Cecil

  Ok this is somewhat encouraging, I must take stock of what looks like
might stop being manufacured in the future.  SMT is ok, I have found
some neat little boards called Surf Boards that can come in handy when
with SMT and the breadboard.  In turn chips mounted on them can then be
treated like a DIP IC in terms of ease of use in a finished board. 
Folk might like such chips premounted and someone can make a few sales
with them that way.

Dan

  "Dual gate FETs should work just fine, back some time they were
considered the cat's meow since they worked so well, they could handle
large signals without distortion (high IP3) especially when used in a
balanced circuit. While being a mixer they can also provide gain.

They are a little hard to get since very few are made anymore, they were
excellent for a receivers RF/IF amplifier since changing the bias on the
second gate could be used to control the gain of the device, and are by
nature very low noise devices.

Their big gotcha is that they are incredibly sensitive to static, so are
easily damaged, I would solder them in place before removing the little
wire that was wrapped around the pins

The SA612A will also work fine also as long as you stay within the chips
input level. By they way I read that they no longer manufacture the DIP
package versions, they now only make the SMT version so enjoy them while
you can, I have about 20 in stock, they are handy little devices.

AMD makes a much better version that sports two mixers and a built in
Quadrature clock generator. You feed it a clock at 2X the receiver
frequency, and it generates the Quadrature clocks for the mixers inside,
it also has a much higher IP3 figures of +19dB, it cost around $4.00,
it's available in SMT only.

Under 20M I prefer switches, but any kind of mixer will work, just some
better than others. Here is a schematic of a receiver with I/Q audio but
uses a Diode Balanced Mixer, there are all kinds of possibilities out
there;

< http://www.hpsdr.com/Public/Parts/Clock/TMschematic.pdf>

Too much fun and not enough time." ....Cecil KD5NWA


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