[Elecraft] strange K2 160m power problem(solved?)

[R. Torsten Clay]

On Wed, 19 Jul 2006, R. Torsten Clay wrote:

> In the process of calibrating my LP100 wattmeter, I was hopping back and 
> forth between bands and transmitting. I discovered a strange problem with my 
> K2/100 #3134. This is what happens:
>
> First, I have the K2 hooked up to a dummy load. I also confirmed that this 
> happens with a different wattmeter in line. I am keying the K2 with a 
> straight key.
>
> 1. I transmit on 28 MHz. I get about 100w out.
>     I press "band -" several times until I get to 1.8 MHz. Putting the
>     key down, I get about 110 w out as expected.
>
> 2. I transmit on 28 MHz. I get about 100w out.
>     I press "band +" once to get to 1.8 MHz. Putting the key down, I get
>     170 w out !!!
>
> In other words, it makes a difference whether I go from 10m to 160m either by 
> pressing Band - several times, or Band + once. Pressing Band + once somehow 
> screws up the tx agc. The problem does not seem to be in the KPA100, because 
> if I turn the power down to 10W I get similar response (10W one way, 15W the 
> other way).
>

I still don't know why it was doing this. Re-aligning the whole rig did 
not help. However, after increasing R98 to 680 Ohms I no longer get 160W 
on 160m.

BTW I also tried to fix the low power on 10M. I rewound T4, T2, adjusted 
the output filters, fiddled with T1, and peaked very carefully. In the end 
I gained maybe 1 W, now 8W max on 10M (without KPA100).

Torsten
N4OGW