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 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 ) × Step )

Where:

• Base = the lower base frequency listed in RRDB.
• Offset = the offset for this entry.
• Step = the step for this entry.

For sites with multiple band plans:

Upper Basen = Basen + ( Offsetn+1 – 1 – Offsetn ) × Stepn

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.

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

Plugging these values into our formula, we get:

For entry A:
Upper BaseA	=	BaseA +	( OffsetB – 1	– OffsetA )	× StepA
Upper BaseA	=	155.415 MHz +	(436 – 1	– 380)	× 15kHz
Upper BaseA	=	155.415 MHz +	55		× 0.015 MHz
Upper BaseA	=	155.415 MHz +	0.825 MHz
Upper BaseA	=	156.240 MHz

For entry B:
Upper BaseB	=	BaseB +	( OffsetC – 1	– OffsetB )	× StepB
Upper BaseB	=	157.200 MHz +	(454 – 1	– 436)	× 12.5 kHz
Upper BaseB	=	157.200 MHz +	17		× 0.0125 MHz
Upper BaseB	=	157.200 MHz +	0.2125 MHz
Upper BaseB	=	157.4125 MHz

For entry C:
Upper BaseC	=	BaseC +	( OffsetC+1 – 1	– OffsetC )	× StepC
Upper BaseC	=	157.470 MHz +	(760 – 1	– 454)	× 15 kHz
Upper BaseC	=	157.470 MHz +	305		× 0.015 MHz
Upper BaseC	=	157.470 MHz +	4.575 MHz
Upper BaseC	=	162.045 MHz

( Click here to download a spreadsheet that will do all the math for you.)

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