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leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:9
Reviews:
·SONIC.NET

anybody here doing packet on 2m?

I'm only just starting with ham radio and got into it primarily for emergency communications purposes. It also seemed at first to be a relatively inexpensive hobby when I saw the prices for wide-band SDR usb receiver sticks ($20) and chinese handheld radios ($35). I have since then been to the local HRO so no need to explain explain prices to me

What I'm currently trying to do is simply listen to packet traffic which for EmComm around here is pretty much all AFSK1200 primarily on the 2m band (some also on 1.25m/220MHz).

The two ways I have attempted to do so are:

1.) SDR usb stick (I tried two different kinds) with gqrx software and its afsk1200 decoder.

2.) Baofeng UV-5R+ with a Kantronics tnc.

So far neither attempt has worked (I never got a single character out of #1 and only rare packets using #2). I should probably add that I tried a number of different antennas with no difference in behavior (I don't think it is a signal strength issue).

What I'd like to know from those that are using packet is what equipment you are using, what has and what hasn't worked for you and probably most of all what kind of tuning is needed to successfully decode afsk1200 ?

There are plenty of reports on the Internet of using either method (or other combinations such as Baofeng to soundcard modem) but very little detail on what exactly was done to make it work. It always sounds as if it simply works which so far it hasn't for me.
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alphapointe
Don't Touch Me
Premium,MVM
join:2002-02-10
Columbia, MO
kudos:2

Can't speak for the SDR problems, but turn off the battery saver on the baofeng... it will clip the packets and they won't decode. (experience talking here...)
--
"When the hammer drops, the bullshit stops"


moonpuppy

join:2000-08-21
Glen Burnie, MD
reply to leibold

I have a Kenwood TH-D7 and it has a built in TNC. My issue is findng software for Windows 8. I got Hyperterm to work in Windows 7 but I switched laptops.



alphapointe
Don't Touch Me
Premium,MVM
join:2002-02-10
Columbia, MO
kudos:2

Putty has serial capabilities and works fine under windows 8
--
"When the hammer drops, the bullshit stops"


lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to leibold

Once the RTL2832U SDR driver ( »sdr.osmocom.org/trac/wiki/rtl-sdr ) is working on a suitable platform (Beagleboards, Raspberry pi, etc), please try out commands like this:

rtl_fm -f 144800000 -s 22050 - | multimon -a AFSK1200 -t raw /dev/stdin



leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:9
Reviews:
·SONIC.NET
reply to alphapointe

said by alphapointe:

turn off the battery saver on the baofeng... it will clip the packets and they won't decode.

Thanks, that is exactly the kind of practical hints I was looking for. I'll try that tomorrow evening (weekly net).

73
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leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:9
Reviews:
·SONIC.NET

2 recommendations

reply to alphapointe

I tried a better antenna and suddenly both the baofeng+tnc combination as well as the SDR usb stick with gqrx (and its integrated multimon) are working fine.

Time to figure out how to put a proper antenna (probably more then one) on my roof.

Thanks again for the help.
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Jazzemt

join:2009-02-12
Granite City, IL
reply to leibold

You will see a ton of traffic on aprs. The most common frequency is 144.39.



leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:9
Reviews:
·SONIC.NET

From what I read about the subject, APRS was on different frequencies in California in the past but now the nationwide 144.39 is used everywhere. This is one of the frequencies I used to for my testing and you are correct about the traffic volume. Before I switched the antenna I wasn't able to receive anything on APRS (I could hear it, but neither the tnc nor multimon would decode the packets).
The strongest signal came from a digipeater (on a different frequency) over about 25-30 miles distance but with the benefit of 3800' of elevation.

As for antenna selection I'm thinking about getting the OSJ J146/440 from Arrow Antennas.
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mattmag
Premium,ExMod 2000-03
join:2000-04-09
NW Illinois
kudos:3
reply to leibold



OT I guess, but I used to be setup as a DX Cluster Node here in the Midwest. I had a 2M link that connected me to another Node about 35 miles to the SE, a 220MHz link that went over 65 miles to the SW, a local-use 2M freq for local users to connect, as well as a 440MHz control link from my house to my shop where the station was located. Had a great time with it, and the main I learned was the signal had to be *very* clean to avoid countless re-tries that would lead to timing out of the connection.