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15926Re: Re: [tracker2] RE: T-2 audio level ?

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  • ve6srv
    Sep 20, 2013
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      The antenna may be mounted on the side of the tower facing south, which would create a null to the north. There may be a building or other obstruction north of the digipeater.

      There could be a number of reasons, but it is impossible to diagnose the issue from thousands of miles away.

      Again, I would ask how you know that KC5HMI-5 stops digipeating your station when you get a few miles north of it. Are you watching the raw packets on RF as you drive around, or are you looking at a website which shows a partial feed of what is happening on RF?

      Without knowing what it is you are doing and how you are making your observations, all I can really do is ask you more questions.

      The observation that your mobile works in all directions except north is probably an incorrect assumption. Your mobile probably continues to work even when you are to the north, but rather you stop getting picked up by the digipeaters when you travel to the north of the digipeaters.

      There's a big difference between your station failing to operate, and your signals failing to be picked up. The first means we need to find out why your radio stops operating, the second means we have to figure out why the signals being sent by your station fail to be heard.

      As for how too many overlapping digipeaters end up in an area, that comes down to people not understanding the basic premise of APRS. The fact that APRS works on simplex is a key factor, but the biggest factor is that ALL digipeaters respond to the same aliases is what causes the biggest problem for people to understand.

      Try standing in a large room full of people, with you on one side and your buddy on the other. If you speak at a normal volume level, you might get heard halfway across the room. You'll need someone in the middle of the room to repeat what you say so your buddy can get your message.

      That guy in the middle of the room passing your message is your "digipeater". If everyone else stays quiet, your messages will get through.

      Now what happens if 5 people all act as a "digipeater" when you talk? They all hear your message, and then all at the exact same time repeat your messsage. What are the chances that your buddy can understand what they repeated? If there's one "digipeater" really close to him, he might be able to make out what the digipeater said. However, if he's not all that close to any digipeater, he might not be able to make out the message. Audio "heterodyning" kills the message reliability.

      In the APRS world, when this happens, some people decide to set up a digipeater closer to home so they can hear and be heard by the close digipeater. So let's add another 10 digipeaters into our room. Does the signal to noise level get better or worse? If you are really close to a digipeater, it gets better, but overall in the room, the noise level climbs a great deal. So what do people do to increase the signal? Yup, increase power... So, now we have a room full of people yelling trying to be heard, and no one wins.

      Get everyone to quiet down, only enable the minimum number of digipeaters necessary to spread the communication around the room, and everyone learn to take turns without making too much noise.

      All it takes is for someone to be gating packets to RF rapidly or sending too many position reports in rapid fire mode, or people to use network hogging paths, and the noise levels will start to ramp up again.

      It takes a lot of user education to teach people about courteous use of a simplex digital network like APRS. Many users never listen to the RF channel load, and many more look at the APRS-IS stream thinking that it shows what is actually happening on the air.

      You need to have people that understand these basic concepts paying attention to the local RF load, and helping educate new users as they pop up doing things that harm the network.

      These same people have to be the bad guy telling "helpfull" people that set up redundant digipeaters that they are not helping, but rather harming the network. This can often cause hurt feelings, and get people upset enough that they take their toys and go home.

      Everyone playing with APRS has to work together to ensure that they are working towards helping the APRS network, not harming it.

      When you can get to that place, you can have a huge network that passes data very reliably over a very large area day in and day out. In my area, we can pass SSn-N packets via 6 or 7 hops across Alberta quite reliably. Normal operations are limited to 2 hops normally, but we occasionally test emergency RF only paths over maximum hops and observe the results. Being able to pass traffic over that number of hops reliably shows that your network is operating quite well.

      Sent from my BlackBerry device on the Rogers Wireless Network

      From: <w5kro@...>
      Sender: tracker2@yahoogroups.com
      Date: 20 Sep 2013 13:02:52 -0700
      To: <tracker2@yahoogroups.com>
      ReplyTo: tracker2@yahoogroups.com
      Subject: RE: Re: [tracker2] RE: T-2 audio level ?

       First thanks for your time and effort helping me with this issue, You have been very helpful and informative, I set up my mobile to digi on Monday night for a demo I was giving from inside a large govt building,   since I was using a  ht with opentracker and handheld gps I needed the digi outside. I don't normally run around like that and it has been disabled.  The fact that we have too many digis too close together will be taken up with some of the clubs . Do you have any idea why I can only get a few miles north of kc5hmi-5 before it stops relaying my position? My work takes me all over town and north of town , Most every direction works fine until I get up north and that is why I put the digi on the tower up north hopefully to get some aprs coverage from mobiles up north. From what you have said the digi is working as programmed and I know my mobile works in every direction except north, Any ideas?

      --- In tracker2@yahoogroups.com, <tracker2@yahoogroups.com> wrote:

      So, this capture is done at KC5HMI-5, correct? It looks to be covering about 22 minutes from 11:35 to 11:57.

      I deleted all the waypoint information from the file. Does the digipeater have a GPS attached? If not, kill the waypoints, and you'll get less noise to look through.

      We can see that this site has digipeated at least 5 packets, because we can see it's callsign in a packet that has been handled by another digipeater afterwards.

              Line 3: K5ARC-2>APN390,KC5HMI-5*,W5KRO-2*,WIDE2*:=3006.16NN09054.51W#PHG9490W2, SSn-N, K5ARC Digi Line 8: N5UKZ>APU25N,KC5HMI-5*,W5KRO-2*,WIDE2*:@182337z3023.36N/09101.15W_197/007g016t085r000p000P001h72b10143/{UIV32N} Line 20: W5KRO>APWW10,KC5HMI-5*,WIDE1*,W5KRO-2*,WIDE2*,:/184300h3031.87N/09102.05W_304/001g006t082r000p001P001h70b10144 Line 24: W5KRO>APWW10,KC5HMI-5*,WIDE1*,W5KRO-2*,WIDE2*,:;146.835-R*182345z3046.44N/09121.01WrMissLou RPT 146.835- Tone 114 Line 29: N5UKZ>APU25N,KC5HMI-5*,W5KRO-2*,WIDE2*:@182347z3023.36N/09101.15W_114/006g015t084r000p000P001h73b10143/{UIV32N}

      This doesn't mean these are the only packets that were digipeated, but because they were handled by another station after this digipeater digipeated them, we see the evidence in the packet.

      We can also tell what alias is being supported. K5ARC-2 and N5UKZ are using a WIDE2-2 path, and we know this digipeater handled those packets.


      W5KRO is using WIDE1-1, and the digipeater also handled those packets.

      So from that, we know that KC5HMI-5 is supporting WIDEn-N up to at least 2 hops.

      Let's look to see if we can see those 5 packets we know were handled by KC5HMI-5 in the APRS-IS stream. Looking through the last 1000 packets for K5ARC-2, we don't see a single instance of KC5HMI-5 handling a packet.

      Looking at the info page for KC5HMI-5, it tells us that it has heard K5ARC-2 5 times this month, with the last time being September 11th. The raw packets you provided however show the date to be the 18th... 
      N5UKZ also shows as not being heard ever.
      W5KRO is reported as only being heard 2 times all month, but we have proof of 2 packets above on the 18th which don't show below.

      callsign ▾pkts first heard - MDTlast heardlongest (rx => tx)longest at - MDT
      K5ARC-2 52013-09-11 08:49:582013-09-11 20:30:00 EM40NC > EM40LO56.7 km 165°2013-09-11 20:30:00

      W5KRO 22013-09-17 07:50:282013-09-17 23:03:31 EM40LM > EM40LO7.7 km 161°2013-09-17 23:03:31

      So, once again I will reiterate that "One cannot use the APRS-IS feed for accurate analysis of RF propagation and network analysis."

      Karo, do you have a capture log of the same time period from your W5KRO station? You state that your station hears more than the digipeater.

      If that is true, then capture logs from both stations during the same time period will show the proof of that statement.

      What else can we learn from the packet log?

      We see that W5KRO-2 is a mobile station using a Tracker 2 with an outgoing path of WIDE1-1,WIDE2-1. We can also see that W5KRO-2 is acting as a digipeater since it is digipeating packets as seen below:


      Mobiles driving around acting as a digipeater are usually frowned upon due to the detrimental effect this has on the reliability of a well planned and deployed APRS network. Shutting down this mobile digipeater would help the network reliability in the area.

      We also see that W5KRO is also acting as a full digipeater from this evidence:

      N5YHZ>APU25N,KD5QZD-12*,W5KRO*,WIDE2*:>261135zUI-View32 V2.03

      K5ARC-2 is a KPC-3+ running v9.0 firmware, running at a reported 81 watts of power at 150 feet with a 9 dB gain antenna and it is choking out the network using a WIDE2-2 path every 10 minutes. A digipeater effectively gets an extra hop based on the fact that it is a digi. This 2 hop path from a digipeater is equivalent to a regular user running WIDE3-3. Proportional pathing would reduce the load this station is placing on the network in the area.
      This digipeater is also sending a number of repeater objects.
      The 147.225 object goes out locally, which is good, but the 145.310 and 146.985 objects go out via 2 hops. Can you access these repeaters from a hundred miles away or so?

      K5LSU-5 is gating echolink objects into the local area via 2 hops at a fairly rapid rate.

      KD5QZD-2 reports itself as a digipeater, yet is asking for help from home fill-in digipeaters because it can't be heard by other digipeaters. Either they need to stop using WIDE1-1 as a path element, or shut down a digipeater that is basically useless if it can't be heard by other digipeaters. The second path element used by this digipeater is not supported. WIDE-2 is not a valid hop request.

      W5LAK as well is a digipeater asking for help from home fill-in digipeaters in order to be heard.

      In Baton Rouge, we find the KD5QZD-2 digipeater, and less than 8 miles away, W5KRO acting as a digipeater, and then just slightly further away, at 11 miles, KC5HMI-5 is a full digipeater. At about 23 miles, KD5QZD-12 is another full digipeater, at 27 miles, K5ARC-2 another full digipeater. Finally W5LAK at about 40 miles acting as a digipeater. We can't forget that W5KRO-2 is driving around acting as a mobile digipeater as well.

      On fairly flat ground, you should be able to get a good 20 miles out of a digipeater with some modest antenna height. That would mean placing digipeaters about 40 miles apart, yet we find a plethora of digipeaters all within close proximity. These digipeaters all are programmed to act on packets heard. With so much overlap, you can end up with heterodyning, and collisions, which causes decreased network reliability rather than increasing it.

      Of course, there can always be local terrain and other issues that may require specific digipeater placement decisions, but I would suspect that there are far too many digipeaters located far too close together to be able to achieve reliable APRS network communication.

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