[Premium-Rx] Clean LOs

[Brian D. Comer]

No it was brand new straight from the factory in full calibration.
 
If you use the higher bands where there are few dividers in operation
and the output level is close to the maximum the frequency locked loop
can be pulled. I my case I was using a frequency of 135.6 for use with a
fairly high level mixer and driving the IF port of the mixer from an SSB
transmitter exciter. Under these conditions the phase noise of the 8640
is not good. I have never done any tests with high level receive SSB
signals but must assume that the results would be similar. 
 
The 8640 has fairly low phase noise but is not the best especially if
the load impedance is varied and the output division ratio is not very
large.
 
73 Brian
 
KF6C/G3ZVC
 
 
-----Original Message-----
From: John Miles [mailto:jmiles at pop.net] 
Sent: Friday, February 11, 2005 7:35 PM
To: Brian D. Comer
Subject: RE: [Premium-Rx] Clean LOs
 
You had a seriously screwed-up 8640B, then.  :-P
 
-- john KE5FX
-----Original Message-----
From: premium-rx-bounces at ml.skirrow.org
[mailto:premium-rx-bounces at ml.skirrow.org]On Behalf Of Brian D. Comer
Sent: Friday, February 11, 2005 7:26 PM
To: premium-rx at ml.skirrow.org
Subject: FW: [Premium-Rx] Clean LOs
 
-----Original Message-----
From: Brian D. Comer [mailto:bcomer at cox.net] 
Sent: Friday, February 11, 2005 4:00 PM
To: 'Michael O'Beirne'
Subject: RE: [Premium-Rx] Clean LOs
 
I do not support the idea that frequency synthesizers are necessarily a
problem and would not consider the using of anything else for a high
performance receiver today. That is not to say that they are necessarily
good and I find the ones in the RA 6830 an example of a bad design or at
least bad implementation. There are of course may other very poor
synthesizers out there.
 
On the great HP 8640, many years ago I had access to one when it had
only just been released to the market. I took it home and used it as an
LO for a home brew 2 meter transceiver. The reports that I received were
that I had very bad FM on the my signal. The HP 8640 uses a frequency
locked loop which can very easily be frequency modulated by strong
signals, so take care when use it as an LO.
 
73 Brian
 
KF6C/G3ZVC
 
-----Original Message-----
From: premium-rx-bounces at ml.skirrow.org
[mailto:premium-rx-bounces at ml.skirrow.org] On Behalf Of Michael O'Beirne
Sent: Friday, February 11, 2005 1:49 PM
To: Premium-Radio
Subject: [Premium-Rx] Clean LOs
 
Dear All,
 
One quick idea to see what a really clean LO can do for a receiver might
be to disable the internal synthesiser and feed in some RF from a good
HP8640B genie or similar from R&S.  G3OSS (Angus McKenzie) did this at
VHF with a professional VHF receiver and was much impressed.
73s
Michael
G8MOB
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