Joel Koltner kirjoitti:
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?

---Joel


Solution for LO maybe is DDS.
The practical solution of DDS is is extremely simple and cheap.
Please google word "DDS"

-- postipoika

"Postipoika" wrote in message
...
Solution for LO maybe is DDS.

That's a big "maybe" -- even the fastest DDSes aren't much better than 1GSps
or thereabouts, giving a realistic tuning range of 0-400MHz... and those parts
are quite power hungry and not at all cheap (e.g., Analog Devices' AD9858 is
several watts and nearly $50 even in quantities of 1000!). On the other hand,
one of the much lower frequency DDSes in conjunction with a mixer would
probably work well -- although it just shifts the problem to how to get nice
and pure, very wide range fixed frequencies to mix with. (E.g., DDS does
0-200MHz, so now you need just, say, a 200MHz+/-IF, 400MHz+/-IF, 600MHz+/-IF,
etc. oscillators to mix with...)

Of course with the very fine-grained frequency resolution of a DDS,
multiplying the output up would seem to be an obvious approach, but I'm told
this isn't typically used due to the relatively high spur levels of the DDS
itself.

---Joel

In article ,
Joel Koltner wrote:
one of the much lower frequency DDSes in conjunction with a mixer would
probably work well -- although it just shifts the problem to how to get nice
and pure, very wide range fixed frequencies to mix with. (E.g., DDS does
0-200MHz, so now you need just, say, a 200MHz+/-IF, 400MHz+/-IF, 600MHz+/-IF,
etc. oscillators to mix with...)

From reading the occasional data sheet and appnote, I have the impression
that (as Tim Wescott says) they upconvert to a high IF, like 3 GHz,
and then convert down from there.

In that case they might have an LO that tunes from 1.7-3 GHz, which is
a much smaller range, proportionally, than 100kHz-1.3GHz.

--
Wim Lewis , Seattle, WA, USA. PGP keyID 27F772C1

On 16 Jun, 22:22, Postipoika
wrote:
Joel Koltner kirjoitti:

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?

---Joel

Solution for LO maybe is DDS.
The practical solution of DDS is is extremely simple and cheap.
Please google word "DDS"

-- postipoika

My Yaesu FT-857D and FT-817ND transceivers use a PLL and DDS. The PLL
cleans up the DDS output and the DDS gives the fine tuning.

The 857 receives up to 450 MHz, and uses a 68.33 MHz first IF.

Leon