1st valve project

[marknotts]

I'm new to this interesting forum so 1st off Hello to all!

Can anyone suggest a really simple valved receiver project suitable for a beginner like myself. I have a reasonable understanding of electrical components, a good selection of tools but my only test equipment is a multi meter!

[The sarge]

Hi, im on my first radio, a Bush DAC 90A it`s not been too bad, mainly needed a good clean and a few bit`s replacing...not too taxing even for me !!!

[Nickthedentist]

Yes, if you're talking about restoration/repair rather than building from scratch, you can't beat a DAC90A - everything's very accessible, and there's a wealth of info here about them.

[marknotts]

I'd like to build from scratch!

[Sideband]

Probably the best thing is to look on eBay and buy a couple of cheap 50's style radio's. That way nothing much is lost if things go wrong and you learn in the process plus you end up with some spares that could be useful for future attempts. Chances are you'll get at least one of them going which will inspire you to get on with the next....and the next....!


Rich.

[Nickthedentist]

And they're sometimes given away FREE here

[Ed_Dinning]

Hi Mark, if you are thinking of home building there are a great many designs available. For a first set a battery one would be a good idea. 10 PP3's or fewer for the HT and no need to build a power supply.
If using minature valves the DF96 series is a good start, if looking for l;arger types try the DF33 series.
PM me if you need additional assistance.

Ed

[paulsherwin]

There are zillions of construction projects from the heydey of valves in the 1950s here: http://vintageradio.me.uk/radconnav/radcon.htm

Paul

[marknotts]

Originally Posted by paulsherwin

There are zillions of construction projects from the heydey of valves in the 1950s here: http://vintageradio.me.uk/radconnav/radcon.htm

Paul

This is the problem, I'm bombarded with information from all the web searches ive already done.
A battery set would be a good start, possibly single valve, any idea's

[OErjan_S]

here you have a simple regen that works ok on just 2 or 3 9v batteries in series for b+ and two 1.5v batteries for the filament.
just the tube, 2 (or 3, there is an option for bandspreading) variable capacitors a resistor and a coil you wind yourself on a tubebase, yes bottom part of a octal tube, i replaced the commercial tube former with a octal tube base.
all in all not very complicated.

http://www.mines.uidaho.edu/~glowbug.../ar55how12.jpg
http://www.mines.uidaho.edu/~glowbug.../ar55how14.jpg
http://www.mines.uidaho.edu/~glowbug.../ar55how16.jpg
http://www.mines.uidaho.edu/~glowbug.../ar55how18.jpg

[paulsherwin]

The 3S4 used in that design is an American DL92. A DL96 should also work and may be easier to obtain.

Paul

[Aerodyne]

I'd like to build from scratch!

Mark, one very simple answer would be to get hold of a copy of Camm's 'Beginner's Guide to Radio' from the 1950s. In it he shows how to build the most simple valve receivers and importantly shows you how to make basic coils for it. I see it as a good starting point. HT batteries can be easily made with series PP3s.
-Tony

[marknotts]

Thanks for all the replies.
The RX in OErjan's reply is just the kind of thing I'm looking for, I will also look up a copy of the book.
One question, What kind of headphones are required and can they be obtained?

[Aerodyne]

Most basic one valve sets will operate with high-resistance headphones (upwards of 2k) and these are ideal for your purpose. Failing that you can use a suitable output transformer with LR phones. The latter are easily obtainable as they are made these days as so-called Hi-Fi headphones, usually 8 ohms. A cheap pair should suffice. Matching the HR output of the valve to the LR phones would require the use of a small multi-tap output transformer to determine the best output level. You might come across one of these on the internet auction site or by posting a request on this forum. Failing that, try a battery valve output transformer or post again, this time for HR phones!
-Tony

[marknotts]

Originally Posted by Aerodyne

Mark, one very simple answer would be to get hold of a copy of Camm's 'Beginner's Guide to Radio' from the 1950s. In it he shows how to build the most simple valve receivers and importantly shows you how to make basic coils for it. I see it as a good starting point. HT batteries can be easily made with series PP3s.
-Tony

Just ordered this book 2nd hand for £3.50 of abebooks:

http://www.abebooks.com/

[marknotts]

Originally Posted by Aerodyne

Most basic one valve sets will operate with high-resistance headphones (upwards of 2k) and these are ideal for your purpose. Failing that you can use a suitable output transformer with LR phones. The latter are easily obtainable as they are made these days as so-called Hi-Fi headphones, usually 8 ohms. A cheap pair should suffice. Matching the HR output of the valve to the LR phones would require the use of a small multi-tap output transformer to determine the best output level. You might come across one of these on the internet auction site or by posting a request on this forum. Failing that, try a battery valve output transformer or post again, this time for HR phones!
-Tony

Is this the sort of thing your talking about:

http://www.schmarder.com/radios/misc...ransformer.htm

[paulsherwin]

Originally Posted by marknotts

Is this the sort of thing your talking about:

http://www.schmarder.com/radios/misc...ransformer.htm

That is a bit over the top.

Modern headphones are typically 32 ohms. You just need a transformer to match that to a high impedence. Lots of transformers will do - you can use an output transformer from an old transistor or valve radio, or a small 6-12V mains transformer.

Headphones vary a lot in sensitivity and most of the very cheap market stall ones are quite insensitive. Choose the most sensitive ones you can find.

The various Sennheiser models are available quite cheaply on eBay and are pretty sensitive. You can use them with your mp3 player too

Paul

[OErjan_S]

the Bogen is a great transformer, but as Paul said, somewhat much for this, a mouser 42TU003-RC, Calrad 45-701 or similar if you will do nicely for something like this.
there are a number of suitable transformers, I should think most that give between 50:1 and 250:1 impedance ratio (impedance ratio is roughly 6x voltage ratio as general rule) could work look around.
also I would wire the 3.5mm socket so that only the tip and ring are used, that way you get sound in both ears, and as bonus higher impedance.
I have successfully used a 240v-->5v 350mA transformer scavenged from a toy charger as a temporary solution on something like this.
also I have made this circuit with many pentodes, DL91 (change to 1.5V A supply), DL92 (3S4), and with slight changesDL94 (3V4), DL95 (3Q4), DL96. i first made one with DL92 then i used that same chassis and modified it some just to see what happened.

[Variometer]

Hi Marknotts,

Try this one, it is very simple, but works reasonably well.
Valve 6C4 triode or any simlar.
C1 100pF
C2 22uF 63 Volts
R1 860 Ohms
L1 & L2 Miniature RF chokes 100uH (Get them from Maplin)
D1 Germanium diode OA90 or similar (Maplin)
VC1 Any capacitor with a fair number of vanes will work

Headphones must be High Impedance. If you haven’t got any, use a small mains transformer (240V in, 12V out, Maplin) as a matching unit. The original mains winding is connected to the receiver & the 12 Volt winding to Low Impedance headphones.

LT: 6 Volts from re-chargeable lead acid. HT: 54V from six 9V batteries connected in series.

Bob

[Variometer]

Curiosity - Have any of the replies been any help, or are you still searching?
Bob