EMRFD Message Archive 996

Message Date From Subject
996 2007-08-30 09:29:07 jr_dakota Speaking of esoteric mixers
Did anyone see the Oct '05 CQ article by James W Graves about the
GRX-1 receiver?

It uses balanced mixers made from 4 NTE618 (MVAM108) varactor diodes
followed by a balanced amp from J309 JFETs (says the J308 and J310
have less gain and won't work unless biased with more than 10
milliamps apiece) It works because of the capacitance has a square law
curve and any RF input unbalances the bridge but the imbalance isn't
linear but follows a square law curve

Unfortunately no IP3 or dynamic range measurements were given (or
taken apparently) He also uses an interesting way of coupling a double
tuned front end filter, basically they are coupled by soldering a wire
to the ground plane through the center of one toroid to the center of
another ... he claims the filter is more symmetrical and has better
isolation between inductors so you can tune one without it interacting
with the other's tuning

Interesting stuff but I can't find a thing about it online, maybe if I
get some time (OK, make some time, I'm on vacation) I'll 'draw up' the
mixer circuit and post it in the files section if others want to see
and experiment with it

997 2007-08-30 10:08:15 Leon Re: Speaking of esoteric mixers
----- Original Message -----
998 2007-08-30 10:16:35 Baruch Zilbershat... Re: Speaking of esoteric mixers
999 2007-08-30 12:59:02 jr_dakota Re: Speaking of esoteric mixers
I don't have a way to scan it and wouldn't even if I could without
permission the author and CQ ... I don't have a problem with posting a
partial schematic of the mixer porti
1000 2007-08-30 13:57:01 Baruch Zilbershat... Re: Speaking of esoteric mixers
1001 2007-08-30 15:54:59 Allison Parent Re: Speaking of esoteric mixers
1011 2007-09-04 04:13:31 Ed Almos Re: Speaking of esoteric mixers
If anybody wishes to build the mixer highlighted at web page
http://www.cqham.ru/trx86_49.htm I now have a better translation into
English available. Please email me at edwardalmos@gmail.com if you
want a copy.

Edward Almos HA6SST