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 Post subject: Re: How to make the Cockaday coil for the 4-circuit tuner.
PostPosted: Jun Tue 12, 2018 2:25 pm 
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Joined: May Wed 16, 2018 6:58 pm
Posts: 16
I forgot to send a photo of the homemade tubebase.

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Buisvoeten1.jpg
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 Post subject: Re: How to make the Cockaday coil for the 4-circuit tuner.
PostPosted: Jul Sun 08, 2018 8:17 pm 
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Joined: May Wed 16, 2018 6:58 pm
Posts: 16
Hi radio friends,

The holiday is over and I have continued with the construction of the radio.

Can I use the tube type CX-301A for the receiver section? Does anyone have experiences with this tube in this radio?

Regards, Henk


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 Post subject: Re: How to make the Cockaday coil for the 4-circuit tuner.
PostPosted: Jul Sun 08, 2018 10:39 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2005
Location: Monroe, NC 28112 USA
Hello,

I have seen the Cockaday circuit used with both dry cell (1.1 V or 3 Volt) and storage battery (5 Volt) filament American valves. So your Type 01-A valves would be good.

Robert


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 Post subject: Re: How to make the Cockaday coil for the 4-circuit tuner.
PostPosted: Jul Mon 09, 2018 6:11 am 
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Joined: May Wed 16, 2018 6:58 pm
Posts: 16
Hello Robert,
Thank you for the positive response.

Greetings, Henk


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 Post subject: Re: How to make the Cockaday coil for the 4-circuit tuner.
PostPosted: Jul Mon 23, 2018 9:47 am 
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Joined: Aug Sat 06, 2011 10:46 pm
Posts: 106
Location: Kurri Kurri, N.S.W., Australia
I also built a Cockaday Four Circuit Tuner with a bit of a twist.

First, I had some severe hand capacity problems with my set until I reversed the leads on the tuning capacitors. Also, because I was not using an original '01A valve/tube I felt free to experiment a little with the circuit and added an extra ground wire to the circuit from the main ground wire from the loading coil switch to the B+ wire between the battery and headphone.

I used a 1T4 pentode as a detector, and it worked well with a 10megohm grid leak and only 9 volts of B+ voltage. I was not using the screen grid as it would normally be connected, I used a 50Kohm potentiometer in series instead. More B+ voltage improved volume but decreased sensitivity.

It has been several years now since I last hooked it up, my goal was battery economy and the experience of using the set. Its sensitivity was very impressive, but its output volume was very low. Every attempt to build an amplifier failed for me with this 1T4 detector and a single power source and sent the set into oscillation. I did not try a separate battery for the amplifier section. Use of an RF choke also caused oscillation in my set. Eventually I coupled the set to a manufactured amplifier using an audio interstage transformer (3:1). I am guessing that it worked only because it was powered separately.

Attachment:
1T4 Cockaday Conversion ARF size.jpg
1T4 Cockaday Conversion ARF size.jpg [ 67.02 KiB | Viewed 916 times ]


Lindsey


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 Post subject: Re: How to make the Cockaday coil for the 4-circuit tuner.
PostPosted: Jul Mon 23, 2018 2:13 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 14378
Location: S. Dartmouth MA 02748-1225 USA
Lindsey,

Interesting, the issues experienced by tube substitution are not unusual in many 20's radios. The low gain tubes of the era when combined with the external circuitry did not cause stray oscillation. Substitutions in Radiola III often have this problem along with difficulty controlling the substitute tube filament current.

I note the schematic appears to call for an 00a, a gas detector. Whereas you mention in your post an '01a. Did you try the circuit at all with vintage tubes?

Also, 25pf is unusually low for a grid condenser, however, the radically different grid capacitance of the 1T4 may have required such a change. The relatively low plate impedance which is presented to the input coil on the original Cockaday and the RF return to the A- is also not present. Those two changes more fully explains what has happened to the input coil both its impedance and the "Q" and is more directly responsible for the hand capacity. FWIK Cockaday makes no use of panel shields, then again, Cockaday likely anticipated a more experienced builder to make adjustments to variable condenser connections. Going to a single grid may require adding capacitance to the grid capacitor.

Have you tried a lower gain tube or tying the screen grid to the plate instead of adding its influence to the electron stream?

FWIW it is likely a carbon compression grid leak was probably used, like a Bradleystat...

Thanks for posting the before and after schematics

Chas

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 Post subject: Re: How to make the Cockaday coil for the 4-circuit tuner.
PostPosted: Jul Thu 26, 2018 2:56 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2005
Location: Monroe, NC 28112 USA
I decided to power-up my one tube Cockaday for the first time this afternoon. (The one shown in the photos on the first page of this thread.) Boy! Is it ever a chore to tune! I was able to eventually find the two local stations that present very high field strength to my antenna. Tuning is very sharp and getting good audio takes very careful adjustment of the filament voltage and the shunt Bradleystat. I don't see how you could ever DX with this set... Of course this makes me think I've got something hooked up wrong or just don't know how to tune it. But the connections are so simple and all check good.

Maybe another session tomorrow will be more successful.

Robert


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 Post subject: Re: How to make the Cockaday coil for the 4-circuit tuner.
PostPosted: Jul Fri 27, 2018 10:23 am 
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Joined: May Wed 16, 2018 6:58 pm
Posts: 16
Progress of the construction of the Cockeday.

I can receive three radio stations with a wire antenna of 30 meters.
I think it has to do with the detector tube, but I'm not sure.
The quality can be better.
When I use my own transmitter, the reciever is working properly.
The radio box is almost ready and actually I am quite satisfied. The front still lacks some text pictures. (see photo's)
I would like to hear reactions for improvement of the reciever.
I am satisfied with the result.

Kind regards, Henk


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Cockaday.pdf [128.8 KiB]
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 Post subject: Re: How to make the Cockaday coil for the 4-circuit tuner.
PostPosted: Jul Fri 27, 2018 1:18 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2005
Location: Monroe, NC 28112 USA
Very good looking front panel. I hope you can post photos of the internal construction.

I tried again yesterday afternoon to tune my vintage Cockaday. I did not get any better results. I do not know what to try next. This radio is so easy to verify that the connections are exactly like the vintage documents indicate. I have other vintage regenerative radios that work much better.

Robert


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 Post subject: Re: How to make the Cockaday coil for the 4-circuit tuner.
PostPosted: Jul Fri 27, 2018 2:17 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1488
Location: Jackson, TN
Hello Henk,

Very nice work on that panel!

Your work brings to mind ARF user billm, AKA exray, who has built some unbelievable early replica sets.

Keep us posted and include more photos.

Thanks, Tim


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 Post subject: Re: How to make the Cockaday coil for the 4-circuit tuner.
PostPosted: Jul Fri 27, 2018 2:37 pm 
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Joined: May Wed 16, 2018 6:58 pm
Posts: 16
Thanks for the compliment. The wiring is temporary.
The wires are round and must actually be square.
I want to have the radio in order before I use square wire.



Kind regards, Henk


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Cockaday binnenkant.pdf [49.1 KiB]
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 Post subject: Re: How to make the Cockaday coil for the 4-circuit tuner.
PostPosted: Jul Fri 27, 2018 3:21 pm 
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Joined: May Wed 16, 2018 6:58 pm
Posts: 16
End this is how it has become.
The round speaker is the Philips pancake and the loop antenna is French made.

I hope you like it too and I want to thank you again for all technical info.

Henk Boeijink


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Complete set.pdf [56.13 KiB]
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 Post subject: Re: How to make the Cockaday coil for the 4-circuit tuner.
PostPosted: Nov Sun 25, 2018 3:51 am 
Member

Joined: Aug Sat 06, 2011 10:46 pm
Posts: 106
Location: Kurri Kurri, N.S.W., Australia
Chas, I'm sorry for my slow response, I am not as active in the hobby as I once was.

I have not tried any other tube than the 1T4 in this circuit, but I have seen other versions published with the 01A listed as the detector.

I suspect there is a point where the coupling between the tuning coil and the stabilizer coil would make tuning the stabilizer hyper-critical if spacing is increased beyond a point. As mine was built there was a wide range of acceptable settings (about 15-20 degrees) for the stabilizer setting beyond which oscillation takes over.

There was a variation published using a split variometer called the 'Miloplex'. It used the rotor as the stabilizer coil and the field as the tuning coil.

I wish I did have a good variable grid leak, I sure would have used it.

Lindsey


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 Post subject: Re: How to make the Cockaday coil for the 4-circuit tuner.
PostPosted: Nov Wed 28, 2018 8:01 pm 
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Joined: May Wed 16, 2018 6:58 pm
Posts: 16
Hi radio friends,
It has been quiet for a while, but I have not been idle.
The results are incredibly good.
I did not know that so many radio stations can be received on the medium wave.
The antenna is a wire of about 15 meters.
Between the antenna and the radio I have build the UN34 http://www.nvhr.nl/frameset.htm?&ContentFrame
Plugged in.
This is just necessary and the result is amazing.
If there are any questions, I'll hear it.

Mvg, Henk


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 Post subject: Re: How to make the Cockaday coil for the 4-circuit tuner.
PostPosted: Nov Fri 30, 2018 2:11 am 
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Joined: May Fri 25, 2018 1:50 am
Posts: 638
Location: Petaluma, California
Hi Henk - your link needs the "E" for English, can't find your device on those pages.
Cheers,
John

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