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Date: Mon, 02 Jun 2014 23:04:45 +0200
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Subject: Re: VLF: W4DEX trans-Atlantic at 8971 Hz
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Hi Paul,

Many thanks for the information.

By coincidence, I am experimenting with an STM32F407 "discovery" board, 
which has a couple of fast A/D converters and a DSP-friendly instruction 
set (an ARM Cortex M4F). May be suited to digitize three analog inputs 
from three antennas (+ much easier GPS sync than on a PC). It's in a 
very early stage of development, though.
About 15 Euro for a uC development board with built-in debugger 
("ST-Link"), 1 MByte fast internal Flash, and 192 kByte internal 
SRAM..quite tempting to do something senseful with it.

Regards,
   Wolf .

Am 02.06.2014 22:43, schrieb Paul Nicholson:
> Wolf wrote:
> > do you have an estimation about how many percent of the
> > transmission time were actually 'blanked' due to sferics ?
>
> Yes, blanking factor is about 25%.  Varies from hour to
> hour in the range 20% to 35% and not necessarily more at
> night.
>
> I combine E and H signals and steer the pattern, then
> apply blanking to the combined signal (as opposed to
> independent blanking of the three components before mixing).
>
> Blanking threshold is 1.2 times the moving mean amplitude.
> I think the default threshold in Spectrum Lab is a bit higher
> but the effect of that difference is very small.
>
> I band limit to 8970 +/- 1500 Hz before blanking. Much
> narrower and the sferics become stretched and blanking
> less effective.
> -- 
> Paul Nicholson
> -- 
>
>
>