This is interesting, Steve. A couple of questions: 1. Just to be clear, Was this a two- or a single-wire Beverage? In my tests here, changing the termination resistance (at the shack end) on my two-wire Beverages had an almost zero effect on the pattern or F/B ratio. That seemed to be true even if I did not use a termination resistor. Others have reported similar results. Of course, that is not the case with a single-wire Beverage terminated at the far end. I assume that yours was.
2. Was your resistor an Ohmite type OX or OY? That's what I and many other folks use. 3. What effect does this have on the F/B ratio? That would be easy to determine during the daytime using AM broadcast stations. There also ought to be an easy way to model how this 10% change (!) in termination R affects the F/B ratio. It *would* affect the return loss. On Tue, Jan 21, 2020, 6:08 PM VE6WZ_Steve <[email protected]> wrote: > A few days ago I posted a video explaining some experiments I did adding > short radials to my feed and termination grounds on the Beverage. > During that week temperatures went as low as -41 C at the station. > > The mystery has been solved. > > ... I also show that the ceramic termination resistor I use has a very > high negative temperature coefficient (-1300 C). This results in an > INCREASE of 30 to 40 ohms in my 470 Ohm termination resistor. Therefore, > the termination could be 40 to 60 Ohms too low!! I show in the video that > the resistor does indeed increase by 40 Ohms when I chucked it out my back > door at -30C for an hour. ... This seems to indicate that the main cause > of the Beverage miss match is the temperature coefficient of the wire and > the termination resistor. ... > _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
