FM APRS

[VK3KYY]

Is anyone an expert in FM APRS

Does anyone know what the generic settings for APRS transmissions should be.

e.g.

Destination is currently set to APN000
Tx SSID is set to 7
Via1 is WIDE2-1
No other vias


Would increasing the message length from 16 to 24 characters be beneficial.

Note. I can't increase message length to more than about 30 characters as there is no space in the CPS data for this, and even then, this would leave no room for other features.

[SA0BUX]

IARU Region 1 recommendations I read says that mobile stations should use: WIDE1-1,WIDE2-1
( Temporarily if it's long path to nearest Igate: WIDE1-1,WIDE2-2
Fixed stations and digipeaters: WIDE2-2
Igates: WIDE2-1


http://wa8lmf.net/DigiPaths/index.htm#Recommended

SSIDs: http://aprs.org/aprs11/SSIDs.txt

[VK3KYY]

IARU Region 1 recommendations I read says that mobile stations should use: WIDE1-1,WIDE2-1
( Temporarily if it's long path to nearest Igate: WIDE1-1,WIDE2-2
Fixed stations and digipeaters: WIDE2-2
Igates: WIDE2-1


http://wa8lmf.net/DigiPaths/index.htm#Recommended

SSIDs: http://aprs.org/aprs11/SSIDs.txt

OK.

So default vias should probably be

Via1: WIDE1-1
Via2: WIDE2-1

SSID for handhelds is listed as 7

-7 walkie talkies, HT's or other human portable

I'm not sure about the MD9600

That list shows

-9 Primary Mobile (usually message capable)

but also

-1 generic additional station, digi, mobile, wx, etc

Not sure about default Icon. I think I will change it to the zero (0) on a black background as this looks a bit like O in OpenGD77

[OE1MWW]

If GPS was on and position aquired, APRS position sent once, next GPS switched off, next RT-3S powered down and powered
up again after several hours,- without GPS - apparently the last position is stored and can be sent via APRS (PTT and short SK1)

Am I right ?

73's de OE1MWW
Wolfgang

[F1RMB]

Hi,,

With the latest beta, the position is automatically updated once à fix is acquired. Hence it will be the default one on the next reboot, before the GPS acquires a new position.

Cheers.
---
Daniel

[OK2MOP]

I am not an expert per se, but I will just add my 2 cents.

Would increasing the message length from 16 to 24 characters be beneficial.

I am not sure if the length applies to user portion of the message or not? I think it would be beneficial to have the option (either by templating or by default) to send (if available) the optional fields (and with them the message length will be exceeded) when reading data from GNSS:

• altitude - /A=aaaaaa e.g. /A=001065, where altitude is in feet
• course/speed - lower priority, format is CSE/SPD where SPD is in knots (placed immediately after coordinates)

For the default icon on handheld radios, I would probably consider '[' which is an icon for walking person, which is also the default for SSID-7. For mobile radios SSID-9 and car icon '>' as default may be a good idea, but this does not solve the situation when they are installed as base station.

Maybe the project could request a custom to-call for APRS if the usage takes off?

BTW, I see in the recorded data, that there is a space character before the comment text after the longitude and marker for the icon. Should it be really there or should the text start immediately after the marker?

[VK3KYY]

BTW, I see in the recorded data, that there is a space character before the comment text after the longitude and marker for the icon. Should it be really there or should the text start immediately after the marker?

Yes there is a space, because it was there in some example data I was using, but I agree, perhaps its not necessary.

I'll remove it and see if the data still decodes

Re:Other data fields

We can do this on radios which have GPS, ie. MD9600 and UV380.

Except currently on the MD9600 we have a hardware problem with the C6000 DMR chip which we are using to generate the AFSK tones.
Unfortunately the C6000 has a maximum tone generation time of 510mS, and if we stop and start the tone generator the audio waveform is ruined

i.e We start a 510mS max length tone, then constantly change its frequency.

There is the possibilty that we can use a pin on the CPU connected to the FM modulator in the MD9600 to create the tones, but the pin is binary / digital only, and square waves are not ideal for AFSK.
To make the binary / digital pin create an approximation of a sine wave, would require the use of high frequency pulse width modulation whose duty cycle is controlled by the samples of the wave table.

But this is not easy to implement.

Hence at the moment the MD9600 message data is limited to only the Lat / Lon + Source , Destination, Icon and 2 Vias

[VK3KYY]

BTW, I see in the recorded data, that there is a space character before the comment text after the longitude and marker for the icon. Should it be really there or should the text start immediately after the marker?

This bug will be fixed in the next release

[VK3KYY]

For anyone interested in APRS there is an experimental version of the CPS here

https://opengd77.com/downloads/CPS/Expe ... .11.01.exe

This has longer message length and generally tidies up the UI as well as forcing the callsign and the Vias and destination into upper case letters etc

There is also a satellite index for the APRS on the ISS which is currently active.




This CPS should work with the existing firmware, but if there are problems, revert back to the previous CPS release

[m1dyp]

thank you