Radio Wave strength
 

I am new the world of radio waves, but I am trying to find out if I
can buy a device which will tell me how strong the radio waves are
coming from a large antenna? This is assuming that I am standing
within 10 meters.

I know that a frequency counter tells me which frequencies are being
transmitted. But what tells me how strong they are? Any idea who sells
them?

Any ideas?
Thanks, Meeker

"Meeker" wrote in message
om...
I am new the world of radio waves, but I am trying to find out if I
can buy a device which will tell me how strong the radio waves are
coming from a large antenna? This is assuming that I am standing
within 10 meters.


Yes.

I know that a frequency counter tells me which frequencies are being
transmitted. But what tells me how strong they are? Any idea who sells
them?


It is called a Field Strength Meter. There are two basic types.
Calibrated, which gives you the actual field strength in Volts/Meter or
Watts/SquareMeter, and uncalibrated, which gives you the relative field
strength, relative to where ever you had the knob set the last time. The
uncalibrated kind are good for comparing two antennas or adjusting a single
antenna for maximum signal.

Do a web search for Field Strength Meter and you will be sure to find a
bunch. Google lists 5530 hits.

The calibrated kind are usually quite expensive.

Jim
N8ee

In the immediate vicinity of a transmitting antenna, there are
generally electric and magnetic fields which are not "radio waves"
(electromagnetic fields). If you really want to know the "radio wave"
(electromagnetic field) strength, you should measure it far enough
away from the antenna. Do a Google search for "antenna near field"
for a whole mess of references. The first that popped up for looks
like a good start: https://ewhdbks.mugu.navy.mil/ANTNRFLD.HTM. After
you have an understanding about near and far fields, have a look at
things like http://www.scott-inc.com/html/nist.htm, or other pages you
can find with a search for "NIST standard antenna." You'll also get a
lot of references from an "electromagnetic field measurement" search,
but a lot of them will be for places that will do the measurement for
you, and a lot of the rest will refer to NIST work. The essence is to
measure the voltage developed across a standard antenna placed in the
electromagnetic field you wish to measure. You can either build or
buy a standard antenna for the measurements.

If you only care about relative measurements, like "did it get
stronger after I did this or that," then you can use any old antenna
and simple detector and meter arrangement and just look for changes.

Cheers,
Tom

(Meeker) wrote in message . com...
I am new the world of radio waves, but I am trying to find out if I
can buy a device which will tell me how strong the radio waves are
coming from a large antenna? This is assuming that I am standing
within 10 meters.

I know that a frequency counter tells me which frequencies are being
transmitted. But what tells me how strong they are? Any idea who sells
them?

Any ideas?
Thanks, Meeker

At night, if you have a florescent tube in one hand on the metal base, and
the tube lights up as you move closer to the antenna, there is too much
power for humans there. (cheap test)


"Meeker" wrote in message
om...
I am new the world of radio waves, but I am trying to find out if I
can buy a device which will tell me how strong the radio waves are
coming from a large antenna? This is assuming that I am standing
within 10 meters.

I know that a frequency counter tells me which frequencies are being
transmitted. But what tells me how strong they are? Any idea who sells
them?

Any ideas?
Thanks, Meeker

"Tom Bruhns" wrote in message
m...
The first that popped up for looks
like a good start: https://ewhdbks.mugu.navy.mil/ANTNRFLD.HTM. Tom

This is a good reference Tom. Thanks for the info.

Al KA5JGV

Many thanks for your help folks. I will have a look.

I am checking out the following one:

http://www.altered-state.com/cgi-local/reload.cgi?//www.ask.co.uk/ix.asp?q=how+do+I+measure+the+strength+of+a+rf&ac= none&xx=0&qid=E4DECE19AE4A2943B1E53A6D9AF1B77F&p=0 &s=1&sp=ix&fn=t&b=0&fo=2&r=10&io=4&fp=4&fr=1&url=h ttp%3A%2F%2Fwww%2Ealtered%2Dstate%2Ecom%2Ftrifield %2Frf%5Ffieldstrengh%2Ehtm&adurl=^/trifield/rf_fieldstrengh.htm

Cheers, Meeker