Van's Air Force
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New Cheaper Tracker
- Thread starter VHS
- Start date
N42AH
Well Known Member
MT-AIO
Mike,
I have just what you need the MT-AIO totally self contained GPS and battery. That is just as soon as I get the new toy MT-RTG. Here is Byonics link for the product description.
http://www.byonics.com/microtrak/mtaio.php Drop me a note if your interested.
Mike,
I have just what you need the MT-AIO totally self contained GPS and battery. That is just as soon as I get the new toy MT-RTG. Here is Byonics link for the product description.
http://www.byonics.com/microtrak/mtaio.php Drop me a note if your interested.
Garage Guy
Well Known Member
Using MT-RTG with Garmin GPS 496
Some comments on using a Garmin GPS 496 to drive the Byonics MT-RTG ...
If you want to use "Aviation In" on your Garmin GPS 496, so it can cross feed flight plans from your panel mount GPS for example, the only choice you have for NMEA output data rate from the 496 is 9600 baud. But then to drive the MT-RTG at 9600 baud, you need the dual speed chip in it:
Another issue with the 496 is its "FAST" vs. "NORMAL" NMEA output stream. "FAST" sends updates every second, "NORMAL" every 2 seconds or more. To get the faster rate, "FAST" sends fewer sentences per update; in particular, it never sends $GPGGA, which the MT-RTG uses for altitude information. On the other hand, you probably want "FAST" if you are using the 496 to drive an autopilot. (At least in our installation, autopilot performance is degraded a lot at the "NORMAL" 0.5Hz rate.) So, good autopilot performance means no altitude tracking on APRS.
I don't mind giving up altitude tracking, and in all other respects the dual speed MT-RTG works perfectly with the Garmin GPS 496. But if you want altitude info on your APRS track, and you need fast NMEA updates out of your 496, you might want to consider a separate puck GPS to drive the MT-RTG.
--Paul
Some comments on using a Garmin GPS 496 to drive the Byonics MT-RTG ...
If you want to use "Aviation In" on your Garmin GPS 496, so it can cross feed flight plans from your panel mount GPS for example, the only choice you have for NMEA output data rate from the 496 is 9600 baud. But then to drive the MT-RTG at 9600 baud, you need the dual speed chip in it:
(Actually, when I ordered my MT-RTG, I didn't realize that; but I emailed Byonics later and Byon sent me the right chip at no charge. Great service, but save yourself some time, do what VHS says and specify the dual speed chip when you order. There's a different TinyTrak3Config utility for the dual speed chip too, if you want to do your own configuration... Byon can point you to the URL to download that.)
Another issue with the 496 is its "FAST" vs. "NORMAL" NMEA output stream. "FAST" sends updates every second, "NORMAL" every 2 seconds or more. To get the faster rate, "FAST" sends fewer sentences per update; in particular, it never sends $GPGGA, which the MT-RTG uses for altitude information. On the other hand, you probably want "FAST" if you are using the 496 to drive an autopilot. (At least in our installation, autopilot performance is degraded a lot at the "NORMAL" 0.5Hz rate.) So, good autopilot performance means no altitude tracking on APRS.
I don't mind giving up altitude tracking, and in all other respects the dual speed MT-RTG works perfectly with the Garmin GPS 496. But if you want altitude info on your APRS track, and you need fast NMEA updates out of your 496, you might want to consider a separate puck GPS to drive the MT-RTG.
--Paul
Byonics GPS versus Ship's GPS
I think that a review of the costs and features will lead most to choose the Byonics GPS that is bundled with the RTG (along with an antenna, rubber duck or magmount) having to slave a serial cable to the wingtip ( if thats where you install the unit) is going to present some challenges, and having a standalone system it seems to me at least, is much less likely to introduce RF noise from the tracker into your other avionics. I like the spirit you showed in tapping your GPS display unit, but the hockey puck is so simple and so cheap, that the cost/benefit of building and running a cable from your display GPS seems extravagant. ( In truth, much of what you guys do seems extravagant to my bailing wire/bubble gum engineering mindset!)
Allen
VHS
I think that a review of the costs and features will lead most to choose the Byonics GPS that is bundled with the RTG (along with an antenna, rubber duck or magmount) having to slave a serial cable to the wingtip ( if thats where you install the unit) is going to present some challenges, and having a standalone system it seems to me at least, is much less likely to introduce RF noise from the tracker into your other avionics. I like the spirit you showed in tapping your GPS display unit, but the hockey puck is so simple and so cheap, that the cost/benefit of building and running a cable from your display GPS seems extravagant. ( In truth, much of what you guys do seems extravagant to my bailing wire/bubble gum engineering mindset!)
Allen
VHS
I agree with Allen. The Byonics hocky puck GPS is a very recently designed unit, with very high sensitivity. I suspect it runs rings around most GPS units that are more than a year old (even the full TSO Garmin units). It commonly provides excellent GPS data with my RV9 still in the hangar and the doors only cracked about 10 feet (yes a metal roof and all metal sides). With all the possible electromagnetic interference issues in wiring from the panel mounted unit, possible corruption of the data to other users of the panel mounted unit (like the autopilot), spring for the dedicated GPS for the tracker. It will make your life much easier.
Garage Guy
Well Known Member
Are many folks using either of those antennas in an aircraft? I would guess they wouldn't work very well, but I could be wrong. As for reviewing costs for a SiRFstar III GPS receiver, www.argentdata.com seems to have slightly better prices.
I was worried about that with the MT-RTG, seeing as it's housed in a nonconductive plastic box. No problem with the present installation here, though I have a ferrite choke balun on my antenna which might be helping with that.
Everybody's avionics setup is going to be different, but if you have one or more NMEA GPS data busses already, and they're accessible, tapping one for APRS might be easier than having to think about mounting another antenna and routing its cable. In my case I already had a serial line run anticipating a 406 MHz ELT install which hasn't materialized, so it was really easy to repurpose that.
Also, there are reports of a dedicated APRS puck interfering with XM Weather, so going that way isn't necessarily a free lunch either.
You want extravagant, I'll tell you about feeding the left gear leg in our RV-6 as a nonresonant folded monopole, with a L-C network matching it to 50 ohms at 145MHz. Works great for APRS!
--Paul
N42AH
Well Known Member
MT-RTG w/Byonics GPS
Paul,
I have both the MT-RTG, connected to a AV-14 antenna, and their hockey puck GPS installed in my 9A. I also have a Lowrance 2000C and Garmin 300XL. I have not experienced any interference issues. Here is the link to yesterdays flight http://aprs.fi/?call=N42AH&dt=1275955200&mt=m&z=11&timerange=3600
The MT-RTG is a great product
Paul,
I have both the MT-RTG, connected to a AV-14 antenna, and their hockey puck GPS installed in my 9A. I also have a Lowrance 2000C and Garmin 300XL. I have not experienced any interference issues. Here is the link to yesterdays flight http://aprs.fi/?call=N42AH&dt=1275955200&mt=m&z=11&timerange=3600
The MT-RTG is a great product
Garage Guy
Well Known Member
Thread drift here, but your track there has some issues I've seen on some of my own tracks, where some of the trackpoint timestamps are out of order for some reason, making the parts of the track rendering on the aprs.fi map obviously wrong. (Unless you were doing a few split-s's or Immelmans on your route...)
I understand that arguably the APRS protocol isn't as well designed as it should be in terms of producing and perserving timing information, but I wonder if it would help overall to configure the MT-RTG to "Timestamp HMS"?
Has anybody tried that? You have to disable MIC-e, I believe, and I don't know how many ground stations would pay attention to it, though from my limited understanding of APRS I think they are supposed to. But for sure your own GPS knows better what time a position sample was taken than random PC clocks on the ground do...
--Paul
