Well, I managed to get the AMT3000 transmitter assembled this weekend, and it went extremely well! I started on it late Saturday afternoon, and it took about three hours to get it assembled, and another hour or so to get it setup and tested. I have to say that this is one of the best put-together kits I've ever run across -- an excellent design, very well-made PC board, quality components, and clear instructions.
When selecting a frequency to use, the instructions recommend staying toward the high end of the dial, because the antenna is supposedly more sensitive at the higher frequencies. I was able to find a nice empty slot at 1610, but then I realized that some of my radios won't even tune that high. The next lowest open slot was 1390, so that's what I set the dip switches to.
It was then necessary to fine tune the RF section by hooking up a DC voltmeter, and adjusting a trimmer capacitor for highest reading. (Should repeat this adjustment when antenna is in its final location.) The antenna itself is nothing more than a 118" long piece of insulated wire. The 72" long ground wire only needs to be used in certain situations, since a low RF impedance path to ground is provided thru the AC adaptor and the house wiring.
With the antenna and ground wires just laying randomly on the floor, I connected my iPod digital music player to the inputs, plugged in the AC adaptor, and fired up the iPod. I adjusted the Gain, Modulation, and Compression pots according to the instructions, and then went into the next room to tune in one of my AM radios. To my great joy and amazement, rotating the tuning dial to 1390 brought in the cleanest-sounding signal I could have hoped for! No hum whatsoever, no distortion, excellent strength.
Naturally, my next step was to grab a portable radio and go strolling about the house to check the range and directionality of the signal. There was not a single place in the apartment that the signal was at all affected. So then I went out to my car to see if that radio would pick up the signal. Sure enough. So then I started the car and drove out of the parking lot and down the road. It was still plenty listenable to the end of the parking lot (about 100 feet from the apartment), but gradually started to fade as I drove further away. When I got all the way out to the main highway (about 400 feet away, I could still make out the signal, although very faintly. I was impressed!
What I really like about this transmitter is that I don't seem to have any of the problems that I've had with FM transmitters: low range, random fadeout, extreme sensitivity to antenna position, etc. The AMT3000 doesn't seem to care where the radio is in the apartment, or what position it's in, or if you walk past the radio, or carry it around. It just sounds great! So, If any of you happen to be driving past my apartment complex, be sure to tune in to AM1390, WPMS, and catch about ten seconds or so of my superb programming.
Based on this experience, I can heartily recommend this unit to anyone who wants an exceptional AM transmitter, and who has basic electronic kit-building skills. You won't be disappointed!
Paula