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[aprssig] 30M HF APRS Blackout Due To Solar Flare: AX.25 vs PSK63

Stephen H. Smith wa8lmf2 at aol.com
Sat Mar 10 20:46:57 UTC 2012

I have been watching the propagation changes and blackouts on 30 meters the 
last few days due to the solar explosions and CME.    I am monitoring both the 
conventional AX.25 3---baud packet-based APRS, and the new PSK63-based APRS at 
the same time, from my location in central Michigan (Lansing/East Lansing area).

The classic AX.25 packet-based APRS uses 10.149.200 MHz / 10149.400 MHz mark 
and space freqs for it's conventional FSK operation, while the new PSK63-based 
APRS uses 10.149.700 MHz.    The two modes are close-enough together, 
frequency-wise, to be heard in the same SSB passband simultaneously, as 
different-frequency audio tones.

In turn, I am using two sound card apps on the same sound card (a Griffin 
Electronics "iMic") at the same time:

o     The UZ7HO "Soundmodem" for 300 baud AX.25 packet.

o G4HYG's "APRS Messenger" for PSK63-based APRS

Posits from both are passed into UIview for a mapping presentation.

As a result, I have about as perfect a side-by-side comparison of the two modes 
possible, using the SAME radio (TS-690), SAME antenna (my homebrew 5-foot dia 
mag loop) and SAME computer & sound card.    There are about 8-10 stations on 
AX.25 up and down the Eastern Seaboard, and in the Mid-West, that beacon 
24/7.   As a result, I have been able to observe propagation changes in real 
time on my all-US 30-meter APRS map.

The massive solar storms completely blacked out 30 meters off-and-on for the 
last several days.    Each day as the sun rose in the eastern US, the band has 
gone dead by mid-morning, both for AX.25 and PSK63.       Then in the 
mid-to-late afternoon, as the eastern US stops looking so squarely at the sun, 
signals start re-appearing.   By late-afternoon/dusk eastern time, most of the 
regulars have re-appeared.  By 8:00 PM EST (i.e. about an hour and a half after 
sunset), I have been hearing a couple of stations on the west coast (W6OTC in 
the CA Bay Area and one in central Washington) fairly regularly.

One of the 30-meter "regulars" is WB8SKP in western KY, about 460 miles (730 
KM) from me. Like me, he also beacons on both modes simultaneously: as WB8SKP-3 
on  AX.25, and as WB8SKP-63 on PSK63.   [As on the APRS-IS, SSIDs on PSK63 are 
not limited by AX.25 protocol and can be anything. By convention, PSK63 
stations have adopted the -63 SSID.]

The really interesting thing is this:  Each time the 30-meter band starts 
recovering from the flare blasts, the WB8SKP  PSK signal has starting being 
received successfully here in central Michigan at least 45 minutes to a full 
hour before I copy  *ANYTHING* on conventional AX.25 (including 'SKP's 
counterpart AX.25 transmission).

30-meter HF APRS over PSK63



Stephen H. Smith    wa8lmf (at) aol.com
Skype:             WA8LMF
Home Page:          http://wa8lmf.net

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