Thursday, 25 October 2012

SAQ UN Day Transmission

Feeling atrocious all night at work, despite the joys of pizza and free doughnuts provided by management. Mostly this was due to having a cold, but also the hassle of having a pocket of transmitters on the south coast failing due to incoming RBR failure. A nasty little high pressure pocket was causing tropospheric ducting all night, in fact i think the lads dealing with the final DSO had an easier time.

Coming home, and with the prospect of plenty of tasks in hand from Julie being away and the boys to look after, I decided to stay up for the UN day transmission from SAQ Grimeton. It was my intention to try an E-Field probe antenna for this, which i had started constructing the day before, having done the case work, layouts etc, and aquired the parts. As a 'back-up' I quickly strung a 45m longwire, which was only a few feet high, draped over things in the garden. This fed the laptop and Wolf DL4YHFs Spectrum Laboratory software, via a simple protective interface to the soundcard.

Well, the longwire ended up being the primary antenna, as when tested the E-Field probe drew nearly 50mA, sent the battery flat, and didnt receive! So, with the longwire set up,  I watched and listened for SAQ. When they began tune-up, I could just make out a signal. Of the transmission, I could make out a few V's being sent, but nothing more. This was disappointing, and probably due to the antenna being low and local noise. I need to get Sam to help me rig a proper long wire high up, to feed his receivers and the FRG-100, and also the VLF systems.

It turns out, that in my weakened, fatigued haste, I had misread the pin-out of the J310 FETs, and fitted them both backwards. Although the J310 has interchangeable source and drain, sadly the gate isnt!. Anyway, once these were refitted (not an easy job) the unit now only drew 5mA, and provided a signal. Phew, I hadnt killed the FETs. The signal was quite a bit weaker than on the longwire, GBZ from Anthorn was visible but nowhere near the strength as on the wire, but then, the wire was 45m long, and the E-Field probe antenna just a 1m whip!

All that remains, is to find a tripod or spike to fit the probe to for proper use. I do however, think its rather a nicely built unit

Heres an internal view, the circuit is build dead-bug, which is great for a simple circuit, until you need to fix it! I need to stick a bit of foam in to keep the battery from moving.

Slightly blurred photo, but this is the completed unit. Signal out from the 3.5mm Jack, BNC for the antenna whip, Ground terminal, and of course an on/off switch.

Wednesday, 24 October 2012


The Ferranti U1032 is now repaired and restored, its not probably working 100%, but its good enough to sit on the shelf as my workshop wireless, merrily playing away radio 2 or 4 depending what mood im in.

The photos below show some of the condition after repair

On the 20th, Sam and I went to the G-QRP club convention at Rishworth school. Armed with a wad of cash, and a list of wanted items as long as my arm, we set out searching the stalls. A donation of books to the children in need bring and buy a book stall, resulted in a donation of a book to Sam! Other stalls were equally generous and Sam aquired a number of free items! Sam in fact did better than me, as I never found a single item from my list! The resulting score - Sam 3, dad 0. Total items bought (not including pie and pies) - two battery holders and a colour burst crystal. I never even needed the crystal, but it was housed in a glass valve body, so i just had to have it. Two of Sams donated items were also crystals - one in a normal shaped glass holder, and one in wartime package.

Sams crystals are not on amateur frequencies, but I plan on using mine in a nice little one valve CW transmitter.

Sams donated book was a very old guide to building a morse practice set, including plans to make your own mechanical buzzer, naturally this is the part Sam wants to build.

Tuesday, 16 October 2012

Little by little

Two of the 47uF 400v electrolytics fitted inside the old TCC tripple can. The empty space of the can has been packed with foam, and a bitumen disk (cut from roofing underlay) used to seal the can, with the wires poking through. The first connection, the ground, has been made, but in order to get at it I had to replace the first of the 2uF electrolytics a bit earlier than planned. This took a bit of planning as the original axial part was much much bigger than the replacement 2u2 250v radial, so some extra wire and sleeving was needed. The first of the Hunts mouldseal 0.003uF has also been replaced with a new 3n3 400v polyester.

It looks like one of the waxies will need to be next, as its in the way of the wiring for the big caps.

Pop a cap in yer... er, cap

The spares have arrived from CPC. Once again, CPC have shown how ridiculous their handling charge is, by sending a handful of capacitors in a 5l box! Heres the box

And heres the contents
Why the heck they didnt just stick them in a jiffy bag i dont know! But hey, its not like its cost them extra to do it this way, since ive paid the full shipping cost of 4.9l of air!

Anyway, on a less bitter note, I do now have the caps needed for the restoration (save for the 22uF 16v, which amazingly were out of stock!). Sadly, the size of the 47uF 400v electrolytics is such that only two will fit in the original can.

The cabinet however cleaned up very nicely, heres how it looked before 
And heres how it looks inside and out now
The first job is the big can capacitor that can be seen at the top of the chassis photo, you can also see some of the Hunts waxies and the TCC oil electolytics that will also be replaced with shiny new modern aluminium and polyester devices
I dont expect much more to be required, but we will see when this is done and the set is powered up (with its nice new modern jacketed mains lead).

This coming saturday is the G-QRP club Rishworth convention, hopefully many more interesting parts will be found there. I have in mind to build a Rockmite...

Saturday, 13 October 2012

Ferranti Restoration

Its been a while since ive updated this blog, but apart from growing older and probably uglier, not much has changed. I operate more mobile HF now, and with the help of Steve G7TAO and Rob M1BBV, we recently ran GB1LDS at the Doncaster Show. Thanks also go to Geoff at FDSprint for creating the QSL cards, which are currently in print and should be with me to send out in the next working day or two

One project I have on the go at the moment though, will be getting documented on here. I have recently aquired a late vintage valve table radio, a Ferranti U1032. This doesnt look to need much work, but a few capacitors need changing, and it needs a good clean up. The capacitors are on order, from CPC. I dont normally like using CPC/Farnell or RS, due to their extortionate 'handling' charges for small orders, but they stock the high voltage ratings needed, where my normal suppliers dont. So the caps have proved to be quite expensive but I will then have a few spares.

I'll start getting photos of the radio on here soon.

Tuesday, 24 April 2012

Mobile HF

Right, so now we have an antenna mount on the roof of the car for HF work. The tailgate mount is still a work in progress. The new mount is an SO-239 type, pretty much an allrounder that will allow me to put on pretty much any antenna, or connect up the field masts and their antennas.

Tried the 20m antenna on it (after proving it with the MFJ-259 and Bird load) and got a nice match in a sensible portion of the band. But 20m was poor today generally, so no QSOs made as yet. The 40m antenna has rather a narrow usable bandwidth, so i will have to decide where to tune that for, im thinking about 7100kHz.

The 80m antenna, well, forget it! Usable bandwidth is tiny, and as for efficiency... Instead, im going to look at using that antenna, or rather its parts, to make a shorter antenna for one of the higher bands. I want antennas for 17m 15m and 10m. 10m theres enough cheapo commercial jobs, so probably go with 17m, which is a favourite band of mine. I'll use a shorting wire to find a point on the 80m antennas loading coil that matches 17m, then  remove the shorted coil section, and shorten the coil former physically. I might look for matches for the other bands as well, with a view to making it a multiband tapped antenna.

I also cut a 2m 1/4w whip for on the M8 mount. This is for use on those occasions when the 5/8ths would be socially unacceptable, or when i need something that will work on 70cm as well. For those occasions when i really need to be able to operate efficiently on the lower bands (down to 40m), im in the process of putting together a link/jumper dipole

Sunday, 11 March 2012

Pop, pop, pop rivets!

OK, so not pop rivets, as yet. Planning the mobile installation, ive decided that a 'cage', in effect, is needed in the boot within which to mount the radio and ancilliaries. This is to prevent anything else in the boot from banging into them. The intention is to fabricate a L shaped frame from sheet aluminium or steel, and bolt this to the wheel arch and the floor of the boot. Within this, a shelf/frame will be fitted. The radio, tuner, fusebox, junction box, interfaces etc, will bolt to the frame or the inside of the cage. A DC socket will be provided as well.

This is where the pop rivets come in. They will be used to attach the framework. To attach the cage to the car, ordinary machine screws will be used, but the car bodywork will have 'nutserts' installed. These are rivet in threaded tubes, and provide a secure and simple mounting.

The tool and inserts to do the nutserts is on order. The pop riveter i'll pick up from ASK when next that way out. The only other thing i might need is a bending brake, to form the bends and flanges of the cage.

The 2.5mm2 DC cable has been routed along the left hand sill, but has not yet been fed through the firewall into the engine bay. This will be done when i have the necessary crimps and fuseholders to attach to the battery.

I had intended mounting everything on the left hand side of the boot, as this seems intuitive. But its not to be, as the spare wheel carrier goes right over to the left! On the right however, there is a 9" space between the wheel arch and the carrier cover board, just enough for the cage. It means i have to route the DC cable around the inside of the boot to the right hand side, but the signal and control cables (head cable, mic cable etc) can run up the right hand sill. Mounting on the right makes perfect sense, in a country who drive on the left, as it means the antenna will be mounted on the right of the tailgate, away from pedestrians, bikes and low branches. Its also, on my car, diametrically opposite the fuel filler cap!

I have to finish the HF mounting. This will need bolting to the car, then continuity testing to make sure the ground path is good, before final paint spray to match the car body, and laquering. Ground strapping will also be needed on the hinges of the tailgate.

I have installed the first Panorama M8 mount, roof center, for VHF/UHF. It currently got the 5/8th 2m whip on it, and working fine. But, I installed it with the view of the equipment being mounted on the left, so the coax routes down the left hand pillar. I'll need to correct this over to the right (which will also mean it doesnt cross over the washer tubing to the rear window!) but that means yet again dropping the headlining. I might wait to do that when i have the next mounts ready for the roof! I'll post the pictures of that install job in the next update.

As regards mounting the control head, i searched every possible location in the car, and short of getting a new stereo with DIN sized fitting, so i can mount it to the blanking plate, the only sensible place is to the right of the steering wheel, where the rig was in the old car! I havent decided on the speaker location yet.

Wednesday, 7 March 2012

Sams Valve Radio - Almost

Work started again today on Sams single valve regenerative set. Up to now this was dogged with troubles as it just simply didnt seem to work. Well, i sought advice from the chaps at G-QRP club, always a helpful bunch, and received loads of info back. It seemed the first task was to up the HT voltage.
So, I went out today and bought 10 PP3's from which to build a 90v B+ battery. Well, they only had six on the shelf, but the assistant was stocking the batteries up. She at first didnt think there were any more, but i spotted a box at the bottom of her trolly. A box of ten. So i bought the whole box. The end batteries, where the connections to the pack are, have had shrouded 4mm sockets soldered on, and then the whole lot taped over, so as to prevent any contact with the terminals. As new, it measured 98.8v! The smaller pack is the present heater battery, 6v, although reading a bit low, using 4x AA's. In the future i'll change this for four C or D cells.

This is the view of the front panel, the big knob, which incidentally isnt big enough with a 600pF variable capacitor, is the tuning, and very delicate it is too! The bare shaft is the regeneration control pot. The 6K7G pentode valve can be seen behind the panel. A bandspread capacitor may well have to be fitted.

It can easily be seen that there is very little to the radio underneath! The view from above shows the main components, the big 600pF air spaced variable, the valve, and the audio transformer. The ferrite rod antenna has had its main winding progressively reduced to bring the tuning onto the MW band at a sensible spot and now has only about 55 turns out of the original 80, the smaller winding is the 20t tickler coil.

In its present state, its possible to find a couple of stations during the day. I think the big problems now are that even with the transformer, the audio output into low impedence phones is poor, and the tuning is far, far too coarse.

Tuesday, 6 March 2012

Mobile mounts agogo

Ive taken the MB-400 mount off. As it turns out, its not that distorting the boot lid, it seems the boots not a perfect fit anyway! Ive decided permanent through body mounts are the way to go. Im not bothered by drilling the car, lets face it by the time i sell it it will be knackered. So, im building a mount to bolt to the tailgate by the number plate, using a right angle section of steel plate. Below this will be fitted to the car a cable gland, to take the RG-58 into the car. Im priming the mount,a nd when im next near A.S.K i'll get some matching touch-up paint, it will look like it was made for the car, which of course it is!

Tomorrow, if alls well, i'll go through the rigmorole of removing the internal panels and lowering the roof lining, in order to drill the roof and fit a Panorama M8 mount for VHF/UHF.

Theres no rush with any of the mobile install, as i havent received the seperation kit yet. But i might as well get the antenna mounts sorted and run the power cable if i can.

Talking of cable, i managed today to run the spare coax feed (from the broken 2m Slim-jim) up the side of the house and into the loft. I'll mount a BNC patch box somewhere up there, and then can try different antennas on it. The first i think will be a 10m dipole!

Friday, 2 March 2012

Mobile HF

The Sharman MB-400 mount is nice, strong and well made. Thats all you can say for it! Its four 4mm 3mm grub screws i doubt will hold out long, and the nice black paint coating is non-conductive - theres no ground path through the whole thing!

The 105ADT 3/8th mount didnt fit the 16mm hole in the MB-400. So, so carefull grinding, cutting and o-ring selection, and ive modified it to fit. Its attached to the car, but i feel that additional work will be required to create a usable ground path, probably straps from the mount to the bodywork.

Im going to test the antennas on it later using the MFJ-259B, and see what the whips are like, at the very least i'll be able to positively identify which is which. I still think a through roof mount is going to be best, although the whips are very long!

Wednesday, 29 February 2012

Slowly, slowly

Well, bit by bit were getting there with the radios. The valve set now has the hardware finished, and the antenna rod mounted on two PVC standoffs. Apart from a bit of further filing to make the base stable again, and a few tiewraps to hold the rod in place, whats left to do now is the electronics. And as there really is only a handfull of parts in this set, that shouldnt take long at all. With any luck it will even work!

Thanks to one of the fellas on the vintage forum, we now have the postage stamp trimmers modified for the matchbox radios. I still need to find a couple of nuts to mount the trimmers with though.

Yesterday, i picked up three HF mobile antennas. Today, a boot lid mount and 3/8ths insert arrived. Well, ive ordered the wrong insert, and this one doesnt fit the mount. Im not sending it back, instead i'll modify it to fit. The mount is going on the bottom of the tailgate, to the left of the numberplate and just above the bumper. A short coax lead will then go in to the rig in the boot. Its not the most ideal location, but i cant yet find a suitable through roof mount for a 3/8th antenna that will fit between the car roof and the roof lining. I also have to decide whether to fit one or both M8 mounts. Not that i can use either yet, as i havent run the power cable from the battery to the boot yet. The seperation kit is on order but coming from Hong Kong so might take a while.

Quite looking forward to a bit of HF mobile though.

Saturday, 25 February 2012

Nice Box!

The Yaesu FT-857 doesnt have a proper S-Meter, instead it has an LCD bargraph that can be selected to show the various levels such as Signal strength, Tx power, ALC level, Discriminator balance etc. But an LCD is always a bit pants. Yaesu obviously realise this, and so on the underside of the control head theres a 3.5mm jack socket providing a meter output. So, a 100k pot, a small box and an old CB S-meter later, we have a nice add-on analogue meter -

The 0-V-0 plods on slowly. Most of the holes are drilled, two of the grommets inserted. One more grommet, a pair of standoff insulators, and the ferrite rod supports still to do, and then we can actually build the electronic side of the set! Couldnt get much done today due to spending most of the day refelting a shed roof.

More old electronic stuff gone on ebay today, including a Kenwood battery charger, some old dot matrix printer parts, the unsold ICs from last week, and my Alinco DR-130 mobile, which has developed a fault. Think i'll miss the old rig, its given me a lot of good service.

Friday, 24 February 2012

Kindle Katastrophe

Been on nights. To pass the time i borrowed Julies Kindle. Im quite getting into this device, its a lot better than i thought it would be. That said, i have loaded the entire back catalogue of sprat onto it!
I tried to connect and download a book at work, well the damn thing crashed! I was forced to reboot it, deeply! And when it finally came back to life, about half an hour later, it had no library! Oh heck! Went online to try and resync it to the stored library on Amazon, but oddly, it eventually recovered and showed all the original books, including the sprats! I decided then to download the books via USB!

Capacitor stock arrived yesterday, but i only picked them up today. Also with the order is a plastic box to build a ladder line break-out box with. This will allow me to add in extra lengths of line to the aerial feeder, to help the tuner match better. Eight 4mm terminals will provide the connectivity. I now think I have everything needed to complete the valve 0-V-0 regenerative receiver.

The audio filter project might be close to finish now. I started this thing sometime when i was about 16, only about 20 years ago! Its from designs in a Bernard Babani book. It really has taken me this long to finish, and all it needed doing was the signal wiring! Anyway, a quick inspection revealed a fairly obvious basic mistake - the regulator is in backwards! Its also the wrong regulator, being a 7810, when it should be a 7809. I'll get that sorted in the next few days, hopefully i havent destroyed the LM353 ICs that the HPF and LPF use.

Wednesday, 22 February 2012

Yet more parts

The cap connectors arrived today. They are a type that allows a component or two to be mounted right at the cap, which is good as theres a parallel capacitor and resistor to go there. Spent some time adding solder tags in apropriate locations, and working out how to do the wiring. Have had to fabricate some stand off insulators as well to provide terminals for some components. Yet i still cant get any further! I need to drill three holes to mount the stand-offs, plus two for grommets to let wires pass under the chassis. I also found i have none of the capacitors needed. So, an order to Bowood. Seems i may have tired Will out a little picking the order - ten each of every value from 1.2pF to 470nF! Oh, and a box sized to make the break in section for the doublets ladder line!

I really hope this radio works after all this effort!

Tuesday, 21 February 2012

Goods In/Out

A few more parts for the valve set arrived today, courtesy of Bitsbox. This is a company i find very efficient, although without the added personal touch of Bowood. However, their P&P is a shade less than Bowoods and they stock a few items different. So we now have the remaining terminal posts, the M3 hardware to do the ground and standoff terminals, and the regeneration control pot. I also decided to treat myself to a cheap analogue multimeter to aid setting up. I had a confirmation email from Electrojumble to say the top cap clips are on their way, and a chap from the vintage forum is helping with the 6BA screws for the matchbox sets. I think i'll build one of these for LW.

On their way out, go the twenty spare NKT213 vintage germaniun transistors, out to vintage forum members. Also, some of my surplus radio kit and batteries have sold on ebay, so thats a nice few bob towards mobile HF antennas.

Monday, 20 February 2012

Lotta Bottle

Many thanks to Phil G4SPZ, for the 6K7G, which arrived safe this morning. We now have the right bottle for the valve regen set. Hopefully the rest of the remaining hardware and connectors will arrive tomorrow, and the top cap connectors were ordered today. Surprisingly, the 6K7 is somewhat smaller than the 6V6, something i hadnt expected!

I did find a reasonably large vintage knob for it, but a bigger one would be better. A mock up with the 6V6 shows a bit better how it might look when operating

The matchbox radios are proving a bit harder to get the hardware for. I can find 6BA nuts and bolts, but in big packs at extortionate prices. But this is the last item to find, so we can modify the postage stamp trimmers. The jack sockets were easy to mod, simply a case of pulling out the tab until the inner terminal springs out, then resetting it closer, so the inner terminal now makes contact rather than breaking it when the plug is inserted.

I also put together a pack of 20x AAA duracell procells, to make a 30v pack, which actually reads 27.7v, which i think will do for the HT. I also completed the wiring on my active audio filter project, something i started building as one of my first projects, perhaps some 20 years ago! The LED isnt working, the lowpass filter has little effect, and the highpass filter no effect! The CW filter works, and the ANL possibly, although i didnt have a signal with the right noise to check it on! Both the HPF and LPF use a 9v supply, and its possible the regulator isnt working, so either their ok but fed wrong, or theyre buggered and will need new ICs!

Friday, 17 February 2012

Metal bashing

Having had little time as yet to play with my new toy, due to not yet having the appropriate cables for the vehicle install, work has commenced instead on one or two smaller projects.

Today has been spent metal bashing. Ive lots of sheets of salvaged aluminium, so selecting a nice anodised piece, proceded to carve it up using the grinderette (fastest way of doing it), to give a six inch square sheet with a 3/4inch lip, and a 6 x 5inch sheet. These have become the chassis and front panel, respectively, for Sams 0-V-0 receiver -

Only those large parts are as yet installed. The valve shown is a 6V6G, this is not the valve the set will use, it uses a 6K7G, but i have not yet received this. Its on its way to me from one of the kind chaps on the vintage forum. I have since found i have a 6K7GT, but they are not quite so picturesque! Its also not in the greatest of condition, the metal screen around its lower half has split and is hanging off, not sure if thats repairable. The ferrite rod antenna has a tapped coil for MW, the tap being to allow an external antenna. The smaller coil shown is the 'tickler' to allow regeneration. This is the third time ive wound that coil, the first was in antiphase, the second wound so tight it wouldnt move on the rod!

A few more holes are needed in the chassis, to allow fitting of earth tabs, power terminals, and the sides of the bottom of the cabinet. A pair of insulated uprights are also needed to hold the ferrite rod.

Ive also wound a deminuitive 60t ferrite antenna 37mm long, this will be the antenna of a ZN414 based 'matchbox' receiver.

Sunday, 12 February 2012

Wakefield Rally

Went to Wakefield radio rally today. Got there just after opening time. Very few dealers this year, but was pleased to see two very good vintage parts stalls, plus a stall by wakefield ARS. Sadly, this was a silent key sale, but it seems the chap was a hoarder. First i grabbed a VHF/UHF Manual for i think it was £3. I then started rummaging. Eventually coming away with four big tubs or old parts, in one of which was a bag of NE602s, which are worth what i paid for the rest! I seem now to have aquired literally hundreds of vintage transistors!

Got a few parts i actually went for, inluding a nice 600pF variable for £3, some 250pF postage stamp trimmers and open frame jack sockets for the ZN414 matchbox radios, and a big stock of brand new ferrite rods.

Some of the ICs amongst the junk i got are of no use to me but still in packaging - there now on ebay. If only a few sell, i will have recouped the days spending!

I missed out on a spares or repair HF magmount with various loading coils, simply because i didnt think it would be cheap. The next chap to me asked the price, and when told 'a fiver' his eyes nearly fell out, his jaw fell off, and he couldnt get his wallet out quick enough! Its a shame, as that would have gone nice with my new toy...

Also, Sam asked me to bring him 'something interesting', well, for 20p I found a wooden bayonet mains plug!

Oh, and mentioning my new toy, thats something else i was looking for, an auto ATU to go with my new to me Yaesu FT-857!

Wednesday, 8 February 2012

Let there be lower wattage light

After some fun and games fathoming out how the kitchen lights had been wired, I now have four 4w cool white LED lamps working, fed from one 26w driver transformer.

It turns out that the supply mains went to one of the lamps, and from there broke off as two spurs, each spur feeding two more lamps as a daisy chain. It soon became aparent that i could reuse the wiring.

I had hoped to pull the feed to the lamp over the door (the one without a LED lamp yet) and keep that one as halogen for the time being, but it proved impossible to pull the cable, likewise there was no way to feed a temporary mains supply. So, that one is also wired for LED, and is awaiting a lamp.

A check of the energy monitor, showed that the lamps are taking the expected 16w. This will be 20w with the fith bulb installed. Thats quite a saving from the 250w the halogens took. With all the halogens converted to LED throughout the house, the consumption will go down from 550w to a meer 44w. And the MTF (mean time to failure) for the LEDs is quoted as 50,000h, against the 5,000h for the halogens. At £8.50 a throw, theyre not cheap, but at about £1.30 each, and needing ten to last the same lifetime, the halogens come out at £13! Assuming the lamps last as quoted, thats about £50 saving in lamps alone, and roughly £60 a year in electricity. It also means that if they all last their lifetime, i shouldnt need to change them for about 27 years!

Early Adopter

Being an early adopter of any technology is not something i would normally do. I like things to have been well tried and tested, and brought down in price, before i use them. I dont have a Blueray player! I dont have a HD TV. I certainly dont, and never will, have a D-STAR radio!

But, there is one technology that i'm happy to try out - LED. I have four 4w LED downlighters and a suitable transformer, ready to try out in the kitchen. The prospective savings over the halogen 50w units, over the lifetime of the lamps, is staggering.

But of course, the builder was never going to make anything in this house easy! And this is certainly the case with the kitchen lights. There is NO access panel into the ceiling void, and no access from above. So everthing has to be arranged and wired via just the five 5cm holes in the ceiling! The LEDs need to go in parallel, fed in a loop from the transformer. The halogens that are in each have their own transformer, and a mains spur!

I expect each of the five lamps to look like this. Hopefully they will all have a mains junction box, which will allow me to safely disconnect the feeds. Routing the new DC ELV cable through the void might prove to be fun!

Tuesday, 31 January 2012

Theremin and CW

Yesterday, I decided enough was enough, and that the power supply for Daz's theremin just had to be completed. So, with a mug of tea, and the fan heater running flat out, i ventured into the garage and cracked on. A bit of customising was required on the case, but the power supply is now finished. +/- 12v dual rail, independently fused, to a standard 5pin 180deg DIN plug. I can now, when i have the time, start working on the main Theremin circuit again.

I also built an incredibly simple circuit - a meter tester. This is nothing more than a 1M linear pot and a AA battery, housed in an old shaving stick. Yet, oddly, it doesnt seem to work properly! Everything seems to measure ok, but when on a meter, its all or nothing. Odd.

Since ive decided to make the concerted effort to master morse, I though as well that getting the practice oscillator running properly was in order. Up until now, the headphone output had a strange 'drop-off' tail on key up. The output transistor, a BFY51, was feeding the speaker via a 100uF electrolytic and a 100 ohm emitter load as a common emitter circuit. I suspect the cap was responsible for the problem with phones at low levels. I tested it today with the load resistor replaced by an audio transformer, and the speaker and phone socket on the secondary, and it seems to work just fine. Only problem, it no longer fits the box its in. So rebuilding it will have to await the Wakefield rally in a couple of weeks to aquire a suitable box.

The next little project is just that, little! I have a stash of ZN414 equivalents, and Sam has shown an interest in a matchbox receiver. Its a long time since i built a little AM receiver, so i think we'll have a go at this. Just need the matchbox!

Friday, 27 January 2012


Well, the weather has been dire today, far too cold and damp to put either mast up, or to run the coax. So, it has been indoor tasks only.

The VHF vertical doesnt fit on the top of the Clansman mast. I need a spare mast section to cut down to form an adaptor to allow mounting of antennas like this, but short of buying a whole spare mast, it might be hard to come by. Ive put the feelers out.

As for the telescopic mast, the big task was meant to be fathoming out suitable guying. I think a stay point at the 4m and 7m levels is needed, the bottom can still be held by the 1m level bungees, and the antenna wires will attach at the 8m level. Except for verticals, the top two sections are too thin to be of use. Ive a couple of sheets of PVC gluing together to make a thick rigid sheet from which to fabricate guying rings. As the mast tapers, each ring will be unique to its level, and so they will only fit in a set order. The other problem is tensioning the guys. The Dacron line i have, whilst incredibly strong, is very thin, some 2mm if that. £3 in Yeomans, i found a pack of ten 'bent-runners', ie guy line tensioners for tents. These have got big holes in them so i didnt think they would work, but the homemade one i fabricated earlier today the holes were too small, and passing the line through would be awkward. A quick trial with one of these and a length of the Dacron however and the seem to hold fast. I might have cracked that problem!

I have played some radio today, tried for HK0NA but the level of idiocy and QRM was astounding! Did work a SOS radio week station in Torquay though.

Thursday, 26 January 2012

Antenna Work & VP8s

Up the side of the house today, removing the remains of the wind shattered 2m slim jim, and salvaging its coax. Luckily, the rain hasnt got into the coax, so that can be rerouted up the rear of the house and into the loft, where i can then use it as a test bed for smaller, short term antennas, with a dipole orientation N-S (so a chance to work the African continent on the higher HF bands!)

Anyone who knows me will know i have no fear of hights, but i hate ladders!

Ive already made an 80m inverted V for use with the 10m mast, plus a 10m J-pole. However, with the new year started and the offer of the SES for the Doncaster Show in september, somewhat more radical, practical and portable antennas are now needed! Apart from 2m FM (the mainstay of town SES'es) such a 2 day event calls for HF, and a selection of bands to cover eventuallities. Ideally of course, i'd be able to use any band, but that would call for a compromise of the G5RV type, and two masts, at least. This may be possible using mine AND G7PZLs 5.4m clansman masts, but it wouldnt be very high. So, a fan dipole/maypole design based on the 10m telescopic mast is needed. The question is - which bands?

In the past, ive found 80m to be a prerequestite for SES. So which others? 40 and 20? What about 15, 12, and 10m? Topband is out on the practicallity side, and 30m isnt needed as this will be a phone op.

Im going to test a few ideas out tomorrow based on the clansman 5.4m mast, at the very least to verify that it will take the 2m vertical without any issues!

On the operating side recently, not much! However, yesterday i was very pleased with my little tune around on 17m whilst taking a break from gardening. Heard VP8LP Bob, calling CQ, no replies, so thinks i, grab him if i can before the EU zoo arrives! So, i called him, little realising i was set to 10w. Anyway, to my immense amazement, he replies! I quickly hit the button to go to 100w, as 10 just wasnt going to be reliable, and instead hit the AM/FM button. A good few seconds later i was back in control, and Bobs phone is ringing! I QRX, he returns and we have a pleasent natter for a few minutes. I give my 73 as i need to crack on with the veg plots, but Bob asks if i'd like to work another VP8 before i go? (Having been after the Falklands ever since i got HF, then its a moot question!), turns out Zorro VP8DNT is visiting Bob, they quickly change over, and ive got two VP8s logged in 10mins!