I guess this post was prompted by Ed's experimentation with isolating transformers. I suppose we've all been down a similar path in the search of the best combination of hardware to maximize reception quality on as many bands of frequencies as possible. First, I'll mention that every location presents a different/unique set of problems to be worked out... ground type (rocky, clay, wet/dry, external noise, etc). The type of antenna that works best at any one qth will be dependent on many factors.
I've went the route of trying to make vertical antennas work here trying endless combinations of transformer ratios with different "mixes"... autotransformer style or seperate grounding... on and on it went. Tie to earth ground or counterpoise? Tried several e-probes with all the variables like common mode choking at one end or both... no chokes at all, grounded probe or counterpoised. Never really was happy with any of them since the pervasive utility line noise was always in the mix. Btw, I still haven't had success with cancellers, phase or otherwise on these antennas.
I thought I'd mention what I'm presently using for an "all-band" general coverage antenna that seems to work at this location.
https://www.dropbox.com/s/iq3q71mluvrmn9x/octagon.jpg?dl=0
I though maybe the best thing to do was try something that wasn't ground dependent, so I went with a loop. Got a 10 ft. length of pvc and cut it up to make an octagon. Since making this, it's been through a fair number of "iterations" but I'll cut to the chase and give you what its present form is. The loops inside conductor is made from aluminium furnace duct tape, folded in half length-wise and ran through the pipe making one (fat) conductor. There is no "shielding". The two ends meet a transformer made from a BN-73-202 binocular. The loops octagon shaped "winding" connects to a one turn pass through the core. The secondary winding consists of six and a half turns of Litz that ties to the long run of 75 ohm coax down the mast all the way to the shack. I chose the number of secondary windings to have sufficient inductance for a proper signal transfer as low as the 2200m band.
The antenna seems to work well from LF to 30 mhz. I leave it in an orientation that the nulls appear directly North and South. Those nulls become less prominent above 40m or so. I don't have a rotor to use to fine-tune noise nulls, but I've found that whatever noise the loop picks up can, more or less, be taken care of with the sdr software noise blankers now. This loop (for me) has been a substantial improvement over the ground-dependent types of antennas I was struggling with previously. I suppose a preamp may help a bit above 20 mhz, thinking of line loss, but I really don't think it's worth the effort. I was copying Australia on 27.385 lsb just fine yesterday. 10m FT8 looked good also. Over-all, I'm happy with this antenna and it's wide bandwidth. It's gonna be fun seeing what this will do for me when the 2023-24 dx season comes around again.
Oh, btw, looking at the pic the mast is wood, not metal. The installation you see is not permanent. It's for testing only. What you see would never stand up to the fierce winds that blow through here and they would snap that mast like a toothpick when the storms come by. However I can mount it, I hope it will withstand the summer and winter storms. Maybe I'll just have to take it down during same.
Ray ... N. Central Texas