[ale] OT cellular protocol versions

[Michael H. Warfield]

On Thu, 2015-01-22 at 19:29 -0500, Phil Turmel wrote:
> On 01/22/2015 06:32 PM, Alex Carver wrote:
> > Sounds like a Sidekick.
> > 
> > What network is he on?  That affects the communication channel.  Not
> > everything is LTE just yet, lots of things are still using various
> > modulations and channel types (2G GSM, 3G EDGE, CMDA, 4G LTE or WiMax).
> > 
> > It might be his phone, it might not be. Tower sharing can cause
> > interference and vegetation can cause other issues.  If the phone gets
> > dropped a lot then the tiny SAW filters used in some phones can be
> > damaged causing poor reception.

> OMG!  Industry is using SAW filters?  (I'm presuming that's "Surface
> Acoustic Wave").  My college department head was an early researcher on
> these, and I played (briefly) with them as a sophomore EE.  Talk about a
> blast from the past.

You're kidding, right?  SAW filters have been used by industry for
decades.

Back in the early 70's I helped install a Harris Corporation High
Channel (channel 10) broadcast transmitter that used a little tiny SAW
filter (about the size of the ceramic oscillators found on most computer
mother boards) for it's vestigial sideband filtering at the modulator
signal level as opposed to the massive reflection cavities and hybrid
ring duplexers operating at 200KW with the old transmitter.

IIRC, most of our GPS receivers are using SAW filters to separate out
the satellite signals in parallel.  That's where your "channels" derive
from.  It's the number of parallel outputs from the filters that allow
you to process multiple GPS signals simultaneously.

> I just looked:  he's still on the faculty.

> http://ece.umaine.edu/faculty/john-vetelino/

> Phil
> 
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Michael H. Warfield (AI4NB) | (770) 978-7061 |  mhw at WittsEnd.com
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