Wednesday, 30 October 2013


One of the items I was pleased to obtain at Rishworth, were a pair of QRPme SBSS clamps. Getting them involved ensuring the cost had been covered by my junk sales, and then being roundly questioned by the proprietor of QRPme over my choice of T-shirt and lack of hat. Now, these clamps are not cheap, at £20 for the pair, but they are remarkably good at what they are for, namely building PCB material boxes. Having bought them, I was very impressed to be shown the original Tuna Tin transmitter built by Doug DeMaw, and kept safe in a wooden box. I was also happy to receive a few free MeSquares and MePads!

The clamps themselves of course are no help if you do a shoddy job of cutting the board to start with, so I was very, very careful to mark and scribe the board prior to cutting. I did make the mistake of not correcting for the board thickness, but that was soon rectified. Using one of the SBSS clamps, I soon had a little 1" x 1.5" box built, in which to rebuild my little VLF to soundcard interface

The picture shows it with the sockets installed. The one big mistake I did make, is that after marking around the washer of the earth terminal, I then forgot to measure the diameter hole needed for the body, and drilled it out the full width of the washer! Luckily, the blue terminal post just stayed in place in that hole (well tightened!) so it wasnt too bad a disaster.

Much effort went into trying to solder nuts in to attach the lid, but they just wouldnt hold. Eventually a pair of hex posts did solder in, but its a loose fit as I dont have any screws of the right thread.

The VLF interface is about the simplest receiver that can be made, simpler really than even a crystal set. It really consists of little more than an antenna wire connection to a soundcard input via a blocking capacitor. My version is a tad more complex, as it also includes three levels of protection - there is a 100k resistor to ground to bleed off static buildup on the antenna; a pair of back-back Germanium diodes that will clip the incoming signal above about 0.3v; and now a small wire ended Neon lamp acting as a gas discharge protector

Next job is to complete the RT-remote clone, which just requires the internal wiring loom completing, so I can then test, and indeed control, the LDG RT-11 Remote Auto-ATU.

Saturday, 26 October 2013


These past few weeks have been a big effort to offload junk and obtain useful, desired items. This all started when an LDG RT-11 Remote Auto-ATU appeared on ebay, something ive been after for some time. This duly bought, I needed to recover the cost, and set about selling stuff off. The RT-11 cost was covered by the sale of a surplus DSP module. A cheque from the Lions in payment for costs for the show was gratefully received, which will cover the QSL cards print costs, some station clocks, and the balun to go with the RT-11. Its also paid for the specialist cable from the Alinco DX-70 to the ATUs remote control box.

But, I dont have the remote control box! So, Im in the process of building a copy. As its literally three buttons, two LEDs and some sockets, its not too hard, apart from cutting the holes in the box neatly! The DB9 connector will be the awkward part.

The few parts I needed but didnt have I picked up today at the G-QRP club convention at Rishworth. I took all my heavy junk to try and sell on the bring and buy, and set off really early to get parked as close as possible. Well, I still ended up parked about as far away as it was possible to be, and accepted some assistance carrying the stuff in. In all most of it sold, netting me £45. I'd taken £50 with me, and after all what I bought, which included a pair of the little vice thingies from QRPme (for building PCB material boxes), a club mug, some slide rules, raffle tickets (not winners) and lunch, I came home with £55 in my wallet! Switched to 17m from 20m on way home to get away from the contest, and added a few QSOs to my mobile tally, including Cyprus. Not quite as good as Lebanon the day before. I now have a 40m antenna for the car, but havent perfected the match yet.

Sunday, 13 October 2013

Where It All Began, Pt 1

I dont really know why i'm doing this post, but for some odd reason I feel the need to relate my history, my amateur radio journey, so to speak.  Its im sure nothing exceptional or remarkable, but its been part of my life since school and its whats ultimately led me to the career im now in. So for what its worth, while im not actually able to do any decent radio work due to shifts for the next couple of weeks, i'll tell my tale here,

Somewhere back in the dim and distant past, around the age of thirteenish, i'd got interested a bit in computers, back then these were 8 bit machines like the Electron and Commadore. I myself had a Sinclair Spectrum +3, 8bit and a whopping 128k of RAM, plus a mental 3inch 'floppy' drive that Sir Clive must have found being given away with far eastern cereals. I was introduced by a friends dad to a local computer club. This was held in a back room of the old Corporation Brewery Taps, in Doncaster. I didnt find it that enthralling to be honest. I'd already realised it was the nuts and bolts rather than the software that interested me.

Somehow, when trying to find electronic components, it had been suggested to me to go on a coach trip with a local amateur radio club to the big radio rally at Drayton Manor. I got permission to go on the trip, and pitched up at the appointed time  at a pick up spot near the supermarket in Edenthorpe. There were a few other people waiting. Particularly, there was a bearded chap and his wife and daughter. This was Eric, G0PAQ, his wife Janet, and daughter Samantha. Being a hormonal adolescent I of course instantly fancied Samantha, who was several years older than me, but it was her dad Eric that who was to start me on my journey into amateur radio.

The trip to Drayton was a real eye opener for me. All the components I could ever imagine, flea market stalls selling anything and everything radio. I bought a huge keyboard that I was convinced was full of goodies (it was just a load of scrap steel!), and half a £5 bag of LEDs for £2 (all I had left), which proved to be about a thousand 3mm LEDs! I also saw the big name stalls like Martin Lynch and Nevada,a dn the shiney new radios.

Now, I have to confess to not being entirely devoid of any hint of radio knowledge. I had a Saisho world band receiver, and listened late in the evening to all manor of stations of shortwave. I sent reception reports in, and got back QSL cards and schedules from the likes of Radio Helsinki, Radio Sofia etc. And there was always, from my bedroom window, the tantalising glimpse of the bizarre aerial at the end of the road! A huge, spider web of wires on a lattice tower, stood in someones back garden...

Following Drayton, Eric suggested I came to the club. This was Mexborough and District Amateur Radio Society. They met on friday evenings, and I could get a lift, along with Eric, from John Dennis, who was Erics fellow plant electrician at International Harvesters. I was told to be at Erics at about half six, if I remember, the following friday...

Tuesday, 1 October 2013

Loopy Earth? Ghosts in the machine?


This carrier balance thing, its driving me mad. Even more so, after this mornings experiments. Nothing I do reduces the carrier level. A mock up mixer didnt show the problem either.

But, a change of probe due to a slightly iffy BNC connector resulted in this interesting spectrum

 Its not the display itself thats interesting here, but look where the probe is! The circuit is over two feet from the analyser, and the probe is not connected at all!

The only things connected to the circuit are the PSU, the Bird dummy load,a nd the AF lead from the Marconi 2955. Wrapping the power leads around a ferrite rod made no difference. Turning the AF generator output on and off made no difference (except to the sidebands), but turning the Marconi itself off, or disconnecting the AF lead, did! The carrier vanished!

It looks like ive hit a serious case of the Gremlins!

Next step then eliminate the 2955 - so I need now either a battery powered AF generator, or to mock up a tone circuit