The Box73 EMV-spion, a very useful instrument for localizing radio noise sources.
On www.box73.de – Bausätze – Funkamateur - i found the “EMV-spion nach DJ3VY und DB1NV,
Komplettbausatz” for 79 Euro + 5,90 Euro postage costs. This instrument is especially designed to find radio noise sources VLF, HF, SW and VHF.
It is a neat set of wired components, with a double sided, through hole metalized and printed PCB, and a drilled and printed housing, including a neat assembling booklet in English. After assembling it worked perfectly.
Warning: a once soldered component is nearly NOT possible
to be removed from the PCB.
FIRST read the WHOLE booklet as certain remarks regarding assemblage are embedded in the text.
- measure each resistor
- read the printed info at each other component
as a fault is easily made.
The wideband EMV-spy reveals clearly different types of noises. Positively recognizable by their sound. Very strong sources are easy to point out, using the logarithmic acting LEDbar signal strength meter. The sensitivity is surprisingly good. From the four dedicated antennas, the narrower band 1.7MHz antenna proved me to be very useful. The to be searched rattle was clearly detectable with it, but annoying other signals from strong pager networks vanished. A rattling/humming/whistling mains adapter can be found immediately.
An FM-modulated signal is not audible. It sounds like an un-modulated carrier, but is still shown by the LED bar.
The EMV-spy also is very handy as a field strength indicator. When tuning antennas, for instance while setting up 80m foxhunt transmitters in the field.
I live in a modern 65+ apartment, above a shopping center and underground parking. I only have one SW antenna, a 10m circumference well balanced loop. I suffer from a high noise level (S8 on 80m, S6 on 40m). And all kinds of noises, one of them was a very strong wide band rattle. Between 1.5MHz and 6.5MHz, upto S9+20dB. Other sources radiated between 3.5MHz and 30MHz up to S8 noise hills and carriers, every 900Hz or so.
Using a good 80m foxhunt receiver and a cheap portable radio, i found out that, in the whole apartment and shopping complex, ALL mains cables, cable gutters, heating pipes, water pipes, lantern posts, metering cabinets, radiated loud rattle. Even on the street, in the supermarket, and in the underground parking (photos 1 and 2). A metal box there (Photo3) seemed to radiate the loudest. But the source was not detectable.
I asked for help at "Agentschap Telecom", an official government organization. Two men
came, searching with a portable spectrum analyzer and a special direction finding loop antenna. They concluded too : everything radiates wideband rattle, but a source can not be
Sadly, the signal levels of the noise hills received by my loop antenna were not high enough for demanding further assistance.
But i still wanted to be free of those loud noises.
After reading http://www.sk5aa.se/wp-content/uploads/2014/08/EMV-Spion_Folien.pdf i gained new courage, and ordered the EMV-spion building kit.
After some practice, i walked around with it. And ended at the same metal box in the sealing of the underground parking (Photo3). From there all kinds of tubing and cabling are going everywhere (Photos 1 and 2). But only then i found out that pipes and cables also went straight up to and from apartments above it.
On all floors above it all cables and pipes radiated rattle. On my own floor, in a corner between two doors (Photo4), i easily could point in the direction of the rattle source, using the H-field antenna, and reading the signal strength on de LED bar.
Once ringed the doorbell, the neighboring lady was very suspicious. Because "That bright green lighting box in my hand could possibly disturb her husbands (hart) warning equipment. In recent weeks the medical emergency team already was called twice for nothing".
After some extra explanation about my presence, i was allowed ONLY to sniff in the electricity meter cabinet inside the apartment. But absolutely not further, and certainly NOT allowed to pull any mains plugs.
In the meter cabinet the EMV-spy green LED bar was nearly showing maximum indication. "Got you". But no further entrance was allowed. Even after i suggested that due to wear, or over voltages, an apparatus could be damaged, possibly a fire hazard. The lady stated bluntly : "Everything works, so a defective apparatus is impossible". Leaving me with a mouth full teeth. A nice noise hunting result, but that loud rattle still jammed my listening pleasure every day between 9:30 and late afternoon. When that neighbor went out on his scoot mobile, the rattle temporarily was gone.
Recently this very ill neighbor was moved to a hospital and died there. Since then the strong rattle has vanished. But the strong noise hills between 3.5MHz and 30MHz still existed.
While walking with the EMV-spy, a doorbell knob (Photo 5) caused a sharp tone in the headphone when i was nearby. Again on my own floor. Only two steps away from it the tone weakened into a background tone. That neighbor friendly cooperated. In the living room, behind the TV, was a PLCbox on a wall socket. It made a very loud whistle in the headphone. It was not in use anymore, and was allowed to be unplugged. Most of the noise hills were gone in the station receiver at home.
This wideband PLC noise was NOT locatable with an narrow band receiver. But with the wideband EMV-spy, the characteristic PLC tone was loudly heard, and easier recognized.
I sniffed to everything in my home, placed a lot of ferrite clamps, and balanced my 10m circumference loop carefully. But i still have S7-8 noise on 80m, and S5-6 on 40m. Plus sometimes some PLC noises. I suppose i have to live with them.