It is common in the Z match for vertical antennas that there is an RF choke center pin to ground to shunt static DC. John TI4JWC

Yes! you can program your ZachTek to have a 1/3 or 2/3 hour delay while set for the WSPR hopping option. Then to protect your RX use an MFJ RF Sense SDR MFJ-1708B- SDRS. This box will ground your receiver antenna connection when you are transmitting. If you study the WSPR manual you will find the frequency hopping sequence timings. You can set the "after transmit delay" to be 1/3 or 2/3 of the hopping hour. Don't forget to account the time for the frequencies in the WSPR table that you may not have in your transmitter. 73 John TI4JWC

Harry, correct, "it's a pretty hard problem." You could start with a SoftRock RX, 160m to 10 m, hopping WSPR frequencies. You will need a programmable external AGC ( amp-pad) to optimize the noise floor 160m to 10m, a large swing for each frequency-to-frequency and hour-to-hour. 8 concurrent frequencies for a KIWI receiver, 12 concurent for the PI-SDR 160m to 6m noise balancing pad, amp is even more complex. I hope someone can design an affordable solution. John TI4JWC

The SWR for each frequency on the AV-680 is tuneable to give an SWR of 1:0 for each frequency except 80 m where it is at 2:1 No Tuner required. The tilt-over mount makes this adjustment easy. John TI4JWC

73 John Clark TI4JWC

I use the hy-gain AV-680. I had to switch from RX to TX WSPR when the Condo added the electric security fence and the LED light on the wall.