Thanks, Jim. It is in the ARRL Antenna Compendium, Vol. 6, starting on page 174. It is an interesting article. The central plot in Figure 1 shoes some very interesting data about the S21 measurements. Indeed it shows a very large increase in attenuation, but it also shows a change in frequency for the coefficient. It is this change that has grabbed my attention. If this is a real frequency shift, then indeed the impedance characteristics, more than just resistance, must have changed. Unfortunately Wes does not go into detail about this shift, which means more research is needed.
I also wonder, at a lower level, if the entire change due to water were just attenuation, then we would have more loss, but retuning should not be needed - the tuner is providing the L and C needed for the conjugate match, and even with more R, shouldn’t the L and C remain the same? If indeed the shift that is indicated in the N7WS figure for frequency is real, then I would expect a likewise retune would be needed to regain the conjugate match, which is the main push for this discussion. And yes, I realize that R is an important part of a conjugate match. So, what am I missing? I have a funny feeling I will be making VNA measurements for rain and dry conditions in my antenna sometime soon. And we are now transitioning from a very wet stretch to a dry stretch... By the way, Vol 6 has a copyright date of 1999, which is 26 years ago. Pretty close to the 30 years Jim guesstimated. Still pretty sharp, my friend! Thanks for the pointer! 73, Jack, W6FB > On Jul 19, 2025, at 10:24 PM, Jim Brown via Elecraft > <[email protected]> wrote: > > On 7/19/2025 7:29 PM, Jack Brindle via Elecraft wrote: >> Sorry, but I have to ask this. If indeed this is the case, why does it not >> apply to open wire, where water has no effect on the line and thus there is >> no need to retune? > > At least 30 years ago, one of the ARRL Antenna Compendiums published > excellent lab work by Wes Stewat, N7WS, showing that the attenuation of > window line increased significantly when it was wet. > > 73, Jim K9YC > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
