[R-390] Antenna matching

[Flowertime01 at wmconnect.com]

Rick,

I am using a short (3foot) twinax cable off the receiver into an antenna 
tuner.
The shield coax out to the metal tuner box and grounded took a bunch of local 
noise out of my receiver. Lets it operate ballanced input and the antenna 
trim works.

In the tuner I have a small core and trifilar winding (18 turns of telephone 
wire nice colors to help sort the windings. This is wired as unbalanced to 
balanced. The center of the balanced winding are grounded to the twin coax shield 
and the core is close to the twinax connector into the antenna tuner box. 
Inside the box is two variable caps and a roller inductor. By doing some circuit 
switching this will match the R390/A input to the random long wires I have for 
Antennas.

I have no clue what the core is. I did several before I found one that worked 
across the HF spectrum. Its a 1/2 hole and 1 inch OD. about a 1/4 thick. No 
paint.

I operate SSB with a Ten Tek Argosy II. I run that into a different connector 
in the Antenna tuner and unhook the R390/A 

Mostly a good balanced to unbalanced transform works.

Try a 75 to 300 core from TV set stuff. Crack the package and just use the 
core and wire. Use the 75 ohm side into the balanced receiver. This will 
transform the 300 Ohm receiver input up to 1200 ohm. That will match the high Z from 
the end of a random wire. A small size variable cap across the wire to ground 
and peak the cap for max noise.

Roger AI4NI