The 'Sweepers' are taking over the band

[G3LVP]

This evening there are two of these 'sweeping' noises on 4m, one sweeping from 70.180 to 70.250 and the other between 70. 430 to 70.460. Both are S9+ and seem to originate from houses approx 1/4 to 1/2 a mile away.

I've made recordings of these noises if anyone wants to hear them & compare notes. I still have no idea what equipment generate this QRM although I have my suspicions.

I lose interest in the band when these noises are present which seems to be a large part of the time at the moment.

I'm now almost driven off 2m by a different sort of QRM.

Back to HF it's almost quieter.

73

Ken G3LVP

[G7CNF]

Until the PLT takes over...

You have my sympathies Ken, I also suffer from a plethora of "transmitting devices" which seem to love hogging the more important frequencies at just the wrong time. Having gone to some considerable trouble to eradicate QRM from SMPSU's in my home and PC equipment (originally band was S7 broadband, now S0) it seems that EMC issues are set to take over.

I can vouch that for VHF, the homeplug style of PLT can be disruptive (for HF quite devastating in some frequencies) and like other areas of electronics it seems that the marketplace is being flooded with kit that is marked 'CE' but that certification is often dubious at best.

All we can do is club together and pool our knowledge and discoveries. The new page here http://www.70mhz.org/uss.htm I feel will be an important contributor, I hope it stimulates an interest in a movement to stamp out some of this annoying QRM.

Like you say, sometimes it all gets too much and although we have a string affinity for this band, one can't help but throw one's hands up in the air sometimes and say "what's the point?"

But why should we have to switch off????

GL Ken, I hope you get your trouble sorted.

73

Nige.

[G3LVP]

Apart from the noises on 4m there is an S9 'signal' on 144.256 which I believe comes from a neighbours house and sounds like 20 wpm CW 'dot's', there are weaker versions of this signal on other 2m frequencies. Just goes to show what a joke CE marking is.

Ken
G3LVP

[G3PTU]

I'm in West Yorks - so you think that whatever causes these Sweepers would be present here.
So - they are present but at a low level (thank goodness) and apear to be NE of me. (These are slow moving CW products )
To 'see' them you really need Spec lab.
Now in Brittany France I cannot see them at all, I've looked to make certain. Very ocationally you can beleive there is one, so low down its dificult to be shure.
Yet in the SW of the Uk Nige for example says they are S9.
What really needs to be done is to find out where they are, maybe some of our devoties should liase to try and DF them?. Maybe it is something thats sold only in that area? Water softeners or indeed what have you? -or- are they further away? Have you tried asking Ofcom? because until you know what they are you cannot do anything about them. Maybe you should ask Ofcom to find them (or it) and then you would know.
I must agree and have long been of the belief that the CE mark is being abused. Perticully is the matter of Switch mode PSU's, I recently found one from 'LaCie' ( a reputable company) spraying out hash. I E-mailed them and got an enthouiastic reply, but since then nothing. Must mean they have to spend money. I would not mind but in 90% of the cases Ferrite cures the problem.
It reminds me of some years ago, in a Renault car we had the electric fuel pump ruiening Long wave reception. After a pump change with no improvement -A 0.1u across the pump cured it. Renaullt however blamed the poor coverage of Doitwitch for the problem and told me to 'REMOVE' the unauthorised modification. The person I phoned could not grasp that whatever the coverage of Doitwitch there would always be an area where the pump interfered! They had paperwork to say the Pump did not interfer with Radio! - et Walla
David G3PTU

[G3LVP]

I spent some time investigating this QRM a little further, I'm fairly certain that one source comes from a group of houses about 300 yds. away although just using the mobile whip I couldn't identify exactly which house. The next move is to go round with a DF loop and see if I can localise the source but what do I do then?

This particular sweeper was centred on 70.318 today and there was another on 70.381 which I couldn't localise. As these sweepers have a sweep rate of about 1/s pinpointing is a bit difficult without a wide band RX and pan display.

I did a quick search around 70 MHz to see if I could find any others and found five more on 68.36, 68.52, 69.29, 73.64 and 79.58MHz all with the same characteristic sweep and T3 note. I'm fairly certain that they aren't all coming from the same location, the sweeps don't start at the same time. Perhaps I'm lucky that they are so badly designed that they aren't all in the 4m band which would be totally unusable if they were.

Surely I'm not the only one who can hear these things? The one on 70.318 is S9 on the beam and about S2 on the mobile outside. When I drive closer to the source the sweeper is S9+ on the mobile RX.

I guess that these devices are some fancy modern gadget which the sensible folks in Yorkshire don't waste their 'brass' on.

73....

Ken

G3LVP

[G3PTU]

I'm in France at the moment and today 2000UTC there was a powerful sweeper on 'the lower end of 4m'. However investigation proved that it was not there but on 28Mhz the IF.
I was not able to discover what or from where it was generated.
Up to now I have not seen any 'sweepers' around 70.2Mhz
Antenna faces north from Rennes.

Wednesday 090708 in the late afternoon the band was S9 full of East Europe Radio signals. This apeared as a scratching noise at first and developed into a full blown opening for perhaps half and hour. There was also a T9 strong carrier on about 70.1Mhz. No amateur signals where heard.

During the field day there was a number of Amateur signals to be heard all with deep QSB. Unfortunatly one station S9 was only heard breifly as I was out of the shock and retruned as he signed. presumably he was not a pirate in France?!
David G3PTU

[G4MDC]

28 MHz sweepers used to be 27MHz RF Diathermy units or RF heaters/welders which had lost their original QRG, These things always swept low to high. They were never intentionally swept they just drifted that way as they heated I think.

Their harmonics did likewise and played merry hell with anything nearby up into VHF.

They were troublesome in the old LB AM police RX band and were certainly present in 2m once upon a time.

[G3PTU]

I should have remembered that ( or those!)
This one drifted low to high, but whatever it is must have been some distance away as the QTH is in the countryside.
The cable from the converter to the prime mover is very short and of couse screened. So it must have been a big signal. Might be from a Yorgurt/ Butter/ Cheese [Bridel] factory in next town, this certinaly pumps out a high noise level, witness driving past in car. I know F4SGU who works there, the place is full of Thyristers etc for the computor to control the 24/7 proccessing.
Signal Not present today, but neither is the eastern Fm stuff.

I have made up a mains filter to get rid of a local MF radio station out of the audio system etc. These have lowered the noise floor about 1/2S point as they are also in the saterlite rx mains feed. A moral somewhere I think.
David g3PTU

[G4MDC]

Very glad to have stirred up old memories - even if not that pleasant.
Raw AC note was another characteristic. 1/2 wave rectified because too cheap to afford the other diode or a bigger reservoir cap

[G3PTU]

The mystery resolved, but only to an extent.
It apears that the Sweeper on 4m (28Mhz) see previous thread, originates in one of my recievers! Its a Kenwood 140. It not only effects that unit in use but rediates freely around the house.
What it is, or why its there for the moment has to be left as is. The reciever works FB and non of the front panel controls apear to alter its apearance. I can now power everything else back up in the house.
David G3PTU

[G3LVP]

Further investigation seems to indicate that the fundamental frequency of the 'Sweeper' that is causing me so much QRM on 4m is 35MHz and what I'm hearing is its second harmonic. As the source appears to come from a residential area I doubt that it's any sort of RF heating device (e.g. a plastic welding machine).
Curiously the noise on 35 MHz is stronger on my 2m vertical than on the triband HF beam. On 70 MHz it's S9+20 on the 6 ele horizontal Yagi but only S9 on a coax dipole. Unfortunately this noise is now on or near 70.2 MHz for much of the time making QSO's on this part of the band almost impossible.

Ken

G3LVP

[G3PTU]

Being residential, Burgular alarm or Central heating control unit is a posability ( I seen these things, they are to avoid putting control cables into houses and are all the rage in the DIY and profesional fit in 5 minutes camps ).
Also 'touch adjust' lamps, these are beside lamps you simply touch to adjust the briliance. The construction of these is abserlute crap.
Which ever, perhaps the time has come for Offcom as it would apear the second harmonic is very lardge.
David G3PTU