Submitted by Tom K1JJ
I wanted to thank Steve, WB3HUZ for his suggestion of using a capacitive
divider for a scope R.F. pickup.
There's many ways to do it, but I promised to post my final product, so here it is.
In the past I've used a separate coil pickup loop for each amplifier final (7 different ones) with a rotary switch to select the proper one to the scope. (what a pain in the ass)
160-75M was clean, but on the 40- 10M bands I would get varing degrees of harmonic lines.
This new capacitive pick up works GREAT! On 160-10M the scope trace is perfectly clean, and the output amplitude is almost constant from 160-10M!!! IE, When using the same power level, I can select different bands and antennas and the scope trace stays very close to the same size.
Here's what I finally came up with...simple:
Take a tiny Bud minibox and mount three SO-239 coax female connectors. Solder two of these connector inner terminals together with a heavy straight through wire.
These two SO-239 connectors are put in-line with the main 50 ohm coax - put it right after the power meter or final common point to all amplifier outputs. (inline connection)
Then solder a short, stiff 2" wire to the third conector and route it alongside the first wire. Put it 1/8" away in parallel but not touching the straight through wire. This wire's end is free, no connection.
This third female SO239 connector connects directly to the scope vertical
input using a standard shielded RG/58 or RG/59 coax jumper.
(remember that this cable carries low level R.F. up to 29mc)