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  #21  
Old 03-04-2010, 08:38 PM
Sam Buchanan's Avatar
Sam Buchanan Sam Buchanan is offline
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Quote:
Originally Posted by mnile View Post
To start, I wish to thank Sam for showing me APRS, so I have something to do while I wait for the economy to turn around and I can afford to buy my RV12 empennage. I have been lurking here for several years, and I hate that my first post is one contradicting one of the great ones at VAF.

After experimenting with APRS for 10 months, I feel that the suggested smart beacon settings are a bit too aggressive if not downright abusive.

Here are the suggested settings for "Smart Beaconing":

The "Min Turn Time" is the number of seconds that must pass before retransmitting while turning.

Consider this "anonymous" APRS airplane track:


There are 10 positions transmitted over a 40 second period. The tracker was correctly configured with a WIDE2-1 single hop path. All 10 packets were picked up directly by Igates, but that doesn't mean that the packet didn't get digipeated. In fact, there are at least 5 digipeaters within 30 miles of this location. At 1000 feet AGL, it is likely that all 5 digipeaters heard the packets. With a WIDE2-1 path every digipeater would retransmit the packet exactly once. Those 10 packets got turned into 50 packets that effectively shut down all APRS activity within range of those digipeaters.

I suggest that the "Min Turn Time" be set to no faster than 15 seconds when in an area of low to medium APRS traffic. In high traffic areas, we should not be be transmitting any faster than 30 seconds when in a turn, and probably no faster than every 90 to 180 seconds when in a straight line. If you are in an area with good igate coverage, consider using NO path when at high altitude.

With a 15 or 30 second "Min Turn Time", you won't be able to draw perfect circles any more, but you will be making much better use of a limited resource.

I know from experience how fun it is to go home and look at your track and see your every move recorded by the magic of APRS. Let's use this resource wisely and be good APRS citizens. If we aren't careful, we may find that airborne APRS users will develop a bad reputation.

--
Martin
ki6wjp
Martin,

Thank you for your considered post concerning aprs config settings. Yours is certainly not the first to call into question the settings many of us use for our airborne trackers. My experience with aprs is limited to a little over two years of actual use so I certainly don't rank as an aprs "elmer".

I only want to address a couple of the points you raised. One is your assertion that our settings are abusive and will result in airborne trackers developing a bad reputation. In regard to our reputation, according to the designer of the most popular series of aprs trackers (who frequents this forum), aviation aprs has provided a tremendous shot in the arm for this segment of ham radio and has resulted in the production of a lot of new ham licenses. Contrary to developing a bad reputation, it seems we are helping to energize this segment of ham radio.

Secondly, the dire warnings about how aviation aprs is clogging the frequency don't appear to be valid at this point. If the majority of aircraft had trackers this might be the case. But a look at aprs.fi will usually reveal only two or three aviation trackers (nationwide) in use at any one moment, and they are usually traveling in a straight line. You stated that my (or anyone's) transmission of ten packets in less than a minute "effectively shut down all APRS activity within range of those digipeaters (30 miles)". How do you reach this conclusion other than on a theoretical basis? How many other trackers in my area tried to send a packet within those forty seconds? Is there any way of knowing? If we can't know, how can we determine whether or not the entire local network was paralyzed for less than a minute?

My point is not to disagree about the need for civil use of the service. I guess I've just heard enough hysterical wailing over the past two years from a very small number of hams, nearly all of whom are non-aviation users, about how we are trashing the system that my patience is wearing a little thin. But the network still works very nicely in spite of the occasional aviation tracker.

In regard to tailoring packet transmission rates to fit particular digi densities and tracker altitudes, we just don't currently have the technology for our simple trackers to adjust beacon intervals based on the environment. What might be "appropriate" for a particular portion of a flight over congested areas would not be best for other portions of the flight over sparse population where safety concerns dictate maximum performance from the tracker. You suggested up to 180 seconds for straight line intervals. You may wish to set your tracker that way, but flying nine miles between beacons ain't gonna cut it for me when the technology exists for a much finer (safer!) resolution, and in my opinion meets the criteria for civil use of the service. My tracker is configured for maximum performance for maneuvering flight close to the ground which is precisely the situation wherein the safety advantages of real-time tracking are most important.

I hope this reply doesn't appear harsh or unappreciative of your input. However, after two years of energetic embrace of aprs by many in the aviation community, the settings in common use seem to be cohabiting with the aprs community very nicely while adding a remarkable dimension to aviation safety. It may very well be that in years to come our approach will need to be reconsidered, but we can face that when a very large number of aircraft are flying trackers.

Best wishes for an enjoyable RV project, whichever one you decide to build!
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Last edited by Sam Buchanan : 03-04-2010 at 09:07 PM.
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  #22  
Old 03-05-2010, 06:56 AM
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Pat Hatch Pat Hatch is offline
 
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I would just like to wholeheartedly agree with and second Sam's comments above.

I also think Sam has been a proponent of responsible use throughout his postings, for example his recommended path of WIDE2-1, which eliminates the fill-in digi hops.

Might I also suggest that, as Sam has done, aviation users of APRS who want to "give back" to the system, consider setting up a digi or iGate of their own to bolster the network, especially in those areas where the network is sparse. This should go a long way in building our reputation within the ham community.
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  #23  
Old 03-05-2010, 07:28 AM
Sam Buchanan's Avatar
Sam Buchanan Sam Buchanan is offline
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Quote:
Originally Posted by mnile View Post

Consider this "anonymous" APRS airplane track:


There are 10 positions transmitted over a 40 second period. The tracker was correctly configured with a WIDE2-1 single hop path. All 10 packets were picked up directly by Igates, but that doesn't mean that the packet didn't get digipeated. In fact, there are at least 5 digipeaters within 30 miles of this location. At 1000 feet AGL, it is likely that all 5 digipeaters heard the packets. With a WIDE2-1 path every digipeater would retransmit the packet exactly once. Those 10 packets got turned into 50 packets that effectively shut down all APRS activity within range of those digipeaters.

I suggest that the "Min Turn Time" be set to no faster than 15 seconds when in an area of low to medium APRS traffic. In high traffic areas, we should not be be transmitting any faster than 30 seconds when in a turn, and probably no faster than every 90 to 180 seconds when in a straight line. If you are in an area with good igate coverage, consider using NO path when at high altitude.

With a 15 or 30 second "Min Turn Time", you won't be able to draw perfect circles any more, but you will be making much better use of a limited resource.


Martin
ki6wjp
Martin,

I thought about this graphic after sending the previous post and thought you might be interested:



This plots the formation entry into the pattern of our local airport of my RV-6 and a pal's RV-6A. We both use the SmartBeacon intervals that you expressed concern about. However, instead of one of the trackers crashing the local network as you predicted, it seems that all the beacons from both trackers successful hit the net even though we were flying mere seconds apart.

Perhaps the aprs system has a bit more capacity than is sometimes predicted.
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  #24  
Old 03-05-2010, 08:36 AM
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mikehoover mikehoover is offline
 
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Quote:
Originally Posted by Sam Buchanan View Post
...You suggested up to 180 seconds for straight line intervals. You may wish to set your tracker that way, but flying nine miles between beacons ain't gonna cut it for me when the technology exists for a much finer (safer!) resolution!...
I love that statement! This is why I am building an RV.

Plus, I wouldn't have been able to do this for my then girlfriend, now very supportive wife:
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  #25  
Old 03-05-2010, 03:41 PM
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mnile mnile is offline
 
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Boy did I poke a stick in a bee's nest. Sorry if I stepped on anybody's toes. I don't want this to become the next "Primer Wars".

While airborne, our trackers cover a much larger area than ground based trackers, and we should behave accordingly. Transmitting every 5 seconds would be frowned upon by every APRS group that I know of.

Just because your packets made it to the internet does not mean you were not impacting the airwaves for hundreds of miles around you. We should be careful to not abuse the privilege.

Just like you can install an O-360 in an RV9, you can beacon at fast rates. In both cases, it is against the intent of the designer. However, there are valid reasons why you would want to do so. You just have to understand the downsides that come with the choice. (My feeble effort to make this as RV related as possible )

I urge all prospective APRS users to understand the configuration settings shown at the top of this thread before you start flying with your tracker. If you are in an area of heavy APRS activity, you should certainly consider slower beacon rates.

--
Martin Nile
ki6wjp (hopefully airborne someday)
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  #26  
Old 03-15-2010, 11:09 AM
jclark jclark is offline
 
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Default Giving Back To APRS ... Seeking Help

Quote:
Originally Posted by Pat Hatch View Post
I would just like to wholeheartedly agree with and second Sam's comments above.

I also think Sam has been a proponent of responsible use throughout his postings, for example his recommended path of WIDE2-1, which eliminates the fill-in digi hops.

Might I also suggest that, as Sam has done, aviation users of APRS who want to "give back" to the system, consider setting up a digi or iGate of their own to bolster the network, especially in those areas where the network is sparse. This should go a long way in building our reputation within the ham community.
In the spirit of Pat's message, I am like many who want to "give back" to the APRS system and hopefully improve its "capacity" to handle all these airborne trackers. :-)

So ...
UI-View32 - check
AGWPE ... check
Packet Engine Pro (for a "BETTER" AGWPE) ... check
Scanner tuned to 144.390 and connected to sound card on home PC ... check

After MUCH time, I get packets coming through my system and can see them with various pieces of monitoring software.

After additional time I get UI-View32 to "send beacon" and my info shows up on aprs.fi in the right location. [UPDATE: Now that seems to not work. :-( ]

BUT .... I keep get the following message (somewhat paraphrased from memory):

" ... Lost the AGWPE connection to 127.0.0.1..."

AND ..

I cannot get AGWPE nor PE Pro to "talk" to UI-View and thus I cannot "i-gate" the stuff I see locally.

Anyone out there with any ideas?? Yes, I read through the links that Sam put up.

I am starting to think maybe a "winsock" matter but all my other internet stuff seems to be working OK.

James
p.s. If someone made a "sure to work PACKAGE" of all this stuff, I would be first in line to BUY a copy. I have spent WAY TOO MUCH time trying to sort it out. :-) :-)

p.p.s. THANKS goes to Sam and Kahuna for the time they let me waste of theirs as well. :-)
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  #27  
Old 03-15-2010, 10:54 PM
edleg edleg is offline
 
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First time posting... sorry if I double post ('puter didn't seem to get it there the first time)...

I have never ran APRS (I came this board because of my interest in aprs), but I have a lot of experience in two similar RF technologies: ham radio VHF packet service and a commercial radio service that transmitted a lot like packet/aprs.

First off, in the '90's I did a lot of ham packet radio in San Jose, CA. Using a 25/50 watt 2 meter rig with an antenna 30 feet in the air. Lots of square miles of coverage in Silicon Valley. Back when there were a LOT of ham radio bulletin boards... and a lot of ham radio packet stations...before everyone was on the Internet. Rarely was there a problem getting a signal through the "ether" to the 'verse. Some re-transmits, but not bad. Communicated with other hams all over usa on vhf packet, almost in real time.

Earlier than that, in the '70s and '80s a high tech company I worked for pioneered using UHF radios with digital-to-RF 1200 baud modems of their design (and patent) for use in warehouses for real-time communications between a forklift truck operator and the warehouse computer system. Computer directed picking of goods and put away of goods. We commonly had 20-40 UHF radios operating (split frequencies, kind of like a repeater) from these forklifts on the same frequency pair at the same time. The ONLY time we had problems was if the forklift terminals were all turned on at EXACTLY the same time. Then there would be a lot of RF signal "collisions" and a lot of re-transmits from the terminals. In fact we tested systems this way by turning on as many RF terminals as we could at once to test the system's software ability to recover from the mass collisions. The only thing we did was insert some code to provide for a random amount of wait time, or delay, for that very first transmisson. After that all those operators rarely had but an occasional re-transmit. It SEEMS like the airwaves were going to be full of all those messages, but looking at it with monitoring and recording equipment, even with 40 radios in the same warehouse, transmitting on the same frequency, in a relatively small space, there was mostly empty airtime.

There is lots of 2 meter aprs airspace...and if we don't use the bands, we stand a good chance of losing them. As a ham, I would rather the bands be crowded than under utilized!

-Ed-
KD6UBY
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  #28  
Old 03-15-2010, 11:17 PM
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petehowell petehowell is offline
 
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Default Welcome!

Hi Ed,

Good to have you aboard. All that radio stuff is great, but you realize you are required to build a plane now!
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  #29  
Old 03-16-2010, 07:53 AM
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Sam Buchanan Sam Buchanan is offline
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Quote:
Originally Posted by edleg View Post

There is lots of 2 meter aprs airspace...and if we don't use the bands, we stand a good chance of losing them. As a ham, I would rather the bands be crowded than under utilized!

-Ed-
KD6UBY
Ed,

Welcome to the forum and thank you for taking the time to post.

Your comment reflects the observations I have made during the two years a tracker has been in my aircraft. The dire warnings by a few (non-aviation) hams about killing the frequency with aircraft trackers just don't seem to be evidenced by reality.

I also have to wonder if the aprs system has seen a net gain in capacity due to the new iGates that have been installed by aviation aprs enthusiasts......
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  #30  
Old 03-16-2010, 05:16 PM
jclark jclark is offline
 
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Default Maybe we are not doing so bad after all ...

Quote:
Originally Posted by Sam Buchanan View Post
Ed,

Welcome to the forum and thank you for taking the time to post.

Your comment reflects the observations I have made during the two years a tracker has been in my aircraft. The dire warnings by a few (non-aviation) hams about killing the frequency with aircraft trackers just don't seem to be evidenced by reality.

I also have to wonder if the aprs system has seen a net gain in capacity due to the new iGates that have been installed by aviation aprs enthusiasts......
Did some back of envelope calculations (which means they are probably WRONG(:-) and concluded that in a "typical" city, you would probably need a density of about 1 device/sq mile transmitting in 1 minute intervals with WIDE2-2 to clog the system. Made a lot of assumptions about randomness of arrivals and thus throughput.

That would be a LOT of airplanes even at 1/10th that density.

It is a good idea for us (as mentioned) to be considerate and ALWAYS mindful of the impact of not being good citizens. So far I think we have been and the short burst nature of our transmissions, the limited time in an area and the limit on the propagations is what makes it all work out nicely (so far :-) )

James ... just trying to understand this more as I try to find the error in my i-Gate setup.
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