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Posted by swlem3 on June 13, 2023 at 20:45:14.
In Reply to: Re: Antennas for general coverage posted by Ed Holland on June 13, 2023 at 19:33:08.
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I could see that your 3x3 tuned loop would work well for hifer. Yes, not so good for tx because of nulls. I've also read up on the vintage ideas for low noise. I've tried a couple with no real results here, doesn't mean they won't work under different conditions. I think your longwire would be ineffective for low HF to mf-lf also because it isn't vertically polarized and too close to the ground in terms of wavelength. As you say, the ground bar is inefficient for low freq work. You say you had it working for 22m with a better xfmr. Perhaps it had a higher ratio ... maybe 9:1 or greater? I'd think the dipole wold be fine for above 20 mhz, but it's a bit low for freqs below that unless NVIS work. About my loop... you're right, untuned and un-amp'd. I do have to add the disclaimer that I'm using the Airspy HF+ that has a built in preamp with adjustable attenuation. If I used a different sdr I might need a preamp at the loop.
Got more info for you. The loop is remarkably tolerant of the xfmr used. Today I grabbed a pot core with an AL of only 300. The loop is about 5-6 uh, so I made a 3 turn primary to arrive at 5-6 uh. I needed roughly 30-35 turns of Litz on the secondary to obtain the same 440uh inductance as is on the binocular (which needed only 6 1/2 turns). Well, I replaced that bino with the pot core and the loop worked just as well... even down at 2200m. As a bonus, even wwvb and the 24khz military don't look too shabby. I think for the time being, my search for another gen coverage antenna is over. One improvement would be to somehow use the loop and maybe another e-probe to see if I can get rid of the remaining noise (that's not on every band now) with a canceller... something I've yet to accomplish. I'd be nice not to have to use blankers because they don't work well when whatever band is being used is filled with strong signals.
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