Motorola Bag Phone RF Info |
Overview
Finally got a chance to look at an old Motorola bag-style cellular phone on an IFR-1200S service monitor.
RF power output and a spectrum analyzer shot are shown before. The phone was in "test mode," with pin 21 on the DB-25 tied to ground.
The test frequency was 837.000 MHz. Enter 110400# on the keypad while in test mode to set the phone to that frequency. The phone's RF output power is set with the 12x# keypad entry. Where "x" is either 0, 1, 2, 3, or 4. Highest output power is with the "120#" option. The RF output seemed unstable while on the "124#" option, so stick with "123#" and pad down the RF power level with a resistive attenuator pad. Most commerical double-balanced mixers needs a +7, +10, +13, or +17 dBm input LO signal, if you use the phone for this application.
| Motorola Test Mode Command | RF Output Power (Watts) | RF Output Power (dBm) |
|---|---|---|
| 120# | 2.57 | +34.1 |
| 121# | 0.85 | +29.3 |
| 122# | 0.30 | +24.8 |
| 123# | 0.10 | +20.0 |
| 124# | 0.02 | +13 |
| 125# | No RF Output | No RF Output |
| 126# | No RF Output | No RF Output |
| 127# | No RF Output | No RF Output |
| 128# | No RF Output | No RF Output |
| 129# | No RF Output | No RF Output |

Spectrum analyzer screen capture of a Motorola bag-style cellular phone, in testmode, transmitting at 837 MHz. The horizontal setting is 20 kHz per division. Vertical is 10 dB per division.