It would be very interesting to do that test... key for 10 sec.. if it is possible - on an early morning, that has frost or snow on the spacers...Look for the one that becomes dry or drippy.
Have a great day, --... ...-- Dale - WC7S in Wy > To: elecraft@mailman.qth.net > From: k2vco....@gmail.com > Date: Tue, 12 Jan 2016 23:24:12 +0200 > Subject: [Elecraft] OT antenna question > > I'm having a problem which has me stumped. I'm going to describe my > complete antenna and feed system because something in it is misbehaving > and I don't know what! > > My system works on all bands from 40 to 10 (or it should). > > The antenna is a full-size 20m rotary dipole. It is all aluminum tubing, > no traps or stubs. Just a dipole. I am feeding it with about 30 feet of > "true ladder line," which is open wire line made of #16 insulated wire > spaced about 3-1/4" with black PVC spacers every 18" or so, except near > the antenna and the rotor where I've added extra ones so that the > spacing doesn't change when the antenna rotates. > > The line comes into the shack and is connected to a static drain, which > is a box with two 10-megohm high voltage resistors to ground and a > couple of spark gaps. Then a piece of 450-ohm window line about 3 feet > long connects it to a pair of large air variable capacitors in series > with each leg which knock out some of the reactance on 40m to make it > possible to tune more easily. Then a very short piece of window line > connects to a big 5kW DX Engineering 4:1 balun, spec'ed for tuner > service, and finally via a piece of RG-213 18" long, to a T-network tuner. > > My K3 drives a TL922 amp and I have an SWR meter in line. > > Now here is my problem: it works OK on all bands except 40 meters. On > 40, it tunes up fine with low power, but when I run more than a couple > of hundred watts, after perhaps 10 seconds of key-down, the SWR starts > to climb. I have watched it go to 4:1 before I stop sending for fear of > destroying something. > > The SWR rises both on the meter in the tuner and the extra one I have in > line. > > Classic symptoms of something heating up. But what? > > - The tuner components are all cold. > - The coax to the balun and its connectors are cold. > - The balun itself is just barely perceptibly warmer (I have to touch > the core to tell). > - The window line, the static drain resistors, the air capacitors and > all the connections in the shack are cold. > > I know the SWR is astronomical on 40 meters, so currents and voltages > are high. But nothing in the shack seems to be heating up. Any more > ideas of where to look? > > -- > 73, > Vic, 4X6GP/K2VCO > Rehovot, Israel > http://www.qsl.net/k2vco/ > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to daleput...@hotmail.com ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
