I did an experiment in which I connected an open-wire-fed 88 foot dipole to my K3 through a large balun. The KAT3 matched it perfectly on all bands, but I wondered about the efficiency of this system compared to a balanced tuner like my old Johnson Matchbox.
So I measured the temperature rise of the balun after transmitting for a minute and recorded it. It was several degrees. Then I added a pair of capacitors in series with the feeders to tune out the reactance (it happened to be inductive on the band that I was testing) and re-ran the experiment (after waiting several hours for the balun to return to room temperature). The temperature rise was much less, almost unmeasurable! I think this showed that the "tuner-to-balun" system can be inefficient under some conditions. I went back to the Matchbox, even though I had to give up the automatic tuning provided by the KAT3. On 3/11/2011 12:22 AM, David Cutter wrote: > Jim > > I like the idea of a battery operated remote tuner and a simple relay > change-over to provide a top-loaded vertical. I'm often bothered by > connecting the antenna feeder into a 1:1 balun and then to the tuner. I've > read that the very large impedance mis-match can lead to large losses in the > balun on some frequencies, though you might not *feel* it with low power. > With a self-powered little tuner, it would be easy to raise it off the > ground a little and connect the ladder line feeder directly to the tuner; > then coil some thin coax through a ferrite toroid to make a choke (see Jim > Brown's excellent articles - K9YC) for connection to your RG213. This > should also result in less noise pick up on receive. Some folks add a > further choke at the shack end to further reduce received noise. > > David > G3UNA > > >> I've been running my T1 remote out under my 88ft dipole which is just >> short >> of 50ft in the air at the midpoint. The ends are a bit higher. The T1 is >> down at the ground under a plastic container and connected to the >> windowline >> via a Elecraft 1:1 balun. I remote control it via the circuit on my >> website >> www.jtmiller.com . I find it gets a 1:1 match on 80-6 meters. It is >> connected to my K3 about 60ft away via RG213. >> >> Obviously the pattern is a bit of a daisy above 20M and is mostly a cloud >> warmer at 80M and below. But that's just what this length dipole does >> independent of match. >> >> I've lately been using the windowline as a vertical with the 88ft as a >> capacity hat on 80-160 and found it works quite well. The T1 is very happy >> matching that on 80M and gets to about 2:1 on 160. I use my K3 internal >> tuner to remove the remaining mismatch on 160 to ensure proper power meter >> readings. The loss due to this level of SWR on 160 with RG213 is >> meaningless. >> >> When used in this vertical configuration the two ends of the windowline >> are >> tied together to one terminal of the tuner and the other side connects to >> 8 >> 60ft buried radials. >> >> 73 >> >> Jim ab3cv > > ______________________________________________________________ > 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 -- Vic, K2VCO Fresno CA 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:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
