[aprssig] WSPR for HF mobile?
Lynn W. Deffenbaugh (Mr)
ldeffenb at homeside.to
Wed Sep 29 09:08:57 EDT 2010
I may be wrong, but IIRC when I played with WSPR monitoring a few months
ago you must have an rock solid accurate time signal. This could be
quite a challenge for the ultra-mobile traveler. I'm thinking it was
sub-second synchronization to standard was required.
Lynn (D) - KJ4ERJ - Tinkerer in digital modes...
Robert Bruninga wrote:
> New APRS HF app?
> This months AMRAD newsletter has an article by WA3LTJ about
> using an extremely low-power HF protocol for HF beacons called
> WSPR. Apparently, using just 1 watt, you can be picked up by
> their HF monitoring network that is linked to the internet just
> like APRS.
> See WSPRnet.org and click on the MAP tab and you can see the
> beacons being plotted live, several per minute.
> I have not fully digested this topic, but as-is, it reports
> position to the nearest 6 digit grid square (less than 3 miles
> worst case).. It hints at possible additional messages
> contained in about 15 additional BITS. If these are in addition
> to the grid, then better position to a mile plus the existing
> fixed APRS comments can be included.
> W3PM already has it running on a small PIC processor apparently.
> Again, if it transmits CALL, GRID and 15 more bits, then we have
> APRS! I'd use the 15 more bits as follows:
> 4 bits for SYMBOL
> 4 bits for comment (enroute, returning, ... Etc + customs)
> 3 bits better latitude (to 1/3rd mile)
> 4 bits better longitude
> Again, I only quickly skimmed the article, and I could be all
> wrong, but this sure looks like the long-haul world travelers
> DREAM APRS app.
> Transmissions take almost 2 minutes each. At 1 watt, that is
> 120 watt-seconds. Using 300 baud HF APRS takes 2 seconds and
> with a 60 watt transmitter would use the same 120 watt seconds
> of power. But the savings is in not having to have a 60W amp,
> and only needing a 1 watt transistor final stage.. Plus WSPR has
> forward error correcting!
> Anyway, something to look into. See the map! No reason why the
> major APRS pages might not capture these same position reports
> and put them on the APRS map?
> I propose a standard SYMBOL when brought over to APRS...
> 1) give them an SSID of -12 (which we are using for all
> non-standard "other system" entries into APRS.
> 2) Use the symbol code "WA" which is an overlay "W" on a box.
> Am I missing anything? (probably)... Gotta get back to work!
> QUESTION? With FSK at 1.46 Hz separation, is doppler at 60 MPH
> a problem?
> Unless I calculate this wrong, at 20 meter band, moving at 60
> MPH is about 1 Hz of doppler. So maybe this can only be used
> down at 80m or so where the dopper would be about 0.25 Hz?
> Bob, Wb4APR
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