[aprssig] netSked

Alex Carver kf4lvz at yahoo.com
Wed Jul 6 15:06:55 EDT 2011

--- On Wed, 7/6/11, aprssig-request at tapr.org <aprssig-request at tapr.org> wrote:

> Hello,
> I'm attempting to write a net sked engine to squirt some
> net objects at the
> local digi and have a few questions (sorry if they are not
> in context of
> this list).
> 1]  Is http://www.aprs.org/info/netsked.txt is
> the most up-to-date spec for
> a Net Sked engine
> 2]  Is Bobs' suggested file format (URI above) now a
> standard or is it
> likely to change?
> 3]  APRS DTI - am I correct it is a plain old Object
> DTI (semi-colon)?
> 4]  Beacon Rate ... using the following line as an
> example
> tuesday   9:30 PM 3/30 NET-AARC 
> 147.105 none R17m VIA WIDE1-1
> Does the /30 mean the Net runs for 30 minutes or that the
> Beacon should run
> for 30 mins, I'm assuming this is actual Net duration and
> the engine will
> start beaconing 10 minutes prior (9.20 PM in the example)?

According to the document that you posted, 3/30 means beacon three times every thirty minutes (so once every ten minutes).  Seems like a poor choice of format to specify N per M minutes rather than a simple period between beacons.  A quick glance doesn't make it easy to figure out the actual rate, you have to do a calculation in your head.  But if the field simply had the period (say just a 10) that would make a lot more sense (10 minutes between packets).

Net duration isn't indicated in the file format at all from what I can see.

> Bob suggests doubling the rate (3 in the above)  ten
> minutes either side of
> Net Start time - can I clarify this means a beacon every 90
> seconds or have
> I mis-unserstood this bit.

Doubling the rate as listed would mean a beacon every five minutes (since he used the format N per M minutes it's 3/30 = 1/10)

> 5]  Could I humbly suggest the keywords "Weekday",
> "Weekend" and "Daily" be
> included in the spec as well as 'nth Mon' and 'Teusday'?

If you do this in the world of Unix/Linux you have half of what you need already by way of the "cron" program.  Cron is very flexible with the date and time specification allowing programs to be executed once per day, week, month, year or multiple times per day, week, month, or year as you see fit.  The cron configuration (a "cron job") could execute a script that would run in the background to inject packets onto the air or via the APRS-IS through various means.  The script itself then only needs to create the packet and transmit it.  Repetition of the beacon can be achieved with the cron configuration or internal to the executed script (that's up to the end user).

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