Looking at this board more, and I'm just getting more dejected. I just
noticed that what appears to be C95 is missing. Is it supposed to be? I'm
about ready to throw this thing in the trash. What a waste of time and
money...
?
Kent
W9WB
On Fri, Dec 23, 2016 at 11:05 AM, Arv Evans arvid.evans@... [BITX20] <
BITX20@...> wrote:
Roy
My post did cover all the transformers, and all the inductors. It even
told you that
the trifilar (3-wires twisted together) wound cores were FT37-43 types and
that the
single wire inductors are on T37-6 cores. All transformers and all
inductors except
T5, T6, and T7 are used in both transmit and receive modes. T5, T6, and
T7 are
part of the RF PA transmit section, and are broadband or transmission-line
transformers. They are wound exactly like the mixer transformers with 10
turns of
twisted wire on FT37-43 cores. There should be no guessing required to
determine
what these are and how they are wound.
Kent
The BITX-40 V3 design avoids having to align anything other than
possibility the VFO
to insure that it covers frequencies that are specific to your license
class and your
ITU region band designation. The L1, L2, L3 band pass filter is broad
enough to cover
the whole 7.0 to 7.3 MHz range. The mixer transformers and RF PA
transformers are
broadband transmission-line transformers which provide close to unity
coupling over
most of the HF range. The L6 and L7 low pass filter reduces harmonics and
other
spurious signals that are above 7.3 MHz. Only tuning you might need to
optimize
performance is some sort of ATU to insure that your antenna presents a 50
ohm impedance
to the BITX-40 v3 antenna connection.
There is some question about your glued-together L2 core. If the broken
and
repaired core still exhibits the same inductance as it did before being
broken all should
work fine. Possible problem though is if the glue introduces a gap in the
core material
it may affect the inductance, even if this gap is small. Replacing this
core and its
winding with a new and intact 6uh inductor should restore things to
normal. If you
have built a simple RF Detector probe you can measure transmit drive level
to the
RF PA section at low end of 40M and again at high end of 40M to see if
signal levels
are nearly the same. Use any voltage difference to calculate the db
(decibel) difference
which should be less than a couple of db.
?Arv K7HKL
_._
?
On Fri, Dec 23, 2016 at 4:11 AM, Kent Vanderploeg kvanderploeg@...
[BITX20] <BITX20@...> wrote:
So while I wait on replacement parts for L2, I'm trying to get some
learning experience out of the radio. I superglued L2 back together and it
looks pretty good, though I'm sure it's not ideal. I have been able to
hear some CW about 1/3 of the way of the tuning range.
I set up my FT-450D to listen and began transmitting on the BITX very
near the frequency where I heard the CW. It appears that my range is off
as the transmitting frequency at approx. 1/3 up the tuning range is
7.006MHz. Is there a simple process to align the TX with the SSB portion
of the band? I don't have any test gear other than a VOM and other
transceivers.
I'm sure this info is listed somewhere else in the Yahoo groups, but I
have no idea how to find it. I'm used to standard forums where info is
much more readily readable and searchable.
Kent
W9WB
On Dec 22, 2016 2:27 PM, "rjinspace@... [BITX20]" <
BITX20@...> wrote:
Arv.
Well, your writings cover the RX, but not the PA transformers T5, T6 and
T7 in
And it does not matter if I use a BITX20 v.3 PA PCB or a breadboard or
whatever - the whole point is that I cut and add traces / jumpers in order
to replicate the PA circuit in
_circuit.pdf. But the schematic as it is now is useless because one has
to guess that T5, T6 and T7 are transmission line transformers 10 turns
bifilar on FT37-43 or FT50-43? And the predriver and driver could be 28AWG
wire, but the output transformer should maybe use a thicker wire.
But I am now out of here. I have wasted enough time. IMO - the ONLY
solution is that ALL INDUCTORS AND TRANSFORMERS are specified IN THE
SCHEMATIC. Schematics that can not be built without guessing are not for me.
Just my opinion and choice - of course. Others may be fine guessing and
experimenting.
Thanks again Arv for your kind help.
Roy
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