There was a discussion here a couple of weeks ago (which I just found out about via the wonders of having a Google vanity search on my callsign) regarding splat and path loss and such. A few comments:
> Hmm... it's an interesting idea. Currently the splat analysis is raster > data, but I think there is some way to have it calculate vector data. Might > be easier to run the raster analysis through a line tracer. I'd love to see > this done with radar data too. Getting vector data out of splat would be best done by generating a ".plo" file, which is just a huge litany of points (they're actually generated along each azimuth line going outward) with the corresponding path loss. Building contour lines from that data ought not to be terribly hard. .plo files are freaking large, though (4 megs for a 100-mile radius calculation, which is actually inadequate for some repeaters sited up on top of a mountain). > Which repeater coverage? Voice-FM or Packet-FM? The two are > different. Bob Bruninga reduced the size of the PHG circles for > APRS mobiles several years back to more closely reflect real-world > conditions. I'm generating raw path loss numbers. It's a judgment call what the maximum acceptable path loss is for any particular application. Some FM HTs may be able to receive a discernable signal as far down as -95 dBm. On the other hand, few repeaters will open for an incoming signal much below -60 dBm, due to duplexer and filter losses, and the general desire for voice FM repeaters to be somewhat "deaf" to reduce the amount of time spent transmitting spurious inputs. I'm currently using -60 dBm as the "incoming" floor for, and -95 dBm for the "outgoing" floor, for my coverage analyses, but that's completely tweakable with just changing a number in a SQL query. It sounds as if somewhat higher numbers will be required for APRS, but it will take some experimentation to find out what those numbers are. Kelly Martin AB9RF _______________________________________________ Xastir mailing list Xastir@xastir.org http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
