Re: BITX-40

Ruud Jongeling <pe2bs@...>
 

As M_Orwell noticed before: there is a small program to calculate the
inductance of ferrite and iron powder ring core. Now version 1.2 is
available and the site has changed to:
http://www.dl5swb.de/html/mini_ring_core_calculator.htm
I always use it to get an idea of the turns needed. After that I do
some fine tuning with an LC meter.
73

Ruud
PE2BS


--- In BITX20@..., "Allison Parent" <kb1gmx@a...> wrote:

RE: Cores

For the transformers 10 turns on FT37-43 ferrite is a good match.
For the tuned inductors and low pass network T37-6 or T50-6 is good.

For 9.6 mhz IF and in both the 20m and 6m version that was what I
used.

Note FT is ferrite and T is powered iron. The latter is better for
tuned circuits.

Allison


--- 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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