Well Ed, I rewound the noise bino that's in the unit twice. I tried the 5/20 turns ratio mentioned as well as 3/12 (keeping the original 16:1 impedance ratio) and I saw no advantage on the lower freqs. I couldn't get good nulls. Changing the number of turns just seemed to mess with the progress I made with it on HF. I returned to the original of 2/8 turns, and while I was at it, wound those turns with Litz for good measure. So I'm back to original performance.I'm doing what you advise on the common mode isolation. The 1:1 bino's at the input of the noise and main antennas at the canceller should do the same thing, whether they're at the ground rod or at the input to the canceller. At least that's my thinking.
With this small investment, so far I've accomplished 90% of my goal. I may have to live with the unit not covering the 2200m band. After all, LF-30mhz is quite a frequency spread to cover with a simple device.
I'd probably be better off using the two verticals in a diversity system to get rid of noise. That would take a larger monetary investment. I'm thinking of the Sdrplay dual-front end sdr that has the software capability of using two antennas working together... phasing them to produce a null of noise or peak a weak signal. You know how it is though, you try to "make-do" to accomplish goals rather than keep spending money on the hobby. :-)
Today I'm going to short the far end of both antenna cables, as you mentioned, and see what the noise level looks like. Maybe also check the noise with them terminated in 75 ohm resistors? I am using 75 ohm coax. I may try a few more things that come to mind. I mentioned the coupling caps in the noise bino circuit. We'll see...
A happy New Year to you also Ed.
73, Ray