--- In BITX20@..., Paolo Cravero as2594 <pcravero@a...>
wrote:
Hi
Great to read about your BITX developments!
I have one concern, though: will it be possibile to efficiently
filter
out unwanted harmonics +-n*10MHz at 144 MHz?
I think VHF&up transceivers use higher modulation IF or a
different
generation method.
Good... good question. ;-)
The Yaesu FT-290R have 4 passaband filters sintonized at 144MHz with
the aid of varicaps as output of mixer (it has also a ring diodes
mixer), it has a 11MHz FI, then I suposse this is not problem,
having some narrow passaband filters (four etapes minimun). The
consecuence of this is that the sintonization range will be narrow
also, but this is not a problem. I want to use only at 144.300 +-
50KHz. ;-) I do not use varicaps for sintonizing..
I make a tranverter for 28MHz to 144MHz a year ago and it also have
a 4 coil passaband filter little trickly to adjust. But no much
problem afterthat.
Howhever I not have made yet the tests. The 4 coil passaband filter
must be enclosed in a box, and the coupling must be soft. A coil
near the other coil assures soft coupling. It woks, as work for my
transverter a year ago.
Thank You for your coments.
Greetings
Manuel
EA7ARX
Just my thoughts,
Paolo IK1ZYW
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