Total posts : 45366
First, I forgot to answer the question of “is this from YouTube?” The answer is yes, it’s from Rick ?? (I forgot his last name) and you can find his page here: http://www.vacuumtuberadio.com/AM_Transmitter/.
As it is now the TX works better than it ever has. Audio is full and “punchy” and the FM’ing problem is much better if not gone. I used to have to tune on the fringes of the carrier signal to get audio. Now, I have a nice peak to tune on to. To visualize this, before the signal was more like a “V” where the audio was on the “ends” of the carrier signal. Now it’s much more like an “A” where the audio peaks on the intended frequency of 1290 AM. I should also mention that I have experienced very little frequency drift as the TX warms up. Good Stuff!
You are correct in that the circuit has not been modified. Well, it has been modified numerous times before but I thought it would be best to get the circuit back to original for discussion and troubleshooting sake. What you see on the schematic is what it is now.
About the “whine” or “howl” I’m talking about. Honestly, I’m not hearing it today! Go figure. I guess everything is great right now. I’ll have to watch this in the future.
Radio’s that I use to test with vary. I have a 1948 Stewart Warner that I use mainly and the TX sounds great. I have also used a Sony Walkman, my car radio parked in the garage, an AM/FM car radio that I use in the garage, and a 1980’s vintage Technics sterio amp and radio in the garage. I use my Grundig G5 to help fine tune the TX frequency, a cheap GPX AM/FM/CD under-counter radio in the kitchen, and an Emerson AM/FM radio in the bathroom. As I type this, everything sounds great. The Grundig G5 gives a little whine when I first power it up but the whine goes away after a few seconds as (I’m guessing) the radio filters this out.