Yes, a field strength meter. Click the link for a Wiki article about it.

There are many frequencies of waves bouncing around, it is essential that you know the frequency range you want to test for, and the safe levels of each, what exposure levels you are likely to encounter, and the accuracy demanded for your test results....There is some hysteria about these waves that is not supported by scientific data...There is a lot of bad science being quoted as gospel...Educate yourself before you go off half cocked, fueled by some internet psuedo-science based BS...

http://en.wikipedia.org/wiki/Mobile_phone_radiation_and_health

http://www.emfservices.com/cell-towers.htm

http://www.eiwellspring.org/HowToMeasureEMF.pdf

http://www.lessemf.com/gauss.html

You are absolutely correct SolarEagle, but there are myriad other factors, which must be taken into consideration in compiling the data I think he is after; and, I am not certain that anyone would want to tackle all the problems presented in this one simple question. Since RF radiation exposure is contingent upon OVERALL energy level - over time, then every single frequency's energy level must be measured over multiple days / months for specific amounts of time during the day(s) that a person is exposed, and then averaged as this is not going to be a constant number especially if there are multiple types of broadcasting equipment providing the energy - ie 2-way radio, TV, microwave, cellular, paging, wireless internet etc. ... Also, Are the antennas electrically or manually down tilted? Are they polarized horizontally, or vertically? OK Lets just say that the tower in question has all of these, there is currently NO official level of Radiation from a tower source of a SPECIFIC frequency from a SPECIFIC source at a SPECIFIC distance over 'X' amount of time, which HAS BEEN PROVEN to be the direct cause of any specific health problem! Which company are you going to blame, as there may be 10 different companies with different equipment, each with varying broadcast energy levels on any given tower. How many other RF fields are there in your home, which are much closer and could be a major contributing cause to any malady? If there is just one, then your case is out the window. Quite frankly, anyone who thinks they can tackle this/these problem(s) AND WIN in a court of law is fooling themselves big time!

Your desire to test "at a discrete distance" indicates that you may be trying to build a case against a communications tower in your area, or are building one for someone else.

Your specific reason for wanting to develop this information is very important.

If you are trying to build a case that will stand up to the rigors of court, do not do it yourself. You will need expert testimony provided by someone recognized by the court as an "expert witness". In that case SE may have some good links.

If you are just curious, you can buy SWR meters at electronics stores that have a simple power meter function built in. Sorta like Doorman's suggestion. These are better at indicating transmitter field strength than indicating specific radiation levels.

Lyn, I believe that you meant FSM instead of SWR. A Standing Wave Ratio (SWR) meter has to be inserted in or closely coupled to the transmission line under study, if it also has a power measuring function it is used in conjunction with a non-reactive dummy load. A Field Strength Meter (FSM) has an antenna and usually tuned circuits to measure the actual voltage levels at certain frequencies at its antenna's location.

If the OP is trying to measure signal strength near a transmitting facility then the use of a near-field meter may be appropriate.

http://www.trifield.com/content/trifield-broadband-meter/

Not bad for $190...

Many times the site owner or manager will have this data. It is required in some locales. Their phone number will be on the fence. There is also an FCC tower number, you may be able to get this info from them by giving them the number. In general if you are outside of the fenced area, you will be safe. The "in general' is relative. The Empire State Building before the WTC made using the old standard Simpson 260 unusable due to the RF. This was in adjacent buildings. When the WTC came on line it was so high in altitude nothing came out. 100 watt transmitters had 1 watt at the input to the antenna due to the combiners. Even so you could still hit the site with a 35 watt mobile on Robert Moses Causeway 60 miles or so away. So you have to specify where you are, at ground level the signal will be minimal, at the antennas much higher.

Back in the "old" days stations had to have an Engineer on site 24/7. This ended in the 50's or 60's. I don't know if there are any medical studies of these folks, but they were exposed to more RF than anyone else for longer periods of time. The ARRL may also have records for some of the longtime "hams".

We had to run surveys on the ship. We fired up the 1KW HF transmitter at various frequencies. Unsafe levels were found at 4 or 5 meters off the deck (11 Meter stick)

at a distance of 5 cm.

Let us know what you find.

Not sure if you are performing tests for the purposes of implementing a wireless communications link, assessing interference issues or for determining safe exposure levels.

If it is one of the former 2 you will need standard antennae and a spectrum analyser.

If it is the later you will need a radiation hazard meter aka RAHAM.

You will also need to know how to use the instruments and to interpret the information that they provide.

Thank you for your inputs!

An article on RAHAMs for PPE...

Finding a Cost-Effective Personal RF Monitor

The host website, http://www.lbagroup.com/blog/ has plenty of other interesting RF related topics to read about if you want to gain more insight into the topic. Enjoy.

Good answer, I might add that even if you have the best meter/analyzer the indications mean nothing unless you know the coupling coefficient. Antenna position, size and location cause variations in the received signal strength that are difficult for professionals in the field to decipher. Your meter will read what it sees, but that may have little to do with the actual signal intensity.

It used to be done like this

http://www.lbagroup.com/blog/how-am-directional-antenna-proofs-were-done-60-years-ago/

and they produced reports like this

http://dl.dropbox.com/u/2065781/WNIX%201951%20Proof.pdf

Vivid memories....