Re: Planning for a BITX40 "ver3"


Hi Bruno
I did it
I have one version 1 working in 40 m
this is the link
I have more videos

2011/3/15 Bruno Luciani <bruno.luciani@...>

Mark I am in the way to modify 20 mtr Bitx to 40 mtr

Sunil says to me to use 120 pf capacitor instead 47 pf in band pass filter
, in a few days I try to modify


--- In BITX20@..., "Mark" <huitmarmottes@...> wrote:

Hi all,

I have a BITX20 ver3 board that I was thinking to build up into a 40M
version. I was wondering if anyone had any advice on the bandpass filter? I
don't have any extra IF cans, so I was planning to use toroid cores for the
inductors and trimmers and follow the circuit for the original BITX (2uH
inductors, 47pF capacitors, and 22pF trimmers). I read a bit in past
messages and some were suggesting to just increase the capacitance and
inductance values by the percentage change in frequency? I think the
multiband BITX will have options for either TOKO type inductors, or toroids
so maybe someone can shoot me a design that's already in place?

Any advise would be very welcome or pointers to the correct formula to

Also, reading up on the BITX20 mods done by F6FEO, some builders here
(vu3wjm) mentioned using his changes to the capacitance values in the
crystal filter for improved audio (82, 120, 150pF). I'm sure I'm missing
something as my background is not so great, but I was just wondering on how
the changes work? The mods show the 150 in the center, the 120s between the
adjacent crystals, the the 82s on the outside. But in that case, how will
the 82pF values be correct since they will be in series with 0.1uF values in
the circuit once the filter is in place?

Anyway, thanks in advance for any help,


"Sólo una cosa convierte en imposible un sueño: el miedo a fracasar."
(Paulo Coelho)
World Amateur Radio Foundation, Inc.

Juan Carlos Berberena Gonzalez

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