Kenwood TM-641A Instruction Manual

Also see for TM-641A: Instruction manual Service manual

Some dial frequency relationships may result in internal heterodyne tones being generated by the TM-641A/ 741A/741E. This is not a defect.The following formulas may be used to determine if a tone will be present with a particular frequency relationship.If any of the following equations are true, a tone may be generated that is strong enough for you to hear it in thespeaker of both bands. These tones can only be generated when more than one band is on at a time:With the optional FM unit UT-1200;(1.2GHz operating frequency) — 59.7MHz) x 2 — ((70CM operating frequency) + 21.6MHz) X 5 = 59.7 MHzor((70CM operating frequency) + 21.6MHz) x 4 — (((1.2GHz operating frequency) — 59.7MHz) /2) x3= 59.7 MHzor((1.2GHz operating frequency) — 59.7MHz) x 2 — ((70CM operating frequency) + 21.6MHz) x 5 = 21.6 MHzFor TM-741A/741E with the optional FM unit UT-220;orFor TM-641A with the optional FM unit UT-440S;((220MHz operating frequency) — 30.825MHz) x 5 — ((70CM operating frequency) + 21.6MHz) x 2 = 30.825 MHzWith the optional FM unit UT-50S;((6M operating frequency) + 10.595MHz) x 7 — ((70CM operating frequency) + 21.6MHz) = 21.6 MHz63