AM/MW Transformers question for Microsemi AN1819

[BrWer]

What modification would be needed for the Microsemi AN1819 board to change the frequency down to AM/MW band , lets say 1.2Mhz continuous . I know the power will be reduced to around 4 times which would be enough for the testing device I am looking for.

BrWer   

[BrWer]

Seems like my project is achievable by modifying the MRF101A by using the MRF300A probably in a push pull configuration 

[jcve...@gmail.com]

Hi BrWer

The input transformer will probably need to be changed. The low impedance side is just a single turn and the way it's made There's no good way to change it. T2 really needs a few more turns but that will throw off the feedback unless you keep the turns ratio the same (close is probably OK), try 11:11:5 also on a bigger core. T3 probably needs more turns of 25 ohm coax I'd say 5 or 6 but that won't fit on the binocular core so you'll have to find something else.

It's going to be quite a bit of work and be prepared to looses some MOSFETs in the process. I tried dead-bugging MRF300's into the circuit but it didn't work very well. 

To be honest this 600W MFR300 design is probably a better jumping off point it looks like you could easily add more turns.

73,

Jim WA2EUJ

[BrWer]

Hi Jim,

Thank you very much for the advise.

Yes, I have found the 600W MFR300 design on the web and that was the reason which motivate me to move in to the MRF300.

I found another good source of modifications to your amplifier mrf-101a  for Low frequencies in the order of 137Khz and 475Khz by  Mark Mattila, VA7MM and Roger Graves, VE7VV; as starting point:

https://www.qsl.net/ve7vv/Files/100WBroadbandLF+MF+HF_RF_Amplifier-R28Jan21.pdf

And Yes, I am ready for the smoke to come out, as I had already saw it in  another PA; same MW band Class D attempt claimed to be 400wts and It was just able to provide 20wts modulated at 100%, non modulated around clean 80watts.  

I will try to collect as much information as possible for the MRF-300 A/B for the input/output impedance operation at 1Mhz.