This is a interesting listing... I'd sooner buy a Cuthbert for less than half the price, but it is interesting.. https://www.ebay.com/itm/257489683476
$250
Description:
This listing is for a Ramsey AM25 AM transmitter, power supply, and antenna that has been upgraded, tested, and works to professional standards. If you're seeing this listing then you're probably already familiar with the AM 25 and Part 15 transmitters. If not, an online search should provide a manual (eBay doesn't allow links in listings).
However, *THIS* AM 25 is like no other:
* The power can be adjusted to meet F.C.C. Part 15 rules (meaning it can actually be legal to use).
* The transmitter can modulate past +125% without distortion (see video). This is a BIG issue with stock AM 25 transmitters.
* Modulation is linear from -100% to +125%.
* The frequency can be set to meet F.C.C. standards for the AM broadcast band (+/- 20Hz).
I'm surprised that all of the Ramsey AM 25 transmitters I've worked on needed modifications to make them usable, meaning sounding loud and clear. The instructions are vague and make suggestions that will result in poor performance. That said, the buyer of this AM 25 can expect these issues to have been resolved.
The transmitter operates on 10kHz channel spacing such is used in North and South America and is most efficient on frequencies above 1350 kHz. It's currently set to 1620 Khz in the expanded band but can be set to your favorite frequency if requested.
The video shows the modulation performance and the pic with the frequency counter shows that the carrier frequency can actually be set exactly. Sorry, neither the Sencor frequency counter nor the Belar modulation monitor are included (I need to write that as I've been asked before). What you DO get:
1) The upgraded Ramsey AM 25 transmitter shown in this listing and video
2) The 12V power supply
3) A wire antenna with RCA/Phono plug
Regarding an antenna, the transmitter will work fine with the included antenna, but those interested in better performance may want to build an outdoor antenna. Again, it's all online if you look. The buyer is responsible for proper operation of this transmitter. It will be set to your desired operating frequency and shipped after thorough testing. Despite what the instructions say, -DO NOT- adjust the bias control. Doing so made the stock AM 25 sound like garbage, and on this one, it is set for optimal performance.
Have questions? Let me know...
Some freebie tech tips for those who already own an unmodified AM 25 (feel free to copy and distribute):