Joel Koltner wrote:
Just curious... does anyone know what sort of architecture you find in your
typical HT or mobile "receives everything from 100kHz - 1.3GHz!" radio to
generate such a vast range of frequencies while still keeping the prices so
low (plenty are available for $200, and I can't expect the LO makes up a
particularly large percentage of that total price)? I would tend to lean
towards something PLL-based given the typically channelized nature of
available frequencies, but a single PLL would still need a VCO with a huge
tuning range. So... perhaps a pair of mixed PLLs, with one doing the fine
tuning and another the coarse tuning (having been multiplied up from a low
frequency)?

I attempted to decipher the schematic included with my Yaesu FTM-10R, but
everything is so tiny it was rather hopeless!

I don't suppose any of the reviews ever go through and sweep the LOs while
watching for the worst case spur conditions, do they?

The HT-class wideband receivers typically will have a first IF in the
45 or 70 MHz range, and use a number of different PLL's one for each
different band. Each PLL is literally less than a square cm on the
PCB, and there's a lot of them.

At least one Sony from the mid 90's had a 10.7MHz second IF, and if
the frequency you wanted was anywhere near the first IF of 70MHz, then
they skipped the first IF and went straight to the second IF.

For FM the 10.7MHz IF is the ending point... for non-WBFM modes there
was a third IF of 455kc with some ceramic filters.

Some of the HT's have 5kHz channel spacing on the HF band with no
finer tuning available (OK for SWLing but nothing else), but the
slightly better ones have finer tuning in the HF range thanks to a the
2nd or 3rd LO being a PLL too.

Image rejection is nearly completely nonexistent.

Tim.