Friday, March 9, 2018

#APRS messenger on HF 2 - MFSK-4

It seems APRS messenger gets more attention worldwide. A number of stations are active now. In my last post about the APRS weekend I had doubts about the receiving capability of the messenger program. Well, Chris G4HYG, the APRS messenger programmer has changed some things in the program and in the last version it has now MFSK-4 capability.

Here are the changes from last week:

The latest latest version 3.37 has a bug fix for a decode problem with MFSK-4. Good packets were being rejected especially if the background RF noise was high. 

Version 3.36 has a new mode option MFSK-4. This is a very slow and narrow (176 Hz) mode which is 4-5 dB more sensitive than MFSK-16 at 18 dB in a 2.4 kHz bandwidth making it comparable to FT-8. Beacons are very slow taking typically 1 minute for the shortest callsign and lat/long position packet. Messaging without acks is available for MFSK-4 but watch your message length, the shorter the better. MFSK-4 transmits 210 Hz higher that the usual frequency used for APRS Messenger messages to allow slow MFSK-4 traffic to run without blocking the "fast" channel. On the 30m frequency (10.1497 MHz) used for APRS Messenger traffic the MFSK-4 signal just fits in between the normal traffic and the band edge. Before you use it check the frequency calibration of your transceiver against WWV on 10 MHz or RWM on 9996 kHz to make sure you don't transmit out of band. A checkbox to select 9600 bd GPS receivers is added to the main window, The GPRMC sentence is used for GPS beaconing. 

Version 3.35 has a new option to stop the start-up timer on the first page, switches the beacon off during messaging, add metric level squelch for MFSK-16 and a minor bug fix and text change. 

Curious about the receiving capability now! Another weekend of testing! The idea is to add -63 to your call to show you're working with APRS Messenger. That way all stations worldwide are easy to find for instance on APRS.fi.

7 comments:

  1. This is a curiously-interesting piece of radio. I've managed to hear lots of signals, but few decodes. I have managed to decode OH8STN and a US station, both only once. Without so much traffic, it's difficult to figure out if the decoding is working as well as it ought to. It would be interesting if there were more operators, but I get tired of waiting for anything to happen!

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    1. Today was a hard day John, it seems there were very bad conditions. Besides that there seems to be a issue with the MFSK-4 decoding and Chris is already busy trying to solve the issue. I had only one decode over the whole day (OH8STN) nothing more and my signal was not decoded at all. 73, Bas

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  2. Hoi Bas , ik heb afgestemd op 10148.20 en wat testjes gedaan met MFSK4, echter zonder resultaat. ook heb ik een passcode aangemaakt en ben ingelogd op de aprs.pa4tw.nl.
    Geen enkele ontvangst en ook geen registratie op de APRS.fi.
    Doe ik iets verkeerd?

    73 Gerard de PA7GMU

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    1. Hallo Gerard, geenidee of de passcode nog moet. Ik heb hem niet meer ingevuld. Ik weet dat jij wel bent ontvangen in Finland als enige uit Nederland. 73, Bas

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  3. Hi Bas, bedankt voor je antwoord. Ik ben natuurlijk erg benieuwd hoe je heb kunnen zien dat ik in Finland ben ontvangen. Ook zou ik het erg fijn vinden wanneer ik je af en toe een mailtje mag sturen met een vraag over digitale modes.
    73 Gerard de PA7GMU
    pa7gmu@gmail.com

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    1. Dat kreeg ik door van Julian. Via Facebook. Prima mail te sturen hoor. Mijn E-mail adres kan je vinden op qrz.com. 73, bas

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Thanks for your comment. Bedankt voor je reactie. 73, Bas