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LF: Re: Drooping signal

To: [email protected]
Subject: LF: Re: Drooping signal
From: "g3ldo" <[email protected]>
Date: Sat, 22 Feb 2003 21:44:13 -0000
References: <[email protected]>
Reply-to: [email protected]
Sender: <[email protected]>
Hi John

Here's the visual evidence.
John Andrews sent (direct) a capture of my signal on the morning of the 22nd
when a fragment was received by KL1X. I feel this droopy signal needs
general explanation so I have replied via the reflector.

Thanks very much for the Jpeg. It turned out to be a much more useful
capture than just a record of frequency instability.
While I was transmitting I was monitoring my transmission on Argo and
noticed the frequency drifting low.
I think you know that I have my transmitter in a shed at the bottom of the
garden, together with the DDS driver. At this time of the year the
temperature can drop to as low a -8C. The DDS frequency is sensitive to
temperature but if the shed stays cold it is unaffected by the transmitter
being on or my presence. When the temperature in the transmitter shack is
around 0C then heat from the transmitter can raise the temperature by about
1 to 2 deg C.
The DDS is moved 0.1Hz per change of  1 deg C. When I noticed the frequency
downward drift I went down and opened the door of the transmitter shed -
hence the reversal of frequency drift.
Now while this is hardly good engineering practice the signal characteristic
enabled me to compare it with the signal received by KL1X and confirm it was
a D he received at the lowest part of the dip of the frequency drift.
The plan is to eventually have the DDS unit, plus a divide by 10 circuit and
driver, in the house shack by the side of the receiver. This will give me
0.1Hz resolution and more stability - and less 'characteristic'.

Peter, G3LDO

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