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| Subject: | Re: VLF: EbNaut transmissions on lower frequencies?, pre-tests: 6.47kHz |
| From: | Markus Vester <[email protected]> |
| Date: | Sat, 7 May 2016 05:16:54 -0400 |
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Thanks Stefan for the frequency change to 6.48 kHz. It did help, but unfortunately the level of QRM happened to have increased dramatically since Friday morning.
Reviewing stored vlf_wide captures reveals that the "noise strip" above 6 kHz shows significant long-term variability: After being fairly strong during until April 22 19:20 UT, there was a relatively quiet period which ended suddenly May 6, 0:40 UT. I do not know what is causing these variations, but I suspect different types of equipment are being used at the railway yard. There are also intense 33.4 Hz spaced lines of similar type around 3 kHz. Maybe we should all lobby for the return of coal-fired steam engines, which were clean (in that sense) :~(
So my 6.48 kHz grabber is currently pretty useless. Stefan says I need a remote receiver, say 20 km from here. Or maybe I should rather consider moving to a different QTH?
All the best,
Markus (DF6NM)
Von: Markus Vester <[email protected]> An: rsgb_lf_group <[email protected]> Verschickt: Fr, 6 Mai 2016 9:26 am Betreff: Re: VLF: EbNaut transmissions on lower frequencies?, pre-tests: 6.47kHz No chance to see anything on 6470 Hz here due to heavy railway QRM. I noticed that the unstable lines seem to be concentrated on odd multiples of 16.70 Hz. Going 8 to 10 Hz up (e.g. to 6480 Hz) would place the signal in a QRM minimum, gaining at least 5 dB on average.
All the best,
Markus (DF6NM)
From: Paul Nicholson
Sent: Friday, May 06, 2016 2:24 AM
Subject: Re: VLF: EbNaut transmissions on lower frequencies?, pre-tests: 6.47kHz
Stefan, Your 200mA carrier comes through well here at 6.47 kHz, nice signal at 0.14 fT during the night. Daytime is 0.04 fT or below and might be a bit of a struggle. I don't need any more carrier. From the raw recording I can optimise filters and blankers and look at most of the diurnal. -- Paul Nicholson -- |
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