Thanks for the input about phase noise. There is some principle that says
even if you measure something you will change it. So anything added to the
PTO will change it and likely add something such as phase noise.
In my installation I am using the varactor that was already installed in the
PTO assembly. So all I am doing is adding a bias voltage to one of the pins
on the Corsair I PTO assembly. I could not discern any perceptible phase
noise but did not make any rigorous measurements as you suggested. Thus my
comment about no phase noise.
So you are correct that my statement regarding No phase noise is not true in
the purest sense, as something will be added but the magnitude has not been
measured. I can only say that any change has not been problematic.
Certainly my somewhat degraded hearing does not qualify as a laboratory
grade measurement device. Perhaps someone on this reflector has such
equipment and an X-lock and can quantify the degree of phase noise
degradation and then we will all know the impact to phase noise as a result
of the X-Lock.
My original problem was a severe drift (for me it was unacceptable) and that
has been fixed. However for the purists, in my original post I never did
specifically quantify the drift problem. But that I did measure. From turn
on to two hours the drift was upward by 500 Hertz in a location where the
ambient temperature was controlled to 68 F. In the first half hour the drift
was most severe being on the order of around 300 Hz and the next period the
drift slowed down and finally stopped at about two hours. With the X-Lock2
after turn on there is about a two second initialization period and it
doesn't move from that frequency thereon. In one test I ran it held that
frequency for 6 hours -- after which I turned off the radio.
Your mileage may vary but for me the X-Lock 2 made a vast improvement in the
frequency stability and if it is at expense of the introduction of phase
noise then for my particular operating approach, stability is more
important. The idea of leaving the Corsair I "on" all of the time was not an
appealing alternative but that would certainly resolve the issue of not
introducing any other phase noise as Charles suggests. The Corsair I
receiver has some excellent specifications. For those who haven't checked
Sherwood Engineering receiver test data, it is worth a look. The Corsair I
ranks higher on the list than other models that are currently in production.
So assuming that any introduction of additional phase noise as result of
biasing the existing varactor is significant, then that would indeed move
the Corsair down the list.
So I guess after all is said and done, it comes down to having a transceiver
with excellent frequency stability and perhaps more phase noise although not
problematic or perceptible to me OR "let her drift" and be happy the phase
noise may be lower. You know what choice I made.
From: "Charles P. Steinmetz" <firstname.lastname@example.org>
Sent: Thursday, January 26, 2012 12:04 AM
To: "Discussion of Ten-Tec Equipment" <email@example.com>
Subject: Re: [TenTec] X-Lock-3
> Pete wrote:
>>No phase noise is introduced into the circuit for it is merely a
>>correction of frequency about a set frequency using a varactor diode.
> The added varactor circuitry will introduce additional phase noise,
> from both leakage current in the varactor and noise on the varactor
> bias (just from the new bias supply, if you use a varactor that was
> already there). Perhaps not enough to be problematic, but it will be
> clearly measurable unless the original circuit was badly designed.
> Best regards,
> TenTec mailing list
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