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Old 7th Aug 2022, 1:01 pm   #27
Join Date: Nov 2018
Location: London SW16, UK.
Posts: 606
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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