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Old 14th Aug 2017, 3:12 pm   #1
allyblack
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Default Wobbulator.

Help, can anyone assist?

I am building a simple wobbulator from Practical Wireless June 1972, so as to become involved in radio alignment procedures. I have bought the specified Denco coil, so I thought' but as you can see there are only two windings. What is wrong?

Has anyone out there built this circuit? If so how do I proceed.
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Old 14th Aug 2017, 3:29 pm   #2
AC/HL
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Default Re: Wobbulator.

Two separate coils could be wound one on top of the other. Are there 6 pins in use, or just 4?
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Old 14th Aug 2017, 3:43 pm   #3
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Default Re: Wobbulator.

This webpage may help:-

http://www.vintageradio.me.uk/info/M...CO/dtb4_p3.jpg

You can use a meter on ohms range to check for continuity of each winding.
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Old 14th Aug 2017, 4:00 pm   #4
ms660
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Default Re: Wobbulator.

2DP is two windings for valve oscillator (Armstrong)

2T is three windings for transistor oscillator (Reinartz)

The PW article to be precise, should have specified Range 2T instead of Range 2 to avoid any confusion.

So it's a Red Range 2T you need.

Lawrence.
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Old 14th Aug 2017, 4:07 pm   #5
John M0GLN
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Default Re: Wobbulator.

I've got a Denco 3t Blue coil and from a cursory glance it appears to have only 2 windings but as AC/HL suggested there are in fact 3 windings with 6 wires going to the pins.

John

Just seen ms660's post, so you have the wrong coil.
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Old 14th Aug 2017, 4:14 pm   #6
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Default Re: Wobbulator.

The construction article can be found here:-

http://www.americanradiohistory.com/...PW-1972-06.pdf
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Old 14th Aug 2017, 4:31 pm   #7
Craig Sawyers
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Default Re: Wobbulator.

https://mullard.org/ seems to have red range 2T Maxi-Q for £15
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Old 14th Aug 2017, 4:31 pm   #8
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Default Re: Wobbulator.

Hi Allyblack, one question, why did you choose it?
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Old 14th Aug 2017, 4:38 pm   #9
ms660
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Default Re: Wobbulator.

You could use an osc coil from an old transistor radio.

Lawrence.
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Old 14th Aug 2017, 6:37 pm   #10
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Default Re: Wobbulator.

I would agree, you seem to have a 2DP instead of a 2T. The DP range were really aimed at valve projects and have only two windings instead of the three required for low impedance transistor applications. You may be able to wind your own coil if you can find a suitable former.
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Old 14th Aug 2017, 8:51 pm   #11
PJL
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Default Re: Wobbulator.

Quote:
Originally Posted by ms660 View Post
You could use an osc coil from an old transistor radio.
I did exactly that and wired in a few varicap diodes and attached it to the scope sawtooth output. It was a bit experimental but was good enough to align a crystal filter and IF of a comms receiver. It's probably in my box of abandoned Vero projects.
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Old 14th Aug 2017, 9:43 pm   #12
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Default Re: Wobbulator.

This can be a bit non-linear in the frequency direction, so you may need to mix in a bit of RF from a stationary sig gen to act as a marker pip.

Keep your eyes open for an old HP 8601A sweeper, sometimes they go for junk money because they look too old and clunky to some people. Can do gentle wobbulation all the way up to 0 to 110MHz sweeps, and has a proper attenuator on the output.
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Old 17th Aug 2017, 2:15 pm   #13
allyblack
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Default Re: Wobbulator.

thank you all so much for your answers. firstly i liked the look of this project, and have constructed everything per the artical in question. my understanding of electronics is somewhat limited compared to the forums but im leaning. i will endevour to obtain a 2t or modify what i have. Ive` always liked grundig radios and will use the instrument on various 70`s models i have.there table radios sounding especially good.
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