--- In [email protected], James Ewen <ve6...@...> wrote: > > Chris, > > Have you read the background information on SmartBeaconing yet? > > I think you're going to be fighting an uphill battle on this one. > > What I would do first, is to measure the data that is output from your > GPS. Put a logging system on the GPS, and record the reported speed > and heading values over a long period of time, say 24 hours or so > while the GPS is sitting still. > > Now have a look at that data. Is the unit reliably reporting zero > velocity, and a constant heading? Probably not. > > The generally recommended low speed threshold is about 5 mph. This > allows for some "drift" of the reported GPS location. > > Also, if the GPS is reporting a location, and a heading zero degrees > (as an example), and then resolves a location some distance south of > that first location, you're going to get a reported velocity and a > heading of 180 degrees. That heading change will trigger > CornerPegging. > > If the GPS doesn't have a nice clear view of the sky, then you > location fix is going to be worse, and subsequently more "wandering". > > Slow speed settings for SmartBeaconing are an issue, not due to the > programming, but rather due to the "noise" of the GPS position > reporting. > > Think of the low speed settings you have as a "squelch" knob. You've > opend up the squelch to where the noise on the frequency is popping in > and out, or has opened the squelch setting completely, and now are > wondering why you're hearing all that racket. You either have to > tighten the squelch a bit, or reduce the incoming noise level to make > it quiet again. > > As others have indicated, profile switching can also be a problem, > especially if you are trying to switch based on extremely tight > tolerances. If you have profile switching where one profile is enabled > at zero velocity, and the other at 4 mph, you could bounce between the > two profiles due to GPS "wandering". You need to have enough > hysteresis to keep from bouncing back and forth between profiles. > > Using a routine that sends after a maximum change in location is > better for pedestrian activity. > > Why the desire for a double beacon on a corner? You've reported the > change in heading (the important information), a second beacon is > redundant. > > James > VE6SRV > > On 7/29/10, Bob Poortinga <bobp+ya...@...> wrote: > >> I was experimenting with a low speed Smart Beacon Profile on a T2 (with > >> integrated 5W VHF transceiver) and encountered an unexpectedly high > >> beaconing rate when parked. > > > > Are you using Profile Switching? Do you have "Transmit when swiching to > > this > > profile" enabled? If so, turn it off. > > > >> My settings were as follows: > >> > >> Slow Speed: 0.0 MPH TX rate: 7193 sec > >> High Speed: 4 MPH TX rate: 61 sec > >> Turn angle: 15 deg Max TX rate: 3 sec > >> > >> The shallow turn angle and fast TX rate was set to see if I could reliably > >> double beacon on street corners. > > > > Why? This just adds QRM to the channel. > > > > -- > > Bob Poortinga K9SQL <http://www.linkedin.com/in/bobpoortinga> > > Bloomington, Indiana US > > > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > > > > > > > Bob,
To answer your last question first. I am interested in double beaconing on corners because only ~40% of my beacons are received in my area. If I double beacon, I can increase the probability that one beacon is heard to ~75%, while the probability that both beacons are heard is only ~15%. If I can increase the probability of corner pegging I can increase the length of time between ordinary beacons. I have looked at what smart beaconing documentation is available and I have also graphed the behavior using excel to better visualize how distance between beacons varies as a function of speed and beacon rate. The expected behavior of my profile was that beaconing would be once every 2 hours when parked and rapidly increase to once per minute a 5MPH and above. However I observed an average beacon rate when stopped of once every 37 sec which is a higher than the MAX rate defined in my profile of once per 60 seconds. While I can't easily log the output of the GPS, I can log the received beacons on http://aprs.fi. I was transmitting speed data. The speed that was received while the high beacon rate was occurring was 0 MPH. Currently I am in the process of attempting to reproduce the anomaly. So far beaconing has been stable for 3.5h at 10 min/beacon with a 33% beacon received rate (7 RCV out of 21 TX). Current settings are: Slow Speed: 2 MPH Slow TX rate: 600 sec High Speed: 4 MPH Fast TX rate: 127 sec Turn Angle: 25 deg Max TX rate: 5 sec New settings are: Slow Speed: 0 MPH Slow TX rate: 600 sec High Speed: 4 MPH Fast TX rate: 127 sec Turn Angle: 25 deg Max TX rate: 5 sec PS. I should have done this testing before I posted Chris KF7FIR
