Mobile Telephone History : Land Mobile (Conventional radio telephone service status)

 

Improved Mobile Telephone Service (IMTS) Table 1 (General Overview) (You are here)Table 2 -- Operational Features

This table from 1976 appears courtesy of the IEEE (external link) It gives a great overview of conventional radio telephone service circa the mid 1970s, just before cellular radio began. I won't question the information below but I will add that parts of Sweden had automatic phone service in three cities, not just a manual system for the entire country. You'll read more about that in the next table. Right click on the table to save to your hard drive. Print out by rotating the image 90 degrees. Make sure to read Geoff Fors comments below the table.

"Public Mobile Telephone -- A Comparative Analysis of Systems Worldwide: R.L. Lagace and H.L. Pastan. Arthur D. Little, Inc. Cambridge, Massachusetts. IEEE Vehicular Technology Group. Twenty-sixth annual conference of the IEEE Vehicular Technology Group: conference record : papers presented at the twenty-sixth annual conference, Washington, D.C., March 24-26, 1976 /, sponsored by the IEEE Vehicular Technology Group, Washington Chapter, with the cooperation of theWashington Section of the IEEE and the Administrative Committee of VTG. [Washington] : The Group ; Piscataway, N.J. : available from IEEE Service Center, [1976] viii, 178 p. : ill. ; 29 cm. p. 21 to 25

Vehicular Technology Society "Connecting the Mobile World"

 

American IMTS Power Output and Frequency Comments by Geoff Fors

 

In the USA column, under "channels per mobile, full service" it should say 11, not 16. For RCC (Radio Common Carriers, independent competitors to the Bell System wireless companies, ed.) , that would be 7. This refers to a channel being a pair of frequencies, i.e. a transmit and a receive channel. 20 Watts VHF output on the USA spec was the original "MJ" VHF specification created by the tariff at that time. By the late 1970's, there were many phones on the market with much more power. The Harris Alpha series was a 50 Watt phone, and some of the Livermore Data installed mobiles were 35-40 Watts. The Aerotron 600TT60 was a 60 Watt phone. Motorola seems to have stuck with the MJ specification throughout production, always making a 20 Watt unit. I found that although increasing the power to above 50 watts might make your signal a bit quieter at the land station receiver, your own receiver started getting more desensitization from the extra power. A trunk mounted antenna would fill the passenger compartment with RF, and on a weak signal, you could squirm around in the seat and hear the coils of the springs rubbing together, the transmission gear selector rubbing in the steering clumn, and about a hundred other things. Also, RF was prone to entering the control heads of the later phones with microprocessors inside, which would then go beserk as long as you were on the air. This was a problem with convertible top cars and jeeps. But now I am off on a tangent....

 

I cannot recall the exact figure, but there was an FCC spec which limited the mobile power output to a certain level. That was not the same as the AT&T spec for "MJ" operation. The 50+ watt phones did not seem to comply with either spec but I don't recall further details.

Geoff Fors maintains this remarkable page:

MOTOROLA EARLY LAND MOBILE EQUIPMENT INDEX, 1938-1946

http://www.mbay.net/~wb6nvh/Motadata.htm

Geoff is an ardent mobile radio enthusiast, please visit his site soon.

More IMTS madness? Of course. Take a look at a company newsletter describing the 1982 cutover in Pac Bell land:

 

Page One/ Page Two/ Page Three/ Page Four

(1) Service cost and per-minute charges table/ (2) Product literature photos/ (3) Briefcase Model Phone / (4) More info on the briefcase model/ (5) MTS and IMTS history/ (6) Bell System (7) Outline of IMTS/ (8) Land Mobile Page 1 (375K)/ (9) Land Mobile Page Two (375K)/ (10) The Canyon GCS Briefcase Telephone

Text link to CellTowerInfo.com

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