Upgrading Bendix King VHF Radios for 2m Amateur Use 

Most Bendix King VHF portables can be readily adapted for two meter
amateur use with little or no loss of performance in the intended
148-174MHz operating frequency range. The two meter conversion requires
upgrading the radio software using a BK/RELM LAA-0725 RS-232 interface
cable and model specific computer software. Some additional alignment of
the synthesizer and receiver front-end may be required.

Bendix King EPH radios are probably the easiest to convert using the
program HAM.EXE which allows operation down to 144 MHz. HAM.EXE is
available in a self extracting ZIP called "Breakfast" . EGGS.EXE is
a program provided with HAM.EXE to re-establish the 148MHz lower
frequency limit. Frequently, it is necessary to adjust the front-end
slugs to provide good two meter receiver sensitivity. Rarely is the
EPH alignment software required.

The process of converting an LMH or LPH radio will only work on radios
with Revision 2.0 or later radio firmware.

I have been informed that older LPH handhelds with Revision 1.0
software can be upgraded by adding a 22K resistor between pins pins 21
and 44 on the CPU U1 processor chip. This chip is located on the System
Board which is mounted to the radio front cover. I have not confirmed
this myself. 

The LMH/LPH conversion process will extend the lower frequency limit
to 144MHz and give the radio 12.5KHz capability. It requires running
a RELM program, LMR.EXE. Within the LMR.EXE program, select the
advanced option and then the option codes. To change the lower
frequency limit to 144MHz and add 12.5KHz capability, the four
hexadecimal option codes must be changed to read 00DC(80DC for the
LMH), 3F2B, E970, 195F. When writing the new data to the radio,
"Yes" must be answered to the question of whether or not to overwrite
the option/control words and "Yes" again when asked "Are you sure?".
Again, as with the EPH radios, VCO slug and/or receiver front-end
alignment may be necessary. The alignment process of the "L" Series
radios is, however, a manual "tweaking" process with no special
software required.