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Confused by APRS features? send only short messages?

Discussion in 'Working Different Modes' started by KD8LUI, Feb 9, 2019.

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  1. KD8LUI

    KD8LUI Ham Member QRZ Page

    I am kind of familiar with using APRS to update and follow tracks. I have recently read a lot about the ISS APRS being back and people sending and receiving short messages?
  2. AG6QR

    AG6QR Subscriber QRZ Page

    What do you want to know? I've used APRS messaging occasionally. It works, but not all APRS implementations support it. Aprsdroid is one common piece of software that supports messaging well.

    There is no guaranteed delivery or handshaking, so if you must communicate something important, tell the other party to acknowledge, and keep sending your message until you get that acknowledgement.
  3. WD9EWK

    WD9EWK Ham Member QRZ Page

    You are correct, that there is no guaranteed delivery. When you send an APRS message to another station, that station needs to be on the air to receive the message. Normally, 5 attempts are made to send an APRS message, in 1-minute intervals.

    As for acknowledgement of a message, APRS provides for an ACK packet to go back to the sender, after the recipient's radio gets a message. This is a mandatory feature in APRS messaging in Kenwood and Yaesu APRS-ready radios, but not in some software packages (like UISS and - I think - APRSdroid) that support APRS messaging. Where the original message may get up to 5 attempts for delivery, the ACK packets sent back to the message sender only get one shot to make the trip.

    With the orbiting digipeaters on the ISS and other satellites, APRS messages can be used to make QSOs with other stations. In this instance, we generally don't rely on getting ACK packets back from message recipients, as stations should be sending messages back and forth in a manner that mirrors making QSOs with a microphone, CW key/paddle, or software for other digital modes. The AMSAT Journal has had articles about working packet through the orbiting digipeaters, which are available as PDF files from AMSAT's Station and Operating Hints web page, including an article focusing on using a couple of Kenwood APRS-ready HTs, using a computer and its sound hardware to work packet via satellite, and working the digipeater on the FalconSat-3 satellite. I also wrote an article that briefly touched on that for the December 2018 QST. And, of course, more about the use of APRS with satellites and the ISS can be found in the satellite forum here on QRZ (among other places).

    KA2CZU and AG6QR like this.
  4. KA2CZU

    KA2CZU XML Subscriber QRZ Page

    ISS packet is alive and healthy. Good pass yesterday evening.
    WD9EWK likes this.

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