View from Oban Bothy

View from Oban Bothy
Showing posts with label Radio. Show all posts
Showing posts with label Radio. Show all posts

Monday, 19 January 2015

Sunday 11th January, Hide and Seek

Playing Radio

To recap, for those who haven’t been paying attention, this is Hide and Seek with radios. Some poor unfortunate will hide themselves away in the area covered by a particular 1:50k OS map. Said unfortunate will be armed with a radio transmitter with which he or she will transmit from time to time. The trick is to find the hidden station, ideally before anyone else does. There can be any number of ‘hunters’, there’s typically 5 – 10 out hunting on a good day.

Following the huge success of the last Radio Direction Finding contest in December (I won / came first / beat everyone else in etc), it fell to me to arrange the next event in the series. Competing in these events is great fun, hiding is just as much fun – it just takes a good bit of planning….and it helps if you have an evil, sadistic streak   ;-)

The hiding place was to the east of Poynton, Cheshire. The exact location was at the edge of Prince’s Wood – the tall trees should have given me loads of opportunity to erect a decent aerial. The bad news was that I’d gone up to the site the previous day with my able support team of Eden & Nat but the bitterly cold strong wind-driven rain, hail and sleet made aerial erection very difficult indeed.

image Where we woz hidden

We managed to sling 130ft of wire up into the trees. The earth system consisted of a 4ft metal spike driven into the wet ground and a long section of barbed-wire fence. I tuned the aerial with my new toy:

http://www.mfjenterprises.com/Downloads/MFJ-259C/MFJ-259C_R.jpg

The MFJ259C has proved it’s worth. Apart from making antenna tweeking a doddle it’s helped me learn more about aerials.

Like I said, we managed to get the aerial up but it would have been almost impossible without my eager assistants – thanks lads!


On the big day a total of eight teams took part, and along with their respective friends, relations, fans etc there was a total of 20 children of all ages in attendance. The children were mainly quite old – some were beyond retirement age.

My support team and I arrived on site in good time on the Sunday morning. Camouflage netting was set up, bacon butties were made (and eaten) and we were ready to go.

imageChris Heys at the start – photo lifted from the group’s Facebook page 

First transmission was 10am but we weren’t heard at the start. In these cases The Envelope is opened. The Envelope is only to be opened in cases of dire emergency – like when the transmitter can’t be heard at the start. This Envelope contains an approximate compass bearing to give the hunters half a clue of where to start looking. The start of the event, the place everyone meets up at to take the first compass bearing, was in Sale, Cheshire – about 10 miles from the transmitter.

image

Multiple transmissions are made, in theory to a sort of schedule. Unfortunately I screwed up the schedule….but only a bit.

My assistants, Nat & Eden, were lurking in the woods. They were armed with a walkie-talkie and were able to keep me up to date with news of approaching hunters. This kept them entertained for a good while. I’m sure they ‘assisted’ those trying to find the hidden station!

First man in was Dave Peacock, who charged up the hill in fine style – arriving around 11.10am, a good 3 minutes before the next man, Chris Plummer. The remaining hunters (apart from one team) arrived over the following half hour. The hunters approached from pretty well the same direction, all were pleasantly confused by the woodland. The DNF (Did Not Find) team managed to locate the apres-event pub. This was A Good Thing, a very pleasant lunch at the Boar’s Head in Poynton  rounded of the day quite nicely. 

Not being heard at the start was a bit of a pain – and a surprise. A huge and resonant aerial system should have been easily heard at a range of 10 miles – particularly when the transmitter was located in an elevated position. This has happened loads of times before, I reckon the transmitter’s knackered. I’ll bring my own next time – I know it works! 

Not much in the way of photographs I’m afraid. I took my camera with me but was so engrossed in remaining concealed that I didn’t get chance to use it.

Wednesday, 17 December 2014

14th December, Radio Direction Finding on Top Band

Variously described as orienteering with radios or hide and seek for grown-ups (or not very grown-up in most cases).

The general idea is that someone will hide themselves away in the area covered by a particular 1:50k OS map, around 1600sq km. They’ll have a radio transmitter with which they’ll transmit for short periods. Some transmissions are scheduled whilst others are random.

The only rules the transmit station has to adhere to, apart from the Amateur Radio Licence regulations, are that they must be located in an area of public access, not be in a building, and once established they must not change position. It’s a given that the transmitter doesn’t change frequency during the event. The fun begins when the competitors have to locate the hidden station – first one in is the winner. Obviously.

The transmitting station operates on Top Band, or 160m. The actual frequency coverage of the band is from 1.81mhz to 2mhz, just below the Medium Wave broadcast band. Because it’s fairly low in frequency (= long wavelength) the aerial needs to be quite long, ideally a quarter-wavelength wire - around 40m long.

The competitors are equipped with map and compass, and most importantly a radio receiver fitted with a highly directional aerial. The radios are home-made, commercial equipment generally isn’t sufficiently portable or affordable.  

imageTop Right: Transmitter, Centre: DF Receiver, Bottom Left: Breton Plotter 

So, on Sunday morning a group of DFers gathered in Sale, Cheshire, and strained their ears (and other bits too probably) to get a bearing on the hidden transmitter’s first transmission, scheduled for 10am. 

image At the start

Unfortunately the signal was completely inaudible. In such cases there’s a sealed envelope available at the start which contains an approximate bearing (+/- 20 degrees) and an idea of distance, usually within 10km. This can still be a huge area to search.

Not being able to hear the transmitter at the start can be a clue – it’s possible that the station is hidden in a valley so that the signal isn’t being radiated too well. It could also be that the operator decided not to bother and stayed in bed instead….or perhaps he/she fell in a river, fetid swamp, or got eaten by an alligator recently escaped from a zoo. Or more likely a private collection.

Anyroadup, the approximate bearing given was 67degrees which passed within 4km of the transmitter, and the distance given was between 10 and 20km from the start. A quick faff with maps, rulers and pencils soon had the hunting area defined on the map, and competitors jumped into their cars to find somewhere suitable to take a bearing from the second transmission.

In theory two bearings are needed to locate the transmitter…..where the lines cross is where the station SHOULD be. That’s if the laws of physics are to be believed. After all, electromagnetic radio waves travel in straight lines – everybody knows that. Except they don’t.

All manner of external influences can distort radiation patterns, the proximity to pylons and overhead power cables being prime examples. 

I’m not particularly mithered about winning, it’s always nice to do well of course, but I just like to enjoy the event. I left the start and travelled around the M60 towards Ashton-under-Lyne at a sedate 60-65mph. I’d pin-pointed a couple of spots where I’d try to take a second bearing and headed straight for the first one, arriving in good time for the second scheduled transmission….nothing heard.

At the third transmission I heard a good loud signal. I plotted the bearing, then jumped back into the car and drove half a mile up the road where I just managed to get another bearing before the station went off air.

Suspicions grew as to where the station might be…..very close to where Gayle and I had walked a few days earlier, Daisy Nook Country Park. I plotted the bearing onto my map and drove close to the point where the lines crossed – arriving just in time to hear another brief transmission.

My suspicions were confirmed, the signal was so strong that it overloaded my radio. I was obviously very close indeed.

I left the car and followed muddy footpaths towards the River Medlock. After much slipping and sliding, charging across the river (I was wearing my fell-running shoes!) and thrashing through very wet undergrowth I spotted the very well camouflaged station.

imageRoger, the station operator, now not hiding himself away. The box closest to him is the transmitter. The white-ish square(ish) piece of kit is my DF receiver.

At approximately 11.27am (exactly!) I officially found the transmitter. Surprise, surprise – I was first in.

image Posing with Roger, a slightly (very) muddied JJ….looking quite pleased with his little self

Around 10 minutes later we were alerted to the sound of someone crashing through the undergrowth on the other side of the river, looking for the hidden station. We kept perfectly still, trying hard not to snigger, as we watched with no small amount of glee as Chris splashed his way through the mud and bog. When he actually spotted us he declared he wasn’t going to cross the river, he hadn’t won so why bother?!

image

Chris, who didn’t come first, was heard to say something like ‘bugger crossing that river’

The next half hour or so saw the remaining competitors finding the transmitter – all coming in from a similar direction….and the wrong side of the river.

image

Chris and Roger, daring each other to cross the river

image

A happy Geoff, officially second in – because he crossed the river

image Determined not to be outdone, Hayley crosses the river

image An excellent lunch at The Hare & Hounds, Luzley

Results:

JJ                              11:27

Chris P                       11:40 (Located the station but didn’t cross the river)

Geoff Foster               11:42

Roger B                      11:48 (Located the station but didn’t cross the river)

Hayley                        11:57

Dave Chipp                 11:57:30 (Located the station but didn’t cross the river)

image

Plotted route shows my route in, a bit all over the place as I was trying to take multiple compass bearings on the hidden station in order to triangulate it’s position

image

The arrow points to the hidden station, the red line is the approx bearing from the start. The station was 10 miles from the start, as the crow flies.

Being as wot I came in first it’s down to me to hide on the next event, scheduled for 11th January.

Monday, 23 June 2014

Saturday 21st June 2014, Bletchley Park

The longest day, a visit to the home of the WW2 'Code Breakers'

First the bad news: the nights are closing in.
It gets better:
When the opportunity to visit Bletchley Park arose it took me around 2nS to decide to take up the offer. One of Mr Branson’s Pendolino trains provided the means of getting to Milton Keynes whilst friends John and Martin provided transport for the last few miles.
20140621_131933The Mansion 
The Code Breakers who were based here were a select group of men and women who had the incredible mental agility to break what seemed to be an impossibly complex system of encoding and ciphering. The codes were generated using Enigma machines – fiendish bits of kit that were capable of generating millions of different codes.
The Code Breakers weren't able to carry out this vital work alone, they were assisted by an army of ancillary staff: wireless operators, those who variously fetched & carried, maintained the decoding machines, and many other roles that we can only guess.
The work was generally carried out in huts, which until recently had been allowed to fall into a state of disrepair. Fortunately 'someone' had the foresight to realise that we were in great danger of losing this important link with our recent past and so money was thrown at the problem.
20140621_131731Hut 1 
The most well known role of the Code Breakers was their involvement in the Battle of the Atlantic, fighting the menace of the German U-Boats.
It is less well known that efforts of the Bletchley Park Code Breakers also played a huge part in other theatres of WW2: the wars in the air and on land.
It's impossible to say with any certainty by what period of time WW2 was shortened by due the work carried out here,  but it was very considerable.
Secrecy was vital, if word ever got out about the work that was carried out here the consequences would have been unthinkable. Even husbands and wives working here never let on to one another about the work they carried out. In fact it’s highly likely that a majority of those working here had no idea what they were doing – just that the work was of national importance. In reality ‘national importance’ was an understatement, ‘national survival’ was nearer the mark.
As the systems used by the Germans became more complex it was Bletchley Park’s code breakers that faced the challenge and succeeded in breaking the codes, eventually designing and building electro-mechanical computers such as the Bombe:
P1020936The Bombe 
P1020935 The inside gubbins of the Bombe
Key to much of this work was the genius that was mathematician Alan Turing:
P1020933Statue of Alan Turning with an Enigma Machine 
As more and more processing power was needed to crack the German codes the world’s first electronic computer was built and designed here. Jack Copeland’s book on Colossus is brimming with information.
My brain is still buzzing from this visit, there’s so much history crammed into Bletchley Park that it’s beyond me to effectively put it into words. You should go yourself to check it out. entry is £15 but that gets you admission for a whole year. I need to go back again, I missed so much.
Rather than any more of my drivel, here are some pics:
P1020922
P1020916  A BSA M20 (or M21?) side-valve
P1020920
A National HRO receiver
P1020929
Reconstruction of a monitoring station
P1020926
P1020928 An Enigma Machine
More photos are here. This album will be added to in the next few days.










Monday, 29 April 2013

For those in peril on the sea

It’s dead easy to get side-tracked whilst browsing t’interweb – this happened to me yesterday as I was searching out information on the now defunct College of International Marine Radiotelegraphic Communications, in Brooke’s Bar, Manchester. This was the college where I took my morse test around 1980.
When I was around 12 years old, I would listen to ‘Trawler Band’, that part of the radio spectrum above 2mhz – or 150m in English. I would spend far too much time listening to the ship-to-ship and ship-to-shore radio traffic from the comfort of home. I thought I knew what life must have been like on the rough seas.
That was until yesterday when I came across Sailing with Hunters – a Radio Officer’s memories of life in the fishing industry. It’s fascinating and quite horrific. Give it a read, it won’t take long A bit more wandering around the web came up with some seriously scary images of fishing boats at sea. They’re from the Daily Mail, despite that they’re tremendously good.
Google Image from Mirror website
It could just make you think twice the next time you grumble about the price of fish.

A squeeze key, great for sending fast morse – but I think they weren’t officially allowed to be used on board ships. If a surveyor came on board to conduct an inspection these keys had to hidden away!

Saturday, 13 April 2013

Saturday 13th April, Coronal Mass Ejection


Don’t rely on your SatNav / GPS devices for navigation this weekend – Thursday’s large Solar Flare and subsequent CME could temporarily knock-out any such equipment. The CME backlash usually hits earth a few days after a solar flare….and that’s about now.


When a CME occurs large amounts of solar plasma are ejected from the sun, taking around 3 days to travel from the solar surface to earth. When this stuff eventually hits us the effects on radio communication and radio-related navigation equipment  are, er, interesting!


This CME may well bugger-up my radio activities this weekend. Ho hum.


Now the good news: events such as these can cause very spectacular auroral displays, the closer you get to the polar regions the more visible they become.


The time-lapse video clip above was taken from Wikipedia.


Have a read of this.

Thursday, 24 January 2013

24th January, A low noise receive aerial


Modern electronic equipment is the curse of the radio enthusiast. The amount of interference generated by computers, television sets etc, is enough to flatten weak radio signals. The RF crud generated by normal household electronics is strong enough to completely wipe out radio reception. Even seemingly innocent kit can cause problems: some mobile phone battery chargers, some low energy lamps, the dreaded BT wireless hubs, the awful PLA/PLT 'data-over-mains' devices, switched mode power supplies, plasma TVs (these really are bad news), the list goes on and on.

For those who aren't radio enthusiasts but live in an urban environment, you can get an idea of how bad this interference is by tuning around on an AM radio, indoors, in the evening. You'll probably hear plenty of radio stations, but you'll also hear lots of whistles, heterodynes, buzzes, mushy noises etc, that shouldn't be there. Put your AM radio next to a (switched on!) PC or TV and I'd be surprised if you can hear ANY broadcast stations.

It's a legal requirement that electrical / electronic equipment shouldn't cause radio interference - but trying to enforce the law is far easier said than done. There's a huge amount of kit for sale on the high street today that's illegal - it just doesn't meet the RFI / EMC regs. Such is the influence and power of large corporations, they very often hide behind their product's 'CE' marking. I could go on about illegal 'CE' markings....but I wouldn't want to bore you.

This is all bad news for me, I've not been able to play radio for a while. I've experimented with different aerials with varying degrees of unsuccessfulness.

My first major attempt at quiet radio reception was this active, untuned loop. The circuit and notes are published on the QSL.net website of Des, M0AYF - and very good it is too. Thanks Des!

This is the circuit diagram:

Loop amplifier circuit diagram.

The active loop aerial is situated about 35-40 ft down the garden, mounted at around 6ft above ground level.

It's certainly better than my 80m dipole on receive but it's still susceptible to picking up man-made noise - although at generally lower levels. I find it pays to switch between aerials to see which receives less noise - sometimes the dipole wins

My latest attempt at reducing received noise is this little piece of kit I put together this evening using bits from my junkbox:


This is the ENTIRE antenna - apart from it's power supply. The aerial bit is the plain bit of board on the left, the electronics on the right is a buffer amplifier that matches the extremely high impedance of the small aerial to the low impedance input of the receiver - it provides a significant amount of gain too.

It receives power down it's coaxial cable, and with a little bit of filtering at both ends, there is no need for batteries or separate power feed cables. 

It's tiny - and it seems to work quite well. Although received signals are down on the dipole, received noise levels are WELL down = much easier to copy weak signals that would otherwise be swamped by man-made interference.

It's an E-Field probe so it receives RF by capacitive coupling to the electric field rather than a magnetic field.
 
There is good evidence to suggest that the magnetic component of interfering domestic sources such as TV line time bases tends not to be significantly confined within a building whereas the electric field tends to be significantly attenuated by the structure. This can work to the advantage of this small aerial if it's mounted at a reasonable height and clear of mains wiring & buildings.
I can't claim any originality for this idea, it's the brainchild of Roelof Bakker, PA0RDT - quite a whizzkid by all accounts, and my thanks go to him.

Details of the aerial are widely published on t'interweb but I settled on the article published on the Crawley Amateur Radio Club's website and my thanks go to them also.

Tomorrow, time and weather permitting, the aerial will be mounted remotely down the garden.

Perhaps lower noise radio-activity will return to Timperley soon.

Wednesday, 12 September 2012

Wednesday 12th September, Getting the aerial up higher

Winter is approaching fast so I’ve been messing about with my aerial system at home.
The aerial is a half-wave dipole for 80m fed with twin feeder. My garden isn’t long enough to squeeze 132’ of wire in a straight line so the ends are folded down. The centre of the dipole was only at about 22’ agl, nowhere near high enough for the system to be an effective radiator. It performed adequately but that’s all.
Time for a re-think. I’ve managed to get the dipole centre up to around 30’, still not high enough but certainly better. This afternoon’s little job is to make a coax balun although the poor weather means it probably won’t get installed today.
The aerial is now certainly a better radiator on 80m & 40m, but receive noise is still a problem. Next door have a noisy TV, it may be plasma…the work of the devil!  Unfortunately my neighbours are unapproachable so I need to deal with the problem on my side of the fence. The RF noise next door’s TV generates makes 80m difficult to use in the evenings. I’ve treated myself to a noise canceller (MFJ1026)but I’ve not tried it out yet, I just hope it works!
image MFJ1026 Noise Canceller
This little box works by mixing signals from the main station aerial with signals from a ‘noise’ aerial – an aerial that is aligned to pick up the interfering noise. The phase and level of the interference is then altered by the box in a manner that allows it to cancel out the noise received by the main aerial = much reduced noise. That’s the theory, we’ll see.
My main interest is using low power (2-3 watts) CW (morse) on the 40 and 80m bands. Winter is a good time to play radio, hopefully my tweaked aerial system will pay dividends.
Apart from the noise canceller, my main station will remain unchanged: Yaesu FT817 transceiver fitted with a narrow CW filter, and a Bencher squeeze key. A ‘T’ Match ATU is used to optimise the match between transceiver and aerial system.
         image image
                        Bencher Key                                                   FT817
My FT817 has a microphone but it’s rarely connected – it just gets in the way!