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APRS drops off

bruceh

Well Known Member
I've got the MicroTrak ready to go model on my RV-9A in the wingtip, running a J-pole antenna. The settings are in line with the recommendations in this forum. As you can see on my last couple of flights, the tracker is putting out good packets in the beginning of the flight, then it goes MIA.

I did a dozen laps around the field and only got this:
Screen%20Shot%202014-04-19%20at%209.02.20%20PM-M.jpg


Yesterday I flew out east from the airport for over an hour and only got this:
Screen%20Shot%202014-05-04%20at%20May%204%2C11.41.17%20AM-M.png


Any ideas on why this APRS tracker poops out after a few minutes of flight?
 
Plugging my Call Sign, N79599, into the APRS.fi window and comparing the info to yours indicates to me that you and I apparently have different configurations. I can't tell you all the settings off the top of my head, but I'm very sure I configured my MicroTrak based on the recommendations of Sam Buchanan.
Check his postings and make sure you are set up per his recommendations. Maybe someone else can post more detailed help for you.
 
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I can't tell your configuration from the raw data but I do see t least on (and perhaps two) misbehaving iGates (or digipeaters) in your area that is messing up your messages. It's probably not the only issue but is is part of the problem.
 
Did another flight today and here is the same result. The APRS just stops transmitting (or the iGates stop receiving).

Screen%20Shot%202014-05-04%20at%20May%204%2C7.49.11%20PM-M.png
 
Couple of thoughts:

I always suspect equipment or connection faults when a tracker performs poorly. A GPS that is dropping out after it gets hot would cause this problem. Also check to make sure the center pin in the coax connector is making good contact. It may be the tracker signal is being degraded by a bad connection to the point that it can't be recieved when flying away from iGates. Looks like you are flying in some mountainous terrain.

As Glen pointed out, there are some flaky digipeaters in your area. Afraid there isn't much you can do about that except:

You might do a little reprogramming of the tracker. Remove MIC-E encoding so you can activate the "timestamp HMS" feature. This might help the bad digis and aprs.fi play nice if there is a time stamp in your beacons. More info here:

http://www.vansairforce.com/community/showthread.php?p=566672#post566672

Once you get everything sorted out try removing the WIDE1-1 sentence so your beacons won't get bounced as many times and contribute to congestion.

Keep working at it. APRS is too good to not use if you have the license and equipment.
 
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Odd pattern

Very strange. If you have a 2 meter portable with the squelch set high, you should be able to determine if your transmitter is actually transmitting. There are not a lot of apparent receiving stations in your area ( If only we knew someone who knew something about setting up I-Gates....) Just from a quick glance, it looks like you are hitting an I-gate from one side of your ship, so my first guess would be Wing-shielding ( Creating a one-side favored transmission lobe as a result of having the antenna on one wing tip, and blocking transmissions with the fuselage in the other direction(s))
This is pretty much a known complication of cross polarization in a one sided installation, but generally the power margin is enough to overcome absorption and cross polarization losses. In your area, it may not be sufficient. Can you check your antenna connection and orientation? ( How about installing a belly whip and bypassing the problem altogether?)

In case I am not being clear, VHF is a Vertical antenna world. You have a horizontal antenna, Which immediately eats up most of your signal. This may not be a deal-killer, but the antenna rotates 360 degrees ( in level flight) in respect to any other ground based antenna as your ship changes bearing. The horizontal antenna has radiation "lobes" (Maximum power) radiating at right angles to the antenna, and radiation "nulls" (minimal or no power) from the antenna ends. Your ship can act as a reflector for radio waves, absorb them, or reflect back power out of phase, cancelling out the transmission by making the receiver see it as two separate transmissions, and failing to achieve the FM "capture" that is required for data transmission. With packet, its all or nothing; Either the receiver sees a perfect packet or it ignores the cross noise and the signal.


73,

Allen
 
Finally back home after 2 weeks on the road. I had time today to pull off the wingtip, connect up the old laptop and see what the settings were that might be causing the problem.

IMG_5261-M.jpg


I did as suggested and turned off the Mic-E enable setting, then wrote the new setting out to the microtrak box.

I don't see any Timestamp HMS setting on this screen. :confused:

I hope to get in the air tomorrow and see if things change.
 
Finally back home after 2 weeks on the road. I had time today to pull off the wingtip, connect up the old laptop and see what the settings were that might be causing the problem.

IMG_5261-M.jpg


I did as suggested and turned off the Mic-E enable setting, then wrote the new setting out to the microtrak box.

I don't see any Timestamp HMS setting on this screen. :confused:

I hope to get in the air tomorrow and see if things change.

Bruce, I see a major problem.

Your screen shot is of the Secondary settings. You have to set the tracker for Secondary via a hardwire connection. If you don't have this connection (pretty sure you don't) then your tracker is actually using Primary settings. Hit the Primary tab at the top of the screen to see the settings the tracker is now using. The Secondary settings won't have any effect regardless of what you do with them unless you force the tracker into Secondary mode.

You will not see Timestamp options until you disable MIC-E. Then the Timestamp box will be active and you can select that option. Also, disable TX Twist and Send DOA, they don't apply to our application.

Reading the doc file in the software download will be helpful:

http://www.byonics.com/tinytrak/tinytrak3plus.zip
 
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Secondary is enabled

Sam,

I installed a switch on the tracker box so I can use both profiles. The first one is for the car and the second one is for the airplane. I have the switch set to #2.

I will turn off the TX Twist and Send DAO and enable the Timestamp setting.

Thanks!
 
Secondary is enabled

Sam,

I installed a switch on the tracker box so I can use both profiles. The first one is for the car and the second one is for the airplane. I have the switch set to #2.

I will turn off the TX Twist and Send DAO and enable the Timestamp setting.

Here is the screen shot after turning off Mic-E, and I can see now that the Timestamp window is enabled. I didn't see that before!

IMG_5263-M.jpg


Thanks!
 
Twist and shout

Respectfully, if you have any of our frequency agile transmitters, you should Enable Twist. The data consists of two tones, one at 1200 and one at 2200 Hertz. Radios and general physics tend to suppress higher frequency stuff at a higher rate than lower frequency stuff ( Stop me if I am getting too technical here) So our transmitters and everybody's receiver "hears" the lower tone better. This results in the low tone being received very well, and the high tone actually being "quieter" or lower in amplitude. When the deviation is set on a transmitter, its set at one frequency, because the actual deviation varies with frequency. Setting the transmitter to 3.5 KHZ deviation really means you are setting the 1200 Hertz tone to 3.5 KHZ deviation, and the higher frequency is attenuated. Based on the premise that there is no human or engineering problem that cannot be solved with brute force and ignorance, enabling Twist causes the 2200 Hertz tone to be broadcast at a higher amplitude than normal, or causing "pre-emphasis", which in nearly all cases will cause the two tones to be received and decoded at closer to equal amplitude, improving decodability.

73,

Allen
 
Respectfully, if you have any of our frequency agile transmitters, you should Enable Twist. <snip>

Thanks for the clarification, Allen. My tracker doesn't have that option, and after reading the doc for the TinyTrak3Plus firmware it didn't seem it would apply to our application since I don't recall it ever being mentioned in regard to our aviation trackers. But I am very willing to defer to your recommendation.

Bruce, I didn't know you were using two configs, sounds like you are on top of it. Hope the new tweaks help.

See...that's what I get for trying to offer suggestions....I shall stay on the sidelines and watch with interest. :D
 
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Success!

I made the changes that Sam suggested and it seems to be working fine. Here is the track from my flight today.

Screen%20Shot%202014-05-18%20at%20May%2018%2C4.19.30%20PM-M.png


Thanks a million!
 
Nice investigation Bruce. Thanks for posting the update.

Allen, now I need to go see if I have "twist" set correctly.
 
Trackky McTrackerson

Nice work Bruce! Great to get help from the pros here.

Sam and Allen keep us all "visible"....
 
Allen - for clarification (because there seemed to be some back-and-forth) is this configuration the same as your recommendation, and is it how a new tracker will come configured for use in an airplane ?
 
Defaults

Allen - for clarification (because there seemed to be some back-and-forth) is this configuration the same as your recommendation, and is it how a new tracker will come configured for use in an airplane ?

No, your settings are very different. To start, you are using the mobile Digipath, of Wide1-1,Wide2-1, which I actually prefer since it works better on the ground. The default for an Aircraft would probably be set by Byon as WIDE2-1.

MIC-E should not really effect ground stations receiving you, but turning it off is a great way to debug the problems. One of the most Common TNC (Digipeater Controllers) has a known bug of delaying packets, and without a human readable time stamp, your ship may appear to be doing things that are physically impossible. Having a time stamp may not fix that, but it will clear up the problem.

Your Fast and Slow Smart Beaconing times are the same, so you may as well use just a timed transmission rate. Given your very wide digipath, once per minute is a bit fast to be considered polite for extended use, so we would set it at 120 second transmission intervals. Since you are selecting your config on the fly, so to speak, it would be more polite to switch to the narrower Digipath at altitude, and go wider at low altitude. This is actually a function we hope to make automatic in the next generation of software for the frequency agile products.

73,

Allen

Setting the Twist Enabled will always improve the transmission, although you may need to recalibrate the deviation control if you swap settings. Its designed to work with the Twist Enabled.
 
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