Hi All,
I am thinking about building a receiver for the air-band (it should be fun to listen to the pilots talking
I have found a few designs on the net but they are either too simple (in fact little better than crystal radios) or they could work but use obsolete components, for example:
**broken link removed**
(MC1350 is obsolete and I don't like to have to use IF transfomers ...)
Probably more like this one:
Super improved AM-Receiver for Aircraft.
but even this one uses obsolete components. I can replace the PLL and mixers (e.g. LMX2306 and SA602 as I have them and they are still in production) but what about the IF amplifier ?
I am not sure which IC to choose for the IF amplifier with AGC. Perhaps I could use a VGA but it seems to me as an overkill (but I plan to try LMH6502 anyway)
I am thinking as a starting point to modify a kit which I own - 2m Ham radio receiver - I'll need to retune the input bandpass filter to the airband and also the 1st VCO - it is a dual-conversion FM receiver based on MC3362P, but still
it is a narrowband FM receiver and I need AM so I need to add another IF amplifier and again, what could be a good IC for this task ? (I do have a few TCA440 (AM receiver IC) which seems to be suitable for the task but it is again an obsolete chip).
Another thing I am not sure is the 1st IF of 10.7 MHz which may be too low to suppress image reception if I want to cover all the air-band. The other possibility is to use a crystal filter (21.4 or 45 MHz - I have 45 MHz xtal filters) but from what I have heard xtal filters are tricky components and require good impedance matching ...
I'd be glad to hear your suggestions on this problem.
Thanks,
Petr