star grounding systems, but what you 
describe is not that. NEC (the National Electric Code), as well as good 
engineering practice, requires that all grounded objects be tied together. Where 
and how they are tied together can make a big diffrerence, and W8JI has 
described what I consider to be a very good method of station grounding.  

>If your system is setup properly, you can run legal limit with your antenna 
>right over the top of your house. 

Yes. W8JI has correctly stated that a very large number of so-called RF 
problems are really antenna problems -- that is, the antenna is poorly fed and 
puts a lot of RF in the shack.  My corollary to that is that most RF problems with 
gear that are blamed on grounding and ground loops are really pin 1 problems 
inside the equipment. 

What's a pin 1 problem?  When a cable shield goes to a circuit board and not 
the shielding enclosure of the equipment.  Examine the RCA connector on Ten 
Tec rigs (and most other ham gear) and notice that they don't go to the shielding 
enclosure, but instead go to the circuit board, wander around for a while, and 
eventually find ground.  

Now, that cable shield is an antenna (you say it's a keyer cable, but Mother 
Nature says "antenna."  When you key your rig, your transmitting antenna causes 
current to flow on that cable shield, and that current flows along the circuit traces 
inside your rig. Those circuit traces have self inductance and resistance, and 
there is voltage drop across those inductances and resistances due to the RF 
current. That voltage appears at random places on the circuit board based on 
how the designer laid out the board and the frequency on which you are 
transmitting!  That's a pin 1 problem.  

So forget all your cockamamie grounding messes and fix your pin 1 problems. 
It's a lot cheaper, and a lot safer. 

Jim Brown  K9YC