The T1 is reported to tune with as little as 0.5 watts, and 2-5 watts recommended. Mine will tune even with repeated dashes. ?I haven¡¯t run into problems with the QCX-20, but I am using an antenna that is maybe 2:1 at its worst. ?I do know that the radio has a slight mismatch from 50 ohms. ?Into a dummy load, the radio puts out 3 watts, but with a manual tuner, I can tweak that to 5 watts with a low SWR. ?My QCX-40 puts out 4 watts into a 50 ohm dummy load but 5 watts through the tuner.
72,
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On Sep 1, 2018, at 2:21 PM, Allen Poland <
atpoland@...> wrote:
Interesting!? With a 3db attenuator installed in a rig that is putting out less than 5w,? the power output drops 50%.? And that is enough power to trigger an auto-tuner???
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When tuning, the T1 auto-ATU may present an impedance to the QCX that causes excessive current to flow through the PA FETs or causes an excessive voltage across them? One solution is to connect an attenuator between your QCX and T1 auto-ATU when it is tuning and disconnect it when a match has been found.? ?This will limit the range of impedance "seen" by the PA FETs.? A 3dB attenuator will ensure the QCX "sees" a load between about 17 and 150 Ohms.? A 6dB attenuator will ensure that the load is always between about 40 and 85 Ohms.??
When I built an auto-ATU for my 20m QCX, I thought that damage to the PA FETs was possible and so while the ATU is tuning an attenuator is switched into circuit by means of a relay.??
