L Match Antenna Tuner
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I chose to build this L Network Antenna match because of its low component count and simplicity of tuning, there being only one setting for optimal antenna match. However, in addition to this, I just happened to have a very nice salvaged high voltage variable capacitor and a twenty way rotary switch, both obtained at a recent rally. The inductor was wound on a large toroid with 40 turns. Up to the first 8 turns taps were made every other turn and then every two turns.
Taps made by twisting loops in as forty were made
Very nice sturdy rotary switch with 2 x 20 contacts.
Tapping points fully twisted and shellac cleaned of with scalpel
After taps were tined they were cropped to equal lengths and soldered directly to one set of the contacts.
Only one ring of switches were used and these were wired as can be seen by the rough drawing to the left and picture on the right. I have no idea what the switch was original manufactured and purposed for, however it looked old complete with a knob. The contact pins had never been soldered which was evident because of being tarnished with age and requiring cleaning up in order to be soldered to.
The Final assembly was placed in a box made up of scrap pieces of aluminium angle and steel sheet from old computer cases.
The Capacitor can be seen to have good spacing between the plates and looks to have been salvage from old military equipment because of the khaki paint on its base. The capacitor should easily cope with a 100 watts and probable considerably more.
A switch was used to enable switching in or out one or two sections of the capacitor.
Graphics software was used to design the case decal and when completed, was printed on to a A4 single sticky label.
To produce the dials for the twenty position inductor and the capacitor, I used the excellent online tool that can be found here: https://www.blocklayer.com/circle-divider.aspx
Take a good look at the other tools on blocklayer.com as there are some really useful tools.
Design printed on A4 label
Decal stuck to already drilled and prepared front plate
Book sticky backed plastic was then suck over the design for its protection and durability.