On Fri, 16 May 2008, Scott Dorsey wrote:

Richard Knoppow wrote:
It seems to me that it should not be too difficult to
design one that is superior to the old vacuum tube models.
There are certainly plenty of receivers out there which
could use an adaptor. Have you any definite ideas about
price range, features, etc?

What I was thinking was to take the AM synchronous detector circuit from
OH2GF which was published in the July '93 QST issue. It is based on an
NE602 which does not have the best dynamic range in the world but seems to
be okay.

A slicer by definition has selectible sideband, and maybe specifically
uses phasing to get it.

They existed at a time when there wasn't much but AM radios, so to get
around the "turn down the RF gain, turn up the AF gain and turn on the
BFO" you needed to add a product detector. Once you were doing that,
you might as well add selectable sideband via phasing, since it didn't
add that much to the cost, but did help improve things when the receiver's
IF was wide for AM.

It lives on today, since most "low end" shortwave receivers that have
synchronous detector uses the phasing method to increse performance
without the cost of an actual better IF filter.

There were external SSB adaptors that included an IF filter for SSB,
but I can't think of seeing any that called themselves "slicers".

Michael VE2BVW

I was first going to make up a PC board layout rather than constructing it
dead-bug style like the original, then I was going to try one of the new
Maxim detector chips in place of the NE602, but retaining the NE804 limiter
and phase detector.

If I were going to do it with tubes, I would look into some of the sheet
beam tubes that were intended for TV chroma detector circuits... many of
them have excellent performance and are very inexpensive (as are all old
TV tubes). The 7360 costs a bloody fortune when you can find one, but
the 6AR8, 6JM8, and 6ME8 are effectively the same basic design but with
less crosstalk.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."