Experimenting with magnetic loops

[mw0uzo]

Loop on top of my garage


Faraday loop feed point


Testing lash up with caps removed from MFJunk atu


Caps inside box and connections soldered as much as my iron could give...


Specs: Main loop ~1.5m diameter, 470cm circumference. Faraday loop 94cm circumference. Power handling is more than expected ~75W (hot dry weather!). SSB was a lot more sparky when testing than CW, I found only very occasional flashover with 100W of CW on 80m.

Had some 20dB over 9 reports on 40m this evening, which is bloody great :)

The loop works on 80m, 40m and 30m.

[mw0uzo]

Very pleased with the performance of the loop, even though according to a calculator it should be only 2% efficient on 80m and 19% on 40m. Adding some radials and raising the height improved TX performance considerably. TX performance is better than my wire antenna.

Made a small 10m loop yesterday for testing. It looks like some sort of bell-end on my roof! Hopefully I'll get a few contacts today and see if its any good.

Need to made a remote controlled high voltage cap. Probably going to go for servo control with a coarse and fine butterfly capacitor on the same axis with servo control from either side. Problem is getting high capacitance for 80m and minimising capacitance when capacitor and its assembly is fully open so the loop has good range.