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

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?