Z-MATCH FOOLISHNESS
I recently did a search on the internet for information on the Z-match. I already knew what a Z-match was. I have used several during the last 30 years. I wanted to know how others viewed this piece of equipment.
Imagine my surprise to find a new, single coil, QRP version of this device. Not only was it single coil, low power, small size, but it also boasted a coil wound on a toroid core. In fact there was even a controversy regarding the use of core material. Some favored type 2 material. Some favored type 6 material.
I favor using an air core and going back to the original, simpler design. I do not understand the reason some folk feel compelled to take a successful, simple design, complicate it for no good reason or advantage, and publish the result as a breakthrough.
The only thing I see breaking through is an astonishing lack of understanding of the original design.
The original Z-match can be found here
The Z-match is an all band (3-30mhz) tank circuit. I suppose you could consider the two coils the equivalent of one coil with a center-tap but you have to ingnore the function of the two coils to do so.
The coils are separate and mounted at right angles to each other to minimize mutual coupling between them. One of the tuned circuits covers 3-14 mhz. The other tuned circuit covers 14-30 mhz. Each tuned circuit is equipped with its own link to couple to a balanced feedline. The feedline must be moved from one to the other depending on frequency of operation.
Winding these coils as one with a tap ensures a maximum of mutual coupling and defeats the intent of the original design. Of course if you do not know what the intent of the original design was, you may prefer a one coil design and reserve any controversy to decisions on what core material to use.
Controversies over things that don’t matter and complications that serve no purpose or advantage are not high on my list of useful endeavors.
If size is of primary concern, you can always reduce the diameter of the originally specified coils and make up the change in inductance by adding more turns on a smaller diameter.
In any case, it helps to understand a design before trying to ‘optimize’ it.