Homebrew Electronics by ex Radio Officers

Shipbuilder
29th April 2008, 08:44
I think most radio officers in their time dabbled in electronic construction projects. What have you built in the past (or even recently)?
Having purchased a few sheets of aluminium on a car boot sale last year (with nothing particular in mind), I later thought I would like to build a variable capacitor. This is my first attempt. Never being much good at theory, it was all guesswork. The vanes were semicircular, but I offset the spindle in a vague attempt at "square law." The size of the vanes were decided purely on the physical size that I wanted the completed capacitor to be.
The end plates were made from acrylic. The brass quarter inch spindle & bushes were made on my small Unimat lathe. After a lot of messing about, it was finally assembled. On putting the capacitance meter on it, I was delighted to see the value came out at 0 to 300pf exactly!

http://img241.imageshack.us/img241/3391/variablecapacitor300pfqj4.jpg

R651400
29th April 2008, 12:24
Posting 1 refers. Gentlemen (Gentlepersons), We're up against a real expert!!
My first attempts at homebrew failed miserably, trying to build a one valve transmitter using a non electric plumbers soldering iron! Every joint probably as dry as the proverbial.

Shipbuilder
29th April 2008, 12:36
Thanks for reply. Your first reply appeared briefly, then disappeared as I watched only to appear again a bit modified. However, I gather you had problems cutting the vanes. I had the same problem when using tinsnips, they curled the edges slightly. Eventually, I sandwiched all of one set of aluminium blanks between two pieces of plywood, clamped at the corners with countersunk nuts & bolts. I pasted a drawing on the vanes on top. Next, I drilled the hole for the shaft using a drill press. Then (In fear & trembling of ruining a bandsaw blade) I cut the vanes out. Because they were all tightly clamped together, the edges did not curl. I cut the curved part first & that, of course, took away two of the fixing bolts, but taking things easy, the final straight cut (through the middle of the spindle hole) was a fairly simple job. I was surprised at how easy it was to cut. The bandsaw was a Black & Decker hobby type. The blade took no harm & even appeared a bit sharper after cutting the aluminium. Since then, I have cut much thicker aluminium with it & have never broke a blade!
Bob

R651400
29th April 2008, 16:40
Bob, Thought it better to keep my first as brief as possible to see how the thread develops.
The circuit of that one valve transmitter held me in good stead for my PMG which asked for a simple circuit for a bfo!
Bit hard to avoid some technical jargon when talking electronic projects.

Gareth Jones
30th April 2008, 02:05
Shipbuilder, you've done a clever and skillful job there, congratulations - but now you've built it what are you going to do with it ?

Shipbuilder
30th April 2008, 06:53
Hi Gareth,
Variable capacitors are becoming harder to get these days although I have a good supply myself. I have written a number of articles on obsolete radio construction & it ocurred to me that others may not have a good supply of them, so it might be a good idea to see if the home constructer could make one. I can always find a use for it although I have not used it so far. I can make most components now, capacitors, resistors, tuning coils etc. I have even tried to make a triode valve & although building the inside is a simple enough task, geting the air out to a sufficient degree has defeated me so far & I have had zero success.
I tend to mess about with vintage radio on an erratic basis. My main amusement it building miniature model ships & I only go back to radio at intervals as & when the spirit moves me. It is not necessarily what to do with them (I never listen to them for any length of time) it is the challenge of building - keeps the brain & fingers active.
Bob

Duncan112
30th April 2008, 08:33
Hi Gareth,
geting the air out to a sufficient degree has defeated me so far & I have had zero success.

Bob

Just a thought but I once evacuated a fridge system with success using a home made venturi fabricated from a brass T piece from the instrumentation spares and compressed air as the driver. Got us home anyhow when we got the vacuum pump fixed. Can't say how high the vacuum was as the only pressure guages we had were the compound ones fitted to the compressor.

Shipbuilder
30th April 2008, 10:34
Hi Duncan,
I know the method, but have no compressed air either. The unsuccessful method that I tried was put a bit of water inside it and heat it up until filled with steam then close it off quickly. Idea was then when steam turned back to water droplets, it would leave a vacuum. Not successful as steam pressure bursted it (wearing goggles, so survived OK) - put the wind up the 2nd R/O though in next cabin aboard S.A. ORANJE!
Bob

R651400
30th April 2008, 12:03
Too difficult to try gettering?

andysk
30th April 2008, 12:25
........ I have even tried to make a triode valve & although building the inside is a simple enough task, getting the air out to a sufficient degree has defeated me so far & I have had zero success .........

Hi Bob,

There used to be a vintage radio guy living somewhere near Gipsy Hill in South London, I think his name was Gerald Wells. His 4 storey Victorian villa, with large range of garden shedding, was a treasure trove of radio and early 405 line TV kit.

I seem to recall he had a working valve evacuation & gettering machine from English Electric and was starting bespoke valve production. As this was about 20 years ago he my well not still be around, but he did have a young assistant at the time, who may be carrying on the interest.

I have just Googled him, take a look at : http://www.bvwtm.org.uk/, but I'm not sure just how up to date this site is.

Cheers

Andy

(ps) Who was the poor 2/R/O ?)

Shipbuilder
30th April 2008, 13:38
Hi Andy,
Thanks for info. I will look it up.

R/Os at the time were Pud Cullen Chief, Roy Mercer 2nd, Myself 3rd & Les Gough 4th!

Bob

andysk
30th April 2008, 14:30
Hi Bob ....

They are all familiar names - I sailed with Les on one of the pax somewhere, and on Rothesay C as 1st trip Junior R/O with Roger Perks (and wife Laurie ?) when Pud had a trip off in early 1971

Had one trip on SA Oranje as 4th with Bill Eckersley (Ch/R/O), Ian Pegg (2/R/O) and Robin Diamond (3/R/O)

Those were the days ....

God luck with Gerry Wells.

Cheers

Andy

Shipbuilder
30th April 2008, 19:01
Hi Andy,
I was with Les in S.A. ORANJE when I was 3rd & he was 4th & again in WINDSOR CASTLE when I was 2nd & he was still 4th (he reversed his promotion by leaving when he was 3rd & coming back again). I sailed with Bill Eckersley when he was Chief in SA ORANJE (I was 3rd) & again in WINDSOR CASTLE when he was again chief & I was 2nd. Ian Pegg relieved me as 2nd one voyage in WINDSOR CASTLE, but never came across Robin Diamond!
Bob

Shipbuilder
30th April 2008, 19:08
PS
Just looked at BVWS website. What a splendid collection of old receivers, takes me back to my schooldays when I would go the to local radio shop & bum an old radio off them to take to pieces. I must have demolished hundreds if not thousands of poundsworth (today's money) in old receivers.

My finest hour was a couple of years ago when I purchased an old Burndept IV (1927) on the local car boot sale for 25. Took it home & wife made me leave it oustide overnight, it was so grubby. Opened it up & felt that it was beyond saving. Lay in shed for a few months & then in chance conversation with Christie's auctioneers London (about model ships) subject of the Burndept came up - could I send it along? I did so & it sold for 2,400 - how about that!

Bob

twogrumpy
30th April 2008, 19:43
Started off with the crystal set with a long wire aerial down the garden, progressed to building transistor sets and 1 & 2 valve TRF's.
There was a little radio shop by the station in Gillingham, and I would go in and buy my "transistor" in a little red and yellow RS(Radio Spares as it was at the time) box. Circuits would be built using transistor sockets so that THE transistor could be moved from circuit to circuit.
Ended up with an old Marconi B28/CR100.
Latest project has been a device sold commercially as the Mosquito, produces high frequency sound to frighten off kids, big advantage being that if you set the frequency correctly the noise caanot be heard by people above the age of 20. So safe for all those on SN.
Was looking at building a stun gun, but info on the output transformer was a little iffy.
Crystal set to internet, amazing really!!
twogrumpy

K urgess
30th April 2008, 19:58
That BVWTM puts my cupboard full of valves and measly collection of half a dozen valve radios and radiograms in perspective.
Latest project was a Webcor wire recorder but I got sidetracked.
Too many projects, too little time.

Never gone as far as trying to build components. I've always had an abundance of spares knocking about.
Used to build computers. Not your PC type thing but from chips (74 type) and breadboard. Gradually got lazier as various bits became more commonly available.

Sounds like you got a good deal there, Bob. Most of my stuff is worthless or at least worth less than when I bought/acquired it. [=P]

Shipbuilder
30th April 2008, 21:17
I never for one moment thought the Burndept was worth much when I bought it. In fact I felt that I had paid rather too much for it when I looked inside. I was only too pleased when Christie's seemed so anxious to get it & was totally amazed at the amount it fetched!

I really don't do all that much radio construction, but it "flares up" from time to time & I have to get it out of my system again before I can get back to ship models.

Bob

K urgess
30th April 2008, 21:27
Every so often I get the urge to build something again but nowadays I mostly prefer to work in wood.
First thing I remember building was my own pirate radio transmitter while at school. Had a range of about 2 miles on about 1200 kc/s. Only as an experiment, you understand. (Gleam)
I was expecting the detector vans to turn up from the moment I powered it up. [=P]
Next thing I have to do is build a digital to analogue detector so that I can still use the Atalanta when the world switches off AM. Preferably using valves.

trotterdotpom
1st May 2008, 00:42
I assembled a kit version of one of those ultrasonic mosquito zappers and got eaten alive. After that I chucked my soldering iron away and now rely solely on my "Waiter's Friend - it's great, it can open anything.

I stumbled on a site called the Siberian Shop the other day, they will flog you an 807 beam tetrode for $3.80. Handy if you want to fix your Oceanspan up but Vladivostok is a bit off the beaten track.

John T.

Sarky Cut
1st May 2008, 01:30
Started off with the crystal set with a long wire aerial down the garden, progressed to building transistor sets and 1 & 2 valve TRF's.
There was a little radio shop by the station in Gillingham, and I would go in and buy my "transistor" in a little red and yellow RS(Radio Spares as it was at the time) box. Circuits would be built using transistor sockets so that THE transistor could be moved from circuit to circuit.
Ended up with an old Marconi B28/CR100.
Latest project has been a device sold commercially as the Mosquito, produces high frequency sound to frighten off kids, big advantage being that if you set the frequency correctly the noise caanot be heard by people above the age of 20. So safe for all those on SN.
Was looking at building a stun gun, but info on the output transformer was a little iffy.
Crystal set to internet, amazing really!!
twogrumpy

Like your style, could you make me one?

twogrumpy
1st May 2008, 19:10
Sarky Cut
If I made you the stun gun, guess I know who you would test it on!
twogrumpy

athinai
9th May 2008, 12:46
My Father was a Home Brew Merchant., '' It tasted like the real thing.''


Among other things he was also a Home Brew Constructor and made a Receiver which was mounted on a Cigarette Tin. Very Good reception all round especially Short Wave. ( If you used it outside you could get ''CHILE''
especially in the Winter. ) .... .. .... ..