The artifacts were clear. I agree we need to maybe find a better spot. For tonite though I will be staying close to same freq as last night, for Hartmut no having to retune right now or maybe gone to bed and miss tonite. Hopefully you can talk with him and I would follow both your recommendations and sure Dex would as well as your the guys doing the decoding!
I will fire up .2 hz higher tonite to try and get in the "clear zone" between "whole" hz.
From:
[email protected]To:
[email protected]Date: Mon, 30 Sep 2013 23:26:02 +0200
Subject: Re: LF: 74.550kHz Sep 29/30
Hi Bob, LF,
These are presumably artifacts from
DCF77 which is only about 160 km from here. In addition to the well known
AM timecode, it also carries pseudorandom phase modulation,
which has been proposed in the 80ies to provide higher resolution timing
(albeit orders of magnitude worse than Loran or GPS). The resulting
sidebands extend a couple of kHz on either side of the carrier, with pronounced
minima around multiples of the chip rate 77500/120 = 645.833 Hz, see
Attached is a spectrogram which was taken
tonight on the resonant antenna. Between statics, you can still
see the fourth sideband lobe which is centered near 74.6 kHz. The
spectral gaps are on
74916.666 Hz,
74270.833 Hz,
73625.000 Hz,
with small and sharp central lines, presumably
caused by slight inbalances or nonlinearities in the
transmitter.
By these criteria, if you have the choice I
would recommend to operate somewhere near these gaps, but not exactly in
their middle, and also preferably not exactly on integer Hz
frequencies ;-)
Best 73,
Markus (DF6NM)
Sent: Monday, September 30, 2013 8:02 PM
Subject: RE: LF: 74.550kHz Sep 29/30
Hartmut;
You make it look easy!!!
That station on
74.548 is WG2XRS/5, Dex in South Carolina. I am sure you will see him when
condx favor his area.
Really great capture-this time I have my transmitter
running correctly. I thought I better drop down .1 hz as I was seeing sigs
on .550 and .549 on Vester's grabber but then remembered you have directional
ant and the sigs come from east of you and are not a problem. I can go to
74.549 from now on.
Thanks for all your good work! Bob WG2XRS/4
NY
> Date: Mon, 30 Sep 2013 17:33.:59 +0200
> From:
[email protected]> To:
[email protected]> Subject: LF:
74.550kHz Sep 29/30
>
> Here are the captures taken last
night:
>
>
https://dl.dropboxusercontent.com/u/50178231/74550Hz-2013-09-30-QRSS60Screen.JPG
>
>
https://dl.dropboxusercontent.com/u/50178231/74550Hz-2013-09-30-QRSS120Screen.JPG
>
> XRS4 was just below 74.549 kHz and very faint traces of another station
> on 74.548. Only visible on the QRSS120Screen.
>
> --
> 73
> Hartmut
>
>
