Order Tray | Contact Us | Home | SIG Lists

APRS RF DX? (Was RE: [aprssig] APRS in Atlanta - flooding the network)

Robert Bruninga bruninga at usna.edu
Wed Oct 12 15:51:34 UTC 2005


>>> dave at emv.co.uk 10/12/05 11:03 AM >>>
>wide3-3..., would just ...[decrement] the ssid...
>to "blank" when it all expires.  Thereby keeping 
>the packet as short as possible.

yes

> Otherwise, it's not much different to the huge 
>routing strings that seem to occur when the likes 
>of Tracen-n is used?

Yes, WIDEn-N now is the replacement for TRACEn-N.
Yes, people think of those as LONG packets, but
that is only because they are using LONG paths.
Since we have detrmined in most of the USA that
paths longer than 3 in most areas and longer than
2 hops in most metro areas are impractical, and
cause so much flooding and collisions, they are no
longer welcome.

Therefore the fact that all WIDEn-N packets now
arrive as a fully traced DIGI1,DIGI2,WIDE2* is 
considered as a great network advantage rather 
than as a problem of excess bytes...

>As to PHG circles.  Nice in principle, but in many 
>places ("non flat"territory etc) you just do not 
>get anywhere near a circular coverage, so
>in many places, it would be very misleading to users.

That is why PHG includes a DIRECTIVITY byte that offsets
the pattern 10 dB or so in any favored direction as
input by the user.   This accounts for most blockage
and favorable subtleties in local coverage.

>It would also need people to actually understand 
>the RF parts of the system again.  Sadly, many...
>"operators" not wishing to know the in's and out's 
>of how it all works,

But any Ham should know the height of his antenna
and its gain and the favorable direction of his location.
APRS software (but unfortuanately not UIview) 
has these parameters for the user to enter during
setup and are just as important as his location:
 - LAT/LONG
 - Antenna Height above average terrain
 - Antenna Gain
 - Transmitter power
 - Favored direction (if significant)

It is very unfortunate that UIview only asks its
users for the LAT/LONG, thus leaving out completely
the RF parameters that make RF network visualization
possible to other APRS users.  Fortunately there is a
PHG add-on, but not enough people use it to make
it worthwhile.

As a result, APRS can no longer distinguish the communicaitons
capability between a house with gain antenna on a hilltop
compared to someone with an antenna on his deck at 6 feet.
Whereas the communications range of these stations may
differ by an order of magnitude.

This is one of the contributing factors as to why
many APRS users these days are quite in the dark
about the RF network around them.  They are
not transmitting it, nor are they seeing it from
others.   Fortunately, the most useful PHG plots
are when looking at the digis, and they mostly
have their PHG coverage included.  But we should 
make sure that UIView home stations acting as
DIGIS should manually enter their PHG string for
the benefit of others.

de Wb4APR, Bob






More information about the aprssig mailing list