Weather Conditions | Dedicated to the relevancy & growth of electronics, maker & amateur radio hobbyists in the Hudson Valley

Monday, May 07, 2018

Field Strength Meter Monday: 3 Real World Applications For A F.S Meter

Last week saw the first article in the "Field Strength Meter Monday" series with a general overview.

Here are three practical applications to use any type of relative or calibrated RF field strength meter for.
  • Check antenna radiation patterns
  • Measure approximate transmitter power power or antenna efficiency
  • Locate hidden transmitters
Which way does your antenna work best?

From a simple dipole for HF frequency operation, to directional beam antennas at UHF ranges, knowing which way your antenna is sending out the most RF energy is helpful to know.

Using a simple relative field strength meter will help you make your own charts somewhat accurately and very inexpensively. 

While the RF source being measured transmits a signal, the relative field strength meter will show a measurement that can be plotted on a piece of graph paper.  As you walk around the transmitting antenna with your field strength meter and note the readings, you can arrive at a chart like the one pictured to better understand your antenna characteristics.

Is my radio transmitting?

A relative field strength meter will also provide some idea as to if your radio is actually transmitting. This may be helpful to know if you hear other stations, but they do not hear you. Some radios will indicate a signal is being sent or tell you how much power it is supposed to be transmitting, but how do you know that for sure?

Using a relative field strength meter wont show you any calibrated power output measurements. For that sort of testing, a watt meter that measures specific levels of RF energy is needed, but that only shows actual RF power output and not how well the antenna is projecting your signal. A watt meter also needs to be connected inline with the transmitter and antenna. A field strength meter does not. 

Perhaps you want to see how well a new hand held radio transmits with the included antenna and another one purchased as a premium accessory? 

You can use a relative field strength meter to see which antenna works best and see how much of a difference you really get when changing from "extra low power" to "low power" and then to "medium" or "high" power output when using different antennas.

Showing the transmit output levels on the Kenwood TH-D74. The manufacturer claims 5 W, 2 W, 0.5 W and 0.05 W on the 3 bands the radio operates on which is 144, 220 and 440 MHz.
Where is that signal coming from?

A relative field strength meter can also be used to find very close by transmission sources.  Using a simple whip type of antenna will help the user find the signal source within a few hundred feet or less depending on how the relative field strength meter was designed.

If combining some form of directional antenna with a relative field strength meter, that creates an even more interesting tool for finding the strength of a signal as well as the direction from which it is coming.  This combination forms a basic radio direction finding tool that is inexpensive and easy to use.

Whats Next?

Next Monday, HVDN will introduce an updated relative field strength meter that blends both analog and digital technologies to create a very interesting tool with even more potential applications.


Please subscribe to HVDN Notebook for additional details on the Field Strength Meter Monday series and other great content along the way too.


Search The Notebook

Subscribe To Future HVDN Notebook Updates Here