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:
- Basen is the lower base frequency for the entry.
- Offsetn+1 is the Offset for the next band plan (for the last table, use 760)
- Offsetn is the offset for this band plan
- Stepn 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.)