The best I can do would be jpeg photo of hand drawn paper page.
Even that takes some effort as only one PC supports USB and this
is not that one. All my schematic capture cadd stuff runs on
VAX/VMS and is generally incompatable with PCs.
I may add the change is not very big. I just turned the circuit
around to reverse the LO and IF ports. The transformer T3 feed
IF and Q9 feeds the balance pot through the .1uF cap.
If there is a prefered PC schematic capture I may investigate
but it must run under NT4 on a slow machine as this box is
generally accessable.
Allison
KB1GMX
--- In BITX20@..., Arv Evans <arvevans@e...> wrote:
Allison
Would it be possible for you do a quick schematic of the changes and
store it
in the FILES section of this forum? That way it will be available
for others
who might not understand all that was changed from just the textual
description.
Thanks,
Arv K7HKL
_._
On Thursday 28 July 2005 09:20 pm, ajparent1 wrote:
One of the things I didn't like in the 20m proto BITX I'd built
was the presence of audio getting into the IF amp on transmit and IF
noise in to the audio on recieve. I'd gone the route of adding an
47uh RF choke from the intersection of the balance pot wiper to
ground
which helped greatly. However, it always bothered me.
So I opened it up and tried a design change that I find pleasing and
also elimiates a number of components. As an engineer I'm the sort
that looks at a design and says "what if..?". The solution was
staring me in the face and also eliminates the PI attenuator as well.
The change is to turn the balanced modulator around and feed the IF
in on the transformer and RF (bfo) in at the balance potentiometer
via the .1uf capacitor. This eliminated the need for the 3 resistors
and the rf choke. I noted cleaner modulation, less RX noise and more
gain available in both RX and TX.
Might as well add this mod to the collection. I plan to use this
mod in the 6M version.
Allison
KB1GMX
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