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Re: LF: Transatlantic beacon tests

To: [email protected]
Subject: Re: LF: Transatlantic beacon tests
From: "Rik Strobbe" <[email protected]>
Date: Wed, 26 Apr 2000 15:30:44
In-reply-to: <[email protected] a.gov.uk>
Reply-to: [email protected]
Sender: <[email protected]>
If using milli-Hz resolution don't foxus only on TX stability but also on
RX stability !
An example : last weekend I installed Spectran in order to monitor Marco's
signal. Monday evening QRN was far too high to listen (look) for Marco, so
I decided to use Spectran to check the frequency stability of the PLL-VFO
of my TX. The VFO is working on +/- 8.8MHz in 64Hz steps and this signal is
divided by 64 to get the 136kHz signal in 1Hz steps.
To get an accurate measurement I twisted a short wire arround the VFO and
connected it to the antenna input of my TS440 so I could hear the 8.8MHz
signal.
I left it running for some time at room temperature (abt 22C) and then
opened the window, what made the temperature drop to abt. 14C in less than
10 minutes.
With Spectran I saw a frequency 'jump' of about 30Hz (on 8.8MHz), so less
than 0.5Hz on 136kHz.
Now I was getting curious how good I could see this 0.5Hz 'jump' with
Spectran, so I Closed the window, let the VFO get bach to its original
frequency and repeated the experiment, now monitoring the 136kHz signal.
And indeed, I could see the 0.5Hz 'jump', but strange enough after some
time (with the window open) the frequenc slowly started to return to the
original value. First I was fussed by this effect, but then I understood
what was happening : the VFO of my TS440 also 'took a cold' (due to the
larger mass and better shielding it happened slower). The second effect was
considerable smaller than the initial 0.5Hz drift (I estimate it about
0.1Hz to 0.2Hz) but when working with milli-Hz bandwidth even 0.1Hz drift
might be unacceptable.

73, Rik  ON7YD

At 12:45 26/04/00 +0100, you wrote:
I was receiving Marco's carrier during the night tests at 20 - 30dB
above noise in a 2mHz bandwidth at a distance of 927km.  Daytime was 10
- 15dB lower.

In a Spectran bandwidth of  0.03 Hz that will correspond to about 12db
less S/N  ie 8 - 18dB - a good visible signal on a waterfall,  so
confirms we are receiving consistent levels between us.

... ETC ...

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