The switches follow the simple binary system.
small 4 switches go from 6.25 - 12.5 - 25KHz to 50KHz
The 8 switches go to: 100KHz, 200KHz, 400KHz, 800KHz, 1600KHz, 3200KHz, 6400KHz, 12800KHz
When they're all set to 0, the board transmits at 86MHz. Now whatever you set on the switches
is added to 86000KHz and you've got your frequency.
Follow the examples and you should be able to work it out easily.
If not, there's still LCD unit, which is really easy to use
Do you have a freq. meter or are you using a receiver to figure this out? A receiver
could be tuning into a spurious signal.