[time-nuts] Anybody experienced in using a prescaler as a wideband preamp?

Bob Camp lists at rtty.us
Thu Jul 28 21:01:59 UTC 2011


Hi

Small signal wise a prescaler looks like a divider. 

Below some threshold you (hopefully) get nothing. Above that point you get
various sorts of garbage (which could include self oscillation) unrelated to
the input frequency. Past another point you get an increasingly solid divide
out. The magic points are level, load impedance, source impedance,
temperature, and supply voltage dependant. 

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Peter Monta
Sent: Thursday, July 28, 2011 4:15 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Anybody experienced in using a prescaler as a
wideband preamp?

Paul Swed writes:

> I agree this does not make sense. There is a divider in the way so its not
a
> preamp.

I'll bite:  what does a small-signal model of a prescaler look like?
As a guess, it might be a (flat? highpass?) attenuator (with a great
deal of loss) up to some threshold amplitude, then above that one
would get the divided output.

But that's with a pure-tone stimulus.  Perhaps a prescaler could be
made to act as a kind of preamp-plus-mixer by pumping it with an LO
just at threshold, then adding in the input signal.  Likely enough,
though, there are better ways to accomplish whatever the system-level
goal is.

Cheers,
Peter

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