The AN-100 dropped in today. TECSUN produces two slightly different MF multi-turn loop aerials for BC-receivers, the AN-100 and the more popular AN-200. My impression, it's just a matter of design. The AN-200 rests on a stylish arc-like stand, while the AN-100 is held by a rather non-stylish foot.
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| AN-100 from below |
My preference was the AN-100, since I believed that the foot could be opened by a bottom plate, it seemed better suited for modifications. And, the dear reader may have a guess... I was guessing correctly. Underneath 4 rubber-foam pads, 4 screws allow access to the inside of the AN-100's stand.
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| screws underneath pads |
Surprise surprise, the foot contains a polyvaricon, actually one of the type that is found in any random cheap broadcast receiver. The trick with those is, they employ little trimmers for basic frequency setting.
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| tuning capacitor |
The modification to resonate the loop at 500kHz was consequently a simple one. One of the polyvaricon's trimmers was not set to maximum but rather to some odd looking position. Obviously that's the one to change. Well, guess what, I did just that, and the lowest resonance of the loop dropped to 494kHz.
Now, that was a simple one, no solder molten.
To drop the frequency even lower, solder needs to be molten. I figure a high quality, e.g. polystyrene, 47pF capacitor parallel to the tuning capacitor will do the trick.
UPDATES:
The most upper resonance frequency is now 1330kHz.
The combination AN-100 & ATS-909 let me presently listen regular CW-QSOs.
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| inside the foot |
Plenty of space in the compartment. Here are some ideas of what could be fit into this space:
- a preamp
- an I/Q-SDR receiver
- a (subharmonic) grabber receiver w/ a USB sound-device, USB powered
