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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 26th Feb 2021, 2:01 pm   #21
Andrew B
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Default Re: Denco (science)

I found this ages ago, http://www.vintageradio.me.uk/info/dencocoils.htm
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Old 26th Feb 2021, 3:03 pm   #22
Craig Sawyers
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Default Re: Denco (science)

Excellent collection of information - thanks!

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Old 26th Feb 2021, 5:30 pm   #23
G6Tanuki
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Default Re: Denco (science)

I think there's a degree of undeserved mystique about Denco coils, in the same way that some people go all squiffy and pay ridiculous prices for early-60s Germanium transistors.

In days-gone-by I built a 1.8/3.5MHz converter using Denco 'T' coils: OC170s for the RF amp and frequency-changer, 1.6MHz IF to feed into a car-radio. I never managed to get it to 'track' properly over the entire waveband despite weeks of fiddling with padder-capacitors well outside the Denco-recommended values.

The antenna-coil also seemed all wrong - there were too many turns on the input-winding and it was too-loosely-coupled to the tuned winding. Maybe OK for a broadcast-radio being fed from a random-length wire antenna but wrong for a 50-Ohm resonant dipole: I eventually reworked it as a 3.5MHz-only radio with a 3x25pF tuning-capacitor, stripped-off the original antenna-input winding and wound abot 10 turns of wire directly on top of the tuned-winding - which worked *a lot* better!

I think a lot of 60s/70s designs specified Denco coils just because they were 'out there' and avoided the need for constructors to wind their own coils.

The results were, I feel, mediocre.

As an impoverished kid/student I never managed to save enough to buy an amateur-bands-only Electroniques QP166!
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Old 27th Feb 2021, 12:05 pm   #24
Andrew B
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Default Re: Denco (science)

With todays 3-D printer technology it would be a simple thing to knock up Denco style "tribute" coil formers. Most, if not all the information required to make them is out there.
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Old 1st Mar 2021, 6:19 pm   #25
Jon_G4MDC
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Default Re: Denco (science)

Just what I was thinking Andrew!

The hardest part about cloning Dencos is the brass screw and attaching the lump of dust iron or ferrite in a nicely concentric manner.

Also I think we are talking about Bernard B Babani publishing here concerning the 1970s books. (Also known around here as Baboon-i books but that's a different matter)
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Old 1st Mar 2021, 6:57 pm   #26
G6Tanuki
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Default Re: Denco (science)

I wonder if anybody's analysed the RF-characteristics of the Denco formers?

I worry when I see random people suggesting "3D-printing" as a solution when they've totally failed to work out whether the plastic-stuff they will be using in their printer is task-appropriate.

[a while back I saw someone suggesting using 3D-printing to replicate a pill-tray that should only ever be produced using medical-grade plastics: I truly hope anyone who followed their suggestion had a few million dollars of insurance]
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