magnetic loop tweaks
14 Apr '10, 15:39
I've made some slight changes to my magnetic loop aerial. Nothing major, but useful none-the-less.
The original design, as copied from G4ILO, featured a T shaped mast with hooks on the left and right of the top bar to support a loop of RG-213 coax. The biggest problem I found with this was establishing the correct loop shape to create a good match. It was easy to squash or expand the loop which could destroy a previously good match.
To overcome this, I've redesigned the mast to a + shape. The same coax is used for the loop but it is now much more rigid than before meaning if I collapse the aerial and re-assemble it later, I am more likely to maintain a good SWR reading.
Other than that, I've now got a large run of RG58 coax to connect the rig to the aerial meaning positioning is much easier. I've also obtained a better fitting knob for the tuning capacitor. The one I was using was too big for the shaft making it off-centre, wobbly and more difficult to tune.
So what do I have still to do? Well G4ILO's design features an inbuilt SWR indicator which I might incorporate although it's not essential for me at the moment.
I'm still thinking about remote motorised control as well although gears seem to be more complicated than I thought. It is only the gears which are the problem though. The capacitor housing is large enough for a motor which will be connected to a long cable run (as long as the RG58) terminating in a small control box which can set next to the radio. All it needs to incorporate is a momentary push button control to activate the motor and perhaps a variable resistor to control the motor speed.
broken images
03 Apr '10, 23:55
It seems I've somehow managed to break images on this site. Goodness knows how mind you.
Until I figure it out, I've disabled the Photography section and removed images from blog posts. I'll put them back when the mystery is solved.
What's most strange is that my recent coding has had nothing to do with images. I did wonder if I'd damaged some of my own PHP functions but nothing has jumped out at me so far.
It is nearly midnight though, so maybe I'll solve it with a fresh head tomorrow.
uk postcode data search
03 Apr '10, 23:09
On 1 April 2010, Ordnance Survey opened up a lot of it's data including a cut-down version of Code-Point - a database of UK postcodes.
Since this data is available free of charge, and has a licence aligned to the Creative Commons Attribution 3.0 Licence; I decided to download the data and incorporate it into an SQL table for use on this website.
I've now completed the import of the data (1,696,088 records not including code definitions) and have created a webpage which can be used to query this information. A user can input a postcode and have all open data which I have available displayed.
Not only that, but I have also been learning about converting geographical data in to different systems. The Code-Point data provides co-ordinates in the British Coordinate System of six-figure eastings and northings. My new page converts this data into latitude/longitude, National Grid Reference, Worked All Britain (WAB) square and Maidenhead Grid Locator. By having latitude/longitude data, a Google Map can also display a marker showing where a postcode is.
Now I've got a bit of a grasp on how to convert data, I hope to extend the page to accept input of other forms of geographic data and have it convert in the same way. For now though, I'll leave it at postcode only.
There's nothing particularly unique about this. Many sites across the internet allow postcode searches and data conversion. This was essentially a two day project which I decided to do simply because it costs nothing but server space (over 150MiB), I fancied doing some coding and I find this information useful from time-to-time as part of my amateur radio hobby. If anyone else finds this information useful then that is a bonus.
Find the link in the navigation menu, above.
pure highway digital radio receiver
23 Mar '10, 18:41
Following my comments about the closure of BBC Radio 6 Music and the availability of DAB receivers for use in the car, I decided to do a bit more research.
Whilst my point about the lack of availability still stands, there are options for listening to digital radio on the move. Rather than limiting myself to searching the Halfords website (who do not stock DAB receivers), I made a wider search and did come across receivers available from stores such as Argos, Amazon and John Lewis.
The choice is still limited. There are not many head units available and those that do exist cost significantly more than analogue radio receivers. There is a cheaper option available though - a receiver which re-broadcasts DAB on to the FM band. I picked up one of these units at the weekend ... a Pure Highway.
This is a unit which is about the size of an old Walkman (the cassette tape variety). It has a windscreen mount to hold it in place and takes power from the car 'cigarette lighter' socket. An internal adhesive aerial is provided which sticks to the windscreen or a fixed window. A few controls provide access to tuning, station presets and a settings menu. Feedback is provided by way of a small LCD screen.
Setting up the Highway is very straightforward; it can be tidily installed in 10-20 minutes. I positioned the windscreen mount to the right of the windscreen, ran the power cable through the fuse box cover and through the centre console to re-appear just before the power socket, and stuck the aerial on the rear right passenger window which doesn't open. The aerial cable is tucked in to the trimming above the door surrounds and is only visible when it appears near the mount.
Initial tuning picks up my local multiplexes: BBC National DAB, D1 National and NOW Essex. Unfortunately reception of the latter is not great and even D1 National has problems in certain parts of the county. BBC National DAB is more or less fine apart from one very small area in my daily commute. Whilst I'm happy with this for the time being; I will probably invest in an external aerial which should improve the reception of D1 National at least.
The Pure Highway incorporates an FM transmitter so that digital radio can be heard via an existing car radio. This works particularly well. On first use, the unit scans the FM band for a free frequency and then instructs the user to tune the car radio to that frequency. On my route I have not heard any hiss or breakthrough from neighbouring FM stations. The car radio RDS displays "PURE DAB" when correctly tuned, although it would be nice if it displayed the name of the tuned station.
If your car radio has a line-in socket, there is no need to use the FM transmitter. A line-out socket on the Highway allows direct connection to the car radio which should offer higher sound quality particularly if the FM band is crowded. My car radio doesn't have this though, so I can't test it.
Another handy feature which I haven't yet tested is the presence of a line-in socket. This allows for the connection of an MP3 player and uses the FM transmitter or line-out to send that audio to the car radio. I no longer need my original FM transmitter since the Pure Highway now fulfills that role!
A final feature that could prove very useful is that the Highway is not limited to use in the car. Of course, any FM radio within it's range can receive it's signals so you could convert an existing home radio to hear DAB signals. More than that though, is that it can be used as a portable receiver. By adding a couple of AA batteries and plugging headphones into the line-out socket, the Highway becomes a handheld receiver. I'm using it in this way as I type this, and sitting at my computer I get perfect reception of BBC National DAB and D1 National. NOW Essex is non-existent however. The lead of the headphones is used as an aerial, so how this will work walking about or on the train, I don't know but in theory at least, this saves the need to buy a separate unit for portable listening.
In summary, I'm very happy with my new purchase. It's brought me back in to the world of digital radio, which I vacated back in 2005 with the loss of my first car and it's DAB head unit (which broke). Whilst I maintain my opinion that there are shortcomings to the DAB system used by the UK, I'm happy to be able to receive the digital-only stations which appeal to me ... BBC 6 Music, NME Radio, Amazing Radio, Planet Rock and Absolute Radio (not digital only, but the only alternative here is AM).
The Pure Highway is available from stores such as Amazon, Argos, John Lewis and Play.com for approximately £80
thompson comments on 6 music closure
10 Mar '10, 22:36
Caroline Thompson, Chief Operating Officer at the BBC, has made comments about the closure of BBC 6 Music and changes to BBC 7.
The Guardian report which details these comments is linked below, but I'm drawn to a few quotes from the article:
"The average age of its listeners - 37 - is at the heart of the demographic targeted by commercial radio", she told delegates at a Westminster Media Forum event.
I'm intrigued to know where the commercial alternative is for those within 6 Music's demographic. Around here, alternative music is played on stations such as XFM and Absolute Radio but the diversity of music pales in comparison to the BBC's offering. By closing 6 Music, can I expect new commercial stations to appear or the aforementioned stations to broaden their playlist? I doubt it. I'd like to be proved wrong, but I'd be very surprised if I am.
There were also questions, she said, about whether the BBC should run three popular music stations - Radio 1, Radio 2 and 6 Music.
Can 6 Music really be labelled is a 'popular music station'? It's not exactly playing Cheryl Cole, Pixie Lot and Scouting for Girls is it? A diverse playlist that leads the listener on a journey of musical discovery and appreciation is not popular music. A playlist that gives airtime to the struggling indie artist is not popular music. Yes, okay, there may be some similarities between these three stations particularly when considering the specialist aspects of Radios 1 and 2. The daytime playlist of those two though is unashamedly mainstream and safe.
...the money saved by the closure would be reinvested in radio, with a particular focus on digital services.
It's interesting that 6 Music is a radio station and a digital service. Am I missing the point?
testing the magnetic loop
09 Mar '10, 20:19
I've been further testing my magnetic loop aerial over the last 24 hours, but haven't made any changes to the setup as such.
I did find out why, just before writing my blog yesterday, I couldn't get a good SWR reading despite doing so the day before. Rather foolishly I'd let the bare braid from one end of the RG-213 loop touch the outer contact of the phono plug to which the coupling loop connects to. Whoops! Once I'd realised that, getting a match didn't prove to difficult.
In actual fact, I think I may be getting used to tuning the aerial. I'm having very few problems setting up for 14.070MHz for PSK31 use. 7.035 doesn't match quite as well, but I can still get about 1.75:1 I'm hoping it's possible to get this better by tweaking that coupling loop - either fine tuning it's length or adjusting the shape.
Disappointingly though, I still haven't managed to make any contacts. I've been calling CQ using PSK31 on 20m and 40m, and also using SSB on 40m but to no avail. I'll keep trying but I'm not entirely sure how well my signal is getting out. The only indications I've had that I am transmitting are the appearance of markers on the PSKReporter map which indicate that a monitoring station has heard me. This has happened three times - in Sweden, Germany and Italy.
It does sound promising, but until I exchange some reports I'm really just speculating as to how well this aerial is working for transmission work.
magnetic loop aerial
08 Mar '10, 19:17
About 6 months ago, I visited the website of Julian, G4ILO who had detailed how to build what he has called a 'Wonder Loop' - a small indoor magnetic loop aerial. Following this visit I was inspired to build one myself.
As is my way, I've taken a little while to get around to building this but I have now completed my first build with moderate success.
I've used a 30-310pf (approx) tuning capacitor which I found on eBay for a few pounds, a loop made of RG-213 coax cable and a coupling loop made from some high current cable.
The capacitor is housed in a rather large plastic box (again an eBay purchase) using a couple of screws and a couple of cable ties to hold it in place. The terminals of the capacitor run to two terminal posts to which I can connect the main loop. The coupling loop is connected to a Phono socket, which runs directly to a BNC socket on the rear of the box. From this socket runs a patch lead to the transceiver.
I haven't been particularly precise in the construction - so imprecise in fact that when drilling holes for screws to secure the capacitor, I managed to mis-judge where on of the holes went. I ordered 2m of RG-213 for the main loop, and initially I used the entirety of this, only trimming it slightly during first tests. The coupling loop was one fifth of the size of the main loop, but since the trimming this is now slightly out of proportion.
The assembly of the aerial was completed yesterday after various trips to Maplin and B&Q to get parts, and initial tests are promising. As a receiving aerial I'm really quite happy. Sitting in the flat, it out performs my whip aerial when tuned correctly. Transmitting is a slightly different matter. Yesterday I managed to get a good match with SWR readings of around 1.5:1 or better on 40m and 20m and the PSKReporter website showed my CQ calls on PSK31 being received in Italy with 10w of power. Unfortunately today so far I can't seem to get a match on either band.
I'm experiencing an issue with the sharp tuning of the capacitor. I don't have a reduction drive so I'm having to be extremely precise with the tuning knob - possibly more precise than I am able to control. Another issue is the effect my hand has on the SWR reading. I've notice today that when tuning I can perhaps get a lowish reading but when moving my hand away, the reading worsens. Strangely I didn't notice this yesterday. I can't think of how to overcome this unless I can motorise the control. I'm not sure how possible that is.
My next steps I think are to look at the dimensions of the loop, and perhaps shorten it a bit. I will also try re-creating the coupling loop ensuring it is one fifth of the size of the main loop. I'd like to investigate the possibility of creating a reduction drive to allow for fine control but I need to source cogs and rods and figure out how to fit them into the existing design. If any readers have ideas of where to get such parts, please do leave a comment below.
Despite these initial set-backs, it's been fun to create what is my first home built aerial and to have it work albeit temporarily. Credit of course goes to G4ILO for his design, which I have pretty much copied, and write-up which was very helpful in aiding construction.
the end for 6music?
02 Mar '10, 18:55
The BBC has today announced cutbacks to it's services intended to save £600m which will be re-invested into programming and original content.
The victims of these cutbacks are the radio stations 6 Music and the Asian Network along with a significant proportion of the BBC's website.
Initially this was reported in the newspapers a number of days ago so the announcement is in no way a surprise but I wanted to wait until it was official before commenting.
I'm disappointed that the BBC deems it necessary to wield the axe over 6music. The station is exactly what a publicly funded broadcaster should be providing - a station that would not exist in the commercial sector. Absolute Radio and XFM are probably the nearest big commercial stations but these do not have the diversity offered by 6music. Losing this station will leave a gap that will not be filled.
Part of the problem of the station has been the number of listeners it attracts. I wonder if this problem is down to it's broadcast medium though. Personally speaking I listen to the vast majority of radio whilst in the car. I do not have digital radio in the car. I therefore cannot listen to 6music. I'd be surprised if this is not the case for many people, and therefore I do proportion some of the blame on to the fact that in-car digital radio equipment is not easy to come by (I've checked Halfords and they have precisely none). Most cars do not have digital radio fitted as standard. Until this changes, digital-only stations may well suffer from lack of audience.
The BBC's proposals have now been submitted to the BBC Trust and will be subject to a 12 week consultation period, so there is still hope for the station. If things go the wrong way though, 6music could disappear by the end of 2011.
The BBC Trust are accepting views on this consultation, so to petition the broadcaster to save the station visit:
https://consultations.external.bbc.co.uk/departments/bbc/bbc-strategy-review/consultation/consult_view
new digital mode
25 Feb '10, 20:34
A new digital mode is on the scene called ROS - a spread spectrum mode ideal for weak signal/QRP use.
The mode can operate at two symbol rates - 1 and 16 baud; the former is ideal for very weak signals with the user guide stating transmissions can be decoded with at up to -35dB S/N. Unlike WSPR (another weak signal mode), this is a 'live chat' mode allowing users to converse in a way not dissimilar to PSK31 (at 16 baud anyway).
I'm keen to have a go. I'm quite fond of digital modes, and anything that means my disadvantage with aerials is not so much of a problem is certainly welcome. Unfortunately though, the software is Windows only.
I know using Linux is my choice, and with that choice comes the expectation that some software will be out-of-reach. I do think that this should not apply to amateur radio software though. In the spirit of the hobby, such software should be portable. It could be just that the source is published so that others can port the software, but however it is done, those that do not use the popular OS should not be left out.
WINE (the Windows compatibility layer) could be a quick option, but a quick attempt has not been successful. I will put some more effort in to getting it going but there's no guarantee of success.
Fortunately the author has promised to release the source once the application is finished. When that will be however, is anyones guess and until that happens, us Linux (and presumably Mac users too) are left high and dry.
man (not) on the moon
01 Feb '10, 22:39
I'm really quite disappointed. President Obama has scuppered plans to send people back to the moon.
George Bush announced the idea back in 2004 that NASA would return man to our nearest celestial neighbour before aiming for Mars. If all had gone to plan, humans could have made the first return journey by 2020.
Unfortunately it doesn't look like that will happen. Owing to budget shortages, and what Obama calls a lack in innovation, he has recommended in the 2011 budget that the Constellation vehicle be abandoned.
A White House spokesperson says this isn't a step back, and that the ambition is still there but I can't help treating the comment with a little scepticism.
My view is that returning people to the moon is important and not just for the excitement for all of us who get to observe. I thought this time it could lead to a more permanent space presence. This would provide opportunities for science of course; a launch pad for vehicles to move further out into the solar system and also as a mining base. It's fairly well known that the element Helium-3 is present on the Moon but rare on Earth. This element could prove vital in providing power from Nuclear Fusion. Solving the world's energy problem seems a pretty good reason to go, and I'd have thought the sooner this happens the better.
Of course, money at the moment is a big problem and there are always other projects and needs which require funding. I've questioned before why there isn't greater international co-operation in space ventures. It doesn't need to be America that returns to the moon. Lets get space agencies from around the world all involved in a common goal and sharing the cost.
newerolder
Last.fm: Last played:
03 Sep '10, 19:10
Jimi Hendrix – Bleeding Heart
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m0gky: Got an #XBox today, but having problems with #XBoxLive. Just me or anyone else? Re port forwarding, is incoming on 80 required?
