I have noticed that my Reliance gets a fair bit of interference at the moment. On switching my other radio ( AWA MANTLE ) on it gets the same but to a lesser degree. Both of them have the new three core power cable. I'm thinking that it may be a dirty earth problem. Is there such thing as a line filter to fix this. I'm thinking about getting some goat shields as well.

Welcome to the modern world where the regulators are asleep at the wheel & you can import any piece of RFI generating junk you like with impunity.

Well built valve radios can pick up lightning for hundreds of Kilometres and are by their nature very good at picking up RFI. Now you have to find the cause and where it is actually getting in, and what is generating it..... pain.

I have acres of 24KV aerials & because of there length & lack of devices to get rid of standing waves. they bring in a lot of RF. Where a set has no decoupling cap or Paper Filter caps have been replaced by Electrolytic this RF can get into B+. Some mains earthing can be dodgy & Silicon Chip did precipitate a lot of discussion on this. At my previous abode I had that solved by tying it to a 125ft bore casing.

The big enemies are the switchmode wall wart & its mates, in computers etc. & I did have a FAX with one getting into the 175kHz of an Autodyne (dirty in themselves); Brush motors & switches are in there and then there is one of the dirtiest: The Compact Fluro. America is having the same issues with them and they are also questioning how such a dirty RFI generator was allowed to be sold? I would love to know the environmental carbon figure on these. A globe is at least a clean resistive load & not a dirty inductive one & its bits are 100% recyclable even if it is an inefficient light producer.

In order to solve your issue, which if you are in city will be a big one ... I,m not: You are going to have to do some research. In my old workshop, one could not calibrate, or get decent DX with a CFL running. In the new you cannot calibrate or get DX with the garbage set top box running, nor one particular Switch Mode wall wart. There are no CFL's

To get rid of Spikes & RFI from the mains I have a few strategic, custom filters. Two of which actually killed their circuits recently ....... which is what they were built to do if it was a big spike. These contain MOV's & capacitors & are in metal boxes in case the MOV's explode.

Mains noise can often be proven by using a 0.01mfd cap to short out the aerial terminal.

Marc

Funny this topic should be raised today, as I have just tonight been scanning the area around my workshop with an AM transistor radio tuned off-station to try to locate the source of some serious RFI that's appeared of late.

It's strongest outside the mains switch room, but it's also very strong in some other areas including my workshop -- which is a few metres from the switch room. It's also very strong outside the mechanical ventilation room and is quite apparent at the carbon monoxide sensors in the carpark.

The RFI itself sounds akin to a single cylinder 4 stroke engine with loose tappets running at about 2000 rpm, so I'm guessing the source is electromechanical.

I'll have a closer "scan" in daylight when I have the keys to those rooms at hand.

It's so bad that I'm going to try to get ACMA to investigate it. (Yes, I realise that ACMA is just a bunch of bureaucrats -- with probably not a single radio engineer on the staff -- but responsibility for such things rests with ACMA.)

Do remember that a transistor radio loopstick is directional & you can null. The fax machine here was using the common phone line to get into the workshop.

Always fun trying to find these things. The frequency can be a dead giveaway. I was at the local hospital where a TV had managed to get off frequency. It was picking up the slow receive send of the routers. so it could be monitoring equipment, sampling & sending? At that speed it could also be a DC motor that has a shorted armature winding. Not overlooking pulse width types in air conditioners etc. & proportional heaters in Lab ovens (relays).

Any Mercury vapour lights? Might have a dud. One could also reverse engineer the maintenance files to see what has been installed, or messed with around that area. I seriously doubt the C2O2 sensors will sniff it out.

Marc

I use my trusty Sony SRF-S83 that I've owned since the 1990s for such DF work:

http://attachment.imp3.net/forum/201212/22/212500z2h8zk6ok549k19e.jpg

It has fantastic selectivity and sensitivity and it is quite effective for DF work on AM. I have also used it a number of times for underground cable tracing, with a sig gen on one end of the cable and sweeping above ground for harmonics on AM.

The point I make about the CO monitors is that the RFI is apparent at them, that is, their cabling is acting as an antenna, and it is the only cabling in the common areas that's at readily accessible level to me, the rest being in cable trays at roof level.

There are no mercury vapour lights, but there are industrial units in the complex with manufacturing and refrigeration equipment. Whatever it is, it's running 24/7.

From the outside of the switch room, the strongest RFI signal comes from the wall on which the supply meters are mounted. Once I get into that room, I'm hoping that I will be able to DF an identifiable unit number.

From the nature of the RFI, I am expecting to find a motor -- or a rotating something -- as the source of it, but I'll probably need an ACMA inspector to help with that. Problem is convincing them to attend these days. The RFI report form is buried deep on their website.

LED lights cause some RFI, but not as bad as the CFL ones. At my old house the circular fluro lights in my radio room was the biggest cause of RFI I found, so I used to sit in the dark searching for short wave stations.

Im not sure how the traditional fluros I have here now will fare, as I'm not quite set up yet

ACMA seems to be a toothless tiger of late. I beleive theres only a handfull of Inspectors left.

Even with commercial systems, the response to RFI is pathetic. Ive had issues with emergency services and basically you have to find the source yourself. They don't seem interested in small fry, its all about broadcast and telcos

Best of luck with your search, it can be frustrating.


Ben

I have not caught the two dumb meters here generating RFI, but there is plenty of RF on the mains. I have a timer here similar to what is used in "Star Delta" starters & I use that for timing out batteries on charge. It generates RFI & I ended up using a resistor & cap to cut it's voltage & decouple it, to shut it up.

It sounds like a task. It took me about an hour to get the FAX machine 20 metres away in the house, the problem being 200kHz. But I had the advantage of knowing that.

There May be DIN rail timers in the box (with switchmode) running security lights? If it's a metal box I wonder then about its ground? Some ferrites around wires may be in order. Plus some Mains type caps, like I have here?

On the obscure, I did have a circuit breaker (2 years old) get picked up for buzzing: Apparently faulty & replaced (still have it).

Marc

Okay, I reckon I've identified (from the outside) the unit that is producing the RFI. It is so strong that I can detect the RFI being reflected in the complex's kiosk transformer on the street.

I managed to catch the owner of one of the neighbouring units and he said that the unit in question has installed some additional refrigeration equipment a few months ago, and that tallies with when RFI started to become and issue for me. Refrigeration would also tend to explain why the RFI is 24/7.

Tomorrow, I will have a word with the manager of the business involved and demonstrate the effect the equipment appears to be having on the AM band, and to some extent FM, too. Hopefully, he'll then see reason and agree to have the equipment checked out.

You may also be able to get ACMA onto this, If that is the source. There were regulations re RFI brought in back in the early nineties, so it may fall onto the supplier of the non compliant equipment to get rid of the RFI.

It might be a first: As I said there are likely tens of thousands of non compliant new devices out there.

Marc

HVAC motor controls involve variable speed drives which vary the speed of motors inside air handling units by altering the supply frequency rather than the voltage or clipping the mains waveform. The wiring to various sensors such as CO sensors, CO2 sensors, air flow sensors and thermocouples would indeed act as transmitting antennas for all this 'dirty' power. Unfortunately for us, what we don't like is loved a lot by an electric motor.

This form of control is standard for HVAC but also lifts and escalators these days.

Now for the bad news - I doubt complaining to the AMCA will bring relief. Worst case scenario will be that the building manager could be forced by a court to turn off any equipment causing interference. He then does so and then will say he can no longer provide an OH&S compliant premises due to the lack of forced ventilation resulting in the building being closed down. The occupiers then sue because they either own or rent space on a strata title. The building manager then in turn sues the air conditioning company because they can't supply equipment that doesn't emit interference. Equipment such as universal motors and bleed resistors are no longer made so there is no alternative anyway. The problems and the problems that follow would go on until well after we're all up there in the sky.

Brad: I won't know for sure until tomorrow, during business hours, but my guess is that the source of the RFI is the refrigeration plant in a particular unit. As I said above, its installation (apparently) coincides with when I began to have issues.

I hope to be able to persuade the business owner to temporarily switch off his refrigeration while I have my "scanner" operating on the spot and see if the RFI disappears.

The unit in question is leased and, if necessary, I can lodge a complaint to the owner via the Owners Corporation of which I am a member. However, I'm hoping that the business owner himself will agree to having the equipment checked out, as it's demonstrably creating a very large amount of RFI that can be detected in half of the complex over three levels, and even in the Ausgrid kiosk.

Well, I do hope that is the cause because it should be comparatively easier to get stopped. Good luck with it.

Jaycar recently had a LED desk lamp on sale....model QM-3546, I'd always wanted one these magnifiying glass type lights that can pivot around on your desk.....so I eagerly grabbed it.... Plus the idea of LEDs as the light source made it all the more appealing!
Now usually while I work on a radio...or at this moment a valve characteristic tester I will have one of my radios going in the background but this lamp obliterates the reception on my AWA R82W & any other in close proximity to the lamp. In the same room I also have LED downlighting which also wipes it out & low behold so do my LED floodlights outside to a lesser degree!! Stuff is made so cheap these days filtering to prevent RFI is just not considered cost effective.....the number of people listening to AM radio is probably a dwindling statistic, everyone at least in the cities is going digital or streaming straight through the web....
Sad sign of the times! Will have to try & filter it out somehow....... :/
Any hints on this greatly welcomed!!

Well, the mystery deepens.

Today the manager of the suspect unit kindly showed me through the whole place and, using my trusty AM radio, I checked every piece of his machinery, including numerous cool rooms, and found none of them to be generating RFI.

However, the RFI was very apparent on the his 3 phase riser which runs up the inside of the front wall of his unit -- the place where I got a strong reading over the weekend.

He expressed interest in seeing my workshop so I showed him around and he took note of the effect the RFI has on my territory and its surrounds.

I also got access to the various service rooms, including the switch room, ventilation room and fire pump room, but the RFI is so strong everywhere there is mains cabling that I am unable to zoom in on a particular source.

The fact that it is also strongly apparent outside the Ausgrid kiosk transformer now makes me wonder if the transformer itself is the source of the problem. The neighbouring transformers are quiet by comparison. However, the frequency of the RFI smacks to me of a mechanical rotating source rather than, say, an arcing source that you get from bad switch/fuse contacts or dusty high voltage insulators.

I did find a noisy pump in an air conditioning plant across the road but its RFI is a different frequency from "mine", and also it fades as I move away from it.

Anyway, have obtained the phone number of the relevant Ausgrid service inspector/engineer for my patch and will call him tomorrow to discuss the issue.

It may be beneficial to have a look at the transformers at night (is it wet there?). I had a problem like that that at the previous abode, which I considered to be arcing as it had happened before, but with more acoustics. I knew it was not the ground rod as I had tied the earth to a steel bore casing.

What I spotted one damp night was a 24kV fuse holder flashing over. Could not convince Ausnet that it was faulty; However, as this type was implicated in fires, after the Vic Bushfire Royal Commission they were changed & sure enough there was the tell tale brown line down the edge of the insulator of one where it had been tracking across.

Often these will "hiss" like the corona discharge of the wires of really HV Transmission towers.

Marc