APRS Coverage in Eastern PA

PHG Plot - Sojourn - KE4ZNU-9
PHG Plot - Sojourn - KE4ZNU-9

I was running my GPS-to-APRS tracker while on a bicycling vacation along rail-trail paths around southeast PA. I expected good coverage in urban areas and not much in the woods, which is pretty much how it worked out.

Here’s a plot of my track (from aprs.fi), with superimposed half-size PHG (Power-Height-Gain) “circles” for the digipeaters that caught my signal. Clicky for many more dots.

The first part of the ride, from BB62 in Camden NJ to Pottstown PA, had good coverage.

A bus jaunt from Pottstown to White Haven, just north of I80 along the Lehigh River gorge, accounts for the abrupt jump. I dropped off the face of the earth at White Haven, riding south along the Lehigh River to Jim Thorpe, then along some undeveloped trails to resurface just north of Allentown.

Strangely, there are no points east from Allentown to the Delaware, then south along the river & canal to Trenton. We stayed overnight on Bull’s Head Island where, as nearly as I could tell, there were no other APRS signals at all.

A plot of all the APRS activity (and, thus, all the active digis) for a different 24 hours shows the gaps in coverage match up fairly well with where I wasn’t heard. These are also half-size circles, but don’t take topography into account. Notice that the trails along the Delaware run right through the no-coverage zone!

PHG Allentown to Camden - 24 hours
PHG Allentown to Camden - 24 hours

I’m not sure why the digis caught me going into Allentown and not going out, but the vagaries of RF propagation remain inscrutable. Even if the digipeater could receive a clear signal, a collision between two transmitters can kill both packets stone cold dead. In addition, I’m using 100 Hz tone squelch and some receivers may not decode packets with tones.

Another possibility is a path (WIDE1-1, WIDE2-2) that allows only two hops to an Internet gateway. In those remote regions, it may well be that I should have had a path allowing three or four hops. However, I wasn’t hauling along all the programming gear to tweak the TinyTrak3+ on my bike. If I lived around there, I’d have a better appreciation of what’s needed to get out of the valleys.

In any event, it was an interesting exercise…

3 thoughts on “APRS Coverage in Eastern PA

  1. I have used aprs.fi quite a bit in the past, but never noticed the PHG button before. Very interesting! (but not necessarily very accurate or useful?)

    1. As nearly as I can tell, the half-size PHG circles give a reasonable estimate of the digipeater’s coverage, for typical 50-W automobile-class transmitters on more-or-less flat terrain.

      The full-size circles (seem to) apply to fixed transmitters with an antenna up above the clutter.

      For an APRS setup on a bike, running 4 W into a crappy antenna in rolling terrain… well, sometimes you can actually get a packet into the digi!

      It’s actually much better than that; the bike lashups work surprisingly well.

      I’m doing some experiments even as we speak. More on that as I get the data collected, but Smartbeaconing looks like a real win.

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