Re: "Radio" Frequency

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

> 1. Just what exactly is Radio Frequency, given that radios seem to work on
> just about every frequency imagineable.

DC to light...

Off hand, as a practical definition, RF is where you have to start worrying
about parasitic reactances of components, and the inadvertent interaction
between components.

It also has something to do with the nature of the circuit, particularly
analog vs digital.  A 30 MHz digital circuit using HCT series TTL isn't
going to be much of an RF challenge, but a single sideband transceiver at 30
MHz would be.  Here, the issue is one of noise, precision, and so forth.

There is also the usual splitting of the spectrum up into bands, nominally
orders of magnitude in wavelength/frequency.  The splits do sort of match up
with distinct differences in propagation mode and typical circuit design:

ELF  300-3k  (1000 to 100 km)
VLF 3k - 30k  (100 to 10km)
LF  30k - 300k (10 to 1km)
MF 300 k - 3 MHz (1km to 100m) - mostly surface propagation
HF  3M - 30M (100m to 10m)  - ionospheric skywave propagation
VHF 30-300M (10m to 1 m) - some ducting, but mostly line of sight
UHF 300M - 3G (1m to 1 cm) - almost entirely "quasi-optical" propagation
everything above is usually lumped into "microwave" or "millimeter wave",
and divvied up by "letter bands": C,X,K,Ka,Ku, etc., or by wavelength (i.e.
3cm)  or frequency (i.e. 94 GHz)