Hi Tim,
A short search found these pages of interest...
On this page:
http://forums.qrz.com/showthread.php?353085-Good-AM-station/page2Glen, K9STH, writes:
The original Heath DX-100 and the DX-100B differ only in a very few components. The DX-100B has 3-capacitors changed to slightly improve the drive on the 10-meter band, the 4-position crystal switch is eliminated and there is only 1-crystal available that has to be engaged by a slide switch on the chassis, the original fixed capacitor with 150 pf variable antenna loading capacitor has been changed to a continuously variable capacitor, the cabinet style has been changed, and the rear of the chassis came with the 2-holes for the SB-10 SSB adapter already in place (you have to drill the DX-100 chassis for these). The original DX-100 transmitters could have a Heath modification kit installed to replace the old antenna loading scheme with the variable capacitor of the DX-100B and those transmitters such modified were known "unofficially" as DX-100A transmitters. The audio circuitry is the same in both the DX-100 and DX-100B
There were several modification kits available from Heath for both the DX-100 and DX-100B. Information on those can be found at:
http://k9sth.com/uploads/Heathkit_DX-100_mods-1.pdfGlen, K9STH
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Sounds like Glen knows the score. And that pdf is a complete DX-100 manual!
If you want to warm up your soldering iron and make some mods check these:
http://www.amwindow.org/tech/htm/dx100.htmhttp://www.amwindow.org/tech/htm/dx100/dx100.htmI had a DX-100B when I was a teenager some 35 years ago. I still remember how warm my bedroom got after a few hours of operation. I also remember my mom having to fend off alot of questions from the FCC about her sons "citizens band radio" operation and the resulting TVI the neighbors were experiencing. Ahh, the heady days of youth! (Thanks mom).
Cheers!
Don