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panbiker
Senior Member


2301 Posts
Posted -  01/09/2008  :  13:48
Hearing Stanley's comment in another thread about someone he knew at Lancaster Uni that made a radio with a bucket and a coat hanger has got me going.

I'm going to need one or two bits and pieces to make this work.

Some wire, a safety pin, a pencil, some kind of earpiece and a razor blade. That should just about do it.

An appeal to all the locals, probably the blokes. Ideally I need one of those old fashioned single sided razor blades (preferably blued), although this could be sorted if its not. A later generation double sided Blue Gillette blade would probably do at a pinch but the single sided ones have recesses in the right place for fixing. Can anyone help?

We shall make music or speech (or both) out of the ether once we get the kit together.


Ian
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Stanley
Local Historian & Old Fart


36804 Posts
Posted - 29/12/2008 : 07:37
I haven't tripped over that transformer yet but when I do I'll let you know. It has not been forgotten.


Stanley Challenger Graham




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stanley at barnoldswick.freeserve.co.uk Go to Top of Page
Tizer
VIP Member


5150 Posts
Posted - 29/12/2008 : 10:28
Quite right to put the family first Ian. I'll keep an eye on the thread for future activity...


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Stanley
Local Historian & Old Fart


36804 Posts
Posted - 30/12/2008 : 09:04
He'll get round to it eventually. I know how other activities can get in the way of the shed. The presure builds until one day you go in to tidy up and that triggers you off again.


Stanley Challenger Graham




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panbiker
Senior Member


2301 Posts
Posted - 08/03/2009 : 14:55
Lateley I have been getting back into fellwalking and have been walking up various hills at the weekends. I was going to do Whernside today but changed my mind when I put the bin out this morning. It was nithering. So, as I have been fairly lax in furthering the Foxhole Radio, I thought I would move it on a bit and post the current status of the project.

I have been watching (and bidding) on various sets of High Z (High Impedance) headphones on Ebay. Contemporary WWII headsets come up quite regularly and would be ideal for the project. I have bid on two different lots so far but both have gone past what I am prepared to pay at the moment for 70 year old headphones. The search goes on.....

I found a piece of wood suitable for mounting the circuit on, it's a piece of oak which used to be part of a table. You can build the circuit onto any suitable insulated mount.

Wood Base

I have fashioned what will become the rudimentary tuning arrangement from a straight piece of heavy wire, I got this from an old style coathanger. I have made a loop at one end so that I can secure it along with the required connections to the baseboard. The circuit will work without the tuning arrangement but I have decided to include it in my version. It may make no discernable difference to the performance of the receiver but then again it might just provide a small amount of selection, we will see. I have placed the coil and the tuning slider on the baseboard to show how this part of the circuit will be laid out. There is plenty of room left to mount the razor blade detector.

Tuning Arrangement

I have the razor blades, so I just need to make the other half of what will become the detector in the design. I am going to try a couple of different methods of making the semiconductor junction to see which one I can fashion best. Securely fixing the coil to the baseboard will have to use some non conductive method so as not to interfere with the resonance. I might do this with a reasonably thin strip of wood passed through the coil and screwed to the board at each side. I could then use these screws to make the connections from the coil.

That's it for now, I will post more after I have experimented with the best method for the detector junction.


Ian Go to Top of Page
pluggy
Geek


1164 Posts
Posted - 08/03/2009 : 17:50
Bit cheaper than a genuine set of WWII headphones and if you cut the plug off would look reasonably rustic :

http://www.maplin.co.uk/Module.aspx?ModuleNo=3256&&source=14&doy=23m8


Need computer work ?
"http://www.stsr.co.uk"

Pluggy's Household Monitor Go to Top of Page
panbiker
Senior Member


2301 Posts
Posted - 08/03/2009 : 22:00
It will do the job but is definately not in keeping with the spirit of the project. I might just as well stick an amplifier and speaker on the end of it and have done with it.
Interesting to note though that the properties of piezoelecrtic materials were first discovered in the late 19C. Advances in developing products using the materials did not really take off until after WWII when more stable compounds had been developed.
I found this site which not only gives the history but shows how diverse the product range now is using piezo technology.

http://www.piezo.com/tech4history.html




Edited by - panbiker on 08/03/2009 22:01:32


Ian Go to Top of Page
Stanley
Local Historian & Old Fart


36804 Posts
Posted - 09/03/2009 : 06:31
Wet cold weather has driven him into the shed......


Stanley Challenger Graham




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panbiker
Senior Member


2301 Posts
Posted - 09/03/2009 : 17:19
The "shed" in this case is the table in the back room. Never really had a shed at this house. I used to have an Amateur Radio "shack" at a previous house. You are right about the weather, didn't like the look of yesterday for the top of Whernside.


Ian Go to Top of Page
Stanley
Local Historian & Old Fart


36804 Posts
Posted - 10/03/2009 : 06:57
Sensible decision I reckon. I always say that the best day for shed or writing is wet and windy.


Stanley Challenger Graham




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stanley at barnoldswick.freeserve.co.uk Go to Top of Page
panbiker
Senior Member


2301 Posts
Posted - 23/03/2009 : 17:29
I posted earlier that I had been keeping my eye on Ebay for some contemporary headphones for the project. I have been sucessful and managed to secure these for what I consider the very reasonable price of £11.50. Not bad for a piece of history.

These are Brandes Superior BBC Matched Tone Headphones, they are British made and were produced throughout the 1920's and 30's. They were auctioned as untested but I was willing to take a risk. They are in original condition with the correct braided polarised cord set.
Brandes Superior BBC Headphones

Brandes Headphone Earpiece

They need a small amount of TLC to make good the odd fraying to the cord and a bit of a clean up. I have tested the magnets for retention of field which can be a problem with older units such as these. The good news is that both of the earpieces can support the weight of the diaphragm insert when removed and attached to the magnet by it's edge. This is the recognised test for fixed magnet efficiency in electromagnetic sounding devices. The windings on the coils looked in good condition and the coil connections to the outer terminals look good. I will test them for continuity when I have refurbished the cord and made up new termination ends. The individual earpieces are about 1000 to 1100 ohms each and are polarity wired in series to give 2000 to 2200 ohms.
The Brandes BBC Headphones were supplied with various commercially made crystal and single valve radios in the 1920's and 30's and also sold to the self build hobby market at the time. The BBC branding at the time was a sign of conformity to standard and fit for use etc. Perfect for the project.


Ian Go to Top of Page
Stanley
Local Historian & Old Fart


36804 Posts
Posted - 24/03/2009 : 06:41
Interesting that the BBC allowed their imprint to be used on a commercial object. Nice to know it looks as though they are OK.


Stanley Challenger Graham




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stanley at barnoldswick.freeserve.co.uk Go to Top of Page
Bradders
Senior Member


1880 Posts
Posted - 24/03/2009 : 12:48
Stanley ....One of the other things that BBC also allowed it's name to be used for was a range of  monitor speakers (to their design) , in the 70's /80's . One of the patterns  was called  "LS3/5a", and were made by the Rogers Company and others, under license.

They are superb but only tiny... and they need a lot of driving ....giving a sound that doesn't  seem possible from such a small "bookshelf" cabinet .

These days they are much sought after ....so if you have a pair ....Hold on to 'em.

BRADDERS.

 

P S Since posting the above I have checked on tinternet and been STAGGERED at what people are paying for these speakers.....

It seems that they were produced by Chartwell, Harbeth, Spendor, Kef and Rogers.

(Jim Rogers worked for the BBC in the early  70's and designed  them as the small monitors that were needed for the outside broadcast vans.)

He later went on to  set up his own company to produce High End Audio equipment........

There is a pair of Chartwell LS3/5a s on Ebay as I write, that stand at £1850 with more than a day to go.

A pair of Chartwells (serial no 170 & 171) sold recently for £3650 ! .........The Rogers versions make £300 to £800.

And they're only the size of a SHOEBOX ...........Can't  really see the logic for all of this , but I wish I had some to sell !

 

Edited by - Bradders on 24/03/2009 3:38:13 PM

Edited by - Bradders on 25/03/2009 12:11:48 AM


BRADDERS BLUESINGER Go to Top of Page
Stanley
Local Historian & Old Fart


36804 Posts
Posted - 25/03/2009 : 07:58
I have some treasures like that in the box and keep thinking they should go on Ebay. A Porter governor for a traction engine, a Buffalo Class A (11) injector and others. I'll bet someone somewhere would give their eye teeth for them.


Stanley Challenger Graham




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stanley at barnoldswick.freeserve.co.uk Go to Top of Page
panbiker
Senior Member


2301 Posts
Posted - 06/07/2009 : 20:25
Here it is Bradders, and has it really been nearly 3 months since my last post! I have had lots of other stuff to keep me busy, notwithstanding new grandchild and another on the way. We went down to Stratford at the weekend to visit said child amongst other things and on the way back happened to stop at the services for a very expensive brew.

Now what has this got to do with the foxhole radio project I hear you ask?

Well in the true spirit of the project, I lifted a few of the wooden stirrers that substitute for proper spoons in these establishments. They should come in usefull to secure the coil to the base board. So you see, the project is still in the making, albeit very slowly.

More good news, I have an extra area of rust that has developed on one of the razor blades, could prove critical when I eventually get it all together.


Ian Go to Top of Page
Bradders
Senior Member


1880 Posts
Posted - 06/07/2009 : 23:06
Good Going Ian (Grandad).......Please keep us up to date on the rust front.......

I  KNEW  that this  radio  topic had something to do with "shed culture" .....

Phew.......... !

 

 

 


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