I'm still wrestling with the bias tee for my 1-of-8 remote beverage
switch. If I use a cliplead to connect a 270-ohm dummy load, bypassing
the relay, and connect an MFJ-259B to the receiver port on the
controller, the impedance looks completely reasonable - with a 3:1
binocular transformer, 89 ohms R and X=5, measured by the MFJ.
However, as soon as I connect a 12V regulated supply to the bias tee -
one of the little radio shack variable wallwarts - the measured R drops
to 5 ohms and the X goes up to 19.
My history major's diagnosis is inadequate isolation between the DC
supply and the RFline, but why? The series RF choke in the DC line is 7
turns on a ferrite core, measures 45 uH at 2 MHZ, and the bypass
capacitor is a 0.01 uF disk, on thesupply side of the choke. Theseries
cap between the Antenna and the RX jacks on the controller is a .1 uF
disk (it was what I had). I do not yet have a safety choke between the
RX side and ground, but will add one before I deploy it, if I can ever
figure out what's going on.
I'd really appreciate some ideas of what to try. Thanks in advance!
--
73, Pete N4ZR
Check out the Reverse Beacon Network at
http://reversebeacon.net,
blog at reversebeacon.blogspot.com.
For spots, please go to your favorite
ARC V6 or VE7CC DX cluster node.
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
|