In article ,
Risto Tiilikainen wrote:

If you think the situation in short waves today:
Russian and their previous satellite country jammers are quiet
Local broadcast is nearly completely in FM
Propaganda is no more effective to transmit in short waves
Commercial data is practically in Internet. and in satellites
Marine communication is in satellites.

All this means less cross modulation products in first mixer than some
sixteen years ago
Atmospheric noise in sw is much higher than the noise of modern front
and mixer stage
Advantage of diode mixer is marginal

There's a good discussion about the advantages and disadvantages of
various mixer types, for different applications, in "Experimental
Methods in Radio Frequency Design", a book I strongly recommend.

As others have pointed out, there's no one right solution. Even for
use in what seems like a simple, constant application (e.g. a CW
receiver for the 40-meter band), the choice of which is more
appropriate can swing one way or the other based on how you intend to
use the receiver.

As one example given in EMiRFD, if you're looking for a simple
receiver which is intended for QRP operation on backpacking trips,
then the low power consumption, and the mixer gain of an active mixer
such as a Gilbert cell (e.g. SA602 and similar) can make this the
ideal. Out in the woods, the RF levels will be low, and the
relatively low IP3 of these sorts of mixers isn't likely to be a
problem.

On the other hand, if you're planning to build a receiver which may
have to operate in a strong-adjacent-signal environment (e.g. for
Field Day or other contesting), then you may want to favor a
diode-ring double-balanced mixer operating at a high LO-injection
level, and the devil take the power consumption :-)

The FET-switch mixers seem to be a really nice alternative, and
although they've gotten relatively little visibility in amateur-radio
applications they've become very popular in commercial use (e.g.
cell-phone handsets). I haven't yet had a chance to play with these
myself but they look like fun!

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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