RE: LF: 74 kHz: XRS and CFH 73.6 kHz

[Bob Raide <rjraide@hotmail.com>]

Markus;
I see that. Can't be great all the time!  Am waiting for an OCXO I have coming to try out your OPDS-really think it will be great on 73!
Congrats on your fabulous development!
Bob
 

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From: markusvester@aol.com
To: rsgb_lf_group@blacksheep.org
Date: Sun, 20 Oct 2013 12:56:37 +0200
Subject: LF: 74 kHz: XRS and CFH 73.6 kHz

Hi Bob, 4000'ers,

 

74 kHz conditions into Germany were marginal again last night. Some slim traces appeared here between after 5 UT, see http://dl.dropboxusercontent.com/u/26404526/74kHz/74k_131020_0600.png

 

As this SpecLab instance is fed by a FiFi-SDR with 72 kHz LO frequency, CFH 73.6 kHz is also in the passband, and it was easy to set up a plotter to track propagation. The attached screenshot (also on http://dl.dropboxusercontent.com/u/26404526/74kHz/plot_131020_0900.png) shows three traces: 

 

The red trace is noise from the Spectrogram around 74.55 kHz, normalized to 1 Hz:

 noise_n(2540,2560)

Note that this noise power includes some junk from the DCF sidebands.

 

The green trace is CFH on 73.6 kHz, measured with SpecLab's MSK monitor set to 300 baud:

 pam0(1600,MSK300,20,L5).ampl

The noise floor of this detector is about 10 dB above the red line. Irregularities between 23 and 1 UT are due to interruptions during my Opera transmissions and manipulations on the antenna.

 

We find that best propagation from Halifax occured approximately between 22 and 6:30 UT, with another weaker period later in the morning. Throughout the night, there seemed to be hardly any short-term fading on this path.

 

The blue trace is supposed to indicate the strength of the Loran line in the spectrogram:

 peak_a(2550.5,2550.7)

This line is not strong enough for a meaningful result. The noise floor is 10 dB below the red line (minus 18 dB for 16 mHz vs 1 Hz noise bandwidth, plus ~ 8 dB for taking the peak bin from a 0.2 Hz range). In the future, I intend to replace this trace by a 77.5 kHz monitor for the DCF77 carrier.

 

Best "73",

 

Markus (DF6NM in Nuernberg, JN59NJ)