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  #11  
Old 11-29-2014, 01:46 AM
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I was afraid of that.
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  #12  
Old 11-29-2014, 05:00 AM
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With the new tracker's data capabilities, it would be possible to encode engine data. Use a unique frequency and set the "beaconing" rate to 30 or 15 seconds. Now you have performance telemetry at Reno.
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  #13  
Old 11-29-2014, 07:59 AM
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Bill Boyd Bill Boyd is offline
 
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Default In air tracking

Glen,

Do you have a means to see APRS targets while you are airborne? I know it exists with some of the Kenwood rigs, just wondering if you have the hardware installed in the RV.

-Bill
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  #14  
Old 11-29-2014, 08:29 AM
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Quote:
Originally Posted by humptybump View Post
With the new tracker's data capabilities, it would be possible to encode engine data. Use a unique frequency and set the "beaconing" rate to 30 or 15 seconds. Now you have performance telemetry at Reno.

It's an interesting thought. We are actually looking at systems to send position and speed data, but the transmission rate would have to be on that order of 60hZ, likely faste (for judging pylon and show-line cuts). However, 8-9 aircraft, at that transmission rate, would probably anger the HAMs a bit, eh! Engine data is an interesting thought…though that is a huge amount of data. No real clue here if the system could handle it…cool thinking though.

In practical application, and thinking along the lines Bill brought up, what would need to be combined with this transceiver to make this a cockpit tool? I remember Pete's experiment with a car GPS screen and APRS. How would one build a pseudo-TCAS and text tool out of, say, an iPad?

More cool stuff from Alan, VHS and Byonics!

Cheers,
Bob
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Last edited by rvmills : 11-29-2014 at 08:33 AM.
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  #15  
Old 11-29-2014, 08:55 AM
VHS VHS is offline
 
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Default The utility of a transceiver

I am certainly not advocating that everyone needs a transceiver, in fact, the TT4 platform ( transmits and decodes) versus the TT3 platform ( Just transmits) requires a significantly higher degree of APRS Gung Fu. By adding the receiver, you can send text messages, "talk' to other stations with a keyboard and LCD, computer, or some GPS receivers, and of course, actually see the position of other APRS trackers and objects ( Digipeaters, weather stations, etc) The transceiver can act as a digipeater and a tracker, but you don't have to do either or both....you have a choice, in fact, the array of choices with a transceiver becomes so great that you can create a nightmare for yourself. One problem that occurs in an airborne transceiver is that the receiver is capable of picking up stations directly and clearly out to the horizon ( which we search and rescue guys know, can be pretty far away) Ordinarily, this means that your transceiver, which is designed to be "Polite" will not transmit until it "hears" a clear channel. At altitude, it will never have a clear channel, since it will be picking up stations quite well for about 15% more distance than the optical horizon. This means you need to make it a bit "Deaf" or it will never transmit. Like the transmitter-only, this means that you can't go hog-wild on how often you transmit.

Also, acting as a digipeater, if you set the digipath too wide, it will store and forward APRS transmissions from other stations, and at altitude, this can wreak havoc, since not only can you receive stations from hundreds of miles away, other stations can also receive your digipeated signal from hundreds of miles away.

There are sneaky ways of getting around this. For air and ground Search and Rescue, or special events when you really want specific coverage without flooding the whole continent with redundant traffic, you might set your unit to only digipeat stations that have addressed their calls to a specific alias, like "SAR" or "Temp" and ignore the others. If you within range of a known-I-gate/digipeater owner, you might convince the operator (if he is the aviator type) to only digipeat received signals on your own "secret" frequency, while still sending your own position reports to the internet so you can see them online on aprs.fi, etc.

By connecting a transceiver via bluetooth, you can run software on your Droid phone or black box with software like Aprsdroid, so you don't have to add more gear to your panel. Personally, I like to marry TT4 or Kenwood based transceivers to the Avmap G5 or G6 display GPS receiver. This receiver will display APRS icons, so a Plane will show up as a plane, a truck a truck, a balloon a balloon, etc. The Avmap will also allow you to send text e-mails from the touch screen, or open up APRS weather stations with a weather station graphic display.

The MTT4B will make a great ground station digipeater for areas where there are holes in APRS coverage. Pretty much all you need to do is add a base antenna and a 12 Volt power supply, you don't even need a GPS. If you marry it to a PC, you can use it for the front-end of an I-Gate, a Weather station, telemetry station, etc., but this is not for beginners without direct support from experienced Hams.

Allen

Last edited by VHS : 11-29-2014 at 09:01 AM. Reason: typos
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  #16  
Old 11-29-2014, 09:12 AM
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Quote:
Originally Posted by rvmills View Post
However, 8-9 aircraft, at that transmission rate, would probably anger the HAMs a bit, eh! Engine data is an interesting thought…though that is a huge amount of data.
The nice thing about the new unit is that it is software frequency programmable, meaning each aircraft could have its own unique frequency, so no worries about packet collisions with other aircraft (or angering the hams... ;-) )

-Dj
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  #17  
Old 11-29-2014, 01:12 PM
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Nice write-up Allen. One other issue is that aircraft need far less transmit power than terrestrial stations, due to lack of obstacles. It is good Karma to use only the power that you need for the task.

I've had good luck with a 300 mW transmitter. I thinK that tx power over a watt or two would be pushing it.

Cheers
Vern VA7VRL
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  #18  
Old 11-29-2014, 01:41 PM
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Quote:
Originally Posted by Bill Boyd View Post
Glen, Do you have a means to see APRS targets while you are airborne? I know it exists with some of the Kenwood rigs, just wondering if you have the hardware installed in the RV.
My "test station" is a Kenwood TH-D72A which I've used as a temporary tracker when flying right seat with others. I've also been known to have it on hand at fly-ins to see if any of the APRS RV's are inbound.

As for using it while airborne to see targets, I did one test with another plane - after a briefing - but I didn't feel comfortable since it "keeps the head in the plane" too much. It could hook up to an AvMap G5/G6 for easier situational awareness with less attention.
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  #19  
Old 11-29-2014, 02:32 PM
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Default lots of possibilities!

http://www.vansairforce.com/communit...ght=generation
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  #20  
Old 11-29-2014, 03:31 PM
VHS VHS is offline
 
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Default APRS Power while airborne

Vern,

Output power is like a pistol or or a fire extinguisher....you don't need it until you need it badly! We have had amazing results, with line-of-sight reception of our MF-15 (15 mW output power) at ranges in excess of 400 miles. Of course, the transmitter was flying above 70,000 feet, where few of us will spend any time.. Many high altitude balloons don't even use a digipath: they just plan on hitting I-gates, which works well at altitude but is a complete non-starter for transmitters in the weeds. I admit in principal that lowering the output power to a few Watts or less would be fine for flight op's, but totally unsat for ground operations ( Especially while you are upside down in the trees with AVGAS running down your neck)
Looking at creative solutions to prevent abuse leads Byon and I more into thinking that Digipaths should be velocity proportional, since velocity generally ( don't say it) corresponds with altitude. Since aircraft have, for our purposes, essentially unlimited power budgets, and you are going to hit the horizon at any height, there is little point in turning down the power. Just using a narrower path at higher altitude also is not good enough, unless we had a built-in atlas to give us Height-above-ground, Vs Height -above-sea-level. With a transceiver, we can get a little more sophisticated, for instance, we can potentially monitor the frequency to see if our packet has been digipeated ( This often happens so fast that your own transceiver won't switch back to receive fast enough to decode it, and you may have to settle for the second "bounce") This potentially could let us set output power proportionally, which would be an outstanding feature in a hand-held portable, but probably just-too-cute for an in-flight system.

I don't think that conventional APRS is a good fit for high speed telemetry in race planes. I would probably look to using 900 MHZ, digital spread-spectrum transmitters, which are cheap, license free at one Watt ( I think you can go to 10 Watts with a Tech license and not using encryption, but I would have to double check the rules) and being spread-spectrum, you can run a zillion of them with high throughput without packet collisions. Many of these units will also do automatic mesh networking, so every ship would pass every other ships traffic.

Allen
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