900 MHZ Spread Spectrum Tracker

I would like to publicly thank Scott Ahrens for test flying my experimental 900 MHZ digital Spread Spectrum tracker around the Napa Valley yesterday. Although the little rubber duck sitting on his panel was not optimal, I was seeing his position at altitude (1200 feet and above) at around 10 KM around my test receiving antenna. Around town, I was tracking at around 1 KM. More experimentation is to be done, but the system shows some promise.

73,

Allen
VHS

igate too?

Now if we can just come up with a simple, self-contained igate to get the packets on to the Internet. Ideally it would would have a receiver built in, and connect to a wi-fi hot spot. Hook up power and an antenna and park outside a Starbucks and you're up!

Anybody played with OpenWRT? Could it do this? I like the idea of Allen's "open" trackker, but now we need the other side to make it useful!

Instant I-Gate

Although putting together an "instant I-Gate" is semi-doable, the amount of R&D required would not justify the limited number of sales. Not having a PC in the I-Gate makes for a somewhat complicated beastie. Plugging one of our MT-TT4's into a PC and running cheap software makes a low cost and relatively simple digi-I-Gate. It just takes a person with a bit of computer savvy.

I have been focusing more on the concept of a portable 10 Watt Tracker/Digipeater to cover those black holes across the Country, and let the existing I-gates handle the additional traffic these help generate. My functional prototypes look just like our MT-AIO, with an 8 pack of AA's built in.

If my 900 MHZ concept progresses, I will build a cross-band digipeater, from 900 to 144 to make access to the APRS-IS a simple chore.

Allen
VHS

Allen,

Pete and I have briefly discussed putting together either a portable igate or digipeater, for the purpose of enhancing the tracking of low-level racers in Sport Air Racing League (SARL). It's been on the back-burner lately, but my thought has been to take it airborne in a non-race airplane, and have it circle mid-course, up fairly high where racers on all parts of the course could hit it.

A computer on the airborne platform (with an internet connection) may be problematic, but it sounds like the unit you are conceptualizing right now might be just what we've been talking about in the way of a digi. Perhaps combined with a portable igate on the ground, below the circling mobile digi would give us very solid real-time tracking of all race airplanes, so as to add to the spectator aspect of SARL.

The added digi and igate might also relieve some of the data traffic jams of 20-30 racers putting out tracks with somewhat hi density for the 30-60 mins of a race (and keep the local HAMs happy!)

Any thoughts, maestro(s)?

Cheers,
Bob

I think the idea of a "highbird" digi would be just the thing for air races! You could transmit on a different frequency than the National APRS frequency to get the level of positional resolution you need, without competing (and really pissing off) the rest of the ham world. You could either I-Gate it to the APRS-IS, or just have a stand-alone PC and website for those that want to monitor in real time, without the latency or too-frequent position blocking of local digis and I-Gates. I think that would be preferable for an air race, where lots of data would be flying through the air.

Allen
VHS

Allen,

I was under the impression that the trackers only went out on 144.39 (US) or the European freq (which I can't recall now). I'll have to get mucho smarter on allowable APRS freqs and limitiations, as well as how to program the trackers correctly (is it as simple as setting up a secondary profile and using a different freq?)

Part of the issue is not everyone has secondary profile capability (actually, I'm not sure how many racers have APRS so far...guess I'm trying to sell more of your units! ). But keeping it simple for the racers may get more participation. Therefore, if they can use their standard profile without monkeying with things, that may be a positive. But these guys are modifiers and tinkerers, so it still could be workable.

I've mulled over how to transmit from several racers and stay friendly, yet give folks a pretty hi-fi way of seeing planes move on the course. Sam recommended turning smart beaconing off, and that may be one way. However, some fidelity in the turns will be lost. I've thought about having all racers set to beacon at 30 second or 1 minute intervals, with smart beaconing off, or maybe set to 10-15 seconds, but that's still talking about a lot of beacons hitting the local digis. Its short duration (approx 30-60 mins for the fastest to slowest airplanes), but very dense. I know those time intervals and the volume of transmissions probably make HAM/APRS purists cringe, which is why I'm exploring options...we want to be good neighbors too, for sure!!

The idea of separate freq's and a stand alone website are very encouraging thoughts...it would be fun to set up a site that captured and displayed live video feeds (as has been done on a couple races' start-finish venues) as well as an APRS race feed...heck, perhaps even info/pics of the various racers and their planes.

I don't want to hijack your thread too far off the mark, but it seems related. There is a lot of potential for your equipment, that's for sure! When we reopen the portable igate/digi work, we'll consult with you on ideas, it that's OK! Till then, I'm trying to get a list of the racers at the first few races that have APRS, to see if we can get some race tracks pushed out real-time over aprs.fi. Will let you know how that goes.

Cheers,
Bob

SARL and APRS

rvmills said:

Allen,

I was under the impression that the trackers only went out on 144.39 (US) or the European freq (which I can't recall now). I'll have to get mucho smarter on allowable APRS freqs and limitiations, as well as how to program the trackers correctly (is it as simple as setting up a secondary profile and using a different freq?)

Part of the issue is not everyone has secondary profile capability (actually, I'm not sure how many racers have APRS so far...guess I'm trying to sell more of your units! ). But keeping it simple for the racers may get more participation. Therefore, if they can use their standard profile without monkeying with things, that may be a positive. But these guys are modifiers and tinkerers, so it still could be workable.

I've mulled over how to transmit from several racers and stay friendly, yet give folks a pretty hi-fi way of seeing planes move on the course. Sam recommended turning smart beaconing off, and that may be one way. However, some fidelity in the turns will be lost. I've thought about having all racers set to beacon at 30 second or 1 minute intervals, with smart beaconing off, or maybe set to 10-15 seconds, but that's still talking about a lot of beacons hitting the local digis. Its short duration (approx 30-60 mins for the fastest to slowest airplanes), but very dense. I know those time intervals and the volume of transmissions probably make HAM/APRS purists cringe, which is why I'm exploring options...we want to be good neighbors too, for sure!!

The idea of separate freq's and a stand alone website are very encouraging thoughts...it would be fun to set up a site that captured and displayed live video feeds (as has been done on a couple races' start-finish venues) as well as an APRS race feed...heck, perhaps even info/pics of the various racers and their planes.

I don't want to hijack your thread too far off the mark, but it seems related. There is a lot of potential for your equipment, that's for sure! When we reopen the portable igate/digi work, we'll consult with you on ideas, it that's OK! Till then, I'm trying to get a list of the racers at the first few races that have APRS, to see if we can get some race tracks pushed out real-time over aprs.fi. Will let you know how that goes.

Cheers,
Bob

Click to expand...

Bob, I have been out of the SARL racing for a couple of years but I am trying to get back to it now. I have one of the new RTG trackers that Allen sells installed in my airplane and it works great. I would like to work with you on this if I can help in any way.

I guess what we will need is a "frequency agile" version of the RTG now.

rpellicciotti said:

Bob, I have been out of the SARL racing for a couple of years but I am trying to get back to it now. I have one of the new RTG trackers that Allen sells installed in my airplane and it works great. I would like to work with you on this if I can help in any way.

I guess what we will need is a "frequency agile" version of the RTG now.

Click to expand...

If there is enough demand, I will happily build a Frequency Agile RTG!

Allen
VHS

VHS said:

If there is enough demand, I will happily build a Frequency Agile RTG!

Allen
VHS

Click to expand...

Allen, RP:

Since I know and comprehend just enough of the tech side of APRS to be dangerous , I'll jump in as sort of an end-user rep in the development of a racing APRS set-up. Not sure of the size of the market at introduction, but if an RTG-FA is made, perhaps it would be buildable to reach a wider market.

Here's the background: SARL races take place in a variety of locations, and due to the design (open course X-C race that starts and ends at one airport, with most courses between 100-150 miles in length...various shapes, but a 75-100 mile radius of the start/finish is a good basic geo area to start with).

Many races invite local residents to view the start/finish, with BBQs, parties etc. However, that's a limited view of the race. Internet video feeds of the start/finish have also been tried (and continue when able) to reach a remote audience. A tracker-based feed to the internet would be one way to augment the start/finish viewing, both local and remote.

Some racers carry data loggers for post race review, and for potential foul resolution, but there is no live output. The SPOT interval is too long at 10 minutes. The iPhone Tracklog app can show multiple tracks, but the site is arduous, and it all depends on the phone connectivity (GPS and 3G).

Therefore APRS seems like the way to go. Whether all racers would adopt APRS (HAM license and $$) is unclear. The league would probably not be able to afford a stock of issueable trackers, and we'd run into license and ID issues in that scenario. With good PR, we could probably overcome the license aversion (hassle factor). If an affordable, plug and play tracker were available, it could be a hit. Combined with an airborne digi and a start/finish igate, it could make real-time race tracking a reality.

One question on the FA feature. Does it mean we can pick a discrete frequency for racers to transmit on? Are there alternate APRS freqs available to choose from, or would we have to apply for a freq assignment? Just don't know enough about this aspect of HAM and APRS. I know the goal is to not bury a local area on 144.39 for an hour with an insane number of transmissions...just don't fully know how to make a dense race transmission environment a friendly neighbor.

A wish list for the race+X-C tracker might be:

- Small portable form, as in the current RTG
- 12V adapter as in the RTG...but perhaps make that adapter removable, with the option to run it from a 9V batt, and thus add the ability to plop it up on the dash for the race with no power wires.
- Integral Power switch as an OEM feature, especially if we add the 9V batt power option.
- Integral Pri/Sec profile switch as an OEM feature, so a second race profile could be added to a basic X-C profile (so we can beacon in a friendly manner en masse)
- The last piece is the transmission antenna. For total portability, the pie-in-the-sky is a cockpit placeable antenna that could hit digis at 500 agl and below. The airborne digi may help that, but this is still a challenge. Racers will not want to add an external antenna (drag), so a jpole in the wingtip may be an answer...that would leave just one cockpit pentration (for the ant lead) and one connection at the unit (in batt mode). Maybe a canopy antenna (stickable to the inside of the canopy) would be a nice option too (if that works, and doesn't create an RF hazard to the pilot/pax noggins).

This type of set up (portable and cockpit placeable with min connections) would fit the widest variety of aircraft, some of which would not be able to fit jpoles in wingtips. Racers are modifiers, but simple is good, to allow their efforts to focus on speed mods versus trackers. That feature set may give it a wider appeal as well, and thus make the R&D worth it, as racers number in the 100 range, and you'll need a much bigger market to justify the development.

Just thinking out loud Allen, and just one guy's thoughts. I'd welcome comments and cross talk to enhance the discussion and make it more productive.

If better, I can start this as a stand alone thread, or Sam, if you'd like to do that as a mod with this post, please feel free!

Thanks, and Cheers!
Bob

Race tracker

You can pretty much operate a tracker legally on any part of the VHF ham band ( the very lowest part would be a little bit of a problem, and operating on someone else's repeater input frequency would draw SAM fire....)

What I was envisioning for race tracking would be a transmitter of about 1 Watt on UHF frequencies. The trackers would be transceivers, so each unit could act as a digipeater for all the other units on their frequency. With a "high Bird" digipeater, we could handle handle traffic with enormous ranges, even without each aircraft acting as a digipeater. This method would also allow more data throughput, and not outrage the ham community. UHF antennas are also smaller. This system would not strictly speaking be an APRS system. In fact, the transmitters I have in mind use GFSK ( Gaussian Frequency Shift Keying) which is pretty much incompatible with almost any other ham radios, and less subject to interference.

These transceivers, married to a display GPS, could also display all the other traffic in (close to) real time, and could be useful for anti-collision purposes. The transceivers I have in mind are relatively inexpensive, and one could easily be married to an I-Gate to port the data to the Internet. I would keep it off the APRS-IS: I think you would want your own dedicated website that is not subject to the vagaries of bandwidth hogs.

As far as licensing goes, the pilot need not be a Ham....Yes, I know many of you will not believe me,but only the "control operator" needs a license. If the guy operating the transmitter ( turning it on, and able to cause it to be deactivated in case of trouble) is a ham, and has his FCC callsign in the comments, its all according to Hoyle. We tracks Dogs and Balloons, and they don't have (Ham) licenses either....

To validate the range of a 1 Watt UHF transmitter, I would need to get a high bird to an altitude sufficient to provide line of sight to the racers. Is this possible? We could also place secondary receivers as digipeaters or I-gates in remote areas if needed.

If I could build these inexpensively enough, it could potentially be a stand-alone tracking/information system just for aircraft. With I-Gates capable of sending info back out to RF, you could do messaging, paging, and general announcements area-by-area, or over the whole network. Any interest?

Allen
VHS

Allen,

Very interested! A high bird at sufficient altitude to "see" all racers on a course is not unfeasible at all, and if spotters are in place on the ground at turn points (some or all) remote digis/igates are very feasible as well.

The concept of coupling the transceiver to a GPS display for traffic awareness is very appealing, given that terrain and obstacle avoidance, traffic avoidance and staying on course are big factors. There is little passing in SARL (compared to Reno), but knowing where nearby racers are is an interesting concept.

We have a website that could perhaps be modified to add a map display page, so we can probably go stand alone with web display.

Going UHF to deconflict with HAM/APRS mainstream is a good idea, though it takes us into a race-only tracker, I believe, so it may narrow the market quite a bit. Racers may be willing to add it to their planes, or it could be a nice transportable race package for distribution for each race.

I'm not sure if this concept is anything like the transceiver/GPS tracker combo Pete Howell put together, but size and complexity concerns me a bit...so I'd like to talk further with you on this, to fill knowledge gaps (which are extensive in my case! )

So cost, size, and capabilities are the unknowns to explore...but it has very appealing potential!

What say you Pete and Sam, and others?

Allen, not sure if you still have my e-mail address, but I'll shoot you a note to your AOL account, and we can talk more. Will copy Pete, and Sam, if you'd like to be copied, shoot me a PM or VAF e-mail.

I'll have to fly to Napa soon, take you for a ride and have lunch...maybe with a little varsity APRS/GFSK 101 training added in (I'll buy gas and lunch!)

Thanks much, and talk to you soon!

Cheers,
Bob

Interesting!

This is some cool stuff you all speak of! I do think keeping this off the "normal" ham bands is good idea, as last time I even hinted at experimenting with an airborne digi, the haministas tried to take my Christmas away.

I also think it would be nice to have a "race std" unit that all the racers could run.

I do wonder if it is a good idea to have an old fighter jock like Mills defining technical requirements. How long before he asks for "afterburner", a "missiles to guns switch" and a volume control that goes to "eleven"

Alan,

Congratulation on you success!! This is MUCH more interesting (from a performance perspective) than the 2 Metre APRS systems currenty being used.

If you are willing to share the circuit details (900MHz Spread Spectrum telemetry) and software, I for one would be interested in doing some evaluation.

Doug Gray

UHF Tracker

Doug,

After experimenting with the license free 900 MHZ Spread-Spectrum gear, I gave up on it. Its range was disappointing. The units operating on 440 should have close to 5 times the range at the same power, but of course, require a Ham licensee to be the control operator. If I had two volunteers to test fly a system, I could have a low altitude plane fly a typical course, and a high altitude ship circle high enough overhead to remain in contact with the nap of the earth craft. ( If they are patient, I suppose the low altitude craft could be a car, but an aircraft would be a better test) The purpose of this flight would primarily be range testing, and validating my theory that 1 Watt should handle it adequately. I like the idea of being able to send much more information than you can port through the APRS network without it gagging.

No circuits or software really yet: Its all just vaporware ( although I do have the 440 transmitters ready to do a range test)I would optimally like to keep it looking like APRS, so that off-the-shelf mapping software and protocols don't need to be reinvented.

Allen

Allen

VHS said:

If I had two volunteers to test fly a system, I could have a low altitude plane fly a typical course, and a high altitude ship circle high enough overhead to remain in contact with the nap of the earth craft. ( If they are patient, I suppose the low altitude craft could be a car, but an aircraft would be a better test) The purpose of this flight would primarily be range testing, and validating my theory that 1 Watt should handle it adequately. I like the idea of being able to send much more information than you can port through the APRS network without it gagging.

No circuits or software really yet: Its all just vaporware ( although I do have the 440 transmitters ready to do a range test)I would optimally like to keep it looking like APRS, so that off-the-shelf mapping software and protocols don't need to be reinvented.

Allen

Allen

Click to expand...

Allen, I can get two airplanes for a test (me low, buddy in a 9A high). Everything you are proposing above sounds very good! Will be in contact!

petehowell said:

This is some cool stuff you all speak of! I do think keeping this off the "normal" ham bands is good idea, as last time I even hinted at experimenting with an airborne digi, the haministas tried to take my Christmas away.

I also think it would be nice to have a "race std" unit that all the racers could run.

I do wonder if it is a good idea to have an old fighter jock like Mills defining technical requirements. How long before he asks for "afterburner", a "missiles to guns switch" and a volume control that goes to "eleven"

Click to expand...

Pete, this is why I invited you and Sam into the "Requirements" boardroom...I'll just sit there and look smart, and not "open my mouth to remove all doubt"...ya know!

Only one issue with your thoughts...OLD?...well!

PS: C'mon, get out here and be the high guy...otherwise its Dan and or Greg...the two APRS RV-9As here.

Cheers,
Bob

I'd be happy to help with a test - as long as I don't have to hang out with the "old" guy too much since it might be catching....

greg

Guys: I can help if you need an "expert" at high bird activities. Dan

Sounds like a lunch in Napa, CA soon, eh! Check your e-mail boys!

Cheers,
Bob

PS: As for your comment Greg..."Pot, meet Kettle!"

Jonesy's steak house at the Napa airport is very nice....

Allen
VHS

Good thing Dan volunteered to be high bird, since we probably want the slowest plane in that position....

greg