Does anyone have any schematic for Direct Conversion receiver that does not
use any FETs, Valves or ICs (e.g. NE602) but uses NPN transistors?

Here's a direct conversion transceiver that might give you some ideas

http://www.intio.or.jp/jf10zl/3trcw.htm

I don't think you will find that this is a particularly good receiver,
but it is the only IC-free DC receiver I know of on the web (and its
VERY clever!).

Or, if you have a circuit that uses a CA3028 mixer, you can easily make
up the equivalent from 3 NPN transistors and some resistors.

73,
Steve VE3SMA

Does anyone have any schematic for Direct Conversion receiver that does not
use any FETs, Valves or ICs (e.g. NE602) but uses NPN transistors?

"Experimental Methods in RF design", section 1.8, page 1.13, has the
schematic for a DC receiver which uses NPN transistors throughout most
of its design (including the product detector). Tuning is done via a
varactor-based VCO - you might be able to substitute a reverse-biased
junction in an NPN transistor for the varactor.

There are two ICs - an LM7805 voltage regulator (for which you could
probably substitute a shunt regulator such as a zener diode or an NPN
transistor wired up as a Vbe-multiplier) and an LM386 audio amplifier
(for which you could substitute the discrete-NPN audio amp design on
the previous page of the book).

I'd say there's a good chance you could modify this design so that
every single semiconductor in it was an NPN transistor such as a
2N3904 or 2N2222 or a similar jellybean.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Dave Platt wrote:
Does anyone have any schematic for Direct Conversion receiver that does not
use any FETs, Valves or ICs (e.g. NE602) but uses NPN transistors?


"Experimental Methods in RF design", section 1.8, page 1.13, has the
schematic for a DC receiver which uses NPN transistors throughout most
of its design (including the product detector). Tuning is done via a
varactor-based VCO - you might be able to substitute a reverse-biased
junction in an NPN transistor for the varactor.

There are two ICs - an LM7805 voltage regulator (for which you could
probably substitute a shunt regulator such as a zener diode or an NPN
transistor wired up as a Vbe-multiplier) and an LM386 audio amplifier
(for which you could substitute the discrete-NPN audio amp design on
the previous page of the book).

I'd say there's a good chance you could modify this design so that
every single semiconductor in it was an NPN transistor such as a
2N3904 or 2N2222 or a similar jellybean.

-- or for the shunt regulator you could use a back-biased base-emitter
junction in a 2N2222. It trashes the transistor, but it makes an
adequate zener.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

You might want to check out VE7BPO's site for DC receiver ideas. He
has lots of experimental circuits using NPNs and he will respond to
emails if you have any questions.

http://www.qrp.pops.net/

Good luck - Roger


Nev wrote:
Does anyone have any schematic for Direct Conversion receiver that does not
use any FETs, Valves or ICs (e.g. NE602) but uses NPN transistors?

There was an article in QST many years ago ( late 1960's ??) which was
one of the early direct conversion articles. This one used 88 mH filters,
and a three transistor audio amplifier. It was written by Doug Demaw, if
memory serves, and it is probably the simplest, but useful, direct
conversion design I have ever seen.

Granted, getting 88 mH coils is not as easy as it was back then, but all
in all, I think this fits the original request. The radio used NPN
transistors thoughout.



Jim
N6BIU

Michael Black wrote:
"Jim" ) writes:

There was an article in QST many years ago ( late 1960's ??) which was
one of the early direct conversion articles. This one used 88 mH filters,
and a three transistor audio amplifier. It was written by Doug Demaw, if
memory serves, and it is probably the simplest, but useful, direct
conversion design I have ever seen.


But one thing about direct conversion receivers is that it took years before
they became good.

The basic premise, beating a signal directly down to audio, is as old as
the regenerative receiver. ANd of course there were explicit mixer/oscillator
type receivers in the decades after that, that all seemed to end in "dyne".

IN 1961, QST ran an article, I can't remember if it mentioned "direct
conversion", that was direct conversion as we came to know it. A mixer
and an oscillator, and if I'm remembering they used two tubes in the mixer
for a balanced mixer.

Then there's the Hayward article, there was a co-author, in 1968, that
actually did make mention of "direct conversion". It used schottkey
diodes in a balanced mixer. And that's when they took off.

But in the articles afterwards used just about any possible mixer,
with varying results. Everyone was trying to get a good direct conversion
receiver, but I'm not sure they really understood them. So the focus
was on another variation of a well-balanced mixer.

It took till 1980, before there was a real change. That's when Roy
Lewallen came out with his "optimized QRP transceiver", which featured
a terminated mixer. I'm pretty certain that's the first time a DC
receiver had a terminated mixer. I can remember the 1974 QST article when
terminated mixers for VHF converters were introduced to the amateur world.

I really do say that 1980 article of Roy's was the dividing line. Before
that, no matter how good the mixer there always seemed to be problems. Then
we moved into an area where simplicity wasn't the first consideration for
direct conversion, but performance came first.

Michael VE2BVW


Granted, getting 88 mH coils is not as easy as it was back then, but all
in all, I think this fits the original request. The radio used NPN
transistors thoughout.



Jim
N6BIU






The direct conversion transceiver is what gave TenTec their start.
They had a few different models in kit, semi-kit, and assembled
formats. QST picked up the craze and there were a number of articles
on building these. Detectors were dual gate fets, CA2028's,
diode bridges, Mini-Circuit mixer modules, and later IC's with
built in vfo's.

Back in the 60's, there was an early direct conversion receiver that
used two 6SB7Y's in a balanced circuit with a B&W phase splitter run
bass-ackwards and an rf phase splitter in the vfo. This was actually
a single signal receiver using the idea of a phasing sideband modulator
in reverse. Today we'd call it an image-reject mixer.

What's old is new again.....

Ken Sharf Wrote:

Back in the 60's, there was an early direct conversion receiver that
used two 6SB7Y's in a balanced circuit with a B&W phase splitter run
bass-ackwards and an rf phase splitter in the vfo. This was actually
a single signal receiver using the idea of a phasing sideband modulator
in reverse. Today we'd call it an image-reject mixer.

What's old is new again.....


I remember that one !! Seems to me, it was in Single Sideband for the
Radio Amateur and I was really tempted to try to build one.

Actually, I was responding to the original request for a direct conversion
using NPN transistors. There are a lot of designs for direct conversion
rigs, and some of them are excellent.

Personally, I like the designs by KK7B and if someone wants to try their
hand at it, the Kanga website has some kits available.

http://www.bright.net/~kanga/kanga/KK7B/minir2.htm

They also carry the R2PRO which has excellent characteristics

http://www.bright.net/~kanga/kanga/KK7B/r2pro.htm

I've homebrewed from scratch some direct conversion breadboards over the
years, but these are image reject and would be a good starting point for a
complete transceiver.




Jim
N6BIU

Try this link:
http://www.phonestack.com/farhan/xcvr1.html



"Nev" wrote in message ...
Does anyone have any schematic for Direct Conversion receiver that does
not
use any FETs, Valves or ICs (e.g. NE602) but uses NPN transistors?

Did u see this one?

http://www.qrp4u.de/index_en.html



--
=========================================
Radio Amateurs - Fill your junk box, from my junkbox!
http://www.hamradparts.com
73 de KB9BVN
=========================================


"Nev" wrote in message ...
Does anyone have any schematic for Direct Conversion receiver that does
not
use any FETs, Valves or ICs (e.g. NE602) but uses NPN transistors?