[ale] OT cellular protocol versions

[Phil Turmel]

On 01/22/2015 09:45 PM, Michael H. Warfield wrote:
> 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.

No, actually.  I saw the research he was doing (playing with selectively
absorptive coatings for dangerous gas & medical sensing) and thought
"that's an interesting niche".  Didn't occur to me that they'd work well
at high radio freqs.  My EE focus has largely been industrial control
systems and plant floor data collection., so no significant exposure to
the state of the art in RF.

> 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.

Fascinating.

Phil