?

My T41 has started doing something weird on 15M and 10M. On 10M, when I
hit the mike button, I immediately get 6W out on my
Telepost 100LP - without talking into the mike!

I piped the output from the dummy load ( actually, a Bird 500W 30dB
attenuator ) into my Rigol SA. Signal at 28.350MHz looks reasonably
normal - carrier about 30dB down from voice peaks.

HOWEVER, when I increased the span, I found a giant spur at 33.305883
MHz. About 15dB taller than the proper output signal ( at 28.350MHz ).

If I go to 24.9MHz and transmit, the same sort of spur appears - at
32.305883 MHz.

If I go to 21.2MHz & transmit, the spur is at 27.9195 MHz. ( Telepost
says 2.7W )

If I go to 18.096MHz - no spur.

14.2MHz and below - no spur.

At a wide span, it looks like a nice clean peak. But if I crank down on
it, it starts to get messy.

This is a latest-greatest V12, with the K9Hz BPF, LPF, and PA.

I connected the output of the RF board directly to the SA - no constant
spur. Plenty of harmonics with no BPF or LPF though.

I can only conclude that the PA is oscillating:(.

As to why it doesn't oscillate on lower bands....some interaction
between the PA and the BPF & LPF?

- Jerry, KF6VB