Questions for Italian or southern European members

[ccaudle]

I am trying to help someone in a different forum who lives in Italy and is having RFI problems, likely from a new 5G cell phone installation near his flat.
Can someone local give advice on where you can source small quanities of components? I live in North America, and DigiKey is my usual source here, wide selection and relatively quick delivery through the mail. We also have alternative mail order sources like Mouser.
Have those become international, or are there better local suppliers in southern Europe?

The specific components would likely be ferrite beads and ceramic caps.

On a related note, would anyone in Italy or close enough in Europe be interested in helping the person out by building a guitar cable with RFI suppression built into the connectors? My attempt would be something like large Fair-Rite type 61 beads on the exterior of the cable, with small Fair-Rite type 61 beads on the center conductor inside the connector, and SMT ceramic capacitors from the center pin to the shell threads of the connector. I have not actually tried that capacitor mounting yet to see if it can be made durable, but I think multiple SMT capacitors in parallel would be the only thing with even a hope of being effective at cell phone frequencies (5G band most likely to cause interference is at 700MHz). Realistically the caps would probably not be effective at that frequency, so maybe something else would be needed. Or maybe the beads would be enough.

This person does not seem to be a hardware hobbyist (primarily a musician and music software hobbyist). I would not mind doing it here in the US, but I am afraid that shipping to Italy would cost multiples of the component costs and would be hard to justify.

Any recommendations for component supplies, or even anecdotes about similar interference problems that have been solved, or at least analyzed a little more technically would be useful as well. This is a guitar connected to the instrument input of a USB audio interface, and the person does not have access to any RF test equipment, so the conclusion that is it cell phone based interference is based on listening to the resulting audio interference, a cell phone broadcast antenna noticed nearby, and the fact that the interference occurs in that location, in the next apartment building over, but not when the same recording equipment is taken to a different location in a nearby city.

 

[Khron]

DigiKey is my usual source here, wide selection and relatively quick delivery through the mail. We also have alternative mail order sources like Mouser.
Have those become international, or are there better local suppliers in southern Europe?

Both Digikey and Mouser do also cover Europe, even with customs-paid shipping. Alternatively, TME in Poland often have lower prices for most "standard" stuff, and the 10eu UPS Saver shipping can even manage next-business-day delivery (if you order early enough in the day).

 

[MicMaven]

I am trying to help someone in a different forum who lives in Italy and is having RFI problems, likely from a new 5G cell phone installation near his flat.

Um ... er ... just offhand, I would almost suggest using Mix 31 or Mix 43 ferrites for 700 MHz interference.

I would try clamp on beads first, to see if they have any effect. If so, I would have him buy lower mix 2 inch ferrite rings and wind the cable multiple times through the center of the ring. They become much more effective with multiple turns through the center - equivalent to several clamp on beads. These can be purchased from many online sources, including ham radio vendors, such as WIMO in Germany and other ham outlets in EU countries. A feller in France sells large toroid rings on eBay.com, along with [re-wound toroidal transformers of various types. Several EU-based vendors may be found on on eBay.com filtering for EU based sellers. I am confident Italian amateur radio vendors carry a suitable selection.

And yet, I sorta, kinda suspect something else may be going on. Cell phones use very high frequencies, and I sorta, kinda doubt they produce 700 Hz harnmonic interference, which is very low for cell phones. Consequently I would look for other causes.

Your friend might use a small, portable AM band (Medium Wave) radio (especially if it has a directional antrenna) as an RF "sniffer" to detect the source of RFI. At that frequency, I might suspect a number of potential culprits, including, but not limited to, washers, dryers, microwave ovens, coffee makers, light dimmers, and various other domestic appliances with built-in timers or IC controller chips. Or, it might be a cheaplyt made wall wart power supply, battery charger, or other device with a cheap power supply or other dirty aspect. LED based TVs and computer monitors, fluorescent lamps with old fashioned ballasts and so forth are other candidates.

Tuning the sniffer radio to 700 Hz "should" act as an ersatz band pass filter that sorta, almost isolates the source - assuming you have the correct frequency in mind. Tune up or down to tune the actual frequency, and walk about with the radio until the interference sounds louder and louder, indicating the source of the problem. He may be surprised at the real cause!

A more flexible wide band test can be performed with an inexpensive ($20 US) RTL-chip TV repair dongle that and widely available free software as a spectrum scope which can indiate RFI in the shack. Used with a tablet or laptop computer, and a very small antenna, even just a paper clip as an antenna, can effectively indicate RFI/EMI in the shack or studio. Carry the kit about to locate a specific source, as signal strength should increase as you approach the offending device.

At 700 Hz, I suspect other sources, perhaps a power tool in the vicinity, or perhaps a poorly designed computer network device (although that "should" produce intererference around 19 MHz ... but you just never know ...) - or possibly power over ethernet (PoE) which is notorious for producing EMI/RFI.

The victim might test with a hand-held wide band ham radio - especially if it can scan a range of frequencies that can determine the actual frequency of the interference. Even better if he has a polarized antenna. Electrical noise is "usually" in the vertical plane, while magentic noise is "usually" in the horizontal plane - the point is to use a directional antenna, such as a small Yagi beam or loop antenna that can be oriented vertically or horizontally, respectively, indicating polarization as well as signal strength, and move about to locate the actual source of interference.

Another test your friend can try at no cost, is turn off all electrical circuits in the building seriatim, one at al time, and listen to see that mitigates or eliminates the interference, indicating the source is a device plugged into that sub-circuit. He might pesuade close neighbors to do the same, although some neighbors just cannot be bothered or will take undue offense at the mere suggestion their toys may be problematic. Amateur radio operarators encounter this all the time, although, at least in the US, they are protected by laws that prioritize the radio service over appliance noise.

In any case, I strongly advocate locating the actual source and dealing with it directly. Most devices are, at least in the US and I presume in the EU, prohibited from causing harmful interference with other devices. It is much better to fix the problem at the source, than have ferrite beads festooned all over the place. I consider ferrite beads or toroid suppressors a band-aid sort of palliative - better to locate and fix the transmitter than attempt to stifle or mask it at the receiver.

These are just a few notions you friend may try. He may contact me directly to develop a more thorough, detailed approach if that would help. Happy trails. / James K8JHR

 

[ccaudle]

I would almost suggest using Mix 31 or Mix 43 ferrites

The Fair-rite datasheet for mix 31 and 43 both suggest "1MHz up to 500MHz," the mix 61 datasheet suggests it for noise suppression "above 200MHz."
In the selection page for suppression components if you pick "Higher frequencies (200MHz-1000MHz)" it suggests 61 material components.

kinda doubt they produce 700 Hz harnmonic interference

Correct, I am not sure what gave you the impression there was any 700Hz interference. The interference sounds like chirps around 5kHz to 5.4kHz range. Definitely not the old style GSM buzzing clicks, but I am not familiar with what demodulated 5G protocols sound like yet.

At that frequency, I might suspect a number of potential culprits

The interference occurs with all electrical items in the apartment turned off with just a laptop running from battery and the audio interface on. That would seem to indicate the source is not directly in his apartment.
Also occurs in another nearby building, but the same equipment has no interference in a different location several miles away. That indicates the interference source is not only in his building (but could be something common to both apartment buildings which are situated beside each other).
There is a relatively new 5G cell station nearby. Only circumstantial evidence, but without any better RF analysis equipment available that cell phone installation is the best guess, and the newer 700MHz bands are more likely to cause interference than the older 1900MHz GSM frequencies.

Most devices are, at least in the US and I presume in the EU, prohibited from causing harmful interference with other devices

The EU also has regulations requiring that current equipment designs be immune to interference from common licensed communication RF sources. The interface is an older M-Audio device, so I guess no guarantee that it meets current EU regulations.