[TenTec] OT Antenna Tuners

[Marinus Loewensteijn]

If I may just throw my humble opinion / experiences in here. I use less that 100 Watts 
so it may not apply to some of the big gun setups. For a balanced feed I prefer very
much the S-Match from PA0FRI. He places a toroid at the input. It is basically a link 
coupled tuner with the link being a toroid and not included in the main resonant circuit.
Tuning is rather narrow band but heavy rain requires me to retune. 

I have just completed my revamp of a Tentec 228 ATU and I replaced the usual T-match
with a 50 => 450 Ohm broadband unun at the TX side and then used a low pass L-Match 
to step down to 50 Ohms again for the coax going to the antenna. Unun always working
in a pure resistive load. I am liking this setup very much, it does however not do as well 
when trying to match an antenna that is far too low in frequency. Very broad matching,
no retuning required.

Both tuners are restricted in the number of bands that can be covered without switching 
in extra capacitance. In both cases I am working FB 3.5 - 21 Mhz without changes.
Both have very low losses compared to the normal "run of the mill" gear. I think each can
relatively easily adapted for reasonable power levels, e.g. up to 500 Watts without major
problems or major expense. Cannot believe the prices that some ATU's command, 
especially when I see the prices of the transceivers in comparisons. Actually same applies
to antenna's, I am homebrewing a clone of the Force12 Sigma XK 40 for less than 1/6 of
the price.

73
Marinus, ZL2ML.

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