On Wed, 01 Mar 2006 01:03:21 -0800, aadu.adok wrote:

hello,

I'm building my first reciver. I can't choose what kind of mixers should I
use. I have read that diode ring mixers are far superior compared to dual
gate mosfet mixers.

It depends on what you mean by superior. The mosfet mixer has gain
and usually has a lower noise figure. The diode mixer will have superior
strong signal handling (higher IP3), but will have about 7dB loss. The
diode mixer needs more local oscillator power. They both make excellent
mixers if they are applied properly.

To get the most bang for your buck, it is hard to beat a ring of
1N914 or 1N4148 diodes at a few cent each. The ferrite 'cups' from
scrap Toko IF transformers can be used as cores for the trifilar
wound transformers.

There are a few other options you should consider. High level IC mixers
like the AD831 are worth considering. Switching mixers using MOSFETs
are capable of very high performance. Search for info about the N6NWP
front-end from QST Feb 93 or the H-mode mixer used in several recent
homebrew designs.
http://uk.groups.yahoo.com/group/picastar/
http://xoomer.virgilio.it/sergiocartoceti/article_7.htm
http://www.warc.org.uk/cdg2000/introduction.htm

If you build the receive mixer as a separate module,
you can try them all and pick the one that works best for you.

73, Ed. EI9GQ.


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