News items for tag interference - Koos van den Hout

2016-06-03 Luisteren naar de PI4AA ronde op 40m met lokale storing 2 years ago
Ik heb weer eens geluisterd naar de PI4AA uitzending. Dit keer heb ik geluisterd via de PI2NOS livestream en heb ik me daarna eens ingemeld via de inmeldronde op de 40 meter band omdat ik toch de endfed antenne had buiten gehangen vanwege een contest in het komende weekend. In SSB is de lokale storing erg duidelijk aanwezig. De storing is ongeveer S9 dus ik hoorde PI4AA zelf redelijk goed met een signaal wat daar net 10 dB boven zat. De meeste inmelders hoorde ik slecht of niet.

Hierbij een klein stukje met Remco PA3FYM als rondeleider.
Listen to audio attachment:
MP3 media: PI4AA ronde op 40m 20160603 (rightclick, select save-as to download)

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2016-05-02 Experiences with vectored VDSL and amateur radio transmissions 2 years ago
It is a while after my last report on Vectored VDSL and the influence of amateur radio transmissions and it's time to share the current experiences especially with the change to the DrayTek Vigor 130 VDSL modem.

The first conclusion is that the modem doesn't matter much. I am now used to the connection dropping and retraining when I start on a 'new' frequency. I haven't figured out yet what the exact definition of 'new' is, when I haven't been active for a number of days on 20M PSK31 the first transmission on that band can trigger the disconnect. There seems to be no direct influence on the maximum speed after the reconnect, it sometimes goes up. A serious change of frequency (different band or a different part of a band) can trigger another disconnect.

In the mean time an xs4all user shared after long debugging of vectored VDSL problems to have found the cause in the PLC (powerline communications) network devices as delivered by xs4all for television over IP. Yet another reason to not use PLC. But in the ideal world the lastmile connections for high speed would be fiber-based anyway.

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2016-02-13 Vectored VDSL and the influence of amateur radio transmissions 2 years ago
Another radio amateur found my earlier experiences with transmitting on 20 and 40 meters and the influence on vectored VDSL, Amateur radio transmitting influence on vectored VDSL and And now vectored VDSL doesn't mind transmitting.

He also has the problem of keying up on 20 or 40 meters and having VDSL drop completely. He shared his signal/noise graphs with me and I noticed a similarity with my first signal/noise graph: an area somewhere else in the frequency space used by VDSL which has had serious changes in signal/noise levels.

I switched the modem to a DrayTek Vigor 130 (for reasons having to do with my setup at home) and the first tests with PSK31 and JT65 on 20 meter show no problems with the VDSL modem. But the varying interference above 16 MHz hasn't returned, so maybe when this interference returns the DrayTek Vigor will disconnect too.

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2016-02-10 And now vectored VDSL doesn't mind transmitting 2 years ago

Vectored VDSL spectrum as reported by the Fritz!Box 7360. The earlier interference seen starting around 16.5 MHz isn't visible.
After a restart of the modem the interference starting around 16.5 MHz hasn't returned. The interesting fact is that now transmitting on 14.070 MHz PSK31 does show in the signal/noise graph of the modem but there was no connection hickup the first time I did that, the bits/carrier just adjusted down and things went on fine.

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2016-01-30 Amateur radio transmitting influence on vectored VDSL 2 years ago
Our VDSL Internet connection was recently upgraded to vectored VDSL which gives us a lot more speed: attainable speeds are now 117057 kilobit down and 42201 kilobit up. The subscription speeds are much lower, but still very nice for a home Internet connection.

The downside is that VDSL uses a lot of spectrum from nearly 0 Hz up to 17664 kHz which includes several amateur bands and vectored VDSL seems to be highly sensitive to other RF signals. For me at least 20 meter (14 MHz) and 40 meter (7 MHz). I already caused several disconnects by transmitting in these bands and even with more recent firmware this problem remains.

I have been active on the same bands since we got faster speeds without vectoring (in the beginning of November 2015) but it did not influence the VDSL stability when vectoring wasn't enabled. The VDSL profile hasn't changed (17a) so the same frequencies are used.
vectored vdsl spectrum
Vectored VDSL spectrum as reported by the FRITZ!Box 7360. The hole in bits per carrier around 14 MHz is caused by my PSK31 transmitting (I can see the influence on the signal/noise ratio while transmitting). The hole above 16.5 MHz (starting near carrier 3840) is caused by some other source of interference.

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2015-06-03 Another case of interference from a VGA monitor cable 3 years ago
For the joint experiment in amateur satellites last Saturday I added a second monitor to the PC so I could watch the gqrx waterfall and the fldigi waterfall at the same time. And on Sunday I noticed some weird new interference around 14.070 MHz which made decoding the PSK31 signals a lot harder. The new VGA cable near the radio was a suspect and indeed after removing it completely the problem went away again.

So if I want a working dual-screen setup, I'll have to find better video cables. Maybe DVI gives less interference. It was nice to have fldigi running PSK31 on one screen and do other things on the other screen.

The upside was that with the current versions of Linux video driver I had to do zero fiddling to make the setup work dual-screen.

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2015-05-21 A Linux-related radio interference problem 3 years ago
Recently I noticed serious interference very visible on 14.070 MHz. Where it annoyed me a lot since that is the regular frequency for 20 meter PSK31 where I make most of my contacts at the moment. I also saw some interference at 28.120 MHz, the PSK31 frequency in the 10 meter band.

Noise on 14.070 MHz
The noise in the fldigi waterfall, click for the full fldigi screen.
The interference showed as steady carriers about 58 Hz apart and sounded like a serious buzzing noise. The first conclusion was that one of the over the horizon radars decided to drop on that part of the 20 meter band.

But later on the interference stayed at exact the same frequency. And active over the horizon radar is also quite visible on the Utwente websdr as I noted before when I noticed interesting interference in the 10 meter amateur band. This specific interference wasn't visible there.

So I kept searching locally for the source. I was afraid a nearby neighbour was using a new interfering CFL or power supply which would make it hard to diagnose and fix.

My own equipment was also a serious suspect. One piece of hardware that recently changed near the antenna was the monitor for the server. The monitor changed from an old CRT to a less-old LCD screen. The power supply wasn't the culprit, but searching further it turned out the video signal to the monitor was! And then I saw what else changed: after upgrading the homeserver to Ubuntu 10.04 and upgrading the homeserver to Ubuntu 12.04 it started coming up in framebuffer mode. Which has a different video frequency from the 80x50 textmode I used earlier.

The problem goes away completely when I unplug the video cable from the computer. I had an extension cable without ferrite cores because an earlier monitor needed the extra length. Removing the extension cable makes the level of interference drop a lot but it's not away completely. So the solution is to unplug the monitor cable from the computer.

Then things are back to the 'normal' noise level on 20 meters and 10 meters. It's still a city environment.
Listen to audio attachment:
MP3 media: Noise on 14.070 MHz (rightclick, select save-as to download)

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2015-04-04 Amateur radio away from buildings 3 years ago
I had this Friday al to myself and decided to try some amateur radio out in the field using the new longwire antenna I recently bought.

I was pondering taking the recumbent bicycle first but the outside temperature in the morning of 5 ⁰C made me chose the car which would give me a warmer shelter to sit in. I drove to a nearby outside recreation area (De Leyen near Groenekan) and there I was shielded from the wind so I could sit outside. I decided to set up the radio on a park bench near a tree.

During the setup someone did ask me what I was doing and I explained about amateur radio. That person asked whether that wasn't normally done from a room in the attic and I explained that being away from radio noise source would be an interesting experiment. This explanation seemed to answer that person's interest.

I used some nylon rope to hang one end of my longwire antenna up in a tree and anchor the other end at the base of another tree. A filled plastic water bottle makes a nice smooth weight to throw a rope over a high branch of a tree. The antenna was sloped downwards in southern direction.
Read the rest of Amateur radio away from buildings

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2015-01-31 Interesting interference in the 10 meter amateur band 3 years ago
waterfall plot of interference I had the radio and computer running checking for PSK31 signals at 28.120 MHz, the standard frequency for PSK31 in the 10 meter band. Suddenly I saw lots of carriers 5 Hz apart and very precise. I checked the websdr in twente and saw the same signal.

So I tried to make a screengrab of it and it went away. To show up at 27.120 MHz exactly the same and annoying some 27 MHz CB users.

I'm not sure what it was, my first guess was over the horizon radar which is 'famous' for interfering on HF amateur bands. Moving 1 MHz down when the HF propagation maximum frequency is dropping is also a sign of something like over the horizon radar.

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2014-04-22 Combining websdr and fldigi 4 years ago
Combining a websdr with fldigi gives me great views of PSK31 traffic, but this evening I also tried receiving APRS, with the audio routed from the java plugin to fldigi using padsp multimon. This crashes a lot, but disabling the scope helps, padsp multimon -s SCOPE. But the 2 meter signal from HF/VHF/UHF WebSDR at the Maxwell Foundation in Eindhoven was too noisy and had interference from other signals to decode anything. I have listened to 2 meter stations via this websdr just fine so I think this could work when the current interference is gone.

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2013-11-20 (#) 5 years ago
To my shame as a radio amateur I must admit I still use a PLC (ethernet over powerline) connection in my home network. It's what makes the shed weather station computer reachable. An upgrade to wifi is in the plans.
gqrx display around the 20 meter amateur band with PLC network idle
gqrx receiving radio signal around the 20 meter amateur band with the PLC network idle.
This evening I played a bit with it and caused heavy traffic on that bit of network using iperf and the results in gqrx are stunning. Around the 20 meter amateur band (14000-14350 kHz) the difference is quite visible. The band itself is clearly notched, but a serious amount of radio noise is visible outside the band.
gqrx display around the 20 meter band with the PLC network loaded with heavy traffic
gqrx receiving radio signal around the 20 meter band with the PLC network loaded with heavy traffic

The gqrx displays are the current signal levels across the frequency spectrum in the top half of the display and a waterfall display in the bottom half. The waterfall display shows the history of those levels as indexed colors.

The upside: these PLC adapters (devolo) clearly use notching. Interference on amateur bands is small. But I don't receive any other amateur radio signals either so I still have a problem.

The downside: outside the amateur bands the interference is quite strong. Weak signals do not survive this.

Update 2014-08-17: Sometimes you notice something after a while: the horizontal lines in the 'idle' and 'busy' graphs are very short bursts that sound like ticking when heard on a radio. These are quite probably the way in which the powerline network tests the connectivity and available frequency spectrum including noise levels.

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2013-11-17 (#) 5 years ago
Das Keyboard with ferrite core to reduce interference In disassembling a very old original Apple external CD player I came across a big ferrite core. I thought this would help solve the problem with 2 meter band interference from the Das Keyboard. And indeed, there is a lot less interference on the 2 meter amateur band. I tested with the Wouxun KG-UVD1P radio tuned to 145.500 MHz and I had to put the antenna of the radio real close to the keyboard to hear interference with the squelch set at 5.

Update: I notified the makers of Das Keyboard of this problem and my solution. The reply was a bit non-committal they will forward the suggestion to development.

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2013-03-18 (#) 5 years ago
Continuing the search for the source of the interference on 2 meter amateur bands. This evening I tried disabling the powerline network completely, unplugging both ends of the link.

First I made a 'baseline' fft graph with gnuradio of the 2 meter band and then I disabled the powerline network and tried to make the same graph. Which failed completely: the dab stick I use for software defined radio has some automatic gain control which made comparing baselines difficult, the graphs had a jump in signal level of more than 20 dB. But I left that run of gnuradio with the fft graph running and switched the powerline network on again. Those two graphs are somewhat easier to compare: the peak signal level on 144.800 (aprs frequency) is nearly the same. The base noise level on the band indeed goes up about 1-2 dB. Listening with a receiver earlier I did notice the noise starts to actually have rattling sounds and high tones in the back yard. Time for more research there.

I should compare the results with receiving and interference on a receiver with powerline networking enabled and disabled, but I didn't find time to do that with all the running around to change the powerline network.

This is what I like in amateur radio: researching how something works or doesn't work and why.

Update 2013-03-19: Some walking around and some testing again: the linksys WAP54G indeed does cause some noise. And the most likely source of the noise in the back yard is the automatic light switch!

The heater we have is a Vaillant with OpenTherm support, but it does not cause interference.

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2013-03-08 Tried receiving PI3UTR on 2m and noted interference 5 years ago
I tried receiving PI3UTR on 145.625 MHz yesterday and noted serious QRM (man-made interference). Time to investigate the possible sources. One serious 'suspect' is the Devolo powerline setup which links the computer of the weatherstation in the shed to the network. In the plans for the future "sundial" weather station and time receiver that link will be replaced with a wifi link. Searching for 2m QRM also gives me linksys router interference to ham radio bands which suggests that the WAP54G access-point we use may also be a suspect.

Time to get out the scanner with some 2meter frequencies programmed and search for the culprit. The linksys router interference article above has an explanation of the procedure:
Here is a handy method of locating many noise sources on the HF/VHF ham bands. Using a 2 meter handheld, adjust it to an unused frequency. Leave the "Rubber Duckie" antenna attached. (Note that you may also use a portable shortwave receiver tuned to the respective hf band with an external "loop" probe setup as described below.)

Stand back several feet from the suspected device or if needed in another room or location if the white noise "floor" is too strong.

Adjust the squelch (on vhf transceivers) just to the point that the white noise stops if possible. If it does not, then you will have to remove the antenna and get much closer to the suspect device. On portable shortwave receivers without squelch, tune as needed for a "quiet" hf frequency in the band you have rfi on.

Now move the handheld or portable receiver around or near each and every piece of equipment in your station that is near your router or associated cables. This includes it's power supply, wall wart, interconnecting cables, etc.

If the squelch breaks and or noise poors from the receiver when you are very close, then you have pin pointed the suspect device! Now remove the antenna from the handheld remembering the device, cable, etc, that caused the squelch to break!

At least it seems our cable provider Ziggo seems to keep the 2 meter band free. One less possible source.

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