Re: Ideas for AM, NB FM Demod and CW filter board
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Agree with Allison. If what you want is a FM monitor receiver, then design and build something
specifically for that purpose. If you want an AM General Coverage receiver, then build one
specifically for that purpose. As it stands now the BITX or uBITX is not a good choice for
either mode. Lots of modifications would be required and would still result in a compromise
design for those modes, and could also degrade the excellent design and performance of your
BITX or uBITX as an SSB and CW transceiver.
There are several ICs that can be used as the back-end of a AM/FM receiver. They come
in WBFM or NBFM models, and some are suitable for both wide or narrow FM. It should be
easy to design and build a simple down-converter to go ahead of one of those chips and
follow it with an audio amplifier stage. For FM you would probably want AFC, and lots of
gain followed by a limiter ahead of the FM detector. For AM you will probably want to include
some sort of AGC.
What does seem to be useful for AM and FM and related to the uBITX or BITX-40 would be to
use a Raduino board as the frequency and mode control for a new design for AM, FM, or both.
The Si5351a is inexpensive and could be a good source of LO signals for the down-converter.
Software for the Arduino Nano could be written to specifically support this layout.
If your goal is VHF or UHF operation on SSB or CW, then a transverter might be the most
cost effective way to go. Doing this would only require that the BITX or uBITX output be
attenuated enough to match input level requirements for the transverter.
My 2-cents worth.
On Tue, May 29, 2018 at 12:10 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
On Tue, May 29, 2018 at 10:26 am, Ashhar Farhan wrote: