@rugster Didn't the Procaster move their processing off the main board and make it a separate component in their later models?-- I presumed they moved it to correct some interference or something.
Yes, I remember reading about that @richpowers. I don't think I had this issue this with my production AMT3000 kit though, so it may be connected to my layout or the way I've wired the pots. I'll investigate, once I've given myself some time to clear my head and recharge!
@richpowers The Procaster was made with the processor separate to have the Procaster outside and the processor indoors.
@richpowers The Procaster was made with the processor separate to have the Procaster outside and the processor indoors.
That makes sense. So maybe it had nothing to do with a conflict on the board. I thought it worth considering since Rugster is experiencing issues.
@mark - there are definite advantages to having the processing inside, such as greater access to the controls. However, the reason for moving the processing from the transmitter enclosure was, in the words of Gerry Herlinger, the designer of the Procaster,
“The very original unit had the compressor up with the transmitter but the RF was causing problems with the audio so it was moved."*
*Quote taken from the review of the ChezRadio Procaster on HB.
@rugster By leaving R7 out of the circuit entirely, the input to the final RF amplifier of the AMT3000 goes above 100mW, but not by much. The question is, what is the input strength without R7?
I don't know @carl-blare. No promises, but the next time I do some finishing-up wiring on it, I may temporarily disconnect that resistor and make some measurements.
Of course the in-built processor could possibly be disturbed by RF energy, there is another significant advantage to the separate and independent Procaster audio module, and that is the benefit of converting an unbalanced audio line to a balanced line for greater reach, so the audio box can be kept indoors and the transmitter/antenna be located as far outdoors as desired.
@rugster Mighty fine! Thank you.
My AMT3000 clone is all boxed up and, at this point, I'm a little reluctant to drag out the soldering iron again to temporarily disconnect R7 - at least for the time being. Sorry about that.
Of course the in-built processor could possibly be disturbed by RF energy, there is another significant advantage to the separate and independent Procaster audio module, and that is the benefit of converting an unbalanced audio line to a balanced line for greater reach, so the audio box can be kept indoors and the transmitter/antenna be located as far outdoors as desired.
Yes, it was a good upgrade for the Procaster. As for the AMT3000, as it's main target customers were vintage radio enthusiasts wanting to broadcast to radios around the house, rudimentary built-in processing was fitting, I think. Most of those customers wouldn't have wanted to go to the trouble of using external processing. Nevertheless, given the choice, I think I'd prefer not to have the processor and preamplification circuitry so close to a source of RF.
@rugster Maybe I can do the R7 measurement. I will be rigging an AMT3000 to operate at 1500kHz to aim for vintage radio listeners who may or may not exist somewhere in my coverage radius. I have a multi-meter. How can I determine how many milliWatts of RF energy are being fed to the antenna?
I don't know how you figure out what power is making it to the antenna Carl, but Neil described how he calculated the DC power input to the final stage at the beginning of this thread.
... but Neil described how he calculated the DC power input to the final stage at the beginning of this thread.
Now that's another person I miss being around. Don't nobody else go kicking the bucket, yah hear?
@richardpowers Are you sure Neil AKA radio8Z died? I hadn't previously heard that. What a loss that would be, he provided much electronic expertise to the forum. Without knowing anything for sure, I was under the impression he went on strike in solidarity with dictator Chairman Bob in the kerfuffle over ALPB.
@carl-blare Wait a minute.. I guess I might be thinking of Ermi Roos... Uh.. Sorry Neil. I hope all is well.
I never was able to make sense of the whole ALPB affair. I was Mia during that