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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 2nd Aug 2022, 12:24 am   #21
Join Date: May 2015
Location: Chatham, Kent, UK.
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Default Re: Denco coils substitute

Hi i use this from Wilkinsons their own multy colored felt tip pens at 1.00 when i last got some, green yellow etc cut to length wind as per details (i have file if needed ) use the white top and glue plastic nut into this use threaded plastic bolt with a dust iron slug fixed to the end reasemble then glue to b9a modifyed valve pin saver (ebay ) makes a very close copy of a denco coil, i have found it makes little improvement to use wave wind and litz wire i will give more details if required Mick
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Old 3rd Aug 2022, 9:06 am   #22
Join Date: Mar 2009
Location: Cirencester, Gloucestershire, UK.
Posts: 382
Default Re: Denco coils substitute

If you want plug-in coils, an alternative is Eddystone (and equivalents) octal-based formers, and ready-wound coils. There are a few on eBay and they aren't too expensive. You can often pick them up for peanuts at radio meetings.

They are much chunkier than Dencos, so easier to handle and to solder to.

The coils are air-cored.

Best regards ... Stef
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Old 5th Aug 2022, 2:40 pm   #23
clay shooter
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Location: Northamptonshire, UK.
Posts: 103
Default Re: Denco coils substitute

Thanks for your inputs but I'm having a rethink on this project, for two reasons,
Firstly as I said I had an accident @work and had to have a skin graft to the back of my right hand, and a tendon replaced, so winding coils is out, I can just about manage to insert component into stripboard.
Secondly, the prohibitive cost of the Denco coils
However, I've found a circuit that I have most of the major components for that uses rRF chokes that are readily available for a pound or so,

Thanks again for your input, it has been appreciated.
If it ain't bust don't fix it
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Old 5th Aug 2022, 3:11 pm   #24
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Location: Newcastle upon Tyne, Tyne & Wear, UK.
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Default Re: Denco coils substitute

Hi, they should work just fine, if you search the forum you will find that other members have also used these inductors as RF coils

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Old 5th Aug 2022, 9:54 pm   #25
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Location: Mareeba, North Queensland, Australia
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Default Re: Denco coils substitute

Originally Posted by Radio Wrangler View Post
Litz wire was made in fair quantities back in the day, though it wasn't cheap. It was only later into the seventies that the price went eye-and-right-arm expensive. I modified some Denco coils and those were at least proper Litz.


While doodling around on eBay, I came across lots of Litz wire, and very cheap too. Many gauges and combinations. I only looked quickly, but I would "guess " perhaps 200 types. As I say, it was very cheap. The quantities were also excellent, in some cases a full reel for about $20 Au. They give lengths and weight as well as construction.

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Old 6th Aug 2022, 8:27 am   #26
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Location: Newcastle upon Tyne, Tyne & Wear, UK.
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Default Re: Denco coils substitute

Hi Folks, a lot of this "Litz" wire is actually "bunched" wire where the individual cores are simply grouped together.
It is a lot cheaper than Litz and is 95% as good as Litz, as well as having a slightly lower resistance.
Litz is actually laid up so that each strand occupies every possible position in the layup and will normally be an odd number of strands. (fitting circles inside a bigger circle)
The Bunched wire is typically 25, 50 etc strands
I did quite a bit of work on the use of bunched in SMPS, operating up to 1MHz and found that there was no significant increase in losses below 1 MHz. For higher RF it will still be advantageous.

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Old 7th Aug 2022, 1:01 pm   #27
Join Date: Nov 2018
Location: London SW16, UK.
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Default Re: Denco coils substitute

If I were to build an SW receiver, my starting point would not be about getting holding of stock Denco coils or winding my own. I would ask myself questions. The main consideration would be the topology; is this a regen, direct conversion, TRF or superhet? It it a valve or solid-state? The next consideration would be the chosen SW band or would be a multi-band SW receiver? Finally, what is the air gang turning capacitor available on hand or is it a varactor-tuned? This dictates the coil requirements, and RF/oscillator/VFO tracking calculations. If it is a SW suphet, things would get complicated. I would have to consider the IF frequency and the IF transformers. Denco coils came with both valve and transistor versions catered for different receiver topolgies. The Denco coils intended for superhet configuration would only work with air variable gang having a specific tuning ratio and padder capacitor value to fulfil the three-point tracking solutions. In contrast, the tracking problems for the regen and direct conversion receivers are much easier.

Often the coil windings information in articles are useless if they only stated the number of turns without the diameters of the coils. The inductance also depends on the core types. At a high-frequency SW band , thicker strands of Litz wires start to become lossy as the skin effect is frequency dependent, and solid core copper wires may be more desirable:
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