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I'm trying to establish an AX.25 connection to a nearby RMS gateway (should be within a mile) using a Baofeng BF-F8+ on 2 meters. I'm trying to establish a connection with either RMS Express and UZ7HO sound modem on Windows or with ax25-tools axcall command with soundmodem on Linux. I am using a USB sound card and VOX mode on my radio. In both cases, I see my radio transmitting SABM several times and a variety of responses coming back, but my call out never seems to advance beyond the initial state of starting a new AX.25 connection. I'm not terribly familiar with AX.25, but it looks like the receiving software never notices the appropriate reply to continue on with. The packets I am receiving are even passing checksums correctly and I can decode some of the text contents I expect the server to be providing. Under Linux, I can even monitor the traffic with Wireshark, but it seems that axcall never sees the packet. Is it possible that my VOX has a hang time that's causing me to loose the initial response to my call?

Here's a sample capture from one attempt with Winlink on Windows:

1:Fm KG7GAN To K7CPU-10 <SABM C P> [17:53:31T]
1:Fm K7CPU-10 To KG7GAN <I C R0 S3 Pid=F0 Len=25> [17:53:36R] [+++]
SanDiego CMS via K7CPU >

1:Fm KG7GAN To K7CPU-10 <SABM C P> [17:53:36T]
1:Fm KG7GAN To K7CPU-10 <SABM C P> [17:53:40T]
1:Fm KG7GAN To K7CPU-10 <SABM C P> [17:53:45T]
1:Fm KG7GAN To K7CPU-10 <SABM C P> [17:53:50T]
1:Fm KG7GAN To K7CPU-10 <SABM C P> [17:54:19T]
1:Fm K7CPU-10 To KG7GAN <I C R0 S1 Pid=F0 Len=21> [17:54:22R] [+++]
[WL2K-3.2-B2FWIHJM$]

1:Fm K7CPU-10 To KG7GAN <I C R0 S2 Pid=F0 Len=35> [17:54:22R] [+++]
;PQ: 45631005
Wien CMS via K7CPU >

1:Fm KG7GAN To K7CPU-10 <SABM C P> [17:54:23T]
1:Fm K7CPU-10 To KG7GAN <DM R> [17:54:26R] [+++]
1:Fm KG7GAN To K7CPU-10 <SABM C P> [17:54:27T]
1:Fm KG7GAN To K7CPU-10 <SABM C P> [17:54:32T]
1:Fm K7CPU-10 To KG7GAN <I C R0 S3 Pid=F0 Len=22> [17:54:36R] [+++]
Perth CMS via K7CPU >

1:Fm KG7GAN To K7CPU-10 <SABM C P> [17:54:37T]
1:Fm K7CPU-10 To KG7GAN <DM R> [17:54:42R] [+++]
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  • $\begingroup$ I am having the same problem. I am using a Kenwood TMV71a and a SignaLink USB. The SignaLink USB is working fine between the radio and my PC running Windows 10. I also have RMS Express. When I attempt to connect and start a Packet session everything appears to work as normal. However all I see is my call sign and the call of the station I am trying to call followed by SABM (Set Asynchronous Balanced Mode). I am using USB port, USB SignaLink 3 for Playback and Recording. Running Kiss Mode, 1200 Baud. UZ7HO Screen Shot $\endgroup$
    – Tony
    Jul 21, 2017 at 16:54

2 Answers 2

Reset to default
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Is it possible that my VOX has a hang time that's causing me to loose the initial response to my call?

Yes, that is definitely possible. You want the lowest possible VOX threshold and, if possible, just turn it off completely and use another mechanism to trigger the PTT.

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    $\begingroup$ Baofeng VOX is pretty high-latency. This would be my theory. $\endgroup$
    – Jim MacKenzie VE5EV
    Oct 25, 2017 at 22:23
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It maybe that the tnc you are connecting to expects SABME (v2.2) AX.25. Some TNCs are not able to accept the older ( V2) AX.25. The comment about VOX is also correct. Usually the minimum VOX delay in a SignalLink will work.

I have a PI3 running Dire Wolf and connecting to the Pi on the house Lan. Wife checks winlink via wireless LAN to Dire Wolf. The Dire Wolf soft modem is set as a KISS TNC. The UA7HO modem works but is about like a TNC2.

73 Ed KE3D

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