A friend of mine (W6AAN) reported a problem with his Alpha-91b (2XGU-74B,
made in Bulgaria): when attempting to send CW at speed more than 5 WPM at
1500W output, the protection kicks on. Nothing similar happens at output
power less or about 700 W. The same RIG (TS870S) works just fine with a
different amplifier. There are more clues:
1. On SSB mode - no problem, Alpha-91b delivers full output power.
2. Tried ALC "on" and "off" - the problem is still there.
3. This happens on ALL bands.
4. VSWR on all bands is less than 1.1:1
5. On CW mode, brick on the key - no problem, Alpha delivers 1500 W as long
as the key is depressed.
As soon as sequence of dots from the rig is being sent to the AMP - the
protection kicks on.
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