Hi Bill,
We have not heard further from you so I assume you have not improved your f/b.
I have been using my Aziloop in K9AY mode for a year now and always managed to get groundwave f/b ratios approaching or more than 30dB over the higher medium wave (1.0MHz) to 3.8MHz. My loop is similar size or slightly larger than yours - 20ft total diameter, apex 15ft high, bottom wire horizontal 4ft high. It is completely in the clear.
I have tried various radial systems, either 4x 12ft insulated radials lying on the ground or (now) 4 x 11ft radials 3ft high (1ft under the bottom wires) there is no earth connection apart from the radials, and I get similar results.
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Possible reasons for poor f/b are:-
?- proximity of metal objects or other antennas, one might expect this worse on some frequencies and directions than others
?- lack of series resistor when using short radial system. Have you modelled your antenna and radial system? This resistor and the loop termination R are interdependent to some degree but both can be optimised
?- connecting both an elevated radial system and earth together
?- common mode affecting your coax feeder. (this affected VLF more on my antenna where the RG6 feeder length is 650ft ). (maybe larger loop size might help for MW-VLF)
?- lack of signal over-ride due poor output of antenna at VLF due to too small loop size or a fault. Have you checked you get in the region of 9 or 10dB noise over-ride when you connect the antenna? (you can do this by disabling the filter for the band you are listening on and LCU preamp, then measuring how much the noise drops on a clear frequency)
?- the K9AY pattern f/b varies with elevation angle the f/b is measured over. The back null can be optimised between about 45 degrees down to groundwave depending on how you connect the earth and type of earthing or radials.
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Please note there is a difference in polar pattern between a K9AY tuned against conventional ground system (rod, buried radials etc.) and a K9AY tuned only against 4 short radials under the wires (either insulated or lying on the ground) with a series resistor.?
The conventional K9AY with ground rod etc. can have a relatively poor groundwave f/b 10-15dB with sharp null in the back lobe at about 45 degrees. Users of K9AYs say this higher null is an advantage when they can null steer using a vacrol to adjust the termination R.
The K9AY loop tuned against 4 short radials in series with a resistor usually between 100R and 560R depending on bottom heights and spacing has a pattern similar to a Flag or Pennant,? with high f/b on GW signals.
Try modelling them both.
Both modes are only single loops so you cant expect miracles, some days it compares with my beverages, others it is down a few dB as you might expect from the comparitive RDFs of a K9AY and beverage. However its remote steerability to 5deg azimuth and termination adjustment make it a very useful antenna like no other on the market.
Good luck
73
John
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PS I hate to buy also and up until now have made all my own RX antennas but cannot possibly replicate Dave GW4GTE's years of development and computer skills designing a desktop DF antenna providing remote site capability and desktop application. Unfortunately it is more expensive now reflecting dealer mark up and support costs.
