Does anybody have knowledge About APRS messaging or message groups? I think this could be useful while off-roading and during public service events. What needs to be done in order to send a message over APRS to a small group of stations?
APRS Messaging
Does anybody have knowledge About APRS messaging or message groups? I think this could be useful while off-roading and during public service events. What needs to be done in order to send a message over APRS to a small group of stations?
Messaging is a very useful aspect of APRS which, in my opinion, is one of the most underrated features of the system. To send a message over APRS, you need a radio with the capability built into the firmware (D700/710, TH-7D, FTM-350R, or VX-8R are probably the most common) or a messaging-capable APRS software suite such as UI-View, XASTIR, etc. Argent Data Systems OT-2 variants can also send/receive messages when used in conjunction with a compatible Garmin GPS and radio. To send a message to a single station, simply send a message to the station in the format "CALLSIGN-SSID". In my case, the D710 in my mobile uses the -9 SSID, so to send a message to my mobile, simply send the message to KE7KUS-9.
To receive messages as part of a group, you can tell your radio or software which groups you want to listen to messages from and you will receive those messages. To send messages to a group you send a message using the following format: "BLN#GROUPNAME", where BLN tells APRS you are sending a bulletin, # indicates the sequence number of the bulletin, and GROUPNAME is the up-to-five character name of the group you are sending to. Probably easier spelled out with an example:
To send a message to the "4XHAM" group, you would send a message to "BLN14XHAM". This indicates that you are sending Bulletin #1 to the "4XHAM" group. Any person who has their radio set up to receive "4XHAM" messages will get the message. The second message in a series of messages would be "BLN24XHAM", the third "BLN34XHAM", etc. If you didn't have a series of messages to send, you could just use the "BLN14XHAM" over and over again. For a more detailed explanation of the formats and uses of messages, see Chapter 14 of the APRS 1.0.1 spec, which is available at the TAPR website: ftp://ftp.tapr.org/aprssig/aprsspec/...01/APRS101.pdf
Hope this helps.
Kurt,
your post did help, thanks! It is nice to have an APRS guru in the group.
Very helpful reply Kurt. Thanks!
K7NAV
As Johnny Carson used to say: I did not know that.
Great Post.
Randy - KC0NNT
"Happiness is to be found along the way, not at the end of the road, for then the journey is over and it is too late."
A new standard?
Glad to be able to help. Since it seems more and more of us are running APRS either in our rigs or at the QTH, it might be really useful to standardize a bulletin group for ourselves. A cursory review of FindU and aprs.fi shows that there are currently no users of the "4X4" groupname for APRS messages. I'd like to recommend that anyone in the group that's interested in getting group bulletins program their radio/software to get "4X4" bulletins. (I'd use the "4XHAM", but my D710 won't let me put in group bulletin filters longer than 4 characters, so "4X4" seemed to be a good 2nd choice.)
This is useful in a number of ways:
1) Info on nets, activities, or other words to group members can easily be passed via APRS, in addition to voice channels and the website. Bulletins are only transmitted over RF, so the sending station must be on RF to get the message to the local group on RF; however, bulletins are gated onto APRS-IS, so any station connected to -IS can also receive the bulletins, just not send them.
2) If you are jumping in the mobile and want to chat with another 4X4 APRS station, simply send out a bulletin to the 4X4 group (BLN14X4) that looks something like this:
CQ KE7KUS-9 MOBILE ON 147.240+ T162 CQ
This will allow receiving stations to be alerted that you are available for local contact on the Shaw Butte repeater here in Phoenix, even if they're listening to another repeater. It's even cooler if you're monitoring an IRLP repeater:
CQ KE7KUS-9 MOBILE ON 444.300+ T100 IRLP-7620 CQ
Now in addition to local users knowing to contact you on the ARA 444.3 repeater in downtown Phoenix, any station getting bulletins over APRS-IS knows to get hold of you, all they have to do is connect to IRLP node 7620. This is an easy way to facilitate DX QSO's between group members.
I'm going to configure my D710 to get 4X4 bulletins and tinker with it over the next few days. I'll have the radio on in the truck 24/7, so if you feel like trying it out, send a bulletin to the 4X4 group and I'll post updates on the ones I receive. (Bulletins aren't ACK'ed like station-to-station messages, so you won't know if anyone receives it otherwise.) I'll also use the bulletins for CQ's over the next few days, so give me a shout on the air if you get one of the bulletins and let me know it worked. This is a first for me on APRS, so I'm curious to see if it works as advertised, or if it's one of those things that looks good in the spec, but doesn't work so well in practice.
Kurt
Last edited by KE7KUS; 07-09-2010 at 12:01 AM.
Excellent post Kurt! I am going to add this to the http://www.4x4ham.com/showthread.php...Field-Exercise event. I think you have provided the 4x4 Ham group with the basis for a APRS messaging standard. Would you be willing to give a APRS messaging talk at the event workshop?
Thanks again for your insight.
David
Last edited by K7DCL; 07-09-2010 at 06:49 PM.
This does look promising. You have provided some excellent information Kurt. Now I have to see if I can make this work with my radios.
So far I have not been able to transmit a bulletin with my VX-8Rs, but I can send a message to a Message Group. The VX-8R seems to be setup to send messages, but not bulletins. Or am I missing something? The Yaesu radios come with some default Message Groups such as All, CQ, QST and Yaesu. I can send a message to one of these groups and receive it on another VX-8R. I will do some more testing with my radios, but I think we need to look at Message Groups in addition to Bulletin Groups.
My D710 documentation wasn't super-clear on the difference between group messaging & group bulletins, so I did a little digging to see the difference. Here's the best I can determine:
In the APRS spec, a message packet is used for individual messages, bulletins, and announcements. The only thing that differentiates a message from a bulletin or announcement is how the sending station handles the transmit frequency and delay of each. The spec is vague on the transmission rates for bulletins and announcements, but it defines the concepts in a way that makes sense and allows APRS developers to incorporate as desired.
Instead of group bulletins, I think Richard is right - we want to go with group messages for this idea. To send a group message, you send an APRS message to an (up-to-9 character) group identifier, instead of a single station callsign. For our purposes, I would recommend using the group messaging callsign "4X4HAM". My D710 will allow setup to receive group messages, and it seems the FT350 does something similar. I've actually been using group messages for a few years and didn't know it, as this is the way SKYWARN and NWS messages are propagated.
Pro's to using group messages are that the messages only go to those who are setup to receive the group. It seems that group bulletins go out to all stations, and the bulletin group name is simply a way to see who the bulletin is for. I'd still recommend group bulletins for things like net or event announcements, as this is a good way to inform other hams on APRS what's going on in the local area. CQ's should probably be done via group message, not group bulletin, if you're just looking to set up a QSO with another group member.
I've set up my D710 to receive group messages to 4X4HAM, so if one of you with a messaging-capable setup wants to try it out, send out a message to "4X4HAM" and anyone who has it setup in their message groups will get it. Like bulletins, group messages are not ACK'ed by receiving stations, so I'll post here on any that I receive.
David, great idea to add this to a field exercise. When voice bandwidth is at a premium for events such as race support, SAR, etc. I have found APRS messages to be a quick, efficient way to communicate basic info back and forth while leaving the voice freq's to relay info that takes more time or requires more two-way interaction. Periodic status reporting, supply requests, updates, announcements, etc. can often easily be sent via an APRS message and, for stations running dual VFO setups, allow a multitude of stations to be working different voice channels, while all having a common data channel to keep them in touch.
I'd be happy to speak on messaging, or other aspects of APRS, at the field event, or any other time we get together as a group.
Kurt,
Thanks again for sharing your knowledge with the group. I will stop worring about bulletins and program 4X4HAM into my message groups.
Richard,
I got your message from about 5:30pm last night (Saturday). Good message, but no text in the message. A quick check of aprs.fi shows the same. I sent a CQ this morning that also got picked up. Looks like group messaging works as advertised. Looking forward to using it a little more in the coming weeks. Glad we opened up this train of thought - I think it has a lot of utility for the group.
Kurt
KE7KUS
I have been wanting to try and get into the messaging part of APRS for a few months now. I just got my tracker setup kenwood TMV71a and a OT1+. The OT1+ can be a limited TNC and I believe it can do messaging when interfaced with UIView or other software like it, but I have yet to figure it out.
It will be nice to get some more people using the messaging feature of APRS. The more people use it, the more useful it will become.Originally Posted by KF7EFI
If you have questions about configuring your setup, try posting them here, we have some people in the group who are very knowledgeable and may be able to help you.
I finally figured out how to send an APRS bulletin from my radio. As Kurt mentioned in Post #10, there are uses for both message groups and bulletins.
I sent out a bulletin about the 4X4HAM net, please let me know if anybody received it.
I received one group message and two bulletins. Works as advertised!
Thanks for the feedback Kurt! I also got 1 response on APRS from a station in Payson.
It appears to me (I have had the radio for a year and just getting into messaging), the VX-8R does not explicitly support bulletins, becuase it does not provide the automatically decaying transmission repetition rate (as KE7KUS mentioned).
However, one can send (manual transmission) a message to BLNnxx and have that recognized as a bulletin/anouncement by ALL others. The radio only allows a six-character call sign as destination, rather than the nine characters normally allowed for a bulletin, because it reserves the last three characters for the normal -SSID. The radio does still expect an acknowledgement (which it won't get), so it does send five times.
I'll be testing this today. I intend to use it to alert everyone in the region about significant traffic incidents on the interstates.
Anyway, its the BLNn as the 'message To:' that counts.
Jim A. (noob)
Last edited by jalles; 08-22-2010 at 08:48 PM. Reason: reading
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