[Elecraft] XV432 Oscillates with Amp connected - FIXED

[Stu2]

Well - probably not fixed, but I was able to find a workaround.

If you haven't been following this thread, the basic issue is that the 
PA on my XV432 self oscillates. Thanks to everybody on the list, 
including Gary from Elecraft, I had several different things to try.

1) Make sure the paint on the inside of the case was removed in the 
appropriate spots (connectors, joints, etc.)
2) Add some vias near U6 and K2
3) Touch up the solder joints
4) Make sure the leads on the resistor specified in the XV432 mod was as 
short as possible
5) Change the PA Bias Adj
6) Add a pad in the TX path between the amp and XV432
7) Add a power resistor on a T connector at the XV432 output (or Amp input)

Ultimately, I found that varying the length of the coax between the 
XV432 and Henry 2004A was the answer.  I discovered this when I got to 
idea #7. First, I used a Bird Watt meter and adjusted the Henry amp to 
match my TS2000. (no reflected power) Then I reconnected the XV432. I 
added a 50ohm 20W dummy load on a BNC T at the output of the XV432 with 
a bunch of different adapters to make the N-BNC connection work. The 
XV432 was still connected to the Henry. This essentially put the dummy 
load in parallel with the Amp. The self oscillation stopped.

So I removed the dummy load to prove the hypothesis and still no 
oscillation. Then I renewed my original track of varying the coax 
lengths and stumbled on a good length, which stopped the self oscillations.

I know the length of cable changes the load. So it would seem the next 
step might be developing a simple matching network at the output of the 
XV432. But since I don't know all the variables (e.g. S parameters) this 
would probably need to be trial and error with some good guess work.

Thanks to everybody on the list who helped out. Perhaps I'll see you in 
Dayton.

73's

Stu2
W7IY