Posts Tagged ‘QRM’

Some Radio Antics

Shack activity has been curtailed with the antenna 'mast' spending a lot of time luffed over due of the winter storms and high winds that have battered the UK over recent weeks.

Thankfully things calmed down and was able to put the antenna back up but I seemed a little deaf on VHF/UHF dropping several S-points on local repeaters and then started to see high VSWR readings. The incessant rain had somehow got into the connector under the collinear despite being generously wrapped in self amalgamating tape. I replaced the connector and removed a couple of feet of coax in case any had seeped into the cable.

Like much of the UK amateur community I have been trying to listen in to British Astronaut Major Tim Peake during a number of ARISS UK school contacts during the Principia mission on the International Space Station. It is pleasing to see the enthusiasm, interest and publicity it has generated for the hobby.

There is another contact tomorrow (Friday 26th February 2016 at 1440UTC) with the City of Norwich School. While reception of the first two contacts proved a little disappointing for me, the one last week was much better and I made a video during the pass.


The Astronauts are certainly busy on the space station and there was an ARISS contact this morning with an Italian school. It was a low pass here only reaching 7 degrees above the horizon but was pleased to capture Tim Kopra conversing. I was using just the X-50 collinear on the FT857-D


The repaired ATU and a new balun on the OCFD has made a big difference to HF. It is much less noisy and I am now able to match the antenna to 80m something I could never do before. While it will be very inefficient on such a short antenna I did run a little over 2W last night on WSPR as a test, and was pleasantly surprised.


I have also been doing some JT65 and for the first time some JT9 inspired by a demonstration at SKARS and I was pleased to make a JT9 QSO with JA5BDZ on 15m using 10W.

A big help to HF has been tracking down the source of my recent QRM, which wasn't as many suggested my evil PLT devices but in fact the now redundant wireless router. While the WiFi was switched off it was still being used as a network switch and for some reason had suddenly become RF noisy, it wasn't the switching PSU but the actual unit and would happen a few hours after being switched on. Funny thing it is not the first time I've had an access point suddenly emit QRM.

A couple of weeks ago I went out with Stewart (M0SDM) to assist him flying his kite antenna and we operated under the club callsign MX0SKR, for a couple of hours, it was great fun.




Last weekend I also helped my brother David (M6GTD) install a couple of antennas at the family home. He can finally use the radio he brought at the Hamfest back in September, a Diamond X-50 dual band collinear and a home brewed 33ft long OCFD should get him on the air! 


David helped me at the Hamfest with the balloon launch


My apologies if this blog post sounds like a bit like an excited child recanting his holiday "I did this, and then I did this and I also did that" I hope to post something a little more coherent and structured soon!

Some Radio Antics

Shack activity has been curtailed with the antenna 'mast' spending a lot of time luffed over due of the winter storms and high winds that have battered the UK over recent weeks.

Thankfully things calmed down and was able to put the antenna back up but I seemed a little deaf on VHF/UHF dropping several S-points on local repeaters and then started to see high VSWR readings. The incessant rain had somehow got into the connector under the collinear despite being generously wrapped in self amalgamating tape. I replaced the connector and removed a couple of feet of coax in case any had seeped into the cable.

Like much of the UK amateur community I have been trying to listen in to British Astronaut Major Tim Peake during a number of ARISS UK school contacts during the Principia mission on the International Space Station. It is pleasing to see the enthusiasm, interest and publicity it has generated for the hobby.

There is another contact tomorrow (Friday 26th February 2016 at 1440UTC) with the City of Norwich School. While reception of the first two contacts proved a little disappointing for me, the one last week was much better and I made a video during the pass.


The Astronauts are certainly busy on the space station and there was an ARISS contact this morning with an Italian school. It was a low pass here only reaching 7 degrees above the horizon but was pleased to capture Tim Kopra conversing. I was using just the X-50 collinear on the FT857-D


The repaired ATU and a new balun on the OCFD has made a big difference to HF. It is much less noisy and I am now able to match the antenna to 80m something I could never do before. While it will be very inefficient on such a short antenna I did run a little over 2W last night on WSPR as a test, and was pleasantly surprised.


I have also been doing some JT65 and for the first time some JT9 inspired by a demonstration at SKARS and I was pleased to make a JT9 QSO with JA5BDZ on 15m using 10W.

A big help to HF has been tracking down the source of my recent QRM, which wasn't as many suggested my evil PLT devices but in fact the now redundant wireless router. While the WiFi was switched off it was still being used as a network switch and for some reason had suddenly become RF noisy, it wasn't the switching PSU but the actual unit and would happen a few hours after being switched on. Funny thing it is not the first time I've had an access point suddenly emit QRM.

A couple of weeks ago I went out with Stewart (M0SDM) to assist him flying his kite antenna and we operated under the club callsign MX0SKR, for a couple of hours, it was great fun.




Last weekend I also helped my brother David (M6GTD) install a couple of antennas at the family home. He can finally use the radio he brought at the Hamfest back in September, a Diamond X-50 dual band collinear and a home brewed 33ft long OCFD should get him on the air! 


David helped me at the Hamfest with the balloon launch


My apologies if this blog post sounds like a bit like an excited child recanting his holiday "I did this, and then I did this and I also did that" I hope to post something a little more coherent and structured soon!

Poetic justice?

Following my last post it is perhaps ironic that for the last few evenings I have been plagued by an increase in QRM.

Trying some JT65 on 40m I was being plagued by S8-S9 of local noise, it is noise I have had regularly (even before the purchase of my PLT devices) so I reconnected up the WiMo QRM Eliminator, which has been collecting dust, to see if I could improve matters.

Using just a short piece of wire as the auxillary 'noise' antenna managed to null out most of it to greatly improve reception. No commentary on the video below but hopefully you can see it working.


Interestingly the noise seems to abate around 11pm when people are off to bed.

Poetic justice?

Following my last post it is perhaps ironic that for the last few evenings I have been plagued by an increase in QRM.

Trying some JT65 on 40m I was being plagued by S8-S9 of local noise, it is noise I have had regularly (even before the purchase of my PLT devices) so I reconnected up the WiMo QRM Eliminator, which has been collecting dust, to see if I could improve matters.

Using just a short piece of wire as the auxillary 'noise' antenna managed to null out most of it to greatly improve reception. No commentary on the video below but hopefully you can see it working.


Interestingly the noise seems to abate around 11pm when people are off to bed.

PLT Devices – Have I welcomed the Devil in to the shack?

I joked recently about turning to the Dark Side, well my conversion really was complete after the Boxing Day sales.

I need to set up the ability to remotely operate the station via the internet as well as experiment with internet linking systems but the wi-fi link to the shack isn't fast or reliable enough. Now if I do a scan looking for wi-fi networks I can see well over a dozen, some of them quite strong and more are popping up all the time and I suspect this congestion is part of my problem.

The Samsung Smart TV in the house was also wi-fi linked but we were having increasing issues with the BBC iPlayer and Netflix with buffering or poor quality images because of poor signal and data rates.

Ideally I would be like to fit proper ethernet cables but it is totally impractical without major upheaval or unsightly trunking a definite no-no. In the end the only workable and affordable solution seemed to be to get some of those evil Powerline Transmission (PLT) devices.

I have suffered strong sporadic QRM myself which I have assumed were neighbours PLT networking devices as I'd read the horror stories, seen the videos and anecdotal reports of mains borne noise caused by them. So I hadn't even considered it until I saw a post and video by Dan Trudgian (M0TGN) about his experiences of using some Netgear devices and the apparant lack of interference to his radio activities. Some members of South Kesteven ARS had also started using them, so I took the plunge and ordered some Netgear ones reduced on Amazon in the Boxing Day sales.


Setting them up was easy, but the acid test was how much noise did they generate? I set up one device in the shack at the far end of the mains cable run to maximise radiation. Streaming internet radio and a HD movie on Netflix I then used the FUNCube Dongle PRO+ SDR connected to the OCFD to see what noise they were generating.

Here are my observations going through the various HF bands. Where noise is present I first stopped the streaming and then powered off the devices to eliminate them as the cause, where they were the cause it seemed eliminating the network traffic was sufficient to greatly reduce the effect.

80 Meters



While the antenna isn't optimised for 80m, signals can be seen as well as noise. Before you get excited this noise has been present for quite a while and isn't being caused by the new Netgear devices. This noise is what I suspected was generated by PLT devices used by my neighbours.

60 Meters


Shocking noise but again this isn't caused by my new devices, the noise has the same characteristics as that seen on 80m.

40 Meters





The band was busy, there is some noise again but not from the new devices, this was looking encouraging. I have also showed the adjacent broadcast band.

30 Meters


Again, largely noise free

20 Meters





Still largely noise free, the QRM that is present still wasn't due to the new devices

17 Meters




This was the first indication of QRM from the new devices, however it appears effectively filtered to leave the amateur allocation clear. The faint noise in the middle picture is not from the new devices.

15 Meters




Again this band was clear of noise

12 Meters



Showing the two ends of the band again the clear signal/noise from the devices again seems effectively filtered

10 Meter

I didn't observe any additional noise on this band, but unfortunately deleted the screen grabs ;-)

So where was the QRM?



While the amateur bands appear to be filtered, the transmission can of course can clearly be seen on some non-amateur bands and apart from 16 meters seems to avoid the broadcast bands.

Conclusion 

These Netgear XAVB5221 devices seem effective, indeed doing a speedtest in the shack was more than acceptable (the dire upload speed is a 'feature' of my cable ISP)


This fairly rudimentary testing has largely given me confidence that they won't be any issues. The band conditions weren't brilliant when I did test, but even with the absence of signals on the band any noise would be evident as seen. Yes they clearly do generate QRM but thankfully not it seems in the amateur bands. I haven't heard any extra noise on any of the radios over the last few days so all is looking promising. I will keep you posted if there is any change.

PLT Devices – Have I welcomed the Devil in to the shack?

I joked recently about turning to the Dark Side, well my conversion really was complete after the Boxing Day sales.

I need to set up the ability to remotely operate the station via the internet as well as experiment with internet linking systems but the wi-fi link to the shack isn't fast or reliable enough. Now if I do a scan looking for wi-fi networks I can see well over a dozen, some of them quite strong and more are popping up all the time and I suspect this congestion is part of my problem.

The Samsung Smart TV in the house was also wi-fi linked but we were having increasing issues with the BBC iPlayer and Netflix with buffering or poor quality images because of poor signal and data rates.

Ideally I would be like to fit proper ethernet cables but it is totally impractical without major upheaval or unsightly trunking a definite no-no. In the end the only workable and affordable solution seemed to be to get some of those evil Powerline Transmission (PLT) devices.

I have suffered strong sporadic QRM myself which I have assumed were neighbours PLT networking devices as I'd read the horror stories, seen the videos and anecdotal reports of mains borne noise caused by them. So I hadn't even considered it until I saw a post and video by Dan Trudgian (M0TGN) about his experiences of using some Netgear devices and the apparant lack of interference to his radio activities. Some members of South Kesteven ARS had also started using them, so I took the plunge and ordered some Netgear ones reduced on Amazon in the Boxing Day sales.


Setting them up was easy, but the acid test was how much noise did they generate? I set up one device in the shack at the far end of the mains cable run to maximise radiation. Streaming internet radio and a HD movie on Netflix I then used the FUNCube Dongle PRO+ SDR connected to the OCFD to see what noise they were generating.

Here are my observations going through the various HF bands. Where noise is present I first stopped the streaming and then powered off the devices to eliminate them as the cause, where they were the cause it seemed eliminating the network traffic was sufficient to greatly reduce the effect.

80 Meters



While the antenna isn't optimised for 80m, signals can be seen as well as noise. Before you get excited this noise has been present for quite a while and isn't being caused by the new Netgear devices. This noise is what I suspected was generated by PLT devices used by my neighbours.

60 Meters


Shocking noise but again this isn't caused by my new devices, the noise has the same characteristics as that seen on 80m.

40 Meters





The band was busy, there is some noise again but not from the new devices, this was looking encouraging. I have also showed the adjacent broadcast band.

30 Meters


Again, largely noise free

20 Meters





Still largely noise free, the QRM that is present still wasn't due to the new devices

17 Meters




This was the first indication of QRM from the new devices, however it appears effectively filtered to leave the amateur allocation clear. The faint noise in the middle picture is not from the new devices.

15 Meters




Again this band was clear of noise

12 Meters



Showing the two ends of the band again the clear signal/noise from the devices again seems effectively filtered

10 Meter

I didn't observe any additional noise on this band, but unfortunately deleted the screen grabs ;-)

So where was the QRM?



While the amateur bands appear to be filtered, the transmission can of course can clearly be seen on some non-amateur bands and apart from 16 meters seems to avoid the broadcast bands.

Conclusion 

These Netgear XAVB5221 devices seem effective, indeed doing a speedtest in the shack was more than acceptable (the dire upload speed is a 'feature' of my cable ISP)


This fairly rudimentary testing has largely given me confidence that they won't be any issues. The band conditions weren't brilliant when I did test, but even with the absence of signals on the band any noise would be evident as seen. Yes they clearly do generate QRM but thankfully not it seems in the amateur bands. I haven't heard any extra noise on any of the radios over the last few days so all is looking promising. I will keep you posted if there is any change.

OFCOM undue interference consultation

Happy New Year!

2015 has started with some important developments. Ofcom have launched a consultation on draft regulations for new wireless telegraphy legislation. The proposals are intended to strengthen regulatory power and keep pace with technological advances with respect to interference of radio communications from electronic devices.

Current Electromagnetic Compatibility (EMC) regulations should prevent electrical and electronic apparatus emitting electromagnetic energy that would cause interference to radio communications but as most licensed operators have experienced this is not the case. In particular the growth of "power line" networking equipment (PLT) in recent years has caused much distress to amateur radio particularly in populated areas. I myself have suffered interference from what I believe are PLT devices.

It is certainly true that most newer devices are much better and are notched to prevent emissions in certain bands but there are still many older devices in use and imported non-compliant devices are still readily available. It is not just PLT devices that cause issues but solar panels with RF noisy inverters, unfiltered switch mode power supplies, plasma televisions and other equipment that pollute the spectrum.

Unfortunately at present Ofcom has limited enforcement powers so are proposing the law is amended to make it a criminal offence to continue using equipment identified as a source of undue interference.

Several agencies such as GCHQ, CAA and emergency services have voiced concerns in the past over the threat of RF pollution (Telegraph newspaper article) so not surprisingly this weeks announcement has been given the 'spooks' spin with some sensationalist headlines "You could be prosecuted over your broadband thanks to GCHQ" as the Telegraph reported.

I feel it is important that UK licensed amateurs respond to these proposals and the consultation is only open till next month it is very easy to respond on line at the Ofcom website

It is quite a timely announcement from Ofcom since I have been forced to use the QRM eliminator that I purchased back in August due to increasing interference. I have not been able to use it in line with the FT857D as it requires the PTT/TX-GND signal from the CAT/Linear socket from the transceiver to activate a bypass when transmitting. The issue being I wished to use the CAT functionality at the same time and this involved making up a harness with the appropriate 8-pin mini-DIN plug/socket. I purchased some plugs and sockets but kept putting it off due to the fiddly nature of the small connectors and I didn't wish to cause any damage to the FT857D by shorting the pins.

By chance I spotted this cable on eBay which is the same as my current CAT cable but with the addition of the PTT/TX-GND signal on a short pigtail with a phono (RCA) socket making it a breeze to complete the installation.

I am hoping to improve the noise performance by putting up a new HF antenna in the future, to this end I have had a nice Christmas present. A Feature Tech AW07A HF-VHF-UHF Antenna Analyzer


Once I have used it in anger I will post a proper report, but it seems a great piece of kit with some encouraging reviews, currently available of £168 on eBay it is a massive £200 less than the identical MFJ-266

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