[Elecraft] KPA500 Issues

[Bob]

The R-8 is a radial-less vertical.  Unfortunately it has a tendency to put
all sorts of RF down the coax as the "counterpoise" system is too short
given the wavelengths involved.

You might want to buy a heavy-duty coaxial choke from DX-Engineering like
the

http://www.dxengineering.com/Parts.asp?ID=1474&PLID=166&SecID=81&DeptID={112450B5-E9E3-4F36-9166-E52FA128D019}&PartNo=DXE%2DFCC050%2DH05%2DA<http://www.dxengineering.com/Parts.asp?ID=1474&PLID=166&SecID=81&DeptID=%7B112450B5-E9E3-4F36-9166-E52FA128D019%7D&PartNo=DXE%2DFCC050%2DH05%2DA>

I used a R8 for years and had trouble even with 100 watts of power.  I
can't imagine how bad it would be at 500 watts.  Your station ground is
going to have to be top notch if you want to avoid trouble.

Good luck!

73, Bob, WB4SON