Because Tentec uses transistors rated for more power than they rate the
radio, but they match the load to them for the rated power. Then those
transistors come from the maker rated for operation into a high SWR,
e.g. able to handle peak currents and peak voltages caused by a shorted
or open feed line. The low pass filter changes the SWR seen at the
transistors from that at the connector. Then with a more than adequate
heat sink the Tentec current limited power supply or fast acting circuit
breaker turns off the supply for those loads that cause excess collector
current that would overheat the transistors in a while.
With the transistor load impedance designed for 100 watts it does no
good to try to drive them to their true power capability, the match
circuit prevents getting more power out into a matched load.
On the other hand the SWR roll back of the Kenwood TS-120 and 130 has
protected those transistors from bad loads with a brick on the key while
manually tuning an antenna tuner quite adequately. So for quick tuning,
I never bothered with minimizing reflected power, I just maximized
forward power and the tuner was matched good enough. I liked the
simplicity of the 130, but it can't hold a candle to the strong signal
handling of the Corsair II that replaced it on 75 meters. Stations that
splattered in the 130, didn't in the Corsair II with no changes in
antenna. The splatter was inside the 130, not from big amplifiers being
overdriven.
73, Jerry, K0CQ
On 4/25/2010 4:44 PM, kc9cdt@aol.com wrote:
Sinisa,
Why do think TT does not have that power roll back safety feature?
73,
Lee
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