This page covers the Range 1 to Range 4 receivers. The Range 0 is a newer (and easier to modify) design.

Basics

The basic receiver is pictured below. Note the UHF R1-R4 receivers have a preselector that's flush with the front panel and only 3 adjustment. This is a dead give away that you have a UHF R1-R4 from the front. Unfortunately there is not an easy way to identify it further than by part number.

UHF RX Front
UHF RX Back
UHF RX Case
UHF RX Internal

The receiver is a high side injection with the 1st Lo operating +73.35 MHz higher than the receiver frequency.

The SCM knows what type of module is inserted by reading voltage divider resistors on the u2600 A/D Converter. Some of these are on ports used for other things, Change Frequency and Lock and then A8 input is used for ID. Note the resistors have the same labels on the UHF boards but on other bands the same parts have different labels. The R2606 and R2607 form a voltage divider feeding the A8 input with the computed voltage in volts.

Range	R2449 Chg Freq	R2450 Lock	R2606	R2607	A8 Volts
UHF R0	0	3300	5600	3300	1.9
UHF R1	0	0	1200	1200	2.5
UHF R2	0	3300	1200	1200	2.5
UHF R3	3300	0	1200	1200	2.5
UHF R4	3300	3300	1200	1200	2.5
VHF	R2413	R2415	R2812	R2814
VHF R1	0	0	2700	1200	1.5
VHF R2	0	3300	2700	1200	1.5
800/900	R2422	R2414	R2816	R2815
900	0	0	1200	4700	4.0
800	0	0	1200	2700	3.5