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The actual power in watts compared to Peak Envelope Power in SSB mode is extremely variable. Table 3 - VERY APPROXIMATE conductor thickness v power level. Tracks on PCB should be a lot further apart because of surface flash over. These gaps should also be used only as a guide where the only gap is air. Gapįlash over will vary on several properties other than just shape such as pressure and humidity. " Flat" means a highly polished flat surface while " point" is a sharp point. Table 2 - Air gaps required for voltage separation of various components. The amount of compression used on SSB is also irrelevant. 300W PEP = approximately 100W of power on SSB however 300W PEP on sideband will have the same peak voltage as 300W of carrier. Voltage separation for capacitors, and all other components, will not depend on the mode of operation ie. The voltages in the above table are PEAK voltages not those necessary to produce the power listed. Please note - this table is only a rough guide and includes capacitors and all other components. Table 1 - Recommended minimum voltage separation for given power levels

This is not just some absolute value but includes an unknown quantity of reactance but, in general, the voltage across the input capacitor will be somewhere near the output voltage. The maximum voltage will also depend on what impedance you are going to match. On the other hand, making the coil out of 6mm copper tube is a good idea at any power level but that doesn't mean the voltage separation will allow more than a few watts. The voltage separation may be 300kV but if the coil is made of 0.5mm wire, it will handle only a few watts. The power the tuner will handle is only relevant in terms of the voltage separation and coil resistance (current carrying capability). (Into a dummmy load.) This is less than if a 4:1 voltage balun is used. Overall, insertion loss in tuner MK2 is between 0.1 and 0.15db on 10 metres matching roughly 500 ohms and less on the lower bands using such a setup. Since this tuner does all the impedance matching needed, nothing more than a simple 1:1 current balun is required and strongly recommended. The major power loss in the units described here is by resistance in the wire that the coil is made out of although there will be others. Neither coils nor capacitors consume power so, provided resistive components are kept small, there should be very little loss. Whether you use a T match, Z match or any other kind of matching network doesn't really matter much. If you really must use a long wire referenced to ground, a simple way of using the same output terminals is decribed below. IT IS STRONGLY RECOMMENDED TO KEEP IT SIMPLE STUPID. All of these complications introduce possible losses and possible problems. In the end, the thing stays connected to one amplifier or radio and to one antenna or type of antenna. Many build tuners and consider a thousand places they can use them and design for all of them. Using coax with a tuner will gain you nothing except a happier radio. The losses are too great using a tuner with coax so it is recommended to include a simple balun (details below). I have tuned my HF antenna to 70cm but only as a test. Normal use will be HF and perhaps some circumstances in VHF bands. Things to look out for - possible problems identified in design variation. Very brief description giving only the basic idea.

Now that a number of people have built them and provided feedback, several things to look out for have been identified. By comparing them, you should be able to construct a tuner to your own particular requirements.

This page details several T-match tuners. VK5AJL - Make your own HF-VHF antenna tuner.