[Premium-Rx] HP Z3801A/Z3816 Freq Std as a Receiver Std

[Dave Emery]

On Fri, Jan 02, 2004 at 01:38:55PM -0800, Dave  Robinson wrote: 

> I was thinking of using one of the HP GPS freq stds on my Harris
> RF-590A.  This receiver has provisions for a 10mhz external std input.  
> My question is: will my improvement in frequency accuracy be offset by a
> degradation in receiver mds?  Which would be better in this application,
> the Z3801A or the Z3816?   Anybody having any general recommendations or
> references for precision frequency analysis methods with prem-rx? 

>	Thanks  Dave 

	Unless the receiver is very badly engineered with respect to its
external reference circuit, attaching a high quality reference
oscillator such the Z3801A or Z3816 should actually improve its LO phase
noise characteristics compared to the TXCO internal standard.

	Whether this would have any measurable impact on minimum
discernable signal is rather doubtful since that is primarily determined
by front end noise figure except in the presence of very strong nearby
carriers when LO phase noise would (by reciprocal mixing) show up as an
increase in the noise floor near a strong carrier.

	And synthesizer phase noise has many contributors, phase noise
of the reference oscillator only being one and not usually the worst one
in a synthesizer not involving high multiplication of the reference (eg
not a microwave frequency LO).

	As for the difference between the Z3801A and the Z3816 - the
Z3816 has a reputation for slightly better phase noise, but both use
precision HP quartz oscillators that are so good you are very unlikely
to be able to measure any difference.

	You also might consider one of the second generation all in one
GPS reference boxes like the Trimble Thunderbolt or the Symmetricom
58540A - these are smaller and somewhat more conveniant and do not
require as much setup or twiddling as the first generation boxes do
(basicly you hook up power - 24 volts - and an GPS  antenna and they do
the rest automagically).

	But once you have such a reference in place your frequency
accuracy should be right dead on ... GPS disciplined quartz standards
are easy to get within a couple parts in 10^12 which is several more
places than the 1 hz of the radio...









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-- 
   Dave Emery N1PRE,  die at dieconsulting.com  DIE Consulting, Weston, Mass 02493