Re: Extra capacitors in your BITX...?

Arvid Evans <arvevans@...>
 

Rahul & Hans

Thanks for the info on the RU designed Desna Xcvr. It is interesting
that they used a valve-type linear instead of solid state.

In the Desna design, Vt2 and VT3 layouts do show one way of obtaining
proper bias when using BJTs in a bi-directional layout.

After looking at the Desna and the PSK-20 by RV3GM, I opened Eagle CAD
and put together a quick conceptual drawing of a minimalist DSB Xcvr
layout that uses this switched bidirectional amplifier idea. The
result has been uploaded to <BITX20/FILES/K7HKL/DSB-Mite "Conceptual
Drawing".gif> if anyone wants to look and comment.
NOTE: THIS IS A CONCEPTUAL DRAWING ONLY...NOT TESTED...DO NOT BUILD
FROM THIS DRAWING.

73
Arv-K7HKL

--- In BITX20@..., Hans Summers <Hans.Summers@t...> wrote:

BITX'ers

Note that if you want to see an English translation, you could try the
Altavista "babel fish" see http://babelfish.altavista.com/babelfish/tr
<http://babelfish.altavista.com/babelfish/tr> . You can type in the web
page, and view the translated web page. It's rather neat. The
translation is
obviously not perfect but it's quite easy to follow the ideas. If
you look
at the home page http://www.cqham.ru/index.phtml
<http://www.cqham.ru/index.phtml> you'll find all kind of gems.
Numerous
transceiver projects etc. Also many downloaded QST articles, and
more. There
is an English flag on the home page which provides a translation, but it
does not work as well as the Altavista page.

73 Hans G0UPL
http://www.HansSummers.com

-----Original Message-----
From: Rahul Srivastava [mailto:vu3wjm@y...]
Sent: 01 October 2004 06:57
To: BITX20@...
Subject: Re: [BITX20] Extra capacitors in your BITX...?


Dear Arv,

From what I could make out of mechanical translations, the concept
among RU
friends was popularised with Ural 84 design. Desna was the more updated
version probably it means dew.

the RU page for Desna design is here:

http://www.cqham.ru/desna.htm <http://www.cqham.ru/desna.htm>

The main board ckt I am posting under files section for thers to
have a look
at another way of implimenting Bi-directional concept.

73

Rahul VU3WJM





Arv Evans <arvevans@e...> wrote:

Rahul-VU3WJM

I did a search (using Google) for :Ural 84" and for "Desna" and did find
some textual mention of these units, but I did not find any web
sites that
showed equipment or schematics. Do you have a URL that we might use
to see
schematics for this equipment?

Thanks,
Arv-K7HKL
_._

On Wed, 2004-09-29 at 22:17, Rahul Srivastava wrote:

Hi!

On mention of PSK mini I also suggest looking at RU designs Ural 84 and
Desna. Similar concepts are used there while using bipolar transistors.

I am sure the coupling caps for filters can be removed. Had I been and
audiophile I would like not to have even one of them in signal path.

73

Rahul VU3WJM



Arvid Evans <arvevans@e...> wrote:

Hello

As I sit here looking at the BITX20 schematic it 0ccured to me that
some of the capacitors may not be necessary:

1) There is a 0.1 mf on the base of Q1, that connects to a 0.1 on
the collector of Q13. These then connect via a 10 pf to the front-end
bandpass filter. Would it not be acceptable to use only one 0.1 mf
between the collector of Q13 and the Base of Q1, and connect the base
of Q1 to the bandpass filter via the 10 pf cap?

2) There is a 0.1 mf on the collector of Q2 that connects to the
crystal filter, and another 0.1 that connects the base of Q12 to the
same point on the crystal filter. Would it be sufficient to use just
the 0.1 mf from the collector of Q2 to the crystal filter, and then
connect the base of Q12 directly to the same point on that filter?
Since crystals do not pass DC, the same amount of DC isolation would
be maintained.

3) There is a 0.1 mf between the end of the crystal filter and the
base of Q3, and another 0.1 mf between that same point on the crystal
filter and the collector of Q11. It seems that it would suffice to
have the 0.1 mf between the collector of Q11 and the base of Q3, with
the crystal filter simply connected to the base of Q3. Again, the
crystal does not conduct DC, so there would still be the same level of
DC isolation.

OK, for all you purists out there, I know that it looks more
symetrical with the "pairs of 0.1 mf capacitors", but are they really
necessary?

What spawned this evaluation is my comparison of RV3GM's PSK-20
schematic with the BITX20 design by Farhan. I was wondering if Oleg's
method of using one transister in bi-directional mode could also be
applied to the BITX20 where we are using pairs of transisters to
obtain bi-directionality.

Arv-K7HKL
_._



_____

Do you Yahoo!?
<http://vote.yahoo.com/> vote.yahoo.com - Register online to vote
today!

Yahoo! Groups Sponsor

ADVERTISEMENT

<http://us.ard.yahoo.com/SIG=1298tr70v/M=295196.4901138.6071305.3001176/D=gr
oups/S=1705063108:HM/EXP=1096604253/A=2128215/R=0/SIG=10se96mf6/*http://comp
anion.yahoo.com> click here

<http://us.adserver.yahoo.com/l?M=295196.4901138.6071305.3001176/D=groups/S=
:HM/A=2128215/rand=154729275>

_____

Yahoo! Groups Links

* To visit your group on the web, go to:
<http://groups.yahoo.com/group/BITX20/>
http://groups.yahoo.com/group/BITX20/


* To unsubscribe from this group, send an email to:
<mailto:BITX20-unsubscribe@...?subject=Unsubscribe>
BITX20-unsubscribe@...


* Your use of Yahoo! Groups is subject to the
<http://docs.yahoo.com/info/terms/> Yahoo! Terms of Service.

*




====================================
D E E P S P A C E R A D I O S Y S T E M S


ENGINEERING SERVICES:
* System Design
* Project Planning
* Project Management
* Deployment
* Operation Planning & Support

CONTACT: arvevans@e...
====================================
<http://us.f414.mail.yahoo.com/ym/Ham_DSRS@...>





_____

Do you Yahoo!?
vote.yahoo.com <http://vote.yahoo.com> - Register online to vote
today!

Yahoo! Groups Sponsor

ADVERTISEMENT

<http://us.ard.yahoo.com/SIG=129v85j3h/M=295196.4901138.6071305.3001176/D=gr
oups/S=1705063108:HM/EXP=1096696597/A=2128215/R=0/SIG=10se96mf6/*http://comp
anion.yahoo.com> click here

<http://us.adserver.yahoo.com/l?M=295196.4901138.6071305.3001176/D=groups/S=
:HM/A=2128215/rand=686284971>


_____

Yahoo! Groups Links


* To visit your group on the web, go to:
http://groups.yahoo.com/group/BITX20/
<http://groups.yahoo.com/group/BITX20/>


* To unsubscribe from this group, send an email to:
BITX20-unsubscribe@...
<mailto:BITX20-unsubscribe@...?subject=Unsubscribe>


* Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service
<http://docs.yahoo.com/info/terms/> .

Join BITX20@groups.io to automatically receive all group messages.