Re: [IRCA] BOG question

[Rick Kunath <k9ao@xxxxxxxxxxx>]

On Friday 04 December 2009 01:01:39 pm Nick Hall-Patch wrote:
> Both radios have two terminals, which one would I
> >put the end of the BOG into (not using coax)?  An old Hallicrafters that
> >I had as a kid had a similar A1 / A2 setup and a little metal "blade"
> >that would short out A2, if desired.  Would plugging the BOG wire
> >directly into one would work and would I need to do a small jumper from
> >that one to the other one (A2)?  Thanks.
>

This was a common setup on receivers that were designed to use either a 
balanced or an unbalanced antenna.

The A1 and A2 terminals go (via the band switch) to the antenna winding on the 
receiver RF amplifier circuit's input coil. These receivers brought both sides 
of the antenna input winding of this coil to the rear panel, so that the user 
could select the appropriate configuration.

For a balanced antenna, the ground strap is omitted and the antenna connected 
to A1 and A2. 

If the antenna is unbalanced, the antenna (usually, but it generally does not 
matter) goes to the A1 terminal. The A2 terminal, the other side of the 
antenna coupling winding, is shorted to ground by the A2-Ground jumper. If an 
external ground was used for the antenna, then the ground connection was 
generally made to the A2 terminal and the chassis ground jumper omitted.

But again, test it for the best signal on any given antenna.

What the A2-Ground jumper is doing is providing a return connection for the 
(unused on a single wire antenna) other connection of the input coupling coil. 
Most of the time, if you omit the jumper, the coupling decreases and the input 
signal levels drop. But again try it. You always get some capacitive coupling 
even with one end of the input coil disconnected.

And with a balanced antenna, the other half of the antenna is providing a 
complimentary current flow into the second terminal of the input coil.

Hope that made sense.

Rick Kunath

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