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KG6BAJ > NWSGRP 02.09.09 14:52l 37 Lines 1220 Bytes #999 (0) @ WW
BID : 10509_N1OES
Read: GUEST
Subj: Re: SA612/NE612 - optimal input signal level
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Sent: 090902/0400Z @:KG6BAJ.#NCA.CA.USA.NOAM #:10509 [Grass Valley] InterGate $
** NEWSGROUP: rec.radio.amateur.homebrew
** FROM : Eamon Skelton <Xnospam@oceanfree.net>
On Tue, 01 Sep 2009 10:01:19 -0700, Michał Słomkowski wrote:
> I'm designing a HF transceiver and I'm going to use SA612/NE612 as a
> product detector. I'm not sure what is the optimal signal level, which
> should be delivered to the inputs from the IF amplifier to achieve the
> best performance?
There are graphs for input IP3, compression and gain in
the Philips data-sheet. The exact value of IP3 will
depend on the supply voltage, frequency and the configuration
of your circuit. The data-sheet figure for 45MHz is -13dBm.
You will want the IF input to be well below this level.
Somewhere in the -25 to -40dBm region should be ok.
The xx612 is a low power, high gain device. It is not a
particularly good choice as a product detector in a superhet.
A simple two diode balanced mixer or a diode ring mixer (DBM)
would give much better IMD performance and costs even less than
the 612.
73, Ed. EI9GQ.
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