Bill said:
>Anyone remember the National MB-150 all band (except 160 and maybe
WARC) network?<
I suspect it would be REAL fun trying to make one to cover all the HF ham bands
below 30MHz. A problem is that you can get it to resonate at two frequencies at
once, where one is a harmonic of the other. For 5 bands, it was an 'all right
I suppose' compromise, but the L-C ratio could be right only on a few bands
(typically 2). But it was convenient.............
Probably the most efficient is plug in coils. I've seen photos of a pre WW2 HF
tx that ran 100kW out: it had 'plug in tank circuits' for the PA. Each one was
on a wagon running along a narrow gauge railway, and to change band, you pulled
out the one, shunted it in a siding, pulled the switch (anglice, 'points') and
a pushed another one into place. Hardly a fast band change. I suppose if you
used vapour phase cooled tubes, you could generate some steam to pull the PA
tank circuits around....
73
Peter G3RZP
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