More than five telemetry channels in Base91 format?

[NN]

Hi,

we are planning a high-altitude balloon launch and have a total of 10 - 12 sensors with readings that we would like to transmit via APRS.

Now, as far as I understand, at least the Base91 format does not allow more than five channels for analog telemetry.

What would be the preferred way to transmit additional data?

a) Shall I use two SSIDs, like DL1XXX-11 for the main balloon and DL1XXX-15 for the additional five sensors?

b) Or embed the additional values in an uncompressed, proprietary comment string in addition to the Base91 one?

c) Or use a second message type for the additional values?

Since our launch is a one-time activity and part of the sensors are interesting only for mission control (like battery voltage), it would not matter too much if others can understand only the five channels sent in the Base91 encoding (supported by proper channel name / unit announcements).

But it would be good if they were nonetheless fed into and available in aprs.fi so that we can monitor them as soon as any station has received them.

Thanks for your support!

Martin

[Nosey Nick VA3NNW]

On Thursday, April 21, 2016 at 3:50:53 AM UTC-4, NN wrote:

Hi,

we are planning a high-altitude balloon launch and have a total of 10 - 12 sensors with readings that we would like to transmit via APRS.

Now, as far as I understand, at least the Base91 format does not allow more than five channels for analog telemetry.

See http://www.aprs.org/doc/APRS101.PDF page 54 for the MIC-E telemetry and p68 for the "regular" telemetry. Both are limited to 5 channels (but the "regular" telemetry has a digital channel for on/off sensors too)

I think I'd have to recommend your dual-SSID workaround if you really need 10 analog telemetry channels and if you want aprs.fi (and others) to graph them for you.

Extra values in a comment string, especially if they are reasonably human-readable and not too "cryptic", would be OK for your personal purposes, but nobody else will graph them for you.

What ARE the sensors? If enough of those could conceivably count as "weather data" (page 64-ish), EG temperature, pressure, humidity, wind speed, wind gusts, luminosity etc, you could presumably then alternate WX frames for 5 "weather-like" metrics and Telemetry frames for 5 others, on the same SSID?

Nick VA3NNW

[Chuck Bland]

Use channel 1 as a group... 0 1 2 3 4..... and the other four for data.

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[Lynn W Deffenbaugh (Mr)]

The Base91 telemetry overlaps the original humanly-readable telemetry in the aprs.fi database.  If you have a station that is transmitting one and then switches to the other, you'll see the same channels on a single graph.

APRSISCE/32 treats this the same way.  There's only 5 channles of telemetry plus 8 digital bits, regardless of which format the telemetry was received in.

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32