[Xastir] Radio frequency question from a simpleton

[Tom Russo]

On Thu, Jul 19, 2007 at 10:21:26AM -0500, we recorded a bogon-computron collision of the <RiverRidge at CenturyTel.net> flavor, containing:
>  I am not Ham literate, but I stayed in a Holiday Inn Express last night and 
>  I have ordered the license prep manual............
> 
>  I have read that APRS is conducted on 144.39 Hz.  My assumption is that 
>  there is nothing inherent in Xastir that is tied to that frequency, but 
>  rather the frequency is set by the radio.  Is this correct?

Yes.

>  My (extremely limited) understanding of the TNC is that it is not frequency 
>  dependent.  Is this something that most Ham operators would have?

Only those who wish to use packet radio applications.  The TNC is basically
a cross between modem that converts data to sound and a "network interface"
that packetizes the data in an envelope with addressing and routing
information.

>  Are the various tracker gizmos (Open tracker, Tracker2, Mini-Track, etc.) 
>  for a fixed frequency (144.39) or can be function on any frequency?

No.  They are basically TNC substitutes that need to be wired up to a radio.
The MicroTrak has a built-in radio that is on a fixed frequency, though.

>  For proof of concept as inexpensively as possible, I have a laptop running 
>  Xastir and have access to several radios (Motorola HT1250) that are tuned to 
>  Sheriff's, Fire, and EMS frequencies.  If I can find a TNC to borrow (or 
>  worst case buy one) and buy a few of the tracker kits to hook to Sheriff's 
>  radios, I should be able to demo it on an existing channel -- right?

Only if the license for the frequency in question allows data transmissions.
Most public safety pool licenses do *not*, because they were specified as
voice channels when the application was made.  The county would either have
to amend their license for those  frequencies, or apply for a new data
frequency with the emission mode specified.  Check the license (you can use
<http://www.fcc.gov/wtb/uls/> to get the details of the license) for the
permitted modes.  Unfortunately, the emissions mode is specified in a funky
code in the FCC database, but "20K0F3E" means "FM voice" for all intents and
purposes.  I believe that FM data would be something like 20K0F1D
(20 KHz bandwidth, FM, Digital, Data, per <http://216.239.51.104/search?q=cache:gxYcO53V4LUJ:www.thespectrumfirm.com/tsf_fcc_application_worksheet___new.doc+emission+mode+FCC+designator+public+safety+pool&hl=en&ct=clnk&cd=4&gl=us&client=firefox-a>).  If the license doesn't have an "F1D" emission mode listed for it,
then it ain't legal to do APRS under that license.

Getting a new license with data emissions permitted will
take quite some time (6 months or so turnaround in my experience to get
a public safety pool license application through the system).

If you want a quick demo, you should get with some local hams and set it up.
See if the local ARES group is willing to help.  

-- 
Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236 AHTB#1 http://kevan.org/brain.cgi?DDTNM
"And, isn't sanity really just a one-trick pony anyway? I mean all you get is
 one trick, rational thinking, but when you're good and crazy, oooh, oooh,
 oooh, the sky is the limit!"  --- The Tick