Monday, March 29, 2010


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:

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. <(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.