OT: RE: [aprssig] D-710 at FCC test site
Stephen H. Smith
wa8lmf2 at aol.com
Tue Aug 7 03:42:16 CDT 2007
Dave Baxter wrote:
> 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
Stephen H. Smith wa8lmf (at) aol.com
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