[Elecraft] KPA1500 Enhancement

[Jim Brown]

Stubs, optimally applied, are an excellent and low cost substitute for 
high power bandpass filters. A properly placed 2-stub filter using a 
decent RG8/213 typically provides 60 dB of attenuation at the second 
harmonic, that in addition to the suppression provided by the 
amplifier's output network.

I've settled for 5B4AGN's W3NQN implementation of filter sets 
conservatively rated for 200W between exciter and power amp. That takes 
care of protecting the receiver and also killing any phase noise the 
other radio is producing.

In my experience with SO2R and other multi-transmitter setups and all 
K3s, killing the amplifier's second harmonic mostly matters between 80 
and 40 CW, and 40 and 20 CW,  because the harmonic lands in the same 
part of the higher band where we want to operate.

73, Jim K9YC

On Wed,4/26/2017 10:50 PM, Matthew Cook wrote:
> So time to get back to working on the 1500W W3NQN filter designs... and the
> high power paperwork requirements from our regulatory body to run that sort
> of power level... sigh.