TM721A.12

Date: Mon, 8 May 89 11:42:21 PDT
From: flloyd@Sun.COM (Fred Lloyd)
To: MBRAMWEL@uwo.ca
Subject: TM-721A UHF Extend Mod



Modifying the Kenwood TM-721A for Extended UHF Coverage

Well I finally uncovered the specifics of the mod which will extend the
UHF coverage of the TM-721A.  This mod changes the UHF receive from
it's factory setting of 438 - 449.995 mhz to approximately 420-460
MHZ.  There are some peculiarities surrounding this mod so I'll
describe them first.

First of all, this mod will allow the UHF digital display to traverse
from 400.000 to 499.995.  The radio will not, however, tune this entire
range due to a combination of a limited synthesizer lock range and the
input RF amplifier bandwidth.  The apparent useful tuning range is
about 420-460, with sensitivity dropping off sharply at either end.
Naturally, the best performance is in the middle (the Ham Band :-).

Similarly, the VHF tuning range is extended in the same manner.  After
the mod is made, the VHF side will apparently tune from between 100-199
mhz but as stated above, there is little or no response outside of the
published range (138-170 mhz), due to the same reasons as stated
above.

As a final side effect, note that performing this mod will remove all
out-of-band transmit restrictions on the rig, for both VHF and UHF.
After the mod is in place, the radio will transmit on any frequency
that it can tune to.

DISCLAIMER:

The author of this report wishes to strongly remind those who perform
this mod that it is ILLEGAL to transmit on any frequencies outside of
the ham bands, EVEN IF YOU ARE OTHERWISE LICENSED TO DO SO.  This is
because of the radio's lack of FCC type acceptance for these
frequencies.  So beware!  Unauthorized use of this feature could be
hazardous to your ticket.  MARS/CAP users are probably OK with a permit.


Now for the nuts and bolts.....
CONTINUED IN TM721A.13