I thought I would take a break from the usual short-wave broadcast and short-wave receiver reviews to chat a bit about the SSTRAN Low Power Medium Wave Transmitter Kit (AMT3000-9KSMNT - 9 kHz frequency increment). It's a 100mW transmitter kit that has been on the market for a while and one that can be readily purchased over the Internet.
Shortly after the kit arrived by mail, I opened the box and found several electronic components, a pre-printed PC board and an instruction booklet. At first it looked to be a formidable challenge, but I soon discovered once soldering iron and manual was in hand assembly went quickly and easily. In total it took me approximately nine hours to complete. Don't misunderstand me, you do need to have some rudimentary electronic and soldering skills. Aligning the ICs to the IC sockets was the most troublesome aspect, but with a little patience and dexterity the components were eventually seated.
Once fully assembled I toggled the DPS switches to a clear frequency -- anywhere from 522 to 1710 kHz -- then powered it up. To tweak its maximum transmission power I tuned the antenna trimmer by setting a volt meter at its T1/T2 points. Once this was done, I adjusted its compression, modulation and gain controls. And to my surprise, I received a wonderfully warm tone with near FM quality broadcasting over the Medium Wave band.
What is its transmission range like? First, let's be realistic. To be FCC compliant, the antenna length must be restricted and the transmitter power must be no more than 100mW, which means ultimately that the range is limited. Using the supplied 10 foot random wire aerial and ground wire, I have adequate daytime coverage for my entire household and yard (which is less than a 100 feet); at night, the range at its weakest point is about an 1/8 of a mile. This is sufficient for my use, since my intention is merely to broadcast Internet radio broadcasts and music files from my computer around the house and yard.
I also want to express my gratitude to Paul -- the engineer and seller of this fine product -- for the excellent customer service I received. On numerous times I contacted him about purchasing a UK power adaptor (US power adaptor is included for North America) compatible for this product, and each time he responded promptly with advise and an explanation.
All in all, this is a very well-engineered product, the manual is well written and easy to follow. I wouldn't hesitate in purchasing another one.
530 kHz - 1700 kHz in 10 kHz steps or 522 kHz - 1710 kHz in 9 kHz steps, depending on order option
Frequency Selection Method:
8-position DIP switch
Frequency Tolerance @ 25ºC:
Amplitude Modulation (AM)
Maximum Modulation Level:
Power Input to Final RF Stage:
118” wire (supplied with kit)
Tunable pi-network. Matches high impedance antenna to low-impedance RF output stage.
4-position DIP switch selects inductance combination, adjustable ceramic trimmer capacitor peaks resonance.
RF Output Metering:
Test points on circuit board provide DC voltage to user-supplied 10 megohm/volt voltmeter. Measured voltage is maximum at resonance.
RF Grounding Options:
Jumper plug options for including/excluding RF isolation inductors in power supply and audio source ground paths.
20 Hz to 20 kHz ±1 dB
Audio Treble Boost:
+8 dB, boost midpoint at 2 kHz. Jumper plug option.
Less than 0.5% THD through audio stages.
Minimum Audio Input Level:
200 mV RMS for 100% modulation (input gain control at max).
Compression ratio adjustable from 1:1 to 5:1. Attack time less than 1 ms. Medium release time suitable for both voice and music.
Adjustable threshold. 15:1 compression above threshold.
Front Panel Controls:
Audio input gain, modulation level, compression ratio.
Rear Panel Jacks:
2 RCA audio in jacks, RCA antenna/ground jack, 2.1 mm power input jack.
120 VAC, 2 watts
5”W x 3.9”D x .062”H FR4, two layers, 1 oz. copper, top and bottom solder masks, top silkscreen.
6.1”W x 4.2”D x 1.5”H ABS plastic. Drilled and labeled front and rear panels.