Switcher interference

I was tuning around the top end of 10m yesterday and noticed a lot of strong bubbly warbly noises, the unmistakable sound of switched mode power supply interference. It didn't take long to track this down to the power supply for my QNAP TS-109 Turbo Station.

The TS-109 is a network attached storage device. But it is actually a small computer with a big hard drive, running Linux. I use it mainly as a backup drive for all our PCs, but it also hosts the shared documents folder so that we can easily exchange files from one computer to another. It runs a script that updates DynDNS when our IP address changes, which it does quite often at the moment. I could even run a web server on it if I wanted. So it really needs to run all the time. But the amount of interference it produces isn't acceptable. I tried adding some clamp-on ferrite suppressors but they didn't make much of a difference.

The power supply for this device is a plug mounted switched mode supply rated at 12V 3A. This is probably over-generous as the specification for the TS-109 gives the power consumption as 14.4W in operation. There are plenty of alternative 12V switched mode supplies available but I have no way of telling whether they would be better or worse than the manufacturer-supplied one as regards RF interference.

The only transformer based power supplies capable of supplying this sort of power are CB radio power supplies such as those sold by Maplin which have a 13.8V DC output. QNAP doesn't, unfortunately, specify a voltage range for the Turbo Station so I don't know if this higher voltage would be permissible. It would be very convenient if I could use the power supply I made for my QRP K2, which these days just keeps the K2's battery charged up, but the output from that is 14.2V.

Switched mode power supplies really are the bane of the radio amateur's life. I don't know how to solve this problem at the moment, except to switch off the TS-109, which is inconvenient.

Noise generator

I heard nothing during my attempt last night to receive signals from KP4AO bounced off the moon. Nothing, that is, except a lot of noise. Sitting at the bottom of the garden with my newly constructed hand-held 6 element 70cm beam, the Moon was above and just to the left of the roof of our house. And the nearer I moved the beam to the house, the greater the noise. This house is truly a disaster area for radio reception!

This afternoon I thought I would try to see where the noise was coming from. With the beam horizontally polarized the noise was a broadband hash, white noise, indistinguishable from band noise except that its level is much greater with the beam pointing towards the house. If I turned the beam vertical then the white noise faded out almost to receiver noise, but another pulsing noise came up. It went kerchunk chunk chunk chunk, kerchunk chunk chunk chunk, ad nauseum. And the level of this noise peaked up with the beam pointing right at the shack window!

I switched everything off in the house and it made no impact on the noise whatever. I decided that it must be something battery powered. There is a radio controlled alarm system in the house that has a built-in backup battery. Nothing I can do about that. However I could not hear any noise increase when I went near it with the TH-F7E and a whip antenna. The noise level goes up and down as you walk about the house, as does the kerchunk chunk chunk noise, as if the noise source is invisible.

Eventually I did locate the source of the kerchunk chunk chunk noise. It was coming from an Ascot radio controlled clock sitting on the shelf in the shack just above my radios. I removed the batteries and after a few seconds the noise stopped. I walked about the house some more and in places I heard it again! This sort of thing can make you start to doubt your sanity.

Eventually I found that exactly the same noise was coming from another clock / weather station in our conservatory. It's a different brand, not radio controlled, and (probably not coincidentally) it receives temperature and humidity readings from the same external sensor. Presumably they have some electronics in common and this is transmitting a signal in the 432MHz band.

But I haven't found the source of the broadband hash, which may or may not be related to the crackly S9 noise that plagues most of the HF bands. I think the noise problems at this QTH are beyond solution. I haven't logged an HF band contact from here since 13th March. It isn't that I can't work anything on HF from here, it's just the demoralizing effect of hearing this dreadful noise as soon as you switch on and knowing that there are interesting signals buried under it that I have no chance of hearing.

Giving up the fight

Back in December I wrote that the RSGB had set up a Spectrum Defence Fund to enable radio amateurs to contribute towards the cost of a legal challenge to the UK spectrum management authority's failure to take action over the interference caused by power line networking devices. Pleased to see some positive action being taken I made a donation and also posted links on my blog and website to encourage others to do the same.

Today I noticed, at the end of the RSGB Annual Report, the statement that "following advice from the Society's solicitors ... it was decided not to proceed at this time with any legal action." So the RSGB has given up the fight and I have removed the links to the Spectrum Defence Fund from my website so that no-one else wastes any money on it.

Although PLT devices are a killer for any radio amateur unfortunate enough to live next door to one, it is clear from the noise at my own station and the comments I received from others with a similar problem that PLT is just the thick end of the wedge. A far greater number of short wave enthusiasts are having their enjoyment of HF ruined because of rising noise levels from a multiplicity of devices that individually would not be particularly intrusive. Whilst it is possible to track down and do something about a PLT installation, eliminating the noise that most of us in urban areas now experience from all directions would require the willingness of all neighbours to co-operate with finding the interference-generating devices and agreeing to replace them. This isn't likely to happen. I fear the battle to keep the short wave bands free of interference is over and ham radio is a lost cause.

The only place to enjoy HF radio nowadays is out in the country, which unless you happen to live there means operating portable or mobile. The question is whether only being able to operate portable or mobile is enough to maintain most people's enthusiasm? Although I recently enjoyed operating from my car on a couple of fine afternoons, it is no substitute for being able to go into the shack on a wet day or a winter evening and have a tune around and make a few contacts. I find I am turning on my K3 less and less often these days and when I do I often turn it off again soon afterwards without making any QSOs.

Will ham radio will still exist in ten years' time? Many former short wave and FM radio stations now broadcast over the internet rather than the airwaves and I suspect that an increasing number of ham radio operators will end up doing the same. They will get worn down by the losing battle against electrical noise and antenna restrictions and be forced to swallow their objections and switch to online "virtual ionospheres" like QSONet and HamSphere (shown above) where there is no QRN. You only need to visit the HamSphere site to see the number of amateur license holders that have taken this step already.

The RSGB's apparent acceptance that it can't fight even a clear case of interference to short waves is clear evidence that this is a war we can't win. Final surrender is just a matter of time.

G4ILO's noise

This afternoon I decided to tune around the HF bands to see how they compared with what I heard when I was out mobile yesterday and at the weekend. It was very depressing. I didn't hear any DX at all. The high noise level obliterated anything interesting and made listening very tiring and unpleasant. From the mobile out in the countryside the only man-made noise was the occasional burst of ignition interference from a passing car and I could copy signals right down to atmospheric noise.

I thought I would use my Pentax digital camera to make a video that demonstrated just what the HF bands sound like from here. It's a ham radio horror movie.