1) Transistors for RX front end: relatively easy to find if based on
dual-gate MOSFET

OK, but you can get better noise figure from a GaAs part.


2) RX band filters: I have decided to have a fixed capacitor and adjust
the inductor.The availability of adjustable coils (Toko for example) has
decreased in the last few years. Digikey only stocks a few of them but
that should be OK in the near term.

Mouser stocks a VERY nice line of low cost VHF shielded inductors. Google
"xicon" and "tunable coil" on the Mouser website.



3) First IF filters: not much choice since 10.7MHz and 21.4 MHz seem to be
the only 2 frequencies stocked (most commercial boxes use between 35 and
70 MHz). The IF inductors/transformers at 10.7 MHz and 455 KHz have
disappeared from Digikey (used to be there a few years ago).

Again, Mouser is your friend -- google "xicon" and "transformer". If I were
doing it, I'd do a 70 MHz. first IF and then 10.7 MHz. second IF. Forget
dropping down to 455 unless you have to.


4) 2nd IF + FM demodulator. The Motorola parts (MC33xx) are gone. The part
that is found in many commercial XCVR is the Toshiba TA31136. This part is
not stocked by Toshiba's distributors in the US (12 weeks lead time if you
want to order 2K of them). Good news is that the Rohm BA4116FV is a
pin-to-pin compatible device and it is available at Digikey for $1.26. I
don't know if this part works since I have not seen it used anywhere...

Phillips makes (made??) a nice line of FM ICs. You might give them a try.



5) 2nd mixer crystal. The 10.245 MHz crystals are easily available but not
the 21.4 +/- .455. This seems to remove the option of using a 21.4 MHz
IF..
6) 2nd IF filter. The 455 KHz ceramic filters seem to have a very limited
availability. The exact type recommended by the IC vendor is hard to
find..

Why crystals? You are going to have a synthesizer for the front end anyway,
why not use the synthesizer crystal as your timebase and synthesize the
mixer oscillator? You said you wanted some stuff for the microprocessor to
do anyway; controlling a synthesizer is one of them. Or, you could get a
parallel input synthesizer and hardwire it to a fixed frequency.


7) FM discriminator. I could not find a source for the ceramic
discriminator recommended by Toshiba/Rohm (CDLBLA455KCAY24-B0 which is the
new P/N for the CDB450C24). I can understand the pain of the distributors
since every FM IC requires a different discriminator. The discriminator
coil that can be used instead is not easier to locate.

A discriminator (or ratio detector) is nothing more than a couple of
transformers coupled bottom to top. You can make a two-coil ratio detector
as easy as buying one.


11) TX low pass filter: will need to be hand made. That's OK but who is
selling tinned wire ?

Why would you need tinned wire? Plain old magnet wire is easy to come by.


Jim