Is there any modification to increase the modulation of the Ramsey AM 25 ?
Is there any modification to increase the modulation of the Ramsey AM 25 ? I see that the SSTran does 100 % modulation, the Ramsey is less ...more like 80 % according to some reports. Perhaps bypassing the audio chain on the AM25, and using a external audio amplifier with a outboard limiter would make a difference?
I can't help you with any modification to increase the modulation of the Ramsey, as I don't know of any. However, I would suggest that you don't waste too much time and money on modding the Ramsey. If you find a cheap and easy mod, I'd try it. Otherwise, it would make more sense (to me) to just spend $100 and get a SSTRAN kit.
The only thing that comes to mind about increasing modulation were the mods to the Radio DJ toy transmitter. I think you will find some information about this here at Part15.us. If not, a Google search will certainly find it.
and those can be found on our review page, here:
Experimental broadcasting for a better tomorrow!
The mods for the Wenzel do not apply to the AM 25 since they are different circuits. The AM-25 is operating class C.
I have done some experimenting with the AM 25 using a dummy load, function generator, and oscilloscope. I have noted the limitation on the maximum modulation where above about 80% the envelope (audio) becomes distorted. I also found that by adjusting the bias (R23) of the op amp which supplies the audio/DC power to the final amplifier higher modulation and reduced distortion can be obtained. It did not achieve 100% however.
The other problem with this is that the 100 mW. input limit to the final may be exceeded depending on the bias setting. In fact, with the "bias" set according to the manual, according to my data it is!
Other than experimenting with the bias, I don't see any simple modification that will improve the performance.
Neil