Review: the GQ EMF-390 EMF Multi-Field/Multi-Function Meter
Don G3XTT takes a look at this handy meter but uses the opportunity for a wider discussion about the new EMF regulations.
Don G3XTT takes a look at this handy meter but uses the opportunity for a wider discussion about the new EMF regulations.
Don Field G3XTT
Alot of attention has been focused recently on matters EMF, with the changes to the licence resulting from Ofcom’s desire to apply ICNIRP guidelines to all radio transmitters in the UK. While the RSGB/Ofcom spreadsheet is based on simple calculations using transmit power, antenna type and distance from people, it is understandable that some radio amateurs would want to know more about the levels of radiation not only from their amateur radio equipment, but from other local sources. This is where the GQ EMF-390 comes in. Indeed, this semi-professional meter has already been selling well since Moonraker included it in their product portfolio.
Overview
So, what is an EMF-390 and what does it do? Here is the explanation from the downloadable manual (which, incidentally, is a ‘must’ – the leaflet that comes packaged with the device does no more than give an overview):
The GQ EMF-360V2/EMF-360+V2/EMF380V2/EMF-390 advanced multi-function digital EMF meter is designed and developed by GQ Electronics, Seattle, USA. It is designed to be a portable and convenient device. It can be used as regular EMF, EF and RF radiation detection. This high sensitivity meter lets you check EMF/RF radiation easily. Examples: computer mouse, car remote key, cell phone, cell tower, cordless phone, static, electric field, WiFi, computer laptop, microwave, electric heater, hair dryer, vehicle engine, light, outdoor power line, monitor the WiFi signal, smart meter signal, spy wireless video camera signal, even track radio signal in air.
The meter features multiple sensors to ensure maximum scale/range measurement and highest accuracy:
• Three axis Electromagnetic Fields
• Electric Field
• Radio Frequency
Additionally, the testing features include:
• Radio Spectrum Power Analyzer (EMF360+V2/380/390 only)
• Real-time (every second) data logging (EMF-390 only).
The meter is able to identify the common source from EMF/RF measured, such as Power Line, WiFi/Cellphone, Cell Tower, Microwave etc. It also comes with built-in audible and visual alarm. The device can be used for EMF, EF and RF detection and monitoring, both indoors and outdoors (the unit must be protected from rain), as well as in other similar environments. The device also features a high contrast black/white LCD module and one front LED indicator. The unique GQ RF Browser feature allows to visualize the RF radiation precisely with an on-screen graph. With the RF Browser, the user is able to see the Digital RF equivalent in bytes as well as an RF power spectral histogram.
When the device is connected to a PC, in addition to charging, the free companion PC software can be used to:
• Monitor the measurements on the computer screen
• Download the history data recorded through the EMF-390’s data logging feature and convert it into a standard .csv file for further analysis.
Specifications
• EMF (Electromagnetic Field)
Triple axis (X, Y, Z)
Range: 0.00~500mG, 0.00 to 50wT Resolution: 0.1/1 mG or 0.01/0.1wT
• EF (Electric Field)
Range: 0V/m to 1000V/m Resolution: 1V/m
Frequency independent
• RF Field (Radio Frequency Field) Range: 0.02wW/m² ~ 9999mW/m² Resolution: 0.01μW/m², 0.1μA/m, 0.1mV/m, 0.001μW/cm², 1dB up to 10 GHz
The RF field can be measured up to 10GHz although as a spectrum analyser, measuring power, its use is limited to five bands as below. It is clear that these are by no means focused on the amateur radio bands but intended to cover the main VHF broadcast bands along with cellphones, WiFi, Bluetooth and other devices likely to be encountered in the home and elsewhere.
• Frequency band 1: 50 MHz -65MHz (FM Radio)
• Frequency band 2: 65 MHz -76MHz (FM Radio)
• Frequency band 3: 76MHz – 108MHz (FM Radio)
• Frequency band 4: 240MHz – 1040MHz (Cell phone, Wireless phone Smart meter, etc.)
• Frequency band 5: 2.4Ghz – 2.5GHz (WIFI, Bluetooth, Microwave oven, Smart meter, etc.)
Why not more? Well, the manual says that the unit includes specific hardware sensors for these bands, and by limiting its use to these frequencies, it contains the cost of the unit.
The unit also includes a real-time clock for accurate data logging.
In Use
I started with the all-in-one display mode to get an idea of what the device could tell me. This shows electric field, RF field and overall EMF, both average and peak. Any one of these can be selected as the main (right-hand) measurement. The device quickly showed the background level in my home and identified it as WiFi/Phone, Fig. 1. This certainly made sense and the reading increased substantially when I put the unit next to my WiFi router.
Some may be confused between the function of RF Browser and RF Spectrum Analyzer of GQ EMF-390. A quick answer would be the RF Browser is to detect the total amount of RF radiation, from all sources that have the frequency bands between 0.01GHz to 10GHz. The Spectrum Analyzer feature focuses on what the manufacturer considers to be the main bands of interest.
I took the meter outside and stood below my 6m Yagi (see also the discission later). I measured 0.2mW/m2 when transmitting, though this was on FT8, so the duty cycle across 6 minutes would be less than half that. In contrast, close to my cellphone, the measurement was about 1.7mW/m2 – somewhat more concerning given that we use these devices close to our heads (but, naturally, Ofcom give a dispensation to cellphones!). Next to my WiFi router the reading went to over 200 and the green warning light started flashing!
As for the microwave oven, the reading went to 500+ closed by and dropped to about 20 four or five feet away.
I was actually quite surprised by the power reading below my 6m Yagi. Draw a sphere round the antenna and at 9m away, the surface area of the sphere is about 1000m2, so if the radiator was isotropic, I would have expected, with, say 200W at the antenna (I have a run of about 70m of coax!), anything up to 200mW/m2. But, of course, we are talking here about a 6-element Yagi with the majority of the radiation going off towards the horizon rather than emanating from below the antenna.
Time to try it on my 80m dipole. Running 400W at 50% duty cycle (i.e. sending a string of dots from my keyer), the reading was around 30mW/m2 with the meter almost touching the end of the antenna, but this fell to below 2 when less than 6ft away. Given that the ends of my antenna are about 6ft above ground (albeit it in the middle of my garden), I guess I need to ensure no one is likely to be standing immediately below them when I am transmitting (the Ofcom rules accept that there is no case to answer if no one is in the vicinity). Look on the RSGB website or at the article in the May issue of RadCom (page 26) and you’ll see a diagram that illustrates this nicely – the measurements I made support the ‘red’ exclusion zone below either end of the antenna shown in the RSGB diagram.
I won’t go into all in the ins and outs of the EMF-390 here because it is a well-featured and versatile instrument. I show in Fig. 2, for example, just some of the display modes it supports. And, as I mention later, you can also download the data to a PC for later analysis.
Ofcom EMF Regulations
To put the discission of the GQ EMF-390 into context, I need to say more about the new requirements from Ofcom as they apply to radio amateurs.
Ofcom have published their final decision on changes to the Wireless Telegraphy Act licences requiring all spectrum users (including all radio amateurs) to comply with the ICNIRP general public limits on EMF exposure. Compliance is required after November 18th 2021 for frequencies above 110MHz, after 18 May 2022 for frequencies above 10MHz but below 110MHz, after 18 November 2022 for frequencies below 10MHz. More information can be found on their web page: ofcom.org.uk/emf
But without going to the Ofcom pages, the RSGB have collected together all the relevant documentation on their website, accessible to all. Included is a down
loadable calculator, based on the Ofcom spreadsheet, but with a ‘front end’ specifically for amateur radio users. There is also a video on how to use the calculator. https://tinyurl.com/353e6948
Assessment Options
In May 21 RadCom, John Rogers M0JAV and colleagues set out the assessment options open to radio amateurs and that are acceptable to Ofcom.
The first is to transmit at power levels below 10W EIRP (effective isotropic radiated power). Easy one but most amateurs will want to run more power than this.
Second is manufacturer’s instructions. This applies mostly to handheld radios where the manufacturer has provided guidelines on how to meet ICNIRP criteria.
The third is to use the RSGB EMF Calculator. There was some resistance to this in the early days, probably because the RSGB spreadsheet was still under development. So, others came up with solutions of their own. But, having used the RSGB spreadsheet myself to assess my own station (more below), I can say that it is very straightforward. What’s more, the front-end overlies Ofcom’s own spreadsheet and, as a result, if you are deemed by the RSGB spreadsheet to be compliant, then that will satisfy Ofcom.
Fourth is to use other EMF calculations, for example by way of a recognised antenna modelling program. This, though, is probably beyond the abilities of many amateurs, at least in terms of doing the calculations to a level at which Ofcom might be satisfied.
Finally, the RSGB is developing a library of ‘pre-assessed station configurations. In other words, they effectively do the calculations for you if your station matches (near enough) one of the configurations they have modelled.
You will have noticed that nowhere is it satisfactory to make your own measurements of electric or electromagnetic field. This is because doing so with anything other than laboratory calibrated specialist equipment is considered not to be satisfactory. So, where does that leave the GQ EMF-390?
And at this point I can do no better than quote reader Roger Dixon G3SNT, who writes: Delighted to see that you intend to review the above instrument. Coming from a background of Science Education (now retired) and overseeing the implementation of COSHH Assessments/regulations in the 90s to a less than enthusiastic large number of ‘respondents’, I see a direct parallel with the required changes to meet the new Amateur Licence regulations from OFCOM. My experience tells me that to help ensure adoption, it has to be simple, meaningful and ideally, seen as a useful exercise − not just box ticking or remote from reality. This to my mind is the huge benefit of direct measurements with this meter. I purchased the above meter and cannot overstate its useful broad-based functionality not only to produce real/live assessments inside the ‘shack’ but of course in the vicinity of antennas. Together with the accompanying PC/Windows software and facility to both read and log/download RF data and ‘see’ it graphically etc, the process of assessment becomes both interesting and meaningful, especially to radio amateurs who have an embedded interest in where the RF is going! I have a fairly typical ‘shack’ and selection of HF/VHF transceivers and a number of vertical and horizontal antennas. My live assessments using up to 200W maximum output in the HF bands have revealed no adverse levels of RF radiation both in the shack and at distances as small as 25cm from the radiating elements of antennas outside the shack. As a bonus to owning such a device it is possible to locate and measure the ‘noise’ being generated by a host of devices in and around the home − a very useful detector for helping the fight against electrical QRM. My assessments to date confirm that I need not worry about any undue ‘warming effects’ to visitors as a result of my transmissions, however I would perhaps urge them to keep a respectful distance from the kitchen microwave if I am making them really welcome!
Assessments suitably annotated and available for scrutiny would not substitute for an RSGB/OFCOM calculator, or using ‘Pre-assessed station configurations’. However, I think you will find when you use, test and review this meter it undoubtedly reinforces:
1. That, in use, amateur radio transmissions do produce ‘EMF’ and it can be seen as a ‘real’ variable and quantifiable product of our activity − not imagined from otherwise a series of complex calculations
2. That it can be measured in real time, in situ and is very useful data for subsequent analysis
3. The measurements may well enlighten users to take precautionary measures or conversely conviction that compliance is being achieved − some conviction that what we are being asked to do is not just a paper exercise
4. Almost like the Grid Dip meter of old (now replaced by the increasingly common VNA), it is a very useful addition to the test equipment in the radio shack.
Having now had the opportunity to use the GQ EMF-390, I very much concur with Roger’s view. Nowadays we are surrounded by RF but have no ‘feel’ for how much of it there is around the place, which are the devices that are most culpable in creating RF fields around the house and garden, and the extent to which our own amateur radio equipment generates fields on different bands and in different locations around the antenna. And in this respect, it’s worth noting that there is a significant difference between ‘near field’ and ‘far field’ effects. Most antenna modelling programs are (for obvious reasons) designed to model ‘far field’ – you want to know how effective the antenna is at communicating with distant stations. But the ‘near field’ (which actually extends only a very short distance from your antenna) behaves very differently and this is where we need to turn to other sources to measure, model and understand.
ICNIRP
One of the documents cited on the RSGB website is ICNIRP Guidelines for Limiting Exposure to Electromagnetic Fields (100kHz to 300GHz).
it for bedtime reading but it’s worth taking a look, if only to understand where Ofcom are coming from with their latest regulations. Ofcom are not, nowadays, a technical body, so they consult Public Health England who, in turn, go to ICNIRP for the necessary requirements.
I have, though, extracted Table 6 from that document here), because it sets out the reference levels for local exposure, averaged over six minutes (which is the basis of the Ofcom regulations). These are measurements that can be made with the GQ EMF-390, if only to satisfy yourself that that your station is ‘safe’ (and bear in mind that ‘safe’ in this context means well within any possible level at which dangerous effects might occur – the ICNIRP guidelines are intended to be ultra-conservative).
The numbers will be too hard to read – I recommend you look at the document itself if you want to follow up.
My Station
I thought, therefore, I would take a look at my own station, at two very different frequencies, to determine where I stand with respect to the requirements. First, I took the 6m (50MHz) band, 400W and FT8 (a relatively high duty cycle mode) into my 6-element Yagi antenna. This, I thought, might turn out to be a problem, but the ‘compliance distance’ turned out to be 7.4m. In practice, this means that unless someone climbed part-way up my mast (and stayed there for six minutes), I am comfortably within the requirement. As suggested, I saved the result as a PDF file, ready to show any Ofcom inspector who happens to come by!
And as I said earlier, using the GQ EMF390, the fields I actually measured at ground level were very low indeed.
The only other antenna I have up at the moment is an inverted-vee for 80m and we have until November 2022 to deal with that one. I did try the RSGB spreadsheet but it actually doesn’t work below 10MHz for the simple reason that the underlying Ofcom spreadsheet doesn’t do so. But, again, I took the opportunity to measure around the antenna with the GQ EMF-390 and found, as I said, that I will need to be wary of anyone standing directly below the ends of the antenna for an extended period or, perhaps, simply need to reengineer the dipole to be less of an inverted-vee, by raising the ends to a ‘safe’ height.
PC Connection
I downloaded the software and USB driver from the net to see what it could do. As can be seen from the screenshot, Fig. 4, this displays what is on the EMF-390’s screen at the time. But you can download the history into a .CSV file for further analysis. The high reading in this case is because the EMF-390 was close to the WiFi router on my operating desk!
Summary
There has been a lot of hot air generated as a result of Ofcom’s introduction of regulations related to ICNIRP. Some have felt that amateur radio is being unfairly targeted. Some have felt that the RSGB should have knocked this one on the head. In reality, Ofcom have felt the need to apply the requirements to all radio users (something similar is happening in the USA) and, thankfully, have worked with the RSGB to facilitate self-assessment by radio amateurs, whether technically-minded or not. And having worked through the RSGB spreadsheet (I tried other bands in anticipation of putting up antennas for them again at some time in the future), the ‘compliance distances’ are far from onerous. For example, for my elevated 20m quarter-wave antenna that I sometimes put up, the compliance distance, even at 400W, is just 3.4m. Given that the antenna is in the middle of my garden, the only people likely to get within that distance are my family, and as I can actually see the antenna from the shack, I would know immediately if any of them got too close.
But where the EMF-390 helps is in giving reassurance, both to you as the radio amateur, but perhaps also to friends and family, that the levels around your antenna(s) are well within what is deemed safe.
The GQ EMF-390 retails for £115 and is available from Moonraker, to whom I am indebted for the loan of the unit for this review. The manual, which is worth a read if you are contemplating a purchase, is at:
And, of course, there are a number of YouTube videos to take you through the setting up and use of the meter, albeit not specifically targeted at amateur radio. https://moonrakeronline.com