I got really annoyed trying to get true frequency accuracy and stability for Medium Wave from the three or four DDS modules I tried.... I gave up, and built a PLL that's locked to the 198kHz BBC Radio 4 transmitter. The 198 kHz rig is run from the National Physical Laboratory's frequency standard source, so the Medium Wave boxen I built were rather more accurate than I could show on my frequency counter!
My question is: how do you prevent the (obviously very proximate) HF transmission from interfering/blocking the reception of 198 KHz?
Incidentally, I didn't mind adding proper gate driver ICs, rather than trying to cane a logic IC for the drive, and generated twice the frequency I wanted, then used a final bistable to guarantee an absolutely 1:1 M/S ratio.
I'm not sure what or whom this is aimed at, if anyone or anything.
The advice given on Steve Cloutier's "ClassEradio" website about component ratings is pretty useful, and has helped me avoid the fireworks displays that others have had!
Steve is a well-known ham who operates primarily (or solely) AM in the New England area of the US. My problems with some of the things he does (currently) are these:
1) Posts on AMFone and his own website suggest that, even though he builds solid state stuff these days, he still relies on (what I call) "boat-anchor construction techniques", that are appropriate for vacuum tube/valve rigs but largely ridiculous in an environment where the FET gate driver better be within less than 2 cm of the transistor it is driving and minimizing parasitic L and C is key.
http://www.classeradio.com/24_fet.htm (Holy shit, dude. If you use some more modern transistors and construction techniques, maybe you wouldn't have to use 24 freaking FETs.)
2) Much of the things on his website use obsolete or ridiculously old ICs and transistors.
3) His main design is essentially a half-bridge Class-E with the upper half being the PWM modulator and lower half being the RF stage. Unfortunately, when you do this sort of thing, you create a scenario where you have great "pull-up" capability owing to the upper half of the half-bridge but there is weak "push-down" capability because the upper half can't push down well, and so I think it is very difficult to not create a distorted (mis-shapen) modulation waveform, as a result of the mismatched capability of the two halves.
Suffice to say, I'm not a huge fan of his work.
Now.... back to designing a little (80W PEP) PWM rig for as little cost as possible.....
Curious to see what you have so far.
