Best coupling option for a MW and a Reaction coil

[SurreyNick]

Mmmm. Decisions, decisions, decisions....

This thread is a spin-off from another of my threads "Working out the size of a Reaction coil" https://www.vintage-radio.net/forum/...d.php?t=108626

I confess I don't know which way to proceed with the coupling of the MW coil and Reaction coil and would appreciate the benefit of others' experience.

I'm learning quick but I still don't know enough about coils to make an informed decision about the arrangement for the MW coil and Reaction coil on this TRF. If at all possible I'd like to try and get it right first time too. It's a complicated (and expensive) custom build cabinet I am making with all the components on show and once I've decided the position of the components and drilled the holes there's no going back! As the coils are going to be on show appearance plays a part, but performance is important too.

The options I have considered are pictured here:

Coil arrangement (A): This is one recommended by FJ Camm. I couldn't find an actual picture of one so I had to re-draw it and therefore don't know if it was ever actually employed in a receiver (although I am guessing it must have been by amateur constructors at least) . There are two vertical formers. The smaller diameter (reaction) coil is positioned concentrically inside the larger coil. The top of the reaction winding is at the same height as the bottom of the MW winding. It's fixed and no 'in-play' adjustment is possible.

Coil arrangement (B): This is similar to the previous coil, but the smaller coil can be rotated within the larger former.

Coil arrangement (C): In this arrangement the coils are wound with a 3mm or greater diameter tube/wire and are self-supporting. They are mounted on beehive insulators and the reaction coil can be pivoted towards, or away from, the main coil. Although in this picture the coils are self-supporting, they could be wound on formers using a much thinner diameter wire. It's the potential effectiveness of the coupling arrangement which I'm interested in.

Coil arrangement (D): In this option the coils are wound on flat spider-web plates and mounted vertically. There are three coils in this picture, but on my TRF there would just be the two. The coils pivot on one axis i.e. to the left and right of each other to vary the amount of overlap and coupling. (Note: these coils could be wound on shallow formers so each wire turn is of equal diameter and these formers could then be mounted in the same way so they can pivot as shown)

Coil arrangement (E): This is similar to the previous arrangement except that the two coils can be pivoted on four axis. They can be turned through 180 degrees, pivoted back and forward and left and right, and also horizontally. (Note: as above these coils could be wound on shallow formers so each wire turn is of equal diameter and these formers could then be mounted in the same way so they can pivot as shown)

So, they are the five options I am considering. I don't know how many would potentially work, nor which is likely to give the best performance. If anyone has any experience of these (or others) I would be most grateful.

Thanks

Nick

All will work quite well, build something and get first hand experience, pretty is not always the best.