Re: LF: Re: Re: VLF SIGS

[Roger Lapthorn <rogerlapthorn@gmail.com>]

What power, antenna and matching for the 1km with the sig gen TX Pete?

73s
Roger G3XBM

On 30 May 2010 11:39, M0FMT <m0fmt@yahoo.co.uk> wrote:

Hi All

 

Simply use your PC sound card as an RX with the very good SDR application from Alberto Winrad. Stuff your antenna into the mic socket. Preferably with a couple of fast recovery diodes back to back to limit the spikes from static build up. Don't recommend it when lightning is about. Never lost a sound card yet ..... to stall the knockers............

 

If you have a modern PC it will have a Hi Def card giving a band width of 196kc/s if you set the LO on the sdr application to 0.000.000 the readout will direct in kc/s. Set you input in the drop down menu to either left or right hand channel or better still both channels added and the display will start at zero Hz or kc/s. The play on at about 19kc/s you see large humps of signals extending up to about 23 or so kc/s these are Mil transmissions and the like. They un-decryptable by the average punter but they come and go. The Alphas are interesting as the operate up to about 10kc/s from memory and are short pulses with one second intervals roughly

 

17.2 kc/s is worth moitoring because this is the frequency on which SAQ Grimeton Sweden operates in plain language CW (Google it). It is a motor generator set that produces the 17.2kc/s signal no valves or sparks just a 200kw high frequency alternator fed into a massive antenna system. It comes on when advertised usually Christmas Eve and other time during the year Lars will e-mail you the schedual if you ask him.

 

Very receivable with the set up descibed above with a short piece of wire as an antenna. Very long wires can be self defeating.

 

Oh my best dx from my home 8.9kc/s setup ... a sign genny into the antenna is about 1km using above set up. Have tried a tuned circuit in front of the sound card 600mm diam air cored joby with little improvement.

 

Good luck to all who try out VLF RX.

73 es GL petefmt

I support www.NotSpotTelecom.Com your community Telco / ISP.

--- On Sat, 29/5/10, mal hamilton <g3kevmal@talktalk.net> wrote:

From: mal hamilton <g3kevmal@talktalk.net>

Subject: LF: Re: Re: VLF SIGS

To: rsgb_lf_group@blacksheep.org

Date: Saturday, 29 May, 2010, 23:43

Jim
The frequencies I quoted have a 750 hz offset that is why I said not
calibrated, just a rough reception guide around the frequency area of
interest.
The signals are all very loud with me. I can accurately calibrate when
necessary.
Not sure if it is a good idea to connect my antennas directly to the
soundcard, maybe via an attenuator for front end control. I also have a W &
G 220 hz - 20 khz RX which is very sensitive but wideband and would be a
better approach if I feed this into the sound card. I have a number of
options available here I just need a beacon on 9 kcs
de mal/g3kev

----- Original Message -----
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Saturday, May 29, 2010 8:35 PM
Subject: LF: Re: VLF SIGS


> Dear Mal, LF Group,
>
> Everyone can receive those signals in the UK, even with fairly poor
> receiving conditions (actually copying the traffic would be another
matter -
> I wouldn't go there ;-)). Most are quite strong, and in a different octave
> of the spectrum from amateur activity, so not really a good receive
> performance check - rather like using BBC R4 on 198kHz as a test for
136kHz
> reception performance. But the frequencies you list are a long way out, a
> few hundred hertz low. There is spectrum display at
> http://abelian.org/vlf/spectrum.shtml with station IDs and accurate
> frequency calibration. Bear in mind that you do need to be able to set the
> RX frequency within a hertz or less, and have much less drift than that,
for
> the kind of DX tests that have been done recently. Better in that case to
> dispense with the converter and RX, and just feed the signals direct into
a
> PC sound card - frequency errors will be much smaller, and if you are
using
> a reasonably large antenna, you probably won't even need a preamp.
>
> Cheers, Jim Moritz
> 73 de M0BMU
>
>
> ----- Original Message -----
> From: "mal hamilton" <g3kevmal@talktalk.net>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: Saturday, May 29, 2010 7:31 PM
> Subject: LF: Re: VLF SIGS
>
>
> Does anyone else copy these signals? If not forget about VLF.
> g3kev
>
>   ----- Original Message -----
>   From: mal hamilton
>   To: rsgb
>   Sent: Saturday, May 29, 2010 5:15 PM
>   Subject: LF: VLF SIGS
>
>
>   Not calibrated
>   16.2, 18.1, 19.4, 20.1, 20.7, 21.8, 23.1, 23.8 Khz
>   All the above freqs active rtty type sigs and strong.
>   nil hrd below 16.2 Khz at present
>   No alpha sigs hrd today
>
>   mal/g3kev
>
>
>
>

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