On Oct 11, 11:21 pm, ShutterMan wrote:
Good answers from everyone, thank you. In looking at the simplest of
tank circuits for radio, I just couldnt understand why you just cant
add more coil windings and different capacitance to increase frequency
coverage.....but it looks like its alot more complicated than that.
Thanks again.

That works over a limited range. It can be pressed into service to
cover 3.5MHz - 30MHz, which is (not too surprising) the range of bands
traditionally covered by a ham-band transceiver. Going down to 1.8MHz
or up to 54 MHz is possible with some cleverness and a number of
recent radios cover those bands too.

All that said, using traditional techniques to do the bandswitching
from the front panel involved a bandswitch shaft running through the
length of the radio coupled to multiple switch wafers for each section
that required switching components for different bands. Some even have
multiple shafts for the bandswitching run by chains or gears.

Since this is the "homebrew" group, I should point out that some
homebrewers with mechanical cleverness have done this sort of
bandswitching in the homebrew receivers, transmitters, and (egads!)
transceivers. But a more popular technique going back at least half a
century is to build a base radio that works in one band (which may not
even be a ham band) and use converters/transverters to use that radio
in the band of interest. Some call this the "tunable IF" technique and
in ham bands the tunable IF typically covers a span of 50,100,150 kHz
(if CW or SSB sub-bands only) or 500kHz (if intended to cover a whole
band). There are gotchas related to images/leakthrough based on choice
of IF, too, but these have been overcome with few compromises with
several popular choices. The result is usually not a DC-to-daylight
radio but one that works on the desired ham bands; this is counter to
what a SWL'er typically expects out of their radio. (It seems that
most today expect to key in a frequency on the front panel and go
right to it). So the "first IF at 45 MHz" approach is more popular
there.

Tim.