I checked my WJ databook, and I was wrong about that GRA-3 pinout. The
SRA-3H does have the same pinout as the M9D, so it is a drop-in replacement.
The original mixer is indeed a Level 20 mixer, which means that you LO
injection level is +20dBm. It is rated at 6.5dB conversion loss over the 2
to 400MHz range. This means that it won't have the greatest performance in
the LW/MW range.
The IP3 is +30dBm, which is a bit better than the SRA-3H.
A better mixer to use would be the MCL TAK-3H. This mixer has an IP3 of
+29dBm and a conversion loss in the 4.77dB range. The TAK-3H is rated down
to 40kHz. I used to use the TAK-3H as a drop-in replacement for the 1st
mixer when I upgraded KWM-380s.
You can't go wrong with this mixer. The original diodes are probably
HP1N5711 hot-carrier diodes. I would throw in the
TAK-3H..........performance will be enhanced over the original design. You
will have a 1.7dB improvement in the noise figure, and to do that without
the need for RF amplification ahead of this stage is a bonus.

Pete


"Henry Kolesnik" wrote in message
et...
Pete
I bought this 8718 as a parts unit and now have it working, somewhat.
The can that covers the mixer is gone, someone was messing inside but the
manual has it as M9D made by WJ I think. I wish I could find a schematic
on it becasue it might be repairable, kind of small but I've looked at it
with my 6-50 stereo zoom microscope and might be able to fix it if I knew
what diodes it used. Without a diagram I'm afraid that I might bugger
something. When I attach a 5 foot piece of wire to one the diodes the
radio picks up all the AM stations and no problem with WWV or 20
meters..Haven't done any other testing. I was told that the SRA-3H was a
good sub and took their word for it. If something else is closer or
better I'd sure like to know. I can't find any reference in the manual to
the output level of the first LO but it covers ~ 43 to 73 MHz.

73
Hank WD5JFR
"Pete KE9OA" wrote in message
. ..
The '3 series of mixer from MCL are good down to about 25kHz. Good
performance can be expected another octave down from there. Does the
synthesizer in your WJ receiver provide +17dBm of LO injection? The mixer
you ordered is a Level 17 mixer. The MCL website does have the pinout for
this device. I like the '3 series, since the SSB conversion loss is in
the 4.75dB range vs other series, which have conversion loss in the 6.5dB
range. This is a very good mixer. Now, which mixer is your WJ receiver
using? Some of the WJ units used a mixer that had a pinout similar to
MCL's GRA-3.

Pete

"AndyS" wrote in message
ups.com...

Henry Kolesnik wrote:.. Any tips on how to
determine the leads and test for performance appreciated.
tnx

Hank WD5JFR

Andy writes:
MSL normally has very good information in their catalogs regarding
the connectors, frequency range, and performance of their mixers.
If you don't have their catalogs lying around, there are two more
possibilities... Do a google to find their website and they may have
everything on online. Otherwise, call their customer service line and

tell them the info you need.... In my previous life, they gave
excellent
support...

Good luck,

Andy W4OAH, in Eureka, Texas