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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

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
_._

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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Allison

Free Schematic CAD software that should run on your Microsoft NT-4.x can be
obtained via the following URLs:







All of these sites provide freeware schematic drawing software for windows
(and for Linux) that would be suitable to use in drawing a partial schematic
for the changes you have made in the BITX design. Of these three, EagleCAD
from CadSoft is probably the closest to a professional CAD program, but the
other two are certainly adequate and may be easier to learn.

And...Yes, there are other schematic drawing programs available. These are
just the ones that I know about and use frequently.

Arv K7HKL
_._

Ok, Looks good which one produced the most usable output
for posting?

Afterall I can post gerber files and vectorlists but they are
hardly easily seen.


Allison
KB1GMX



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

Allison

Free Schematic CAD software that should run on your Microsoft NT-4.x

can be

obtained via the following URLs:







All of these sites provide freeware schematic drawing software for

windows

(and for Linux) that would be suitable to use in drawing a partial

schematic

for the changes you have made in the BITX design. Of these three,

EagleCAD

from CadSoft is probably the closest to a professional CAD program,

but the

other two are certainly adequate and may be easier to learn.

And...Yes, there are other schematic drawing programs available.

These are

just the ones that I know about and use frequently.

Arv K7HKL
_._



On Thursday 28 July 2005 09:52 pm, ajparent1 wrote:

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
> >
> >
> >
> >
> >
> >
> >
> > SPONSORED LINKS
> >
> > Craft hobby
> > Hobby and craft supply
> > Ham radio
> >
> >
> > Hobby supply
> > Ham radio outlet
> > Ham radio sales
> >
> >
> >
> > YAHOO! GROUPS LINKS
> >
> >
> > Visit your group "BITX20" on the web.
> >
> > To unsubscribe from this group, send an email to:
> > BITX20-unsubscribe@...
> >
> > Your use of Yahoo! Groups is subject to the Yahoo! Terms of

Service.

YAHOO! GROUPS LINKS


Visit your group "BITX20" on the web.

To unsubscribe from this group, send an email to:
BITX20-unsubscribe@...

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

Allison

All can produce posting quality files. I usually use "Dia" and set it to
make .png (Portable Network Graphics) output. You have to save a copy in
native .dia format first, then "export" the drawing and set the file type to
".png" or ".jpg" as desired.

There are examples of Dia produced schematics on my web sites
<www.k7hkl.webhop.net> and <www.qrp.webhop.net>. There are also some Dia
built schematics at BITX20/FILES/K7HKL/...

Arv
_._

Dia was a dud, could not get a file that would unzip from any of the
hosts.

The other two are really poor for schematic capture. I found the
libraries more suited to digital design. I'll keep Eagle around for
digital stuff. For analog that has lots of passives like trifilar
transformers, forget it.

I'd forgotten how horrid PC based schematic capture tools are.
Last one I used a lot was CADD6 (G-cadd) I have that but the
files are not easily viewed without cadd or autocadd. Microcadd
was easier to use but didn't run well under NT but is decent on
a simple dos machine wich also limits portability as you need
microcadd to view files (it's a really small program).

Much too much time spent on this already. I may just take paintshop
and tweek and existing image.

Allison
KB1GMX

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

Allison

All can produce posting quality files. I usually use "Dia" and set

it to

make .png (Portable Network Graphics) output. You have to save a

copy in

native .dia format first, then "export" the drawing and set the file

type to

".png" or ".jpg" as desired.

There are examples of Dia produced schematics on my web sites
<www.k7hkl.webhop.net> and <www.qrp.webhop.net>. There are also

some Dia

built schematics at BITX20/FILES/K7HKL/...

Arv
_._

On Friday 29 July 2005 09:36 am, ajparent1 wrote:

Ok, Looks good which one produced the most usable output
for posting?

Afterall I can post gerber files and vectorlists but they are
hardly easily seen.


Allison
KB1GMX

--- In BITX20@..., Arv Evans <arvevans@e...> wrote:
> Allison
>
> Free Schematic CAD software that should run on your Microsoft

NT-4.x

can be

> obtained via the following URLs:
>
>
>
>
>
>
>
> All of these sites provide freeware schematic drawing software for

windows

> (and for Linux) that would be suitable to use in drawing a partial

schematic

> for the changes you have made in the BITX design. Of these three,

EagleCAD

> from CadSoft is probably the closest to a professional CAD program,

but the

> other two are certainly adequate and may be easier to learn.
>
> And...Yes, there are other schematic drawing programs available.

These are

> just the ones that I know about and use frequently.
>
> Arv K7HKL
> _._
>
> On Thursday 28 July 2005 09:52 pm, ajparent1 wrote:
> > 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
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > SPONSORED LINKS
> > > >
> > > > Craft hobby
> > > > Hobby and craft supply
> > > > Ham radio
> > > >
> > > >
> > > > Hobby supply
> > > > Ham radio outlet
> > > > Ham radio sales
> > > >
> > > >
> > > >
> > > > YAHOO! GROUPS LINKS
> > > >
> > > >
> > > > Visit your group "BITX20" on the web.
> > > >
> > > > To unsubscribe from this group, send an email to:
> > > > BITX20-unsubscribe@...
> > > >
> > > > Your use of Yahoo! Groups is subject to the Yahoo! Terms of

Service.

> > YAHOO! GROUPS LINKS
> >
> >
> > Visit your group "BITX20" on the web.
> >
> > To unsubscribe from this group, send an email to:
> > BITX20-unsubscribe@...
> >
> > Your use of Yahoo! Groups is subject to the Yahoo! Terms of

Service.

YAHOO! GROUPS LINKS


Visit your group "BITX20" on the web.

To unsubscribe from this group, send an email to:
BITX20-unsubscribe@...

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

I posted a file to the KB1GMX folder as a quick jpeg of
the modulator turned around. It isn't pretty but saves
guessing.

Allison

Allison

Thanks for posting the schematic of your BITX modulator modification.
With the different languages and varying skill levels involved in the
BITX forum, sometimes a picture or schematic is necessary for all to
understand the more technical aspects of some design & construction
activities.

Arv K7HKL
_._

-

Good old PSP was the tool.

Finally got DIA to crack using gunzip with no shortage
of complaints, installed it and it crashed hard after
looging a long list of errors. Apprently it has a lot
of dependancies on MS products. The system here is NT4
with SP6A but NO MS loaded products including OE and IE.
Its' a security thing.

I'll hunt around for a decent too to eiter convert the DXF
files from cadd6 or maybe a different cadd tool that really
works for schemtaic capture.

I have more schematics comming but I need a better tool
for the PC environment.

Allison
KB1GMX