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1-10 of 12 messages
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Full Quieting Required for Packet Receive?
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by KG9NZ on April 26, 2008
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I am experimenting with APRS using an old KPC3+ TNC (firmware version 7). I'm using an indoor J-Pole antenna since I do not have outdoor antenna options. Although I can hear fairly strong signals (S7 and S8), I was not receiving any packets.
I switched PASSALL on, and I see that I am receiving a lot of packets, but they have errors so are not being passed. Here is an example of some of the packets I see:
KC2PNN-9>TRUY3W,KC2QZF-2,K2ILH-2*,WIDE2-1:255.90NI(7844.33W0EcholinkD215,K2ILH-2*,WI
`jKSn!r>/]"5p}Moailest,MY (Sweet Hom
K2NV>APU25N,K2ILD-2*,WIDE2,WIDE2-2:S/R NO PL, - BARRA -0·654.13W#PHG466
>100008zUI-View32 V2.03,WIDE2-2:GI 1.7)
N2NJH-3>AHD215,K2ILH-2*,WID%2-1:
}N2LYJ-10>APVR30,TCPIP*,N2NJH-3*:;IRLH-4884*261915z04255.50NI07844.33W0Echolink
146.55 1(7.2 IDLE
WX2BUF>APW272,K2ILH-2*,WIDE2-2:
=4256.46N/07823.18WWPHG5±20/National Weather Service - BufValo, NY -NYERIBUFFALO
-17˛,<530>
N2TIF>BEACON,K2ILH-2*,WIDE,WIDE2:
=4256.95N/07846.39W-Paul inAmderst NY USA EN02OW {UIV˛*N}
Adjusting the volume on the radio does not seem to help. I can make things worse, but the best I can get is similar to that above. I've tried a variety of locations for my antenna, and have tried using two different radios, also with results similar to the above.
I have not tried running APRS programs due to the packet errors. However, I have tried manually sending a few packets. When I do this, I see them reliably on findu.com.
The station I am apparently getting most of the packets through, K2ILH-2, is 14 miles away from me. Should I expect to be able to receive packets over this distance? I have no problem using repeaters at this distance, although they are not full quieting. Is full quieting required for reliable packet reception?
I am able to receive packets from closer stations on a different frequency, and usually even receive a few packets from R0ISS-4 if I tune my radio to its frequency during a pass. So I know my TNC is not totally broken, although it is possible it is not as good at decoding packets as it should be.
73,
Frank KG9NZ
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RE: Full Quieting Required for Packet Receive?
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by KG4PID on April 27, 2008
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Looks like the K2ILH-2 digi is north of you. Try moving your antenna around and listen closely to your receiver. You want the cleanest signal, not always the strongest one. You could be getting interference from a local electrical device which would explain why you can send but not receive. My linksys wireless router causes me problems on receive but my packets still go out. How much power do you have to use to show up on Findu.
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RE: Full Quieting Required for Packet Receive?
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by KG9NZ on April 27, 2008
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I am heard reliably running only 5 watts.
I tried numerous locations for my J-Pole antenna. Tried moving it slightly, using different rooms, right against outside wall (it is a brick building), away from it, etc. None worked significantly better.
I did try listening carefully to the signals, and it appears there is some "popcorn" noise on them. The noise is a low frequency popping sound, almost like some cars used to cause on AM radios before the days of electronic ignition. I was able to reproduce this noise by tuning a portable scanner to a weak VHF station (weather radio broadcast from Environment Canada). The scanner allows me to select the mode, and I only hear the popping if I select narrow FM. Don't hear it if I select AM, also do not hear it in the white noise between stations. With a stronger signal (such as the local NOAA station) I don't hear it. I was not able to find anything in my place that seemed to be creating the noise, and its strength seemed to be close to the same nearly everywhere. Outside well away from the building, the noise was gone however.
73
Frank KG9NZ
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RE: Full Quieting Required for Packet Receive?
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by AA4PB on April 27, 2008
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The popping noise that occurs at any time during a packet will surely corrupt the packet. You need to locate and eliminate that noise.
Normally, with an open squelch, a TNC will decode a packet down near the noise level. It doesn't have to be anywhere near a full quieting signal.
If your TNC can run "open squelch" then you are better off opening the squelch on the receiver because the delay in the squelch circuit can cause missed packets.
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RE: Full Quieting Required for Packet Receive?
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by NA4IT on April 27, 2008
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A couple of things:
1. You say the packets contain errors. I really didn't see any. I did see some that look like gibberish, but I know that they are compressed beacons that will decode to an APRS client software OK.
2. In that Kantronics, if you will set the "CD" command to "CD SOFTWARE" you can run your rig open squelch.
3. I have found that a rx packet does have to be fairly robust and have good quality audio. Say S-3 or better, with audio no more than 3.5kc wide.
Good luck. Keep tweaking. You'll get it!
de NA4IT
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RE: Full Quieting Required for Packet Receive?
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by KF6IIU on April 28, 2008
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Make sure any noise blanker and DSP is OFF.
The DSP on my IC706mkIIIg will wreck packet reception.
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RE: Full Quieting Required for Packet Receive?
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by KG9NZ on April 29, 2008
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>You say the packets contain errors. I really didn't see any. I did see some that look like gibberish, but I know that they are compressed beacons that will decode to an APRS client software OK.
There are generally single-bit errors. For example
N2NJH-3>AHD215,K2ILH-2*,WID%2-1:
It should be "WIDE2-1:" at the end
WX2BUF>APW272,K2ILH-2*,WIDE2-2:
=4256.46N/07823.18WWPHG5±20/National Weather Service - BufValo, NY -NYERIBUFFALO
Should be "Buffalo, NY" for location
>In that Kantronics, if you will set the "CD" command to "CD SOFTWARE" you can run your rig open squelch.
This is already the case. I also have squelch turned off on the receiver and no audio processing.
Thanks for the suggestions. It looks like the noise is causing me the problems. A small number of packets, generally short ones, get through with PASSALL OFF, but it is probably less than 1 in 100. Using MIXW in VHF packet receive mode in place of my TNC actually reads more than half the packets successfully. But I can't connect that to an APRS appliaction. AGWPE did no better than my TNC.
The next thing I will try when I get time is going mobile to see how far I have to get from the building (or how much closer to the the digi I have to drive) to get reliable reception. Too bad there are no digis closer to me. There is one station a few miles from me I can receive direct, but it is not a digi. I may try to contact that call to see if he is able to reliably receive the digi.
73
Frank KG9NZ
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RE: Full Quieting Required for Packet Receive?
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by NA4IT on April 29, 2008
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I think the problem you are seeing is with K2ILH-2. According to the APN382, K2ILH-2 supposedly is running a Kantronics KPC3 with the 8.2 firmware. It could also be not programmed correctly. Considering it shows the K2ILH-2 consistently doing it, I would suspect it could be the culprit. One digi programmed wrong or acting up can mess up an entire area.
Scott NA4IT
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RE: Full Quieting Required for Packet Receive?
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by KG9NZ on May 5, 2008
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I did some tests this weekend, and made a surprising discovery that has helped my packet reception quite a bit.
I started out by moving everything to my car. I powered both an HT and my laptop using their internal battery. I used power from a 12V plug in the car for my TNC, and used a mobile 2m antenna on the roof. Since I don't have APRS set up on the laptop, I used a terminal program connected to the TNC with monitor on.
Sure enough, I started receiving packets as soon as I got my setup in the car. So I quickly concluded that it must be local noise inside that was preventing me from receiving packets. After driving around a bit with stops to monitor reception, I returned home. I reconnected everything and set up for APRS as usual, then went away from my computer without paying much more attention.
When I returned to the computer a couple hours later, I was surprised to see numerous stations on the APRS map. Before, I was never able to receive more than one or two occasional packets, and here I had almost 20 stations on the screen. I wasn't sure what might have changed, since everything was set up exactly as it was before. Then I noticed that although I was now receiving signals, I was no longer hitting findu with my signal. I sent some sample packets and I saw that my radio was not keying up. Since receive was still working, I assumed that the mic connection had come loose from the TNC when I moved it.
I opened up the TNC connector, and sure enough, there was a wire that had come loose. However, it was not the mic wire - it was the ground wire! I soldered it back in place and transmit now worked - but I was no longer receiving packets. Not believing this, I unsoldered the ground wire again. Sure enough, I was receiving packets this way - with only the audio wire and not the ground wire connected to the TNC!
I realized that the TNC must have a high input impedance, and some of the audio was getting capacitively coupled to ground. But why would this improve reception? I realized this setup would be sort of a high-pass filter. So I went about constructing my own high-pass filter between the radio's audio output and the TNC. I put a 0.1uF capacitor in series with the audio line, and tried various resistor values between the TNC audio input and ground. I found that 150 ohms gave me the best reception.
So now, I am able to receive the majority of packets from the closest main digi, although I don't receive any other packets direct. And I can transmit, hitting findu reliably.
I'm real surprised that adding a simple filter to the audio output of the radio improves reception so dramatically. I would have thought the TNC would already have optimal filtering in its audio circuits.
73
Frank KG9NZ
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RE: Full Quieting Required for Packet Receive?
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by KL7EDK on May 8, 2008
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This may not be related to your problem but I had a bunch of popping noise on 2 meters. I shut off the power to my house and could still hear it on my 2 meter radio. Took several days but tracked it to the neighbor's house who had a police scanner on an outside antenna. Once he took the scanner out of scan the noise went away. Many scanners leak RF out thru the antenna. Just a thought.
Other comments about 'clean' vs 'strong' are correct. A good clean signal works just fine even if it is just barely moving the S meter. I run packet over 80+ miles paths with 5 watts just fine.
Good luck.
Jerry
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