radio.setFrequencyBand support (#2495)

* setfrequencyband support

* revert line change

* add bounds check

docs/reference/radio/set-frequency-band.md

@@ -0,0 +1,34 @@
+# set Frequency Band
+
+Change the transmission and reception band of the radio to the given channel. Default is 7.
+
+```sig
+radio.setFrequencyBand(50);
+```
+
+## Parameters
+
+* ``band`` is a [number](/types/number) between ``0`` and ``83``. Each step is 1MHz wide, based at 2400MHz.
+
+## Simulator
+
+This function only works on the @boardname@, not in browsers.
+
+## Example
+
+This program makes the ``radio`` use frequency band 50.
+
+```blocks
+radio.setFrequencyBand(50)
+```
+
+## See also
+
+[received packet](/reference/radio/received-packet),
+[send number](/reference/radio/send-number),
+[send value](/reference/radio/send-value),
+[send string](/reference/radio/send-string)
+
+```package
+radio
+```