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Message-ID: <65AECDF1F89AD411900400508BFC869F0D74F9@pdw-mail-1.dera.gov.uk>
From: "Talbot Andrew" <ACTALBOT@dera.gov.uk>
To: rsgb_lf_group@blacksheep.org
Subject: LF: RE:ARGO Build 113.]and propagation monitoring
Date: Wed, 10 Jan 2001 09:01:40 -0000
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Ko Versteg NL9222 stores some of it on his website, but can't remember
if he has the latest ultra narrow band software.  

Most of the time I only need two progs for the 56002 itself.  One,
called DECIM01.CLD,  mixes the audio frequency with a commandable local
oscillator anywhere in the range 0 to 3.2kHz to generate I/Q channels at
zero frequency then filters and decimates by a commandable factor to
4000 / 2000 / 1000 / 500 / 250 or 125 Hz sampling rate with a bandwidth
of 0.8 times Fs,  then outputs the resulting samples at this rate to the
serial port.  Commands to set centre freq and decimation are sent to the
56002EVM via the serial port.  The PC then uses these 16 bit Zero
Frequency I/Q samples for FFTs, phase plots etc.   The second prog,
DECIM03.CLD,   adds another /64 stage of decimation within the EVM to
give output data sampled at 62.5 / 31.25 / 15.626 / 7.8 / 3.9 and 1.95
Hz.  (I would like to combine both into one EVM routine but can't be
bothered !)

The ultra narrow band monitoring software uses this lowest data rate
from the EVM, then performs yet another decimation and filterieng
operation, now within the PC, again at a commandable factor up to 64
times  to give a sampling rate that can go down to 0.03Hz.   A 256 point
FFT on this gives 0.0002Hz resolution but down at this level, the raw
I/Q data is better saved to disk for later analysis.   The frequency
accuracy of the whole proces is that dictated by the receiver (locked to
a master reference) and the 8kHz sampling within the EVM which could be
locked to the reference but isn't.

What a pity that none of the VA/VE stations transmitting can maintain
the sort of accuracy needed by this.  The ability to make vector
measurements of absolute phase over hours in mHz bandwidth would reveal
infinitely more about LF long distance  propagation than just power
measurement alone.  For instance, it would reveal directly any Doppler
shifted components, be able to separate out ground and skywave
components and show whether fading or enhancements are caused by
multipath or changing ionospheric conditions.

Andy  G4JNT

>From I2PHD
> Then you could go in the milliHz region, as by example Andy 
> does with his
> EVM56002 (I have one, where can I download your software 
> from, Andy ?),


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