Hand-Held RF Meters: Pros vs. Cons

Pros:

Hand-held RF meters are cost-effective and easy to use. Those with a logarithmic periodic antenna are particularly good at identifying general source points, such as smart meters, cellular antenna ports and towers, wifi, cordless phones, BlueTooth, etc. For this reason, the Gigahertz Solutions HF59B and HF59D hand-held meters serve well the excellent work that an Electromagnetic Radiation Specialist, EMRS, provides you.

The Gigahertz Solutions HF59B, one of the best hand-held RF analyzers (Made in Germany), is most responsive in the ‘Sensitive” setting and measures RF signal power to a resolution of a microwatt per square meter (µW/㎡) for power readings. Unfortunately, it does not take much to overload this setting, so the max settings that bump the measurement units up to a milliwatt per square meter (mW/㎡) are often required. It has a running RMS (Root-Mean-Squared Average) setting and a PEAK and PEAK-hold function that do not average but sum the three highest received peak frequencies. By the FCC, this mathematical method is acceptable as a viable calculation method.

The isotropic antenna (Isotropic is a “donut-shaped” pattern above the antenna) has a typical zero dBi (decibel-isotropic) gain. This means the measurements are relatively linear (consistently representative of the actual signal strength across all frequency bands) and do not require antenna factor calculations. (The logarithmic periodic antennas and all other log-per antennas require compensation calculations because the dipole antennas that make up a log-per antenna resonate with specific frequencies more than others. So, these resonating frequencies will be received better than others. The weaker resonating frequencies will be received as a weaker signal than in reality, so compensation for the signal as measured weaker than it is are needed for those specific frequencies. This compensation is termed the antenna factor, AF.)

Gigahertz Solutions HF59B, the best hand-held RF analyzer in the world (Made in Germany) is most accurate in the ‘Sensitive” setting in RMS mode or on “Medium” Sensitivity with the RF attenuator. — The Gigahertz Solutions HF59B, an excellent hand-held RF analyzer (Made in Germany), is most accurate in the ‘Sensitive” setting in RMS mode or on “Medium” Sensitivity with the RF attenuator.

Cons:

The typical hand-held meter is a scalar measuring instrument that can exaggerate the measured power density levels. It can also under-measure.

A Gigahertz Solutions RF Analyzer and most hand-held meters can under-record a cell tower measurement. Today’s 5G antenna ports emit five different frequency bands. So, if the analyzer is only summing three of the highest amplitudes, it will not account for the two bands with weaker signals. (The effect of RF on electronics and persons results from power density and other factors such as frequency, phase modulation, pulse amplitude variations, and distortion.)

In addition, because these meters cannot measure phase, any impedance mismatches and reflections can add in and out-of-phase distortion with the incident signal you are measuring, resulting in magnitude uncertainty. This typically occurs while measuring inside any room or on a New York City block because of multiple reflective surfaces. An EMRS is aware of this issue while measuring indoors and tries to account for this during the assessment.

Most hand-held RF meters are broadband and not frequency selective. As a result, all unwanted signals caused by the meter’s circuitry will get averaged into the measurement, often causing false or inaccurate readings. This is why we throw out spike readings that do not correspond to a smart meter’s demodulated audio signal.

Intermodulation resultants are signals generated by nonlinear interactions within the transmitter components. For example, the internal mixer which processes the RF signal has a nonlinear behavior. The mixer outputs the sum and difference of three input signal frequencies via diode sensors, and then the output is isolated. Most high-end meters have an IF Filter (Intermediary Frequency Filter.) The higher frequency summation is a process known as up-conversion, meaning that the output frequency is higher than the second input frequency.

The problem with using any mixer within the circuitry path is that mixers can present signal combinations along with their harmonics and leakage of the input signals to the output. The frequency and amplitude of the intermodulation resultants will then change with a delta in the input signals, resulting in yet another way to get an incorrect measurement. Care and experience can minimize this effect in specific environments, but it is nearly impossible to avoid in a dense RF environment such as New York City.

We term any unwanted signal as a spurious event or spur. Spurs from internal circuitry leakage and external radiative coupling may occur at any frequency or power level. If you use any hand-held RF meter or hand-held spectrum analyzer, there is a good chance that your peak readings will have spurs. Therefore, we recommend monitoring the RMS (root-mean-squared) readings, taking extended-time measurements, and voiding any one-time spike readings.

Often, you can use your own eyes to locate RF sources unless you are in a big city or a rural area with dense foliage and do not have an FCC mapping of licensed antennas in your vicinity. Generally, a hand-held RF meter is not the correct tool to acquire data for scientific assessments of RF signals, except for a specific few makes and models. Still, meters such as the Gigahertz Solutions HF59B and HF59D will work for general residential work where you want to get a sense of the relative power levels entering your space.

Usually, if you want accurate isotropic broadband measurements for scientific purposes, then either ascertain an isotropic broadband antenna with a dedicated spectrum analyzer or find a hand-held meter that isolates the antenna from the electronics, has internal RF shielding with a built-in attenuator, and monitor the RF signals for a longer time-span.

Calibration and Professional Meters:

A professional meter, for most applications it is designed for, has an up-to-date ISO 17025 calibration certificate. This certification includes a detailed report of the +/- decibel (dB) error or percentage level of uncertainty for each frequency and measurement traceability to a specific up-to-date calibrated tool.

If the meter has a NIST (National Institute of Standards) traceable certification only, then it is helpful as a reference tool but not for taking critical high-risk measurements such as for the aviation industry, industrial safety, pacemakers, etc.

If your meter has a factory calibration, measurements are generally certified by the manufacturer at their stated accuracy for one year. Most measuring equipment used frequently will go out of calibration within one year.

Up-to-date calibration certificates should be included in your report. If you are a professional providing high-risk assessments, we recommend you use ISO 17025 certified-calibrated equipment.