Re: BITX-40

Ruud Jongeling <pe2bs@...>
 

Hello Uelson and Arv,

In my BITX20 and my new BITX8020 (IF-9MHz, not ready yet) I used FT37-
43 with 13 turns trifilair of bifilair, 0,3mm for all transformers in
the mixer, the demodulator and the driver stage.
In my DRM radio (3995 kHz, direct conversion) I used FT23-72 with 10
turns, trifilair, 0,2 mm in the mixer.
I have no experience with FT37-61.

73
Ruud
PE2BS

--- In BITX20@..., Arv Evans K7HKL <arvevans@e...> wrote:

PY2UAT

Since I used Farhan's air-cored toroid idea (small plastic rings as
coil
formers) I am probably not the best person to answer your question
about
which ferrite type toroid core material is best for your
application.
Possibly some other member of the BITX20 forum could answer this
question?

As to wire size, the currents involved are rather small, so the real
question seems to be how small can the wire be and still be
reasonably
easy to work with in winding the transformers. For my plastic core
transformers I used #26AWG which is approximately 0.404 mm or
British
SWG-29.

The number of turns will depend to some extent on which ferrite core
material you use. There are published tables which show the number
of
turns required for a specific inductance for each type of ferrite
mix.

For the non-resonant transmission-line transformers used in the
mixers
it is usually adequate to have between 7 and 11 turns per winding
if you
are using ferrite based toroid cores. I am using 16 turns with my
air-core transformers.

Arv - K7HKL


Please, I am constructing the BITX-40 v3 version of Rahul, but I
want
to construct it (T1, T2 and T3) with FT37-61 or FT37-43 which of
the
two would be better? And how many wire returns AWG would be
necessary?

Thank You!
Vy's 73
Uelson de Almeida Toyama - PY2UAT


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