APRS Embeded into Get-R-Done Horse Ride, Inyokern, CA

KG6STR Operating as Net Control

I embedded my MT-AIO tracker into a Horse Ride that the local club was providing communications for. I was also a volunteer for the event, I assumed Net Control at Base camp for a few Hours. This gave me the perfect opportunity to test my tracker in the field. I prepped my tracker (KI6PSP-3) with Energizer Lithium batteries. The higher voltage would provide a bit more power output, vise the rechargeable batteries that resulted in 3 watts of output while running off 10.5 volts. The tracker was started early in the morning, with the first packet reaching the internet via my local digi (WI6RE) at 7:12AM, just as the rider, Sue Benson and her horse Rocky began Loop 1. I quickly setup my low powered APRS computer station in the control booth at base camp. I soon realized that the El Paso Peak Digi was probably not hearing every packet the tracker was sending, so I enabled digipeating on my station, and set it for 10 watts. The antenna I was using was a 3db magnet mount, on top of a box fan.

As Horse 509 carrying my tracker and its rider crossed Brown Rd, heading South back to base camp, I picked it up on my computer. It was really interesting when I was able to see exactly where they were, then look out the window and saw them during their Vet Check. The tracker has an SMA connector for the antenna. I picked up a $15 1/4 wave flexible antenna from Fry's Electronics (Premier Antenna RD-9), and used that on a SMA-BNC adapter. This allowed the antenna to stay vertical, and not get in the way of the rider. During their 30 minute hold, I inspected the antenna and snapped a few pictures. The antenna got slightly bent, but that was why I used the cheaper short antenna. The tracker was located on the front right pocket of the saddle, and you can see the antenna if you look closely at the picture.

Heading back out

Plot from Event

I was unable to attend the whole event, but I left my computer station to act as a fill-in digi. With the digi in operation, I was able to track horse 509 as it finished Loop 1, returned to camp, proceeded through Loop 2, completed its final Orange Short loop, then returning to base. The tracker shutdown around 5:22PM, operated for just over 10 hours, with a transmit interval of every 2 minutes. Distance traveled was about 55 miles. Top speed tracked was 9 MPH along a stretch of Loop 2. During this event, 7 packets were heard directly by WI6RE Digi, and 59 Packets were digi'd by my computer station. I do still plan on building a new APRS Server for the Digi on El Paso Peak, with an alternate receive freq that we can operate on for events like this, as the MT-AIO doesn't listen for activity before transmitting. If I combine this with a better antenna at base camp, with slightly more elevation, I think this system will work well. As the evening set in, I recovered my computer station with the assistance of my 2 year old daughter. She had fun telling me where every horse was that she could see. I am unsure if she would rather ride the horses or help with tracking them.

MT-AIO

I received my MT-AIO this last Friday, and I immediately purchased 8 Duracell NiMH Pre-Charged batteries for it. I began testing it out, and of course, looked at the settings. I started to notice that it was "wandering".

Its not super critical, but I was looking at the results, and one time it put me around 800 feet away, and up in elevation about 1200 feet. My first reaction was that the GPS was not on long enough before it was transmitting its plot. I started googleing around, but couldn't find much. Interestingly enough, another MT-AIO showed up on my local digi, apparently it is easier to find another MT-AIO, than it is to find user data beyond the manual on them. Then I remembered several of the yahoogroups I was already subscribed to and receive the digests every morning. There has to be somebody else that has commented on my MT-AIO dancing around. I found this post:
http://groups.yahoo.com/group/MicroTrak/message/1150

In the evening of Sunday, completed a cable, and used it to change the "Power Switch Time" setting to 10 seconds, and it appeared to clean up a lot of the "wandering" or dancing. The screenshot on the right is 6 hours on the new setting.                     Accuracy Improvment Vertically:                 84% Horizontally:             63% The wandering went from 800 feet to about 300 horizontally, and 1200 to 200 vertically.

Within the post, it mentioned that they enabled Smart Beaconing, which keeps the GPS on constantly. Maybe I will do that later, but that sounds a but counter productive for what this unit is designed for, or intended to be used for. Further in the thread, someone mentioned changing the "Power Switch Time" setting from 5 to 10 seconds. For the majority on a Sunday, my MT-AIO sat vertically against a window that faced an igate. The screenshot to the left shows the result of the 24 hour period.

During this research, I noticed a pattern with the plots and learned that APRS doesn't use the 3rd number in the GPS strings.        hh.mm.sss <(The last s)

So a bit of averaging, combined with an incomplete GPS lock on the MT-AIO, makes it wander and dance around. I can't change the averaging, but I can improve the result of the average without sacrificing much battery power.

One last setting I changed that might be good info, is the “Auto TX Delay”, it was 500 milliseconds. Why would I need a half second pre-amble. I adjusted that down to 120 and it seems to work just fine, and it isn't transmitting 10 watts as long, so more run time.