About 10 years ago I did a lot of experimenting with SWR meter RF Sensor
pick-up circuits. My favorite of all is the Stockton bridge using two toroids
(Dave, you're brilliant!)
Regardless of the RF Pickup Sensor design, whether it be single toroid Bruene
circuit, two toroid Stockton bridge, or other experienment, the below
problems and solutions were always the same, and the solution given below
worked 100%
of the time to cure the problems noted.
A BIG PROBLEM with inability to null, instability, forward / reverse other
than 180 degrees diff, etc. and this PROBLEM was always found when connecting
the RF pick-up Sensor to the coax and NOT using nearby coax ground but instead
by utilizing the chassis ground as the RF return between the in / out
connectors and the RF Sensor bridge circuit.
Therefore I ALWAYS designed the PC boards (or even the perf board layout) to
include a ground connection running parallel to the "hot coax center conductor
line" between the connectors and running through the RF Sensor pickup
circuits. My GROUND circuit on the RF board was from the XMTR connector , to
the
board, and connected next to and parallel to the XMTR IN "hot circuit" and Out
the ANT circuit to the antenna connector.
Good luck all... RF Sensor circuits are great, simple, fun, and great money
savers. I've picked up some beautiful and sensitive meter systems in nice
enclosures with bad RF sensors for cheeeep and made various DIFFERENT sensors
to
cover HF, VHF, QRPp, QRP, QRO, and other circuits... all switchable and using
the same meters. Oh yes..........mine all track with my Bird if that's any
interest...
Bill K5BDZ
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