The 'Sweepers' back

[G3LVP]

After a few months through the summer the 'Sweeper' which I've reported in the past has now moved down the band from the FM section to sweep over the SSB section sweeping from about 70.180 to 70.230 at a rate of about 1 c/s, this signal is present 24 hrs. a day.

When I beam towards the source (SE) which appears to be in an area of houses about 4 - 800 yds. away it's S9+10. In spite of walking round with a scanner I've not managed to pin the source down.

There are at least two more of these sweepers which I can hear around 67.63 & 70 97 (in the band used by Fire & Rescue), way down on 20.86 there's another at around S4. These sweepers all have similar sweeping characteristics and are all T3 modulated by 50 c/s mains hum. They don't appear to be directly related either harmonically or exact sweep rate.

As the temperature is only a chilly 3 deg. C. this morning I assume that the source which I hear on 4m is affected by temperature and as the WX warms up hopefully it will drift back up the band.

Whilst there's not much hope of getting these annoying QRM sources turned off (imaging knocking on 'Joe Bloggs' door to ask what electronic kit he has....I'm conducting a survey!) I'm really curious to know what devices causes this QRM, they obviously aren't intended to radiate and can't be compliant with EMC regs.

Surely this is not the only area where these things can be heard? I would be very interested to hear any reports of similar signals.

73...

Ken G3LVP

[G3PTU]

I cannot hear similar "sweepers" but can see them on [say] 'Speclab' in West Yorks.
Very low level
I think these will be some from of non stablised remote control stuff, possibly remote control bedside lamps? [ yes you can get these!] off supri off cordless burgular alarms / Weather thermostats.
If you look at some of this stuff, you wonder why things are not worse than what they are.
I Would not adise you to knock at the door, if you value your teeth, most people probably, quite rightly, beleive that what they have spent their brass on is Ok to use.
In any case they do not see why they should not use anything at all, like driving above the speed limit!
Remember every simgle component in what ever it is has been sruitinised to see if the thing would 'work' without its presence.
David L G3PTU

[G3LVP]

David,

Thanks for your comments, I believe that most 'approved' low power remote controlled equipment like car key fobs, bathroom showers (!) etc. operates around 433.9 MHz (I wonder which idiot approved that frequency?).
I wouldn't expect any of these equipments to be causing QRM on lower frequencies and in any case most of the TX's appear to be crystal controlled. I've recorded a WAV files of these 'signals' if anyone wants to hear what they sound like let me know and I'll email the file (I don't have a web page). Now that it's a little bit warmer (8 deg C) the in-band sweeper has moved up and now sweeps from 70.21 - 70.3 MHz.

73...

Ken G3LVP

[G8YMW + M0LUY]

I think you're right Andy. These used to be on 409 MHz (I think) but shifted up to 70cms because of PMR QRM.
Lucy and I found this out at the NEC a few years ago during Naidex (An exhibition of equiptment for disabled people, carers and professional carers, NHS, Local Government et al)
BTW Lucy has a vested interest , she pilots a wheelchair.

[G3LVP]

I'm under the impression that 433.9...has only been an ISM frequency in fairly recent times. I doubt if it was in use when I had my first 70 cm QSO back in 1957! In any case it would have been a bad choice as some of the high power RF heaters on 13MHz used to radiate harmonics all over the place.

73..

Ken G3LVP

[G3TCT]

Ken
When I was on the band a few decades ago (!) I used to hear these things regularly and the received wisdom at that time was that they were plastic welding machines. I seem to remember someone investigating and finding they ran a kW!

73
Graham G3TCT

[G3PTU]

Back in Yorkshire; and last night there was one on 4meters very low level at this QTH. Time about 21-2200Hrs UTC. Very nice Clean and T9 on Speclab.
Came from the heavy engineering area of Leeds, North East of me.
It could be that they are some form of thermic welding, but as far as I remember and certinaly last night, they only go HF, very liniearly at the rate as mentioned of about 1Hz/Second. Do they ever turn around and come back?
On the other hand, quoting our colleges posting why would such a proccess be used in a house? Only a thought, but could it be the form of oscillation found in cheap Fillament lamps (remember band I tv days??). Forget the name but PL81's used to do it as well (Barkhousen??).
David G3PTU

[G3LVP]

Interesting thoughts,

G3JFH (sk) used to maintain RF welders & I remember tales about the early ones which were very crude devices however there's no sign of the sort of QRM that these machines used to create anywhere in the 13 - 14 MHz region which would multiply up to 70MHz. (the frequency would shift as the plastic items being welded were brought into the RF field).

If the offending device is running a process h24 in an ordinary house I would be surprised as it would be turning out a lot of widgets.
My suspicions are still focused on either a burglar alarm (may be an outside unit therefore subject to temperature changes and also high up on a house connected to long lengths of cable) or a 'scale inhibitor'.

I can't find any technical details about these devices other than the fact that they generate RF and the lengths of 'ariel (sic) wire which 'transmit variable frequency radio waves creating an electrical pulse in the water' look suspiciously as if they would resonate near 4m.

One company which sells them admits to knowing nothing about how they work as well as not being able to spell.
see:

http://www.tradeplumbing.co.uk/assets/i ... ibitor.pdf

The manufacturers website is even less informative and avoids any mention of transmitting.

http://www.calmagltd.com/artman/publish ... e_11.shtml

I must make some more enquiries about these units.

If it weren't for the fact that these things cost £50 probably don't work and anyway we don't need one I would but one just to see what was inside the box.

73...

Ken G3LVP

[G1HBE]

Hello all. I've just returned to 4m after a break of a few years, and I've noticed the band is considerably more noisy than it was when I left. I now have a low level 'grrrrrr' noise all across the band, with peaks every 100KHz. I suspect these are harmonics from a switcher power supply. Sometimes it's not so bad, other times it destroys weaker FM stations.
The sweeper is quite strong here in north Cheshire, and drifts across the band quite quickly, appearing on a channel for a couple of seconds before moving off.

Andy.

[G0MJW]

Are these the same ones bugging me? Sounds like data and it is actually the second harmonic of a signal at 35MHz. I think they are alarms for immobile people. If it is the same they are very annoying and considering their fundamental frequency is in the model aircraft control band, probably illegal.

Mike

After a few months through the summer the 'Sweeper' which I've reported in the past has now moved down the band from the FM section to sweep over the SSB section sweeping from about 70.180 to 70.230 at a rate of about 1 c/s, this signal is present 24 hrs. a day.

When I beam towards the source (SE) which appears to be in an area of houses about 4 - 800 yds. away it's S9+10. In spite of walking round with a scanner I've not managed to pin the source down.

There are at least two more of these sweepers which I can hear around 67.63 & 70 97 (in the band used by Fire & Rescue), way down on 20.86 there's another at around S4. These sweepers all have similar sweeping characteristics and are all T3 modulated by 50 c/s mains hum. They don't appear to be directly related either harmonically or exact sweep rate.

As the temperature is only a chilly 3 deg. C. this morning I assume that the source which I hear on 4m is affected by temperature and as the WX warms up hopefully it will drift back up the band.

Whilst there's not much hope of getting these annoying QRM sources turned off (imaging knocking on 'Joe Bloggs' door to ask what electronic kit he has....I'm conducting a survey!) I'm really curious to know what devices causes this QRM, they obviously aren't intended to radiate and can't be compliant with EMC regs.

Surely this is not the only area where these things can be heard? I would be very interested to hear any reports of similar signals.

73...

Ken G3LVP

[G3PTU]

If you suspect "Invalid alarms" Let me recall this again through these pages.............
Some years ago I was aproached by a neighbour who said that this "cordless phone" ( this is in the days of the analouge systemn) did not work. He in no way blamed me, simply asked my advice.
It was true that his cordless phone would not work in a lot of places in the house, however in others it was OK.
So I tried a Fm radio and found that the background was covered in a sort of chuffing mess.
Now another nieghbour asked my advice as well, she was in her 90's and relied on her cordless phone, but she had a dongle around her kneck.
So we went looking and found that she had a similar analouge unit to the first chap. In Her house the phone did not work at all.
We took the chaps phone to her house and it did not work at all. Next was to swtich off the base unit of the dongle contraption - all the problems cleared. So I rang the local authority and found a completly untechnical unhelpful woman on the other end. She said unless It did not work at all ther was nothing they had to do, after some time I got hold of her boss and who only after threatening Ofcom the regularoer did she agree to send an engineer. I feel sorry for this bloke who arrived. He had a laptop and a 2p scewdriver. He ran the laptop and said all was well, so we illisrated the problem to him. His reply was that radio and cordless phones where incompatable with his alarm system and as such there required replacement / modification!
We said he should get another unit out of his van and try that - his reply was that the companies policy was to never admit to anything, they know nothing about radio and had no test equipment. It was against his orders to replace any unit for any reason. What was a major problem for him was that the spare unit out of the van did not produce hash all over the place. The base unit which was mains powered also had no PAT testing cerficate, another fact that went over the companies head or wallet.
I told him that if he wished I would get Ofcom to deal with them and as such because he was refusing to fix a known fault they would presumambly deal with him [them] severly. He said he know nothing about Ofcom and did not recongise them as any authority. So we bundled the old unit up, put it in his hand and through him out of the house. He protested about this job and getting the police etc then drove away.
I got a telephone call from the local authority saying that had been billed for this replacment and their lawyer would be in touch - nothing hapened.
The device was crap, the engineer was crap and the other two parties appear to be crap. I live some doors away and the noise level went down on 4 meters so I was pleased. Beware with these you are dealing with the really low end of the market, run by disalutioned idiots.

David G3PTU

[G3LVP]

[quote="G0MJW"]Are these the same ones bugging me? Sounds like data and it is actually the second harmonic of a signal at 35MHz. I think they are alarms for immobile people. If it is the same they are very annoying and considering their fundamental frequency is in the model aircraft control band, probably illegal.

Mike

Mike,

It sounds very much as if this might be the same sort of QRM, I only recently discovered that the 'signal' that I hear on 4m is actually the second harmonic of a fundamental down around 35 MHz. I don't think that there's any intelligence on this 'signal'. Its frequency stability is so poor that I doubt very much that it's intended to be received. I don't know much about the 'pendant' type alarms for the elderly but I think that they operate on VHF and in any case only transmit when the button is pressed, I also doubt that they would have the range that this particular device has (in the order of 300 yds). Perhaps we'll get to the bottom of this particular source of QRM one day.

As you say the 35 MHz band is allocated to model aircraft control.
In passing I see from the UK Radio Control Council site (http://www.ukrcc.org/) telemetry - model to operator - 'the band 433.05 to 434.79MHz is available using approved radio transmitter and receiver modules.' and 'For aircraft use, 434.025 to 434.775 is recommended'. Not a popular choice with 70 cm repeater users but fortunately most models don't stay up very long, however I'm not sure that the use of this band for airborne use is legal.

73...

Ken

G3LVP

[G3PTU]

I agree the penants 'tx' when the button is pressed. The problem we had was the rx - presumably super regen.
It was not the psu, that was linear not Switch mode and was a plug in 'lump'. Most of the crap apeared to come out of the telephone line port.
David G3PTU

[GI0GDP]

I think alot of modellers would be upset by the comment that they dont stay up for long !
Most of the serious fliers have moved to 13cm spread spectrum, and i think the UHF alocation is 459 MHz, anyway mine is.
regards
Geoff Pike

[EI2IP]

My heli's on 2.4Ghz....exact qrg not sure.