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Do you suffer from QRM?


#1

I did search the reflector for a suitable topic to post the this on, but did not find one, so I have started a new one. I hope this is ok.

The increasing problem of man-made interference on the short wave bands is a topic often discussed on the air, online & in the amateur radio press. However, Up until recently I have not experienced anything as severe as I have heard about, other than a relatively high noise level on 6m.

That all changed a couple of weeks ago, I cannot be exact with the date, as I had not powered up my station for several days prior to discovering the problem, but from the time I first heard it, I have kept a log of it. After the first few days when after going off late at night, I was not up early enough to catch its start time, I set up 24 hour monitoring using my computer.

I had of course firstly eliminated anything in my property, & due to limited time, for the first couple of days all I was able to do was take a short walk around nearby properties looking for a somewhere that the noise would peak. I found nothing conclusive as the noise seemed more or less as strong within 3 or 4 properties in any direction from my own.

Whatever the source, the offending equipment generates an S7+, 100Hz buzzing on AM mode,(S7+ mush on SSB) across the entire 80m band for 18 hours a day. On my main station aerial the noise is detectable from 2.225MHz all the way up to 5.700 MHz but is above S6 between 3.0MHz to 4.3MHz. My normal S-meter reading on 80m when the noise is not present would be zero apart from the occasional static crash, hence I originally thought it was very close by.

When I had a little more time I went for a walk & widened my search area, & found the noise detectable on a portable SW receiver up to 300m away from my property, but did find one small area where the noise was much stronger than anywhere else.

Last weekend with a little more time, I tracked down what I believe is the offending property, which is 130m away from mine, but so far have not managed to get any response from the people that live there. So for now, my sincerest apologies, but for the time being, my 80m chasing days are over, unless you happen to activate a summit between 22:30 & 03:45 utc when whatever it is switches off. HI!

I have contacted an RSGB EMC advisor, & what I had already done was exactly the approach they would take, so in the short term I need to continue trying to establish contact with the people at what I believe is the offending property.

Having only once had a complaint several years ago that I was causing “interference” to a neighbours equipment, which was easy to fix with a few ferrite ring chokes on the hi-fi cables & a braid breaker/high pass filter on the TV coax, it is a very different experience knocking on doors some distance away suggesting that their equipment may be causing me problems!

Thankfully, the people I have spoken to so far were very understanding & co-operative, so I must be going about it the right way.

I now fully understand the problems that many amateurs are experiencing with PLT/PLA & similar “QRM generators”.

For anybody interested, here is a 30 second mp3 of what my QRM on 80m sounds like using AM mode. This could be one of several things,but it is certainly something mains powered.

If you have experience of this particular type of noise, that fits with the times I mentioned above, please let me know. Any advice or suggestions will be greatly appreciated.

You can email me at

mark@brownhill.demon.co.uk

I understand that EMC issues play a major part in the current UK amateur examinations, but I do wonder…

If the main purpose is tuition along the lines of “How to deal with problems you may cause to your neighbours”, maybe more emphasis should be placed on “How to deal with problems your neighbours may cause to you”.

With apologies to the relevant people if this is already part of the syllabus.

I know of many chasers who suffer from this totally unnecessary man-made QRM from things such as non-compliant electronic & electrical apparatus, so in the absence of a more appropriate topic please post your experiences here. I am certain that any experiences you may have had, especially if you have found a solution to your own problem, will be much appreciated by many amateurs & SWL’s alike.

Best 73,

Mark G0VOF


#2

In reply to G0VOF:

Hi Mark,

This is definetly the same noise I heard when I lived in Helsby. As soon as I pulled into the close the noise went 9+60db.

After investigation, I found it was my own BT PLT/PLA system that was causing it. This was before I had heard of the problems these devices caused.

I disconnected them and used a RJ45 connection to my BT Vision Box.

And when I moved here they were about to fit them in again and I told them NO!!!

I have to put up with a extra long cable from Router to BT Vision box but this is well worth it!!

hope you sort it soon

73

Tony


#3

In reply to G0VOF:

This may be helpful http://www.rsgb.org/interferencereport/


#4

Some people might find this useful:

http://www.rsgb.org/emc/are-you-getting-interference.php


#5

In reply to 2E0LAE:
Your interference does NOT sound like PLTs. They give a very characteristic 1kHz-ish tone when received as AM, and the amateur bands have, or should have, very deep notches. Yours sounds rather more like an unfiltered switch mode power supply - computer PSU or a wallwart. I fixed my PC one by adding the omitted filter components, but that clearly isn’t an option on somebody else’s gear.

If you have not heard by the way, BT are currently recalling the existing Comtrends, allegedly because a safety issue with the plastic case but we suspect as a way of getting round the QRM issue - unfortunately the model they are replacing them with are not clean either…

73 Dave G3YMC


#6

I have to agree with Dave G3YMC here. It sounds like what I got when a ‘wallwart’ power supply went faulty on a router I had. It started causing a problem on one band and gradually spread until everything from 80m to 2m was unusable I tracked it down with my 817 on a rubber duck, but we turned off everything in the house and then turned it all back on one thing at a time to find it. Since then I have had a laptop power supply and a mobile phone charger do the same thing, although I tracked them down much faster.

Regards Steve GW7AAV

For comparison PLA interference http://www.youtube.com/watch?v=wD4ZLMLlShA
You will hear the note change as data is transfered.


#7

In reply to GW7AAV:
Driving around a built up area listening to 20m lets you hear all different forms qrm, Once out away from buildings and the qrm is gone.
I mostly operate from the car in the hills or from a summit as I can hear a lot better.
Sean W4/M0GIA/P


#8

I’m getting a similar but slightly less definite buzz on 80 metres, typically S6-7, which sure makes those 80 metre SOTA CQs at 3.666MHz hard to hear, never mind answer. I’d figured it was a problem with living in the suburbs, but having read Mark’s account, I grabbed a handy short-wave receiver and wandered around my house. The noise gets a whole lot stronger when the receiver’s whip antenna is near any of the plumbing, with central heating radiators being particularly noisy. I guess it’s time to try the “turn everything off” trick, just in case it is something as easily sorted as a wall-wart…

Edit: But I did manage to have a QSO with M/LA1DNA/P on SP-013 just now, with signal exchanges between five and one, and three and two… :wink:


#9

Strange stuff, this noise. Over the weekend I was able to listen around 80 metres without finding more than the occasional spot where the noise was over S2 or S3. This morning I can’t find a spot where it’s anything less than S4, and often it’s S7 or S8. Some of it’s definitely man-made. The rest, I don’t know. Either way, there’s not much chance I’ll be hearing Jimmy MI3EYP on 3.615 from the top of GI/CA-004 here… Oh well…


#10

In reply to M6LEP:
Looking like they were away for the week-end?


#11

Hi Rick,

Conditions were not good on 80 metres this morning when I was activating Croslieve GI/CA-004. I worked Don G0RQL and Frank G3RMD on 80 metres this morning where I received a 3 and 7 report from Don and a 4 and 7 report from Frank. I could also hear Steve GW7AAV and John M0HEM calling me on 80 metres but I didn’t manage to work them because of the conditions on that band. Before I was on 80 metres I made 2 contacts on 2 metres which means that I did qualify the summit for SOTA. I am the first activator to activate Croslieve GI/CA-004.

Jimmy M3EYP in EI


#12

In reply to M3EYP:
Glad you managed to qualify it. I could, just, hear a couple of folks who might have been talking to you, but the general level of snap, crackle and pop made it hard to decipher even their callsigns… :wink:


#13

An update on my 80m QRM problem.

Despite finding the geographical location of the above mentioned QRM within a few days of it starting, it has taken until the last couple of weeks to actually make contact with the people who live at the offending address. I had called round on numerous occasions & had never had an answer. I posted a brief note requesting that the people at one particular property contact me by telephone in order to eliminate any equipment they had, but that brought zilch.

On my last visit, I took the opportunity to take some more readings of the strength of the QRM & found it was at it’s strongest at the passageway between two properties, which would indicate it could have been either one of them.

The last thing I would want to do is annoy the people who live at either property, as their co-operation is vital in resolving these matters.To move things forward I draughted a more formal letter which explained the problem, & asking them to contact me by telephone at their convenience. I also added that if I could not resolve the issue myself I would need to report the matter to Ofcom, who may well levy a charge for any repair or replacement of the offending equipment.

Last week I walked round to the properties again with the intention of posting these letters if I did not get a reply when I knocked on the door. As with many places in the UK, we have had some snow recently, & as I approached the properties I saw a young couple (well younger than me anyway) clearing Snow from their car.

I could see that they lived at one of the properties so I introduced myself. In my opinion, it is always preferable to deal with people face to face. I explained the problem & that I suspected something electrical in either theirs or their neighbours property. I mentioned some possible causes & that whatever it is, it is controlled by a timer & I gave them the times the equipment currently switches on & off. I also mentioned that this only started at the beginning of October.

Straight away the gentleman said that those times correspond with the times his heating operates, & that they had only lived there for a few months. He even mentioned that he had suspected something might be wrong with his heating system because it was quite noisy. I am not sure in what way it is “noisy” but it was looking very much like this heating system was the culprit.

The couple were quite taken aback that their heating could be generating such interference & were most co-operative. If the weather had been warmer I am sure they would have agreed to switch off their heating altogether if I had asked them to, but that would be absurd in the current conditions & I would not ask them to anyway. I did mention that it causes me the biggest problem on Sunday mornings when I read the GB2RS news for the North of England on 80m. The gentleman was more than happy to alter the “on” time of his heating by hour which would at least allow me to hold an “after news net” when it is my turn to be Newsreader. I left a copy of the letter with them & asked them to call at their convenience if he wanted to do some tests to ascertain if the heating system was at fault.

Last Sunday when I read the GB2RS news for the North of England, the QRM was not present until after 12 noon, plenty of time for an after news net & well over an hour later than it would normally start.

Since then, I have had a call from the couples landlord, who also is being co-operative. I have of course mentioned that as a licensed radio amateur I am “trained” (The self training I have done has proved more useful HIi), in identifying & curing sources of interference, & that there is a wealth of knowledge available from people who specialise in the subject, for example the RSGB EMC Committee. Advice from them & from me is available free of charge to any electrical or gas engineer the landlord brings in to look at the heating system. It is quite possible that an engineer would find nothing wrong, as the installation probably works fine for it’s purpose, but obviously, it should not be transmitting broadband noise across a large chunk of the HF spectrum :wink:

So, in summary, a good result so far. I have found the definite source of my QRM, I have co-operation from both the householders & their landlord, & can operate on 80m when I need to the most.

Not a complete resolution yet by any means, but I am more than happy with the current arrangements until the heating system can be looked at in the New Year, preferably when it is warmer. I am certain others would have got to this stage sooner, & I am also sure some would have gone too far & been too aggressive early on & got nowhere.

“Softly softly, catchee monkey”

Maybe not world Peace, but I will be happy with this result for Christmas :slight_smile:

Merry Christmas & a very Happy and Healthy 2011 to all!

Best 73,

Mark G0VOF


#14

In reply to G0VOF:

Well done Mark. I fear that I have a PLT problem and so will have to follow your lead!

73

Richard
G3CWI


#15

In reply to G3CWI:

You have my sympathy Richard, those things are the bane of so many radio amateurs.

I hope you manage to track down the source, it will not be as easy to find as mine was given PLT’s intermittent nature, but if it is a new piece of kit in an otherwise quiet environment, you should be able to find it.

Once found, it is the co-operation of the owner of the equipment that is the key to curing it.

Best 73,

Mark G0VOF


#16

Well, I have to say, the past two weeks have been marvellous. This may be due to the couple at the offending property being on holiday, but in any case, my severe 80m QRM problem has not been present since just after Christmas :slight_smile:

What this absence of the severe QRM did un-mask, was the general level of QRM caused by devices within my own property, that for the past few months I wouldn’t have noticed.

A couple of nights ago I found that despite my main source of QRM being absent, I still had an unreasonably high noise level on 80m, better than over the past few months, but still higher than it should be.

I decided to investigate this & found that switching off everything in the house one by one, & then finally switching off the mains I could reduce the noise to a quite acceptable level. While powering things up one at a time, while avoiding a source of QRM I already knew about,(My Broadband Router), I found that a simple re-organisation of some power cables, as well as disconnecting an item in the shack that was not being used although still powered up, reduced the noise significantly.

It has been very nice to be able to work on 80m again with normal noise levels (for a built up area), but still I had the switched mode QRM from my Broadband router which was now more obvious on both 60m & 80m, as well as completely obliterating 160m.

For some time I had intended looking at the router to determine why it produced such horrendous QRM that meant that if I wanted to use 160m I would have to switch it off. The most obvious culprit would be the plug-in-the-wall power supply, a small switched mode type as they all tend to be these days.

Earlier today I decided to investigate & found that the Router only needed 12Volts DC at 1 Amp to function, so I found a handly partially discharged Slab & made up a lead with the right plug to fit the Router. I pressed the power switch & the router fired up without any problems, & lo & behold, absolutely no QRM anywhere in the HF spectrum :slight_smile:

Of course, I could have left it at that & swapped over to battery power whanever I needed to use top band, but a more permanent solution would be better.

After sourcing a few 12V regulators on the internet with a view to building a new power supply, I realised I must have an “old fashioned” Transformer & regulator circuit type 12V 1A regulated power supply knocking around & a very quick search of the shack produced such an item.

So, with a nice clean “Proper” power supply, my router no longer produces any QRM & I can use top band, without having to power it down. This has also made 80m & 60m much quieter and apart from a sproggy around 1990KHz from my Freeview box (which I can switch off very easily), & a similar sproggy around 3777KHz which I think is external to my property, the HF bands are now as noise free as they should be :slight_smile:

So today, I have succesfully chased Carolyn GW6WRW/P, twice on 80m SSB & even had some good results on Top band SSB after this evenings GB2RS news, being able to work up to Edinburgh & down to Yeovil in Somerset with just 32 Watts of SSB into my very poor top band antenna. And all without powering down my router :slight_smile:

What this does now mean is that when stations do activate on 160m, I will be able to spot them much quicker as I will not need to use SMS, or connect my PC to the net using a mobile dongle in order to do it.

So maybe something as simple as a “proper” clean power supply to some of the electronic gear in your property could reduce your noise levels. Companies only supply the small “Wall-Wart” switched mode power supplies now because they are much cheaper to manufacture, not because they do the job better that the old fashioned, and heavier, transformer, recifier & regulator circuit type as they all were some years ago.

All in all a very good day, I shall go to bed a happy man tonight :slight_smile:

And it was my Birthday too :slight_smile:

Best 73,

Mark G0VOF