The term bandwidth as oppossed to frequency.

When referring to oscilloscopes (and virtually all general test equipment including sprectrum analyzers, logic anlyzers etc) the term bandwidth has a very specific meaning and indeed is by far the most commonly used term. Although the manufacturer will state what it is, the most common definition is where the gain response of the instrument is at -3dB. Instrument bandwidth is used, but so is the term 'effective frequency range' on some older equipment. Note this carefully - it means you can't measure a 100MHz signal with a 100MHz (bandwidth of DC to 100MHz) scope and expect accurate results (to say nothing of the fact you need special probes at that frequency anyway).

I use the term 'frequency' (personally - there are many variants, and it can start a holy war) for those occasions I have a specific frequency or set of frequencies in mind. That said one might inquire as to the frequency range of a signal or the (for instance) transmitted bandwidth of some other signal. In such cases, the two terms are interchangeable.

Other times I personally use the term frequency is when I have a known set of discrete frequencies. In this case, I would refer to the set as a set of frequencies spanning a range (or bandwidth).

Much of what you ask is down to personal choice, though. As you can see, sometimes there is no difference, but generally the term bandwidth is used for contiguous frequency ranges as it is a single word solution to the opposing 'range of frequencies'.

Cheers

PeteS

You wouldn't use either term if you were to assume the same mindset Sencore did when they wrote the manual for my trusty SC61 workhorse of an analyzer -- they don't even call them scopes; how elitist can ya get? Instead, you'd say, "frequency response is 60MHz; useable to 100MHz". Most techs buy these scopes for the additional accuracy (and speed) afforded by the separate LCD readout of the various waveform parameters. So, while "useable to" may be technically correct -- and may have a psychological marketing effect on some -- it's amusing, since the user won't get the same level of accuracy out to that end of the bandwidth. Oops, I said bandwidth, sorry Sencore. ;)

OK, I'm going to attempt to answer my own question above. Witout getting too finicky, 'frequency' should apply to a signal, and 'bandwidth' to a medium. Any better offers?

The very fact that you've decided to answer your own question (i.e., determine how you will apply the terms), validates what people have been telling you (i.e., it's largely a matter of personal choice). As for the standard definitions:

from the Illustrated Dictionary of Electronics (5th Ed.):

frequency: "The rate at which a phenomenon is repeated. The basic unit of frequency is the Hertz (Hz), which is 1 cycle per second."

bandwidth: "see bandpass, 1." bandpass 1: "The frequency limits between which a device or circuit transmits ac energy with negligible loss."

from Webster's Collegiate Dictionary:

frequency: "1 : the fact or condition of occurring frequently

bandwidth: "1 : a range within a band of wavelengths, frequencies, or energies; especially : a range of radio frequencies which is occupied by a modulated carrier wave, which is assigned to a service, or over which a device can operate

Better? Don't know, but here goes. A single frequency is useless when one needs to convey intelligence (information). A frequency source must be modulated to carry information and that process adds sidebands (frequencies above and below the single frequency). The more information or intelligence one must add (assuming time is valuable and thus the data rate has to be reasonable) the wider the bandwidth. So, bandwidth is a resource, because as one uses it up there is not enough left for other purposes. Frequency is just the center or average of the bandwidth.

Does that help you? Yes? No?