[TowerTalk] 1/4 wave vertical with counterpoise

[Jim Brown]

On 1/17/2026 6:28 PM, Jim Lux wrote:
> IM3 is a popular, and straightforward to measure, number - but not 
> necessarily directly relatable to performance with complex waveforms or 
> with amplifiers with transfer functions that aren't nicely represented 
> by a low order polynomial function.

Exactly. It's another thing we learned from Dick Heyser -- the effect 
can be much easier to measure (and often is more meaningful) than the 
that simple number. For IMD at RF, I look at the sidebands from the 
transmitted signal -- how many dB down at various spacings from the 
signal. This pdf is work I did about ten years ago in coordination with 
ARRL Labs tests. It's another example of plotting data for multiple 
measurements of the same quantity for different test subjects.

http://k9yc.com/TXNoise.pdf

This pdf documents measurements I was able to do with the Spectrum 
display that Elecraft sold for the K3 transceiver.

http://k9yc.com/P3_Spectrum_Measurements.pdf

73, Jim K9YC