🚀 go-pugleaf

On Sun, 18 Jul 2010 11:38:39 -0700, JC Dill <jcdill.lists@gmail.com>
wrote:

>> I think you might be mixing technologies.  During the 1980's, long
>> haul truckers were using IMTS phones (and CB).  
>
>In the early 1990s, some were starting to use cell phones.

Sure.  Most of the short haul truckers were using Fleetcall, which
later became Nextel in 1993.  They're an SMR (specialized mobile
radio) that leased 800MHz repeater service all over the country.
Nextel was never intended to be a cellular service and is still
required to have PTT service in order to use the SMR frequencies.
However, the repeaters were mostly located in metropolitan areas
making is a marginal proposition for long haul trucking.  To the best
of my knowledge, the long haul truckers held onto IMTS when everyone
went digital and the prices for cellular service dropped.

>> Checking the FCC rules at:
>> <http://www.hallikainen.com/FccRules/2010/22/913/>
>> it proclaims:
>>    The ERP of mobile transmitters and auxiliary test transmitters
>>    must not exceed 7 Watts.
>> ERP (or EIRP) is "effective radiated power" which includes the gain of
>> the antenna.  The traditional AMPS mobile antenna has about 4dBi gain
>> or 2.5 times the xmitter power output equals the EIRP.  
>>    7 watts / 2.5 = 2.8 watts
>> which is where the 3 watt limit came from.

I left out a detail.  The FCC allowed for coax cable losses.  The
standard car antenna has 5dBi gain.  Subtract about 1dB coax loss for
the stated 4dBi figure.

>> Going back as far as possible to 1997:
>> <http://louise.hallikainen.org/FCC/FccRules/1997/22/913/>
>> This rule has not changed.
>
>I was told the rule changed "a few years" prior to my buying my first 
>cell phone, the 3 watt bag phone I bought circa 1992 from Cellular One.

Well, it's possible.  I do have (somewhere) printed FCC Rules and Regs
dating back to the the 1970's.  I'll see if I have 1977 or 1978, when
cellular first appeared.

I found where the 1.2 watts came from.  Looking at the AMPS control
protocol, the SCM (station class mark) has 3 possible xmit power
levels.  
  0.6w continuous (full duplex) handheld xmitters
  1.2w non-continuous (half-duplex) transportable xmitters
  3.0w continuous (full duplex) vehicle mounted xmitters.
<http://www.tech-faq.com/scm-station-class-mark.html>
<http://affordablephones.net/CellularTelephony.htm>
Note that "transportable" does NOT mean a bag phone, unless it has a
PTT button for half-duplex operation.
-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558