Osmor SWQ2 coils

[mrmagoolew]

Hi, Guys,

I'm from the US, and I'm trying to find out some information on the above coil. Can anyone tell me anything about it, such as the diameter, height, and the windings and spaces between them? Ideally, I'd like to find someone that may have one for sale. I have a schematic for a one tube SW radio that uses a 954 or 955 tube, and would like to build it. I have no formal training in electronics, and wouldn't have any idea about how to wind the coil without some help. Anyone know where I might buy one? Thanks, Lew

[Ed_Dinning]

Hi Lew, Osmor are long since gone, but some serious Googling may well reveal more details of the coil. They produced a wide range of coils for both setmakers and amateurs.
In each coil range there were several different coils to cover different frequency bands.

They were normally coded "Q", "HF, A, O" (for function), then 1,2,3 etc for frequency range.
There were several other manufacturers who produced similar products
You are looking for one for an SW radio; if you get one for the broadcast band the set should still work; in fact many of these sets used several coils the were plugged in to change bands.

Good luck in the search, Ed

[mrmagoolew]

Hi, Ed,

Thanks for your reply. I've looked on Goggle for info on the coils, but have come up with just about nothing. I did find a chart of the coils they made, but wouldn't you know, the chart had the info on all the other coils, but not on the ones I'm interested in. I have a box of coils that I'll have to go through and see if there is anything in it that I can use. All I know about the Osmor coil is that it had three windings on it, and I only know that from looking at the schematic. I'll keep looking on Goggle, and elsewhere and see if I can come up with anything. Again, thanks for your reply. Lew

[Ed_Dinning]

Hi Lew, that sounds as if it has an input (usually the largest winding) an output winding (usually connected to the next grid and a tuning condenser) and a reaction or feedback winding which is usually the smallest winding.
This will be a TRF circuit, so Googling for that may give you some links.
You should find that coils by Denco and some other manufacturers will also do; sadly as far as I know, Wearite coils were only 2 winding types so not suitable for your circuit.
I have a boxful of Osmor 2 winding types, all coded with paint spots, but I've no idea of what the coding means.

Ed

[AC/HL]

Some data here: http://www.electrojumble.org.uk/osmor.htm
Unfortunately, yours get just the basic coverage detail.

[Junk Box Nick]

Hi Lew

There was a circuit in Practical Wireless (UK) March 1964 that is probably similar or the same as that which you describe.
See here: http://www.vintageradio.me.uk/radconnav/acorn.htm

All these one valve circuits are very similar and you could use Denco coils or Repanco coils instead. The snag is that these will probably be just as hard to find as the Osmor coil as all these firms are long out of business.

So why not wind your own? For short wave this is not as daunting as winding a coil for the AM band and the relationship between the coil and the tuning capacitor, etc., is pretty constant no matter what circuit it is in, thus you can borrow from another circuit.

You will find details of simple receivers on the sites below and in the text you will find details for winding the coils which you can borrow for your set. The Osmor coil you specify has a third winding to couple to the antenna but you could replicate this on your home made coil by making a third winding of a few turns. You may have to experiment a little with the number of turns but that is half the fun of making sets like these!

http://makearadio.com/tube/sw1.php

http://w5dxs.tripod.com/receiver.htm (scroll down and look for the regenerative receiver and the one tube radio)

Good luck!

Nick

[Wendymott]

Hi Guys.... see my attached photos for a simple coil winder
Regards
Wendy G8BZY

[mole42uk]

How do you count the number of turns?

Richard

[Wendymott]

Hi Richard. I should have said......... I don't use the motor to wind... I rotate the chuck manually, and then count... and tick off each 10 turns...........the coil I wound recently was an IF coil for my Hammerlund HQ170, which was 160 turns........

[mole42uk]

Originally Posted by Wendymott

I don't use the motor to wind... I rotate the chuck manually, and then count... and tick off each 10 turns

Ah, thanks Wendy - I was a bit puzzled.

I built a coil winding attachment for my lathe which has a clicker to count each turn and a variable speed so I can control the build-up of the coil.

I recently had to make a choke with about 500 turns.....

Richard

[Ed_Dinning]

Hi Richard, keep a look out on e-bay for reversible and resettable counters, the often go cheaply and are very useful when winding.

Ed