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.

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.


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

Noises Off – WiMo QRM Eliminator

As I posted at the end of June I was almost on the point of giving up on HF due to the high levels of QRN/M suffered at home.

In desperation I had been looking at some of the noise cancellers available from MFJ and others. I had heard conflicting options on their effectiveness but was willing to try one if I could obtain one cheaply. The MFJ units are in my opinion expensive to purchase new so I bid on several that came up second hand on eBay but they invariably also went for silly money. I was even contemplating building an home-brew one from the numerous designs available.

Then I discovered the WiMo QRM Eliminator, made by the German company WiMo Antennas and Electronics. Several online reviews and numerous YouTube videos seemed to indicate its effectiveness and taking up the then summer discount offer I ordered one for the princely sum of €147 including postage, around £116.

Due to heavy demand and low stock levels following the International Ham Radio Exhibition at Friedrichshafen I was told the unit wouldn’t be available till the middle of August, so I was pleasantly surprised when the unit turned up last Friday morning.

New toy in time for the weekend 😉 Thank you @wimo_de
— Andrew Garratt (@nerdsville) August 1, 2014

I have connected it up and briefly tried it out and am impressed, as this video illustrates.

Even using one for a short time I would agree that they are something of a black art to set up and use and can understand why people might consider them useless, but this may be due to lack of understanding of how they work.

I have created a diagram showing a typical scenario.

The operators main antenna is designed to pick up distant signals, not necessarily DX but signals not emanating from the immediate vicinity, however they will also pick up locally produced QRM as shown, perhaps generated by a neighbours TV or PLT device. 

The QRM eliminator has a second antenna which isn’t as efficient as the main antenna and ideally just receives the local QRM at a similar level to the main antenna. The device then takes this second signal and inverts the phase so when it is mixed with the main antenna signal the QRM is cancelled out.

The principal is quite simple, if you take two in phase signals and combine them you will end up with a signal with a larger amplitude. However if the signal is 180 degrees out of phase, the positive and negatives of the waveform cancel each other, producing a null signal. 

The tricky part is making sure the noise antenna just picks up the noise, if it picks up the main signal then that will also be cancelled out. The WiMo unit has three controls a gain and two phase controls it is a case of altering all three to maximise the cancelling effect without losing the main signal.

At present I just have several meters of wire running as the noise antenna along the side of the shack and this seems to fairly effective.

The unit is powered from 12V and can be left in line, but requires the PTT/TX-GND signal from the CAT/Linear socket from the transceiver to activate a bypass when transmitting and I don’t have the appropriate 8-pin plug at present. If the unit is powered off the bypass is automatically engaged.

All in all, first impressions are good and looks like a worthwhile purchase.

Noises Off!

Radio frequency interference (RFI) is the bane of a lot of amateur radio operators. Sadly it is becoming a real issue at my QTH.

RFI is referred to as QRM or QRN and I am learning the difference.

QRM means “I being interfered with” and is interference coming from someone using radio equipment. This covers deliberate jamming, people tuning up or just normal operations on a crowded band that causes QRM.

QRN means “I am troubled by static” and technically means interference from a natural noises but has come to refer to interference coming from anything that is not an intentional radio emission and interferes with reception of transmissions. So now covers atmospheric noise, static or the noise generated by electronic devices.

Noise isn’t a new issue here as I have posted before. It has tended to be sporadic and bearable but since becoming licensed I have become more sensitised to it. Until now I have tended to focus on the VHF/UHF side mainly contesting venturing only briefly onto HF.

My HF set up is limited at the moment with just a single antenna which isn’t optimal for the lower bands. Due to the day job I am largely restricted to evening/night time operation when the upper bands have largely been closed anyway so haven’t really attacked HF with much enthusiasm apart from data modes such as JT65 and WSPR which have immunity to noise.

When I have got the chance for some early morning daytime operation or at the weekend I have struggled with noise.  Recent weekends have seen some special event stations operating for the Museums On The Air and the GB1JSS Summer Solstice which have been predominately on the 40M band but I just cannot hear anything on that band due to noise.

I am aware the Sun has been particular active recently producing a number of large flares and CMEs that have caused a number of radio blackouts, but this noise isn’t due to atmospherics I am certain it is man made by one of neighbours.

I made this video last weekend

and this video was from the weekend before that

This weekend was the 50MHz Trophy Contest which I was looking forward to, sadly it was also to become a victim of the QRN as this screenshot from my SDR will confirm, for much of the time I was operating I was just listening to noise.

I wasn’t operating constantly, just grabbing a few minutes here and there and I did manage to make some decent contacts when the QRN subsided even catching some of the sporadic E opening to get EF7X in Spain.

I have ruled out any noise being generated by myself by powering everything off and running on battery. This leaves me in a bit of a quandary I could go around and locate and confront the culprit or even contact OFCOM but at the same time I don’t want to antagonise anyone who could then object to any antennas I might want to put up in the garden.

Rotating the 6M Moxon around at the weekend during the contest as at least pointed me in the direction of one strong noise source. I am also convince that much of my problem is due to an evil PLT device in an adjacent property.

Following on from the weekend last night was the UKAC 50MHz contest and yet again I was troubled with noise leading to mostly local contacts.

I have been looking at some of the noise cancellers that are available from MFJ and others. I have heard conflicting options on their effectiveness but I am willing to try one if I can obtain one cheaply, or even home-brew one from the numerous designs available.

These devices work by using a second antenna which receives just the noise which is then mixed out of phase with the main antenna signal hence nullifying the noise. By all accounts they are tricky to use and often  need constant adjustment but may be my only viable solution at present.

My WRT54G has become noisy!

I haven’t done much ‘radio stuff’ over the last few weeks due to work/family commitments and holidays but when I have found time I have been exasperated by huge levels of interference all across the HF/VHF bands which has suddenly appeared. Manifesting itself as huge regular bands of hash across most of the spectrum (as pictured below)

I assumed that a neighbour had purchased some new electronic device that was responsible. However last night I decided to go around the house again just in case, and discovered my ancient Linksys WRT54G router was the source.

I have had issues with QRM before and I was aware that this router was responsible for some noise in the VHF bands, but I had mitigated this by replacing all the network cables with brand new properly shielded network cables (screened shielded twisted pair) and ferrite clamps. This noise is something new and appears even with the network cables unplugged.

I naturally assumed it was the PSU as poor quality switch-mode power supplies used by most peripherals can be sources of interference, but interestingly the PSU for this router is actually a huge linear type judging by its size, weight and the temperature it runs at. I did try another compatible supply with the same results.  

Doing a Google search shows these routers seem to have a reputation for being RF noisy, but until now I haven’t had any real issue on HF.

Due to my ISP upgrading the network I got a Virginmedia SuperHub last year but was forced to put it into ‘modem’ mode and use my existing WRT54G after struggling to configure it. I couldn’t find anyway to configure the LAN to use the correct subnet (it kept defaulting to never mind configuring the port forwarding and wireless access! The GUI and firmware was atrocious and I refused to go around reconfiguring all my devices. Maybe I might have to swallow my pride…

Away from the noise

High up and a hillside in Cumbria at the moment, nine metre fiber glass fishing pole and 10 meters of wire, a ground spike and my FUNCube Dongle PRO+ and the laptop and what a revelation!
The entire HF spectrum spread out before me with little or no noise anywhere, signals booming in! and this was the view last night
As they say Location, Location, Location!

QRM – It is a very noisy Friday

My last post was about the joys of SDR, this one is about the bane of not only SDR but radio in general namely the amount of electromagnetic rubbish that is thrown into the ether by shoddy equipment, with SDR you just see just how much s**t there is.

These are some waterfalls captured today, first exhibit showing lovely evenly space spikes, and a mass of hash and splatter.

A little further up the spectrum, another splatter, this I am convinced is some form of Power Line Network Adapter. You know the ones someone thought was a clever and expensive solution to that problem “How do you get network data from one room to another without the hassle of running a cheap proper shielded network cable or using wifi?” Their answer was to use unshielded mains wiring to transmit data at radio frequencies turning them into efficient antennas!

Mind you even using shielded network cabling isn’t always the answer especially if you have cheap probably Chinese made network equipment which some one is using nearby. It generates this pretty pattern right across the VHF 2 meter band, especially bad on 144MHz.

Hold on VHF is immune to PLA interference you say? Yeah right!

I have posted before about problems I have had before including some videos including the one below. Thanks to my direction finding skills I know which direction this annoying interference was coming from, but I haven’t seen it for a while, someone got themselves a new Plasma/LCD TV?

I am aware some of my equipment generates some noise, but even powering down the entire house and running on laptop batteries I see just as much rubbish, rubbish that disappears as soon as you remove the antenna.

ARISS school contact reception despite the interference

Yesterday morning (10:57 UTC) saw an ARISS School Contact with participants at Ecole Les Muriers, Saint-Maur-Des-Fossés, France.

This was a nice opportunity to listen in since the position of the ground station at the school meant the UK could listen in to the majority (if not all) of the downlink. Usually when it is further east in Europe (Germany/Poland etc) you get the initial calling and the start of the contact but the ISS goes out of range before the session ends.

So I set up my FUNCube Dongle PRO PLUS connected to the discone in the loft and the new SDR-Radio V2 Preview software. I had to start the recording remotely as I was in work, but have played back the IQ file and made a video showing the decoding.

As you can see/hear I appear to get the full contact and the questions were (source)

1. What is the temperature outside the ISS?
2. What does the Earth look like from the ISS?
3. What does the Moon look like from the ISS?
4. Have you already passed through an asteroid belt?
5. Are you able to go outside the station, into the space?
6. What is your speed? Can you feel it?
7. How do you sleep? Do you have the same sleep pattern than on the earth?
8. Do the crew members sleep one after the other, or do you sleep all at the same time?
9. How do you know if it is morning or night on board?
10.Do you do any sports and physical activities? Do you lose weight?
11. Do you shave every day? If so, how?
12. Do you see any space debris? Can you see evidence of pollution of the earth?
13. What are your hobbies on the ISS after a day of work?
14. Are you happy to come back home at the end of your mission?
15. What is your current mission?
16. Why did you choose to become an astronaut?
17. How do you cook food? What is a typical meal in the ISS?

I was lucky to receive it given the interference monster was back! It does manage to get in on the act a few times but thankfully doesn’t stop the show completely.

Over the last few months I’ve been suffering from increasing interference on the VHF/UHF and HF bands. Some of which I know about, the router I have puts out quite a few spikes on VHF but something local to me is putting out huge amounts of QRM.

I know it isn’t internally generated as it disappears when I remove the antenna. I have gone around and powered off all the potential culprits in the house and discovered a switch-mode power supply for an external USB hard drive was throwing out some HF noise as was a digital photo frame.

I’ve suffered with interference on and off since getting back into the hobby back in 2010 and appreciate it is something I have to live with but it is quite annoying at times. I suspect the interference might be one of those power-line networking devices, but if anyone has any idea I would welcome a comment!