Denco (science) - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Andrew B · 26th Feb 2021, 3:01 pm

I found this ages ago, http://www.vintageradio.me.uk/info/dencocoils.htm

Craig Sawyers · 26th Feb 2021, 4:03 pm

Excellent collection of information - thanks!

Craig

G6Tanuki · 26th Feb 2021, 6:30 pm

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!

Andrew B · 27th Feb 2021, 1:05 pm

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.

Jon_G4MDC · 1st Mar 2021, 7:19 pm

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)

G6Tanuki · 1st Mar 2021, 7:57 pm

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]

26th Feb 2021, 3:01 pm	#21
Andrew B Heptode Join Date: May 2015 Location: Bradford, West Yorkshire, UK. Posts: 512	Re: Denco (science) I found this ages ago, http://www.vintageradio.me.uk/info/dencocoils.htm __________________ worried about the electrons entering the circuit and the smoke leaving Andrew

26th Feb 2021, 4:03 pm	#22
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,982	Re: Denco (science) Excellent collection of information - thanks! Craig

26th Feb 2021, 6:30 pm	#23
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,997	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!

27th Feb 2021, 1:05 pm	#24
Andrew B Heptode Join Date: May 2015 Location: Bradford, West Yorkshire, UK. Posts: 512	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. __________________ worried about the electrons entering the circuit and the smoke leaving Andrew

1st Mar 2021, 7:19 pm	#25
Jon_G4MDC Nonode Join Date: Nov 2015 Location: Welwyn Garden City, Hertfordshire, UK. Posts: 2,015	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)

1st Mar 2021, 7:57 pm	#26
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,997	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]