A bit of research turned up a few articles of interest. It seems that Joel Halas, W1ZR, and Bob Allison, WB1CGM, wanted to follow up on N7WS’s article and research. Their article is in the November 2009 issue of QST, which is available at the ARRL site (if you are a member). In their case they tested not just ladder line but open-wire as well. Their results were not as drastic as the N7WS tests, with losses when wet for the ladder line being considerably less that the Stewart results. Interestingly, their tests also showed that open-wire line is indeed not affected by being wet. Sounds like it is time to bring some of that stuff back. One thing of interest is that both N7WS and W1ZR.WB1CGM used a wetting agent to make the water stick to the ladder line. There is no discussion about the effects of that wetting agent other than a (questionable) general assumption that it had no effects.
On-line, G3TXQ read both articles and decided to do his own testing. His article is at: http://karinya.net/g3txq/wet_ll/ His article shows that there are velocity, some loss and some impedance changes when the ladder line is wet. These recover quickly when the line dries. He also tried laying the ladder line on the ground and discovered much greater loss. And, in one test he placed an aluminium (this is British after all) ladder at the center of the ladder line span. The losses skyrocketed, just as our fields and waves professor said should happen. The sis also an interesting read. It also shows that the move from open-wire to ladder line was one of convenience but not really a good change. There is more research to be done, but I think we can safely say the when the ladder line gets wet there will be some additional loss, the velocity factor will change at least a bit, and indeed the impedance will change some amount. Put these together and the op will need to hit the tune button on the tuner and retune. Again, the use of open-wire feeders should eliminate this situation. I am sure there will be more to this discussion. I look forward to additional data and info! 73, Jack, W6FB > On Jul 19, 2025, at 11:21 PM, Jack Brindle via Elecraft > <[email protected]> wrote: > > 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] ______________________________________________________________ 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]
