[aprssig] APRS-WSPR APRS from anywhere!
bruninga at usna.edu
Mon Oct 10 09:39:00 CDT 2016
For mobile HF APRS using WSPR, we need the best band that works 24/7/365
but ONLY over the distance of say about 250 miles. Assuming there is
nowhere in the USA for example that is that far from an APRS WSPRgate.
My recollection is that the lower bands are usable for short range during
the day. But the absorption and noise is so high that it is painful to
use. But with WSPR giving 27 dB processing gain, wouldn't that overcome
the high noise level.? So, what would work best? 80 meters?
Another reason I want to keep the range low in this particular concept is
so that we can get a 100 times higher position resolution in the same
number of bits by not having to encode the entire world but just the
nearest 500 miles.
On Sun, Oct 9, 2016 at 3:20 PM, Robert Bruninga <bruninga at usna.edu> wrote:
> The more I think about it the more I get excited about building up an
> APRS-WSPR Gateway system. With the 27 dB signal processing gain of WSPR,
> then a 1W transmitter is the same as 1000 watts. And for receive, since
> APRS can have HF receivers everywhere, then this can really expand the
> usefulness of APRS anywhere in the world including on the fringes of our
> existing network.
> QST in September showed the $29 TAPR WSPR daughter board that plugs onto a
> Rasberry pi and although it is only a 100 millliwatt transmitter, with
> enough WSPRgates, that should not be a problem. But adding a 1W PA will
> always help!
> I already have come up with a compression technique that can improve on
> the existing gridsquare (60x120miles) down to (18x12miles) and down to 3
> miles or nearly a half mile for 5 and 4 letter calls.
> see http://aprs.org/aprs-wspr.html
> Lets get those WSPR boards on the air!
> Bob, WB4APR
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