Calculating upper base frequencies

Custom Band Plans (800 Custom, VHF, UHF) require that you enter both a lower and an upper base frequency value. Here's how to determine these values.

The Easy Way

Use this spreadsheet to calculate the values for you: CustomBandPlanCalculator.xls

The Hard Way

The Lower Base Frequency (or Base ) is always the base frequency as provided in the RRDB. The Upper Base Frequency is calculated from the following formulas:

For sites with a single band plan:

Base + ( (759 – Offset ) x Step )

Base + ( (759 – Offset ) x Step )

Where:

Base = the lower base frequency listed in RRDB.
Offset = the offset for this entry.
Step = the step for this entry in MHz (convert from kHz to MHz by moving the decimal point three places to the left).

For sites with multiple band plans:

Upper Base_n = Base_n + ( Offset_n+1 – 1 – Offset_n ) x Step_n

Upper Base_n = Base_n + ( Offset_n+1 – 1 – Offset_n ) x Step_n

Where:

Base_n is the lower base frequency for the entry.
Offset_n+1 is the Offset for the next band plan (for the last table, use 760).
Offset_n is the offset for this band plan.
Step_n is the step for this band in MHz (convert from kHz to MHz by moving the decimal point three places to the left).

For example:

Custom Frequency Table

Entry Base Spacing Offset

A 155.4150 15.0 380

B 157.2000 12.5 436

C 157.4700 15.0 454

Entry	Base	Spacing	Offset
A	155.4150	15.0	380
B	157.2000	12.5	436
C	157.4700	15.0	454

Plugging these values into our formula, we get:

For entry A:

Upper Base_A = Base_A + ( Offset_B – 1 – Offset_A ) x Step_A

Upper Base_A = 155.415 MHz + (436 – 1 – 380) x 15kHz

Upper Base_A = 155.415 MHz + 55 x 0.015 MHz

Upper Base_A = 155.415 MHz + 0.825 MHz

Upper Base_A = 156.240 MHz

For entry A:
Upper Base_A	=	Base_A +	( Offset_B – 1	– Offset_A )	x Step_A
Upper Base_A	=	155.415 MHz +	(436 – 1	– 380)	x 15kHz
Upper Base_A	=	155.415 MHz +	55	x 0.015 MHz
Upper Base_A	=	155.415 MHz +	0.825 MHz
Upper Base_A	=	156.240 MHz

For entry B:

Upper Base_B = Base_B + ( Offset_C – 1 – Offset_B ) x Step_B

Upper Base_B = 157.200 MHz + (454 – 1 – 436) x 12.5 kHz

Upper Base_B = 157.200 MHz + 17 x 0.0125 MHz

Upper Base_B = 157.200 MHz + 0.2125 MHz

Upper Base_B = 157.4125 MHz

For entry B:
Upper Base_B	=	Base_B +	( Offset_C – 1	– Offset_B )	x Step_B
Upper Base_B	=	157.200 MHz +	(454 – 1	– 436)	x 12.5 kHz
Upper Base_B	=	157.200 MHz +	17	x 0.0125 MHz
Upper Base_B	=	157.200 MHz +	0.2125 MHz
Upper Base_B	=	157.4125 MHz

For entry C:

Upper Base_C = Base_C + ( Offset_C+1 – 1 – Offset_C ) x Step_C

Upper Base_C = 157.470 MHz + (760 – 1 – 454) x 15 kHz

Upper Base_C = 157.470 MHz + 305 x 0.015 MHz

Upper Base_C = 157.470 MHz + 4.575 MHz

Upper Base_C = 162.045 MHz

For entry C:
Upper Base_C	=	Base_C +	( Offset_C+1 – 1	– Offset_C )	x Step_C
Upper Base_C	=	157.470 MHz +	(760 – 1	– 454)	x 15 kHz
Upper Base_C	=	157.470 MHz +	305	x 0.015 MHz
Upper Base_C	=	157.470 MHz +	4.575 MHz
Upper Base_C	=	162.045 MHz

This page applies to the following scanner(s): BCD996XT BCT15X BCD396XT BC346XT BC346XTC Users Guide