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LF: Re: Frequency accuracy

To: [email protected]
Subject: LF: Re: Frequency accuracy
From: "g3ldo" <[email protected]>
Date: Wed, 19 Feb 2003 21:17:34 -0000
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Brian Rogerson said
> Hi Alan, I transmitted for a short period this morning on 137774 or
> using my original DDSVFO if that sheds any light.  73, Brian
John Andrews, W1TAG said.
Never having attempted integral calculus on an 8-bit microcontroller, how
did you train that DDS to perform that feat? Or do you just have a little
warm-up problem?
I switched my DDS off once at the end of a transmission, then switched it
back on again because conditions were better than I thought. It took half an
hour for it to settle down, exhibiting just over one Hz drift diring the
warm up period. I leave it switched on all the time now. I do get some long
term drift because the DDS unit is located in the outside shack and it gets
rather cold there - about -1deg C at the moment.
I am not sure of my exact frequency. My DDS readout for this T/A and KL
stuff is 137,773 and I thought my frequency was actually 137,773.5. I had
calibrated Argo on 60kHz with Rugby but the offset does not seem constant
when the receiver frequency is changed.
From W3EEE's Argo capture my frequency appears to be 137,772.9, about 1Hz
lower than Laurie.
I had a slow 0.1Hz drift low due to the shack warming up before the signals
So, using the W3EEE display as a reference, I will be transmitting on
137.773 from say 0500z tomorrow morning. I will cut down the inter-character
gaps and send my complete call.
Received a very interesting 3D display of Laurie's and my transmission. This
shows Laurie's signal a couple of dB up on mine.

Peter, G3LDO

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