[CQ-Contest] Coax Stubs for SO2R

[Jim Brown]

On Sun,7/17/2016 11:08 AM, Rudy Bakalov via CQ-Contest wrote:
> Just wondering, why use stubs at first place?

Properly done, they can kill second harmonics of the power amp. That's a 
big deal when you're operating SO2R CW on 80, 40, and 20.

> What's the advantage compared to LPF or BPFs?

Most of these filters are designed to run at the 100-200W level, so must 
be between the transceiver and the power amp, so they do NOTHING for 
power amp harmonics, which can be quite strong, depending on antenna 
spacing.

Here's an applications note I wrote for NCJ. 
http://k9yc.com/LocatingStubs.pdf

4O3A makes bandpass filters rated for high power, and can be put on the 
output of a power amp. They're not cheap. :)  5B4AGN measured some of 
them and sent me the plots. They're part of this report. They look very 
good.

http://k9yc.com/BandpassFilterSurvey.pdf

http://www.4o3a.com/index.php/products/high-power-filters/

73, Jim K9YC