While waiting for my new Bernafon Versa 9 CT hearing aids to arrive at Costco, I've been passing the time experimenting with home made loop systems. Yesterday I made a small, square loop, 12 turns of #28 copper wire, 2 feet on a side on a piece of peg board. The d.c resistance of the loop measured 6.75 ohms.
The only amplifier I had to play with was a 10 watt guitar practice amp which logic told me would be woefully inadequate. Undaunted, I fed an audio signal from a a small FM radio to the mic input of the amp. I connected the loop to the headphone output jack of the amp, primarily to mute the speaker. Lo and behold, when I switched my antique Rexton canal aids over the the T-coil mode I could hear the radio perfectly from the loop. With the small amp the range was only about 3-4 feet but that was enough to convince me the system would work.
Late last night I was cruising around Craig's List on my laptop and just for the fun of it I did a search for "UniVox." I was very surprised to find an older UniVox loop amplifier (Model 2A+) for sale about ten miles from home. The price was $10 which was absolutely unheard of. I picked it up this morning, hooked it to my loop this afternoon and was blown away with the performance. My next project is to build a larger loop, perhaps 10' x 10' to put in my attic.
If you've ever considered playing with inductance loops, my suggestion is to go for it. They really work. When those Bernafons arrive I'm going to be in loop heaven.