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Re: LF: my results on VLF 05-08 May 2017

To: [email protected]
Subject: Re: LF: my results on VLF 05-08 May 2017
From: DK7FC <[email protected]>
Date: Thu, 11 May 2017 13:26:34 +0200
In-reply-to: <[email protected]>
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Hi Paul, Alex, VLF,

Paul, thanks for working out the decode and timing problem, good work.

Alex, i don't know if this is just a PC time problem. At least what i can recommend is to control the PC clock by SpecLab! ...because there is no internet access in the garden. Not sure if you are already using this function.

Make a right click on the SpecLab icon, select properties and enable "start as administrator".
Disable the time sync (from a time server) function in windows.
Now when starting SpecLab, you need to confirm that the program will be started with admin privileges.
Since you are using a GPS module which provides PPS+NMEA, SpecLab knows the accurate time.
Open the GPS receiver function and enable the function "periodically synchronize PC's system date/time with data from GPS".
Before doing this, take a look on the value from "Current measured difference (System -GPS time): sec".
After enabling the function, this value should be in a range of 0.00x sec.

On the cope function of the Samlping rate Correction, what does the PC and EC show, or what is the ratio EC/PC? It should be less than 5% maybe.

Maybe it helps...

73, Stefan

Am 11.05.2017 09:02, schrieb Paul Nicholson:

Alex wrote:

> I think I have only false decodes of
> {05 May 19:15 8270.1 4-char}

I got a successful genuine decode of the 4-char message
from Alex's file


Eb/N0 = 0.0 dB, constant reference phase

carrier S/N: 13.62 dB in 31.2 uHz,
            -31.43 dB in 1Hz,
            -65.41 dB in 2.5kHz

The decode needed a time offset of +1001 seconds
which doesn't agree with difference between the WAV
timestamp and the start of the message.  Something
wrong with the clock at the RX site?

Alex, try the decode again,

 Symbols: 40.0
 Message length: 4
 Start offset: 1001
 List length: 100

Now I go look at the 2-char....
Paul Nicholson

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