Re: [IRCA] Laptop computer requirements for an SDR or similar

[Guy Atkins <dx@xxxxxxxxxxxxx>]

Mike,

You are comparing "apples to oranges" when you say that there should be a
conversion from Perseus WAVs to FLAC or MP3. These audio formats are NOT the
same as the data recorded on the special WAVs that Perseus generates (same
thing with the SDR-IQ's files...they are not audio). The data on the waves
have what's called I & Q (in-phase and quadrature) information that
represents the RF spectrum at the bandwidth and frequency range chosen. It's
much more complex, but that's my low-tech explanation. You might want to
look at Gerald Youngblood's pioneering first article on SDR technology:
http://www.flex-radio.com/Data/Doc/qex1.pdf  See page 4 in particular.

Chuck mentioned in effect that you can't practically listen to all the
frequencies of a full night of recording on a Perseus, and should just
collect a few minutes on the hour and half-hour. My preference is to capture
a continuous stream if possible, especially if conditions are looking good.

What you do is apply a strategy for review; you don't actually listen to ALL
minutes of ALL possible MW channels. One approach (and I think the quickest)
is to tune a single frequency at the start of a session, and quickly skip
ahead every 3-5 minutes, keeping an eye on the waterfall display for any
sign of signals that may be breaking into audio (~10 dB s/n on Perseus, for
intelligibility). If something appears or I see an indication of a
co-channel fading in, I stop and listen for a bit. The Perseus files are
recorded sequentially so it is easy to skip ahead while remaining tuned to s
single frequency. I pay particular attention to the hour and half-hour for
IDs, and give more attention to all parts of the hour when it's around that
crucial "max dawn" period of sunrise enhancement (when conditions can change
quickly).

After you pretty much exhaust a single frequency of the DXpedition in this
"fast forward" method, you start on the next frequency and repeat
the technique. I review faster and skip more minutes, between the hour and
half-hour; but the data is always there for checking another time if I want
to dig deeper. I think it's better to be safe and have captured "everything"
so that you can throw away "anything" later, than to have not recorded the
band continuously. Hard drive space is cheap these days...

73,

Guy Atkins
Puyallup, WA
http://fivebelow.squarespace.com






> From: Mike Hawkins <michael.d.hawkins@xxxxxxxxx>
> To: Mailing list for the International Radio Club of America
>        <irca@xxxxxxxxxxxxxxxx>
> Subject: Re: [IRCA] Laptop computer requirements for an SDR or similar
>        receiver.
> Message-ID:
>        <98e446a10910262039w3e74f352se6f8197fbf9a4bb1@xxxxxxxxxxxxxx>
> Content-Type: text/plain; charset=ISO-8859-1
>
> I've been out of work for almost a year.  I've got time...sadly.  If I had
> something like that for FM when there's skip (or meteor showers), I'd be in
> heaven.  I still think there needs to be an on-the-fly conversion to MP3.
>
> Mike
>
>
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