Mar 302013
 

Electrolytic’ Capacitors may smooth out our ripples but they do need some TLC or they will blow your equipments main fuse. They do benefit from a regular top up of electricity but some are neglected and need a little bit of extra TLC to bring them back to life.

electrolytic capacitorThis short article is covering the poor neglected electrolytic capacitors that have not had an electron pass through them for a very long time and is to give you advice on giving them that extra TLC. More information on electrolytic capacitors can be found on the Wikipedia. While this topic is on unused equipment it is also relevant to New Old Stock capacitors recently bought.

Important!! There is controversy about using the methods in this article  on switch mode power supplies. If your equipment has a  switch mode power supply, then use at your own risk!

If a piece of equipment has not been used for some time that has a linear power supply, the electrolytic capacitors electrolyte deteriorates and can in fact blow the main fuse of the equipment straight away. Caution is required before switching on the equipment and a reduced voltage on power up usually helps.

A technique called re-forming is used to bring the capacitors back from the grave and all that is involved, is to apply a small voltage to start with and gradually over time increase the voltage till you reach the maximum voltage. On equipment this can be achieved by powering it up with a Variac transformer and slowly increasing the voltage over time. A quick method that can be used is to put the equipment in series with a 40 Watt light bulb and the same effect can be achieved though not as good as using the Variac Transformer. Basically what you are doing is using electricity to re-form the electrolyte dielectric see Wikipedia.

Warning! It’ is OK to start with reduced input but does not always guarantee ‘no bang or smoke’ !!

Mar 302013
 

RSGB Regional Club of the Year PresentationSteve Boden G4XCK Regional Manager for Region 13 Presenting Lincoln Short Wave Club Chairman Mark M0ZLE with the RSGB Regional Club of the Year Shield, watched on by Ian G4XFC who designed the layout for the LSWC entry and local Deputy Regional Manager Steve Burke M5ZZZ

Regional Club of the Year SheildThe presentation was well attended by club members and everyone enjoyed the buffet meal provided by our club secretary Pam G4STO and Steve M5ZZZ.

A toast was given for our late Chairman Chris Jones G0PIO who suddenly passed away at the end of November last year. It was noted that is was the hard work of Chris that helped us to win the RSGB Regional Club of the Year.

To highlight the end of the evening our Chairman Mark M0ZLE announced to club members that he had received a letter from the RSGB informing the club that Lincoln Short Wave Club has been selected as one of the three national finalists in the Club of the Year 2012. Fantastic news.

Results will be announced at the RSGB AGM on Saturday 20th April in London, starting at 12.00 noon.

Please let our Chairman Mark M0ZLE know if you wish to attend.

 Posted by at 6:54 pm
Mar 302013
 

Having recently started being interested in HF Linear Amplifiers I needed a voltmeter to measure the High voltage on the anodes of the valves, I have a Bradley meter but it will only go up to 1.2 KV and I needed a 2.5 KV voltmeter to monitor the voltage on the Linear Amp that I was building.

100uamp MeterI had a 100uA meter in my junk box with a scale of 0 to 25 so I though that I would use that with a series resistor, (forget what it says on the scale as this can be easily changed) so the next thing to do was the calculation for the voltmeter. To find out the value of the series resistor using the formula V/I = 2500/.0001 = 25 Meg-ohms minus the internal resistance of the meter which was 540 ohms so the series resistor would need to be 24,999,460 ohms for FSD and to find the power to be dissipated in the resistors using the formula W=V X I = 25000X.0001=.25W. (I would recommend a 100uA meter because of the power rating of the dropper resistor, a 1mA meter would need a power dissipation of 2.5Watts)

For the dropper resistor I decided on a chain of .5 watt metal film resistors, these have a voltage rating of 500volts so you would need a least 6 resistors in series to be on the safe side. I decided to be extra safe and have a chain of 19 X 1.5 meg-ohm resistors ending with a variable resistor for calibrating the meter. Although not necessary it is best to put the variable resistor and the meter on the earth side of the circuit where the voltage in the circuit is low.Dropper Resistor Chain

To calibrate the meter, I used a Variac transformer to set the voltage on the power supply to 1KV with the Bradley meter then using the variable resistor set the voltage on the 100uA meter to 1kv and the job was done and the meter was ready for wiring into the linear amp.

Although this meter has been designed for 2.5 KV using the formulas above you can measure any voltage. This article comes with a health warning HIGH VOLTAGE KILLS, make sure your dropper resistor chain is properly insulated as high voltage can arc across an air gap. If you want to build a stand alone voltmeter for high voltages make sure you use a good insulated box to put the meter in and hard wire the high voltage leads into the insulated box, High Voltage Probes are essential.

Mar 302013
 

The Lincoln Short Wave Club will be holding an Intermediate License course starting Saturday 1st June 2013. The course will be held every Saturday and Sunday throughout the month of June 2013 the examination being held on Sunday 30th June 2013. Candidates for the course should in the first instance complete the contact form on this website or visit the Lincoln Short Wave Club at The Shack, Village Hall Lane, Aisthorpe, Lincoln. on either Wednesday Evening from 19.30 or Saturday mornings from 09.30. The club Training Officer is Les Clarke  G1LQB he will be happy to take your details and register you for the course. You must register by Saturday 18th May 2013 at the latest.

 Posted by at 2:26 pm
Mar 282013
 

Valve Linear Amplifiers WILL  KILL!!!  If you make a mistake there is no SECOND CHANCE, so you have to be VERY VERY careful before you start working inside them.

I am writing this because of some stories I have heard that frighten me, as we are talking about HIGH VOLTAGE in excess of 2.5 THOUSAND VOLTS with high current which is a lethal combination. and I hope that I have managed to scare you into taking notice of the safety measures which should be adhered to. I have worked with mains voltages and above since the age of 16 and have a healthy regard of electricity and know that it can bite so always take precautions when working with it. With the high voltages found in linear amplifiers you have to be extra careful as it does not bite it KILLS.

Before working on a linear amp, if the high voltage circuit has been activated then you have to leave it for at least half an hour for the power supply to discharge before touching anything. I built a 2.5KV high voltage meter into the linear amplifier that I am building so that I would know when it was safe to put my fingers inside it. DO NOT short out the EHT as you can damage the linear doing this. You LIVE LONGER with a little bit of patience.

Recently I heard a story of someone who wore Marigold Gloves as a safety measure when working on a live linear amp, I personally think it safer to work with bare hands with the power supply fully discharged. This same person upgraded his power supply from 800 volts to 3 thousand volts to get more power, his valves actually exploded. If something goes wrong in a linear amp, because of the power there is usually a BIG BANG.

The motto of this story is to Listen to people who know what they are talking about, research your amp so you know more about it and don’t work on a live linear, stay safe to be able to use the linear and make sure it is not sold in a Silent Key sale. (I asked Jonathon G6JUT if he would like to place an advert for his business on this post but he declined as he thought it would be in poor taste.)

Mar 282013
 

A recent conversation with Des G4UHZ prompted me into writing this post about the changing ways of today’s Radio Amateur. For those who are wondering what a Boat Anchor is, in radio terms all vintage electronic valve equipment becomes encompassed with the term because it is a heavy piece of equipment with large transformers and tied with rope is suitable for mooring a boat. This is theoretical and I am pleased to say that vintage equipment it is not normally used for this purpose.

This post is not about restoration, but more on the loss of essential skills that are dying out because of the way that amateur radio changed. Today most radio equipment is digitized and computer controlled all squeezed into a small black box that makes it impossible for the normal amateur to repair and is generally sent back to the manufacturer for repair.

Today more and more radio amateurs are becoming operators and although the terms on the radio license also state it is for experimentation and self training, this part is being ignored. We are losing the ability to repair our own equipment and the skills used for this are disappearing, the self satisfaction of bringing a radio back from the dead is no longer being felt by the majority of radio amateurs.

Information is readily available on the internet and search engines can be your best friend, if you have a radio or any other equipment you would like to find out more about and try and get the manual for then you could be lucky. You will find that someone somewhere has already done what you are looking to do and a mass of information will be available to download. A typical search for “boat anchor” turned up the Boat Anchor Manual Archive

More information on this topic will be published soon

Mar 262013
 

Eddystone 730/4

Built during 1956 – 1962 the Eddystone 730/4 is a professional commercial receiver based on the 680X  with 15 valves, 2 RF stages, 2 IF stages (450kc/s), BFO, IF cathode follower output, variable IF selectivity, xtal filter, xtal calibrator, adjustable scale, noise limiter, S-meter, audio filter for CW, fully tropicalised. Cost at time of manufacture £230. This receiver was ordered by the Ministry of Defense in large quantities and used by the Royal Signals

The opportunity arose for me to purchase an Eddystone 730/4 spares or repair from the family of a Silent Key at a reasonable price, so I was pleased to purchase it as a project without prior knowledge of its condition.

On examination of the receiver I found that the tuning dial was not working and underneath the chassis there was about 10 wires disconnected so I had to research the receiver to be able to get it in a condition that I was able to apply power to it without blowing myself or the set up.

My first port of call was the Eddystone User Group website which is full of information to refurbish old Eddystone radios and also to join the group Forum

I downloaded the User Manual and other useful articles from the Eddystone User Group and set about the task of taking the front panel off so that I could sort out the problem with the tuning dial. Before starting this long winded task I gave all grub screws on the knobs a squirt of WD40 and left them for a couple of hours to loosen them up as previous experience with old sets had found undoing them could be a pain.

Taking off the front panel is a major job and several different size screwdrivers a large allen key and spanner are necessary to detach it from the main chassis. Full information on how to do this task can be found at the Eddystone User GroupEddyston 730/4 opened up

The picture above shows the front panel with the tuning capacitor gearbox attached, the gearbox was seized and had to be completely dismantled and the rust that had formed round the steel drive shafts that was stopping it turning was cleaned off.  Everything else in the gearbox was also cleaned and greased so that the gearbox rotated freely then the pointer drive cord was fitted and the front panel was ready to be fitted back onto the chassis. Before fitting the front panel back, I thought it would be a good opportunity to clean all of the switches and variable resistors as I did not want to have to take the front panel off again.

Before power could be applied, I had to figure out what had been done to the receiver which was a bit of a mess with disconnected wires under the chassis.Eddyston 730/4 Chassis Comparing it to the pictures I had of untouched receivers, I found out that a tag strip was missing from the right side of the picture where all the wires from the wiring loom should be attached, so I had to rewire it up again and I also found  that a couple of valve heater wires had also been disconnected from the bottom of the valve bases. The switch under the chassis was the AF Filter switch and where that should have fitted on the front panel, a  variable resistor had been added and fitted to the front panel where it had been wired in. I removed the modifications and rewired the receiver to its original condition and switched it on. Much to my delight everything lit up and after a few seconds sound came from the loudspeaker, I tuned into a AM broadcast station and everything sounded OK so the receiver was working and now it was just a case of checking voltages and replacing faulty resistors and caps and tuning it up properly to get it back to A1 condition. PROPER JOB!

I would like to thank the Eddystone User Group Forum for all the friendly advice and help I was given with this project.

Mar 222013
 

Saturday 15th March brought about one of my personal favourites in the contest calendar ,this along with ARRL DX are in my opinion more fun…As we will see things nearly went to plan apart from the huge CME that was as the contest started hurtling its way towards good old planet earth… ‘thanks for that Sol’!!

Well, things started off great with the blocking of the frequency we intended to use at start of the contest . I started calling a general CQ at 11:00z beaming Russia 50 degrees ish and this is where the fun began. First caller in the bag a YV (Venezuala) on the back of beam, glowing report recieved I reversed the beam to beam him +30-40 over was reply  ‘good’ I thought ‘bands in cracking shape’.  Next caller in was a nice gentleman driving the length of Florida going home for the weekend as I rotated to him my report from him was I was endstopping him, he was +30 to G5FZ so far so good. Steve took over to continue blocking as the clock was ticking nosebag to be had and tea to be made before kick off …….now in my humble opinion just before a CME lands the bands seem to become ‘wide open’ whether i will be stood corrected I don’t know but every time a coronal mass ejection is 12hrs or so out good dx is to be had for hardly any effort or RF output and please don’t ask why this is just my experience as a humble op lol !!

In RDXC the rules are simple work everyone but the more Oblasts (postcodes) you work of Russia the bigger the mult. Working Russia gives 10pts +any oblast mult,a qso with your own country 2pts,a qso with a different country but on your continent 3pts and a qso with another continent (ie Stateside) 5pts….And the contest lasts 24 hrs no long haul this time !

We kicked off at 12:00z with myself on the mic, and as some of you know, if its slow i get bored and fed up quickly so Steve(M5ZZZ) took over and was more relaxed than I’d ever seen on a mic !! With a nice and steady start I made the decision to move band to 15m as qso rate was good but not excellent which we did with some good results , peaking in the first hour with 117qso which cant be sniffed at.Mark (M0ZLE)arrived at just before 14:00z with Steve leaving as himself and I where going to be pulling a late one ….Staying on 15m was producing results as you can see. While working an OH(Finnish) station the whole band blacked out +30-40 of noise he kindly waited to finish exchange  but it was an ominous reminder of what was on its way !!

Notice how flat Sunday was !!

RDXC2013 ………. Notice How Flat Sunday Is !!!

We remained on 15m until it was felt we had wrung the band dry at roughly 17:00z we moved on to 40m which some might say suicidal , thats  too early i hear you scream in droves, maybe, but this is where the fun begins. Russia is 3hrs ahead and already in darkness working JA, VK, etc the move payed off ,then Mark left as Steve had duly arrived for our late shift ! . I left Steve to nip to local kebab emporium for a tasty snack to bring back to Aisthorpe…

When I arrived back we had a visit from Pam (G4STO) who sat with us for a bit and watched me demolish said mixed kebab ! Around this time 40m was starting to get overfull with people setting up on us and calling which is normal for a contest but really peeves me off !The decision was made to now jump up to 20m as we was entering grey line and I felt we could run a bunch of stateside for an hour or two…

The move payed off for the first hour but the band was dying earlier than of late and we moved reluctantly back to 40m about 22:30z but finding a ‘home’ was difficult, and the run rate was very poor ,plus  the qrm was appalling +20 with all the bells and whistles on !! Stateside had at this time just, just, just started to open working my friend Walt K1QS. A special mention for Walt K1QuiteSexy as he managed to work us on every band we run on and as always a cracking signal !!  Appreciated, thanks buddy !! We surrendered at 23.20z as Steve was having to go and I knew that I wouldn’t last all night, so we left  with a heavy heart knowing full well that the bands would be poor the following day….

I arrived at shack at 6:00z on the Sunday and firstly checked progress of CME which landed at 06:01 that morning and I hesitantly turned on my trusty steed , cursing myself for going home to my warm bed . My curses increased as I monitored 20m and normally strong stations where very weak  and the band reports where far from rosy !!

A quick cup of tea and biscuits later and off we went for a second day which was that slow I had to fight myself nodding off , luckily Steve turned up at 8:00z and we started swapping knowing full well we had to run 20m and 10m to collect the mults. We continued to soldier on and at 11:00z  dropped onto 10m to see if there was life and much to my amazement there was but working them was hard labour best dx on 10m was HS0ZIN who said he would be thankful when 12:00z came!! He was our second to last caller as sitting and cq’ing was getting nowhere and we had searched and pounced all we could pulling the plug at 11:46z .

Overall a good result working 978 stations 140 Oblast and 128 Dxc for an overall score of 1,598,084 operating for a total of just over 16hrs a good effort overall we bettered our score from last year which was 443 qso for 362,780 , if before the contest knowing the cme was on its way and you had asked me what I would be happy with I would of answered 1,000 qso. I wasn’t far wrong and yes I am still cursing our luck.!! !

Thanks to my operators Steve and Mark for your time !

 

Footnote: Walt K1QS will be operating in CQWPX  30&31 March , so keep your ears out for him on 15m !!

 

Best 73’s Sy M0SIY

 

 

 

Mar 192013
 

2nd and 3rd of March 2013 saw the annual ARRL DX 48hr  Contest. This contest is maybe one of the easier contests in respect that we can only work Stateside/Canadian stations. Basically point beam to 300 degrees and call !!

ARRL DX 2013

ARRL DX 2013 Final Score !!

I decided due to lack of operators to limit our involvement much the same as last year trying to optimise running time during daylight instead of cramming onto 40m in the night with most stations working splits ie. listening above 7.200 and operating below as you know states have a higher 40m band plan, it is allowed to receive on lets say 7.210 and call on 7.180.

Anyways back to the crux of the matter, so i tried to run much the same as last year when we ran with just myself and Jeremie which was productive always busy running when we was operating, culminating in 1st in UK, 16th in Europe and 29th in world for 16 hours operating!!

We kicked off on Saturday about 10:30z starting on 20m as you can see from picture things were steady most of States still in bed hi hi !!, and propagation a bit flat .Also we had our friend Murphy in shack as pc kept muting the auto voice keyer!! Mark (m0zle) and I managed to sort it while I was doing cartwheels around shack…Steve (m5zzz) took over but had to leave as did Mark at just before 13:00z . At this time i switched to 15m for a marathon run which would last for nearly 5 hours at mic, during first hour I worked 122 stations the pile up was nice and steady ebbing and flowing, if at peak of flow it had carried on during 13-14:00z I peaked at 260 qso an hour average on run rate but unfortunately it didn’t continue hence 122 qso much to Sys’ disappointment!!

Steve then took the reigns at just after 17:00z for his ‘Jedi’ training with me resting voice and a much-needed comfort stop !! Dropping back down to 20m to try to achieve some more multipliers (each state/province is a mult) saw rate drop but not to unacceptable levels so we carried on until about 20:00z then switched to 40m due to a technical hitch which was out of our hands ……We stopped not long after just as 40m started to open but problems persisted so we sacked it feeling very frustrated !

On the Sunday I started about 09:45z on 20m and we stayed on 20m all day to pick up more mults and hopefully to get a nice run rate as we had worked a lot of stations on 15m the previous day…Run rate was steady to say the least with Steve arriving to help at 12:00z after his news-reading.Steve unfortunately had to go again so it was up to myself to perform …Our second biggest peak run occurred at 15-16:00z with 110 being worked in the hour then things started to slow up just a bit but was ready to work into the night with the dreaded drop down to 40m !! Unfortunately this was not to be as  problems out of my control scuppered this and had to surrender my pile up at 17:30z ….Hopefully since, this the problem will not occur again !

Overall a very productive weekend taking into account limited running time hopefully it will be enough to successfully defend our 1st in U.K. place from last year. We worked more stations than last year 1062 last year 1200 qso this…378,777 points last year 406,461 this…. 12hrs 47m operating last year compared to 17 hrs 7m this !!!

My thanks go to Steve for giving me quite a bit of time and patiently listening to my advice I gave resulting in a more relaxed operator in chair and a higher run rate for himself !! Well done mate, you are truly on your way to becoming a Jedi master !!

I hope you enjoyed my first attempt at being an author any comments are welcomed !!

Best 73 de Sy M0SIY

 

Mar 152013
 

Atlanta Radio Club hosted an evening with Martin F. Jue and have posted a series of videos on You Tube where Martin gives a series of demonstration on how you can use MFJ’s Antenna Analysers. Well worth watching for those who like to play about with antennas and a list of the 20 videos can be found here.  More video’s of the MFJ Antenna Analyser can be found here

Thanks to Des G4UHZ for pointing me in the direction of these links.