[TenTec] TenTec 228 ATU

[Marinus Loewensteijn]

Just bought a 228 ATU. Front is immaculate, bottom and top have some scratches but a paintjob will take care of that.

The SO239 sockets are well used so those are replaced with N-sockets in line with all my other gear. 

When the cover was off it showed that the toroid / switch has the plastic melted on one side. Further inspection revealed that the capacitor connections were swapped around: the TX is connected to the antenna side and the antenna is connected to the TX side. This may have had an influence on not optimal tuning practices but more likely it has been used with a badly macthed vertical antenna and too much power.

I've been looking for an alternative configuration that will minimize  / avoid this problem of high losses in the main inductor. 

What I have discovered sofar is that the greatest losses in a T-match appear due to: (too) small variable capacitors combined with low frequencies and low impedance.

I intend to use this ATU for coax-coax matching for "tuned" antennas in order to get a 1:1 SWR across the band. 

I am considering to use an 1:4 impedance transformation at the output using a meaty toroid (T184-2) and have the tuner "see" a nominal 200 Ohm output towards the antenna which gets "down transformed" to 50 Ohm for the coax.

Using the ARRL TLW software indicates this should at a minimum half the losses in the main inductor while at the same time the capacitor values become well within a range of far more practical values. 

I know that there will be additional losses in the impedance transformation toroid but that should dissipate without causing damage.

( Since I will be working with matched antenna's I do not expect any great reactances or abnormal high impedances on the feeder. The impedance transformation toroid "should" therefor run within a reasonable load area and "should" not have extreem losses. )

Any feedback on the above proposed change will be greatly appreciated. 

73, Marinus, ZL2ML

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