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OT: RE: [aprssig] D-710 at FCC test site

Stephen H. Smith wa8lmf2 at aol.com
Tue Aug 7 08:42:16 UTC 2007


Dave Baxter wrote:
> Hi...
>
> Does this imply that in the US, many celular phones still use analog FM
> for the audio?
>
> I thought (wrongly it would seem?) that 99.9% of the developed world had
> long since changed over to GSM (digital) for mobile phones, I know both
> my GSM phones work OK in the US, 

The U.S. mobile telecomm scene is a totally chaotic mis-mash of 
proprietary and semi-proprietary standards, both for private radio 
land-mobile and for cellular telephony, due to the total failure of the 
federal comms authorities to set any standards.   

Analog (AMPS) is still supported by SOME cell carriers, especially in 
the rural areas of the US where user loading hasn't yet forced carriers 
to digital for the expanded channel capacity.      In more populated 
areas, carriers will complete the phase out of analog systems in 2009, 
when the FCC drops the "must support" mandate.  In the mean time, the 
digital side is split between GSM (ATT & T-Mobile) and CDMA ( Verizon 
and Sprint) spread across two bands ( 800 MHz and 1900 MHz ) and 
Nextel's Moto proprietary iDEN format on 900 MHz. 

Most new cell phones sold today by the major national cell carriers 
don't support analog.   However, phones sold by the smaller carriers in 
regional markets do often still have an analog mode.  

Because the available cellular mobile spectrum is so hopelessly 
fragmented between 5 carriers on 3 bands, the US is FAR behind the rest 
of the developed world (at least a half decade)  in implementing 
wide-band 3rd and 4th generation truly high-speed wireless applications.


In the private land-mobile side, there are three proprietary digital 
formats (Motorola's Astro Digital, M/A-Com's (the company formerly known 
as GE) "OpenSky" over-the-air IP protocol, and  EF Johnson's Digital 
LTR, in addition  to the continuing use of several analog trunking 
formats ( GE/MA-Com EDACS,  Johnson LTR, and Motorola  
SmartZone/SmartNet).    In addition,  open-standard APCO "Project 25"  
digital voice (both conventional and trunked) is increasingly used by 
public safety authorities for it's supposed "interoperability" between 
jurisdictions.  However many authorities have opted to go with the 
various proprietary formats instead, partly because of their superior 
audio quality.



--

Stephen H. Smith    wa8lmf (at) aol.com
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