Mixer Diodes

[Talen]

Joe... will also apply to your situation


------------------------------------------------------
Mark, use a quad set of matched HP Schottky
Barrier Diodes  (5082-2800) designed for mixers,
which will work fine.

The 1N34As which were originally used are good (real
inexpensive) and you can try using them in unmatched
sets but Germanium diodes are not real stable over time
and if you want known good, known matched, I would
go with these HPs. They can be used  in the solid state
mixers in Heathkits (104 uses 5 sets) and I've found them
to be equivalent to the original FH-1100 Hot Carrier diodes.
By the way, if you get ANY diodes off the same batch
(same date code, tape-on-reel strip, etc), chances are
they are "matched" because they probably came off the
same wafer.

Some people may suggest the really common 1N914s
which are Silicon diodes. They have a substantial voltage
drop (greater than the Germanium, Hot Carrier or Schottky
Barrier diodes) which may not be a problem in Tx mixers,
however it's bad deal for any Rx mixer. I've made signal
measurements showing them to be a disaster relative to
the Hot Carrier diodes or the HPs.....and they are still
not matched. There was a reason Collins selected a signal
diode with a low voltage drop. Also unmatched diodes
can result in unwanted mixer products (spurs). Someone
ought to give us info off a Spectrum Analyzer comparison
of the different diodes if you really want to get into it.

73s  Kees K5BCQ



>
>At 02:02 AM 11/26/2000 -0800, mark adams wrote:
>>Ok folks, I was sitting here at work and went to the
>>online manual for the KWM-2.  It does say they are
>>fa4000?
>>
>>Not sure whats up with that, the other diodes are
>>marked right.
>>
>>Now the question is who sells the 1n34a as a matched
>>quad?
>>
>>Take care and sorry for the earlier question.
>>
>>73 Mark
>>

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