Markus,
Excellent !
I can provide a GPS locked signal at any power level, my
limitation at the moment is the keyer which only goes to QRSS60 - I
may have to investigate another way of keying the TX.
73 K2ORS/WD2XGJ
On Wed, Aug 31, 2011 at 2:05 PM, Markus Vester <[email protected]> wrote:
> Dear LF,
>
> inspired by the very fruitful narrowband weak-signal detections on VLF, I
> have set up a temporary LF spectrogram, using Rubidium locked oscillators
> and a 0.438 mHz FFT bandwidth
> http://www.alice-dsl.net/df6nm/grabber/TAnarrow.jpg
> (updated every two hours).
>
> Frequency:
> The receive band is currently 7 Hz wide around 137777.5 Hz, within which the
> visible display slots can be shifted around a posteriori on request. At the
> moment I'm showing two slots around European Loran lines
> 137778.3705 Hz (GRI 7499 from Sylt and Lessay),
> 137775.0000 (GRI 8000 from Slonim and Simferopol).
> I chose the TA slot for the availability of other grabbers, but maybe a
> dedicated ultra-narrowband slot (eg. 10 MHz/73 = 136986.301 Hz) would be a
> better option - suggestions welcome!
>
> Sensitivity:
> Compared to my own 21 mHz TA grabber, the bandwidth reduction should provide
> a 17 dB reduction of noise, or 11 dB versus Argo-120 at 5.3 mHz. Of course
> you will need to transmit a much longer dash (eg. one hour instead of one
> minute) with good frequency stability. A GPS- or Rubidium-derived carrier
> would be the best option, but a good 1e-9 class OCXO would work just as
> well.
>
> Groundwave:
> In quiet daytime conditions, a radiated power of only 10 nanowatts should be
> able produce 10 dB SNR. This could be achieved by sending 5.5 mA up a whip
> at 1 m effective height! Or perhaps even from Lubos' ferrite antenna in TX
> mode?
>
> Skywave:
> During a few nights in Februrary 2006, John W1TAG transmitted GPS controlled
> straight and 15-minute phase-cycled carriers. Receptions in Europe by G3PLX
> and myself revealed long periods of stable skywaves, well suited for
> sub-millihertz analysis. Some details and spectrograms can be found in
> http://df6nm.bplaced.net/LF/slow_psk/
>
> Now I hope to see some really feeble signals soon...
>
> Best 73,
> Markus (DF6NM)
>
>
>
--
73 Warren K2ORS
WD2XGJ
WD2XSH/23
WE2XEB/2
WE2XGR/1
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