HFU HF Underground
Technical Topics => Equipment => Topic started by: ChrisSmolinski on September 20, 2020, 2057 UTC
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My crossed parallel loop (Build notes on the Crossed Parallel Loop: http://www.radiohobbyist.org/blog/?p=2340 ) had a third party version of the LZ1AQ pre-amp, but was never happy with the performance. So today I removed the pre-amp and went back to a passive configuration. I made a custom version of my Cyclops Transformer, with 5 turns on the input and 13 turns on the output, as the loop presents a fairly low impedance. I must say, it's working much better as a passive antenna. Strong signals, and still quite directional, even on HF, I was able to drop CFRX 6070 from S6 to S3. Much more directional on LW and MW of course. I'll seal up the transformer once I am sure I am satisfied with the turns ratio (although I think I am).
This brings up a question - would there be interest in a Cyclops Transformer kit? The PCB, ferrite core, and choice of UHF or F connector. Maybe some wire wrap wire for folks who don't have any magnet wire? Thoughts?
(https://i.imgur.com/xD5Dnya.png)
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How does this loop antenna compare to a single loop antenna? Sometimes with a proper match with a step up transformer you can achieve good gain to the receiver without the added noise of using a matching preamp.
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LZ1AQ has some information/theory on the Crossed Parallel Loop here: https://www.lz1aq.signacor.com/docs/wsml/wideband-active-sm-loop-antenna.htm
The most important properties of CP loops are the ability to built loops with large area and low inductance which still preserve the small loop radiation pattern. Their short circuit current is higher compared to a single turn loop with the same area.
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The S/N factor from the design of this wide band loop antenna is a big factor. Reducing the loops inductance can help. If the gain is not sufficient with your passive transformer you can design a different active per amp circuit with a acceptable noise floor.