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LF: Re: T/A JAN 31

To: [email protected]
Subject: LF: Re: T/A JAN 31
From: "Alan Melia" <[email protected]>
Date: Tue, 31 Jan 2006 11:15:04 -0000
Delivery-date: Tue, 31 Jan 2006 11:40:59 +0000
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Hi Roelof, I dont think ARGO "needs" noise, I think it would be fairer to
say that the noise should be used to set the "theashold levels". ARGO is
very sensitive and it only requires an increase in signal strength of about
4 dB to go from "nothing seen" to "O" report signals. Thus I normally set
the sensitivity to show a little "snow" on the screen.....I often saw 30%
but that is just a feeling, you need to imagine what a weak signal will look
like amongst that noise. There is always the possiblility that added noise
can enhance signal visibility by pushing the level over the next
digitisation threshold occasionally. If one sets it up for a totally dark
screen you may be set too far below threshold to detect a weak signal.

As far as RX bandwidth is concerned I find that it makes little diffference
if the band is clear of big signals. I have experimented with weak locally
injected signals and the IF bandwidth makes no difference to the ease of
detection of signals at or around the noise level. If there are strong
relatively local signals then it helps avoid cross-mod problems to use a
narrower filter. I use a pair of AOR 7030s and both have Collins 300Hz
filters installed.

Cheers de Alan G3NYK

----- Original Message -----
From: Roelof Bakker <[email protected]>
To: <[email protected]>
Sent: 31 January 2006 10:15
Subject: LF: T/A JAN 31

Hello all,

Last night I tried ARGO.
The band started very noisy, but I got captures of WD2XKO and WD2XGJ.
VO1NA appeared later.

I have heard rumours that ARGO and SpecLab need some background noise to
compare the signals against and hence should work better with a (relative)
wider bandwidth.
At present, I am using a 12 Hz bandwidth and both programs seem to work
Can anyone shed some light on this?

Thank you in advance,

Roelof Bakker, pa0rdt

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