no, there is no 'standard'. the bandwidth depends on what is important to
you. you could be interested in forward gain, f/b ratio, swr, or maybe
something else. manufacturers pick what they think their best qualities are
for advertising of course. then of course there is the gain rating
controversy, is it dbi or dbd or db-something-else, and it it measured
properly or just calculated... again, there is no standard and lots of
methods exist.

on the 150-174mhz antennas. in that band you typically buy an antenna for
your operating frequency as that area of the band is channelized and
licensed here in the states. a typical license may include a couple
channels, but they are usually close together so a single antenna will cover
them. in this are the local police and fire are all on channels between
153.75 and 155.3 so if they buy an antenna made for 154.5 or so it should be
ok over all their channels. these are not normally things stocked in retail
stores, you order them for the frequencies you want to cover and they are
tuned at the factory or distributer for you.

"Richard" wrote in message
...
Hi. Is there a standard way to measure antenna bandwith? Is it within
3dB
down of maximum gain, or is it between SWR limits?

I'm looking at an FM receiving yagi that is advertised as covering the
frequency range 87.5 - 108 Mhz. And I'm wondering what this means. Is the
received signal going to be 3dB down at the band edges or what?

I notice that there are commecial yagis (that are probably suitable for
transmission) that have 150-174 Mhz in their description. Yet they are
stated as having a bandwidth of say 1.3 Mhz. What's the deal here?