Wednesday, 13 January 2016

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.

Friday, 1 January 2016

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.

Friday, 25 December 2015

Repaired my ATU

Merry Christmas!


Not wishing to contend with an evening of dire XYL style Christmas TV (Strictly Come Dancing, Call the Midwife and Downton Abbey) I escaped into the shack and decided to repair my Vectronics VC300DLP Antenna Tuner. I got this ATU second hand last year and while it has been serviceable it had become temperamental of late. The units rotary inductor switch had become stiff and suddenly I was unable to match the OCFD on some bands so it had clearly broken.

I had a 12-position switch (rated at 5A) and knob, originally sourced for an abandoned project and hoped it would be suitable. The existing switch knob on the ATU wasn't an original, I'd assumed it had replaced one lost or broken. When I removed the cover it was clear that the whole switch had already been changed at sometime.


I also noticed a prominent burn mark inside the inductor coil, caused by a clear break in the insulation of the wire which was resting on the grounded bottom plate.


I know the previous owner of the ATU has a 300W RM BLA-350 linear amplifier, whereas I only normally operate around 30W maximum at my QTH, so not sure how much of this arcing I had caused but it needed sorting! A little over half an hour with the soldering iron and I had replaced the switch and slipped some heat shrink over the broken insulation and re-soldered the wire, lifting it off the ground plate.


The ATU seems to work well, now fitted with a new knob (just missing a cap at the moment) the switch turns nicely. I also cleaned up the SO-239 connectors on the back as they were tarnished and oxidised. I used a small bit of contact cleaner on some cotton buds to clean up the threads and the centre pins, removing a surprising amount of crud. The patch and antenna leads now screws on much better.


With the Mother--in-law staying with us over the festive period I suspect I may be in the shack quite a bit, I have plenty of jobs and half finished projects to keep me busy!

Tuesday, 22 December 2015

DMR - Joining the Dark Side!


As a birthday present to myself I have just ordered a Retevis RT3 DMR hand-held off eBay which should be delivered just after Christmas.

South Kesteven ARS had a talk in October by Sean Burton 2E0ENN about amateur DMR where he demonstrated some handsets and the new DV4Mini which allows gateway and internet linking for the various networks, DSTAR, DMR and System Fusion. This piqued my interest in the DMR scene.

As I posted last time I dabbled a few years ago with decoding PMR DMR using software and a sound card but they were very hit and miss at the time. I reacquainted myself with the various projects and using the FUNCube Dongle Pro+ and the latest version of DSDPlus (support forum at RadioReference.com) monitored the nearby GB7RR DMRPlus repeater managing to get some reasonably clear decodes of some amateur transmissions.


I decided to dig out my Realistic PRO-2022 scanner and using a discriminator tap fed into the sound card got slightly better quality decodes.


Doing some research and reading a couple of reviews had decided I was going to get a Tytera TYT MD-380 when funds allowed but spotted the Retevis RT3 which appears to be identical and slightly cheaper.

I know some people wince at the thought of DMR and issues with proprietary technology used in some of the systems but I think the genie is out the bottle and it isn't going away soon. Adoption of DMR appears to be growing with talk of restructuring of talk groups needed to deal with the growth (whatever that means!) so I should at least get my feet wet and understand the technology.

I registered for an ID, now off to decode the jingo and understand all this talk of codeplugs, talk groups and time slots.

Friday, 20 November 2015

Latest antics

Here I am a month after the last post and it is has been a month of very little 'radio antics'.

I was acutely aware that since the end of September my wife had become a radio widow so promised not to lock myself away in the shack for a while and have been doing some much needed painting and decorating around the house.

I haven't been in much of a radio mood anyway as I have been unwell and am still not fully over my last wobble. Band and weather conditions have been rubbish with a sustained period of high wind and rain including storms Abigail and Barney. As a precaution I dropped the pole and it became apparent I had some maintenance to do on the OCFD.


The shack too had been in need of some sorting out, which I thankfully I did muster enthusiasm to tidy up.


While being largely uninspired I haven't been completely radio silent, I did get on air for the South Kesteven ARS 2m net but found myself suffering some QRM again


It isn't the first time I've seen this sort of signal, but I had thought it had gone away, it seems it is back and stronger! This was an ARISS contact I monitored back in 2013 before I was licensed with a similar noise.


After using the SDR to identify the noise I realised I have been neglecting the FUNCube Dongle for far too long. So ordered some new SMA adapters from HamGoodies and pressed it back into service. I have been using it to decode the telemetry from the FOX-1A (AO-85) satellite with the updated software and have now got myself on the leader board even if the collinear is currently horizontal about four feet off the ground!

South Kesteven ARS had a talk in October by Sean Burton 2E0ENN about amateur DMR where he demonstrated some handsets and the new DV4Mini which allows gateway and internet linking.

I remembered I dabbled a few years ago with decoding PMR DMR using the SDR and a scanner with a discriminator tap using various programs but they were very hit and miss at the time. I reacquainted myself with the various projects and had a go at decoding some amateur transmissions.

I downloaded the latest program called DSDPlus  (support at RadioReference.com) and monitoring the nearby GB7RR DMRPlus repeater managing to get some clear decodes with little effort.


Finally this week I gave a presentation at SKARS on the subject of HABs and how to plan a HAB launch. Following on from the Eggsplorer-1 and Hamfest "Pigs In Space" HAB launch I decided to try to explain everything I had learned for anyone else contemplating giving it a go!

It was a long talk (perhaps too long) as I covered everything from building the electronics, software, making the payload box, getting the right balloon, parachute, gas, obtaining permission and then the prediction, launching tracking and recovery.



It was a great turnout with a lot of interest.

Sunday, 18 October 2015

A wonderful weekend of JOTA

What a difference a week makes, last week I was feeling somewhat low and as a result ducked out of the RSGB convention as I wasn't feeling very sociable.

But this week I had to get my head straight since the South Kesteven ARS (of which I am Chairman) were involved for the second year in the Scouting Jamboree on the Air (JOTA) weekend operating GB5FSG for the 1st Foston Scouts.

But before that we were also involved with another local scouting group, the 1st Barrowby where we assisted in a class of 12 Cubs with their communication badge.

Together with Stewart (M0SDM), Sean (2E0ENN) and Konrad (2E0KVF) we spent an evening giving them a introduction to amateur radio. Konrad who is an ex-scout leader explained the hobby, Stewart and Sean helped them pass messages via a radio. There was also a timely visible pass of the International Space Station during the evening and I hoped they might be able to see it while I demonstrated transmitting APRS messages via the onboard digipeater.

Using my new dual band Yagi, laptop and FT857D in the boot of my car I did successfully get messages digipeated and igated however the cloud and rain prevented the cubs seeing the ISS pass overhead (I put the coordinates in slightly wrong, so are shown slightly south of where we were)



The evening was a great success and the enthusiasm shown by the Scout leaders hopefully means SKARS will be involved in more activities for the Barrowby Scout group. Interestingly we were not the first local club they approached to assist but after they were given the cold shoulder by them we were happy to take up the challenge. The Barrowby group were also interested in being involved in the Jamboree on the Air (JOTA) next year.

So on to the main event this week, the GB5FSG JOTA station, operated by Stewart, Sean and myself. It is exactly a year since I gained my full licence and this was my first Notice of Variation for a special event station, last year under the previous chairman we had run GB2FFC with some success but this year we hoped to improve the experience for the Cubs/Beavers and Scouts.

Firstly we had a much improved antenna installation, with Stewart's Land Rover and impressive pushup mast we had an excellent OCFD dipole, resonant on several bands including 40m along with another smaller pole holding up an end fed long wire for the datamode station. We also put up a collinear for a 2m VHF station.


Last year we were hampered by the noise of excitable children in the main room of the scout hut which made operating and hearing contacts difficult. This year we asked for some separation from the hubbub and had planned to use a tent. Instead we setup in the storage area in the back of the hut which proved ideal as it allowed us to control the number of children and allowed easier working conditions - it was a little chilly but much warmer than a tent would have been.


On Saturday we used Stewart's FT897 as the main HF rig, Sean operated a 2m meter station with a number of contacts. Like last year I had my FT857 operating a datamode (primarily PSK) but a damaged feeder issue curtailed this for most of the day and we soon concentrated on the HF SSB voice contact as conditions were good and the band was busy with other JOTA stations.

In keeping with the aims of JOTA we didn't chase numbers instead we had some lengthy quality contacts, including a marathon 30 minute plus contact with I believe was GB2WSG the 2nd Wellington Scout Group with lots of two-way greeting messages being sent to really give the children a full experience of using the radio.

The day before I had quickly constructed a Morse code oscillator (since I didn't have one) using an arduino board and an old computer speaker for added volume and this proved popular as the children tapped out their own names, their friends names, call signs, their ages and various words.


I had created some certificates and stickers to reward the children and to prove they had completed the tasks should they need them for any future scouting badges and awards.

Sunday we just operated for the morning and since Stewart couldn't attend I brought along my FT450D and Sean and myself operated on HF SSB. Sadly my poor Morse oscillator failed quite spectacularly in a puff of smoke but all was not lost as again conditions were excellent and we were able to pass lots of greeting messages again. I haven't used the FT450D in anger so it was excellent to let it stretch its legs and the audio and DSP proved excellent in dealing with the QRM from the contest running at the same time.



Working with the Scouts this week has really was a therapeutic exercise for my soul and made me glad I got licenced and was able to get involved with this. I am not naturally comfortable with children, since I am not a parent. But it was rewarding seeing the look of wonder on some of their faces as they passed messages.. like it was magic ;-)



Saturday, 10 October 2015

Black Dog Days

This time last year I was preparing to take my advanced licence exam at the RSGB Convention (which I passed) and I vowed to attend this years convention proper.
 photo 28940_m.gif
Unfortunately I have a had a bit of a wobble emotionally and despite having booked day tickets I have decided at the last minute not to attend.

The past few weeks have had plenty of euphoric moments, with the successful flight of my the high altitude balloon at the recent hamfest and my first satellite QSO however following these highs I have suddenly found myself in a bit of a low, this is due to a number of factors.

This isn't the first time I have been in one of these dark moods. Sadly apart from my hobby, which has become a crutch I realise I am again stuck in a rut and I know I have to make a number of major decisions to put things back on track.