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Antenna tuner question
On 5/17/2015 6:53 AM, Helmut Wabnig wrote:
hello, I am a newcomer in amateur radio shortwave and so far have built a dipole antenna with ladder line. Not a G5RV, not a ZEPP, not a DOUBLE ZEPP, not a DOUBLETT, but a dipole, a non-resonant antenna, if you know what I mean. Unfortunately the antenna feedpoint is 25 meters away. Now I am searching for a remote automatic tuner for balanced feed line, aka hen's ladder, and coax input. Presently I am using a BG-430 military Generalstab radio tuner. http://www.radiomuseum.org/r/zellweg...em_se_430.html It is the lower right foto, the thing in the center with the 4 black feet. Works only 80 and 40 meters. In more detail: http://www.radiomuseum.org/r/zellweg...geraet_ag.html Look at the schematic, upper part. The input coax connects to the "balun" transformer, and two variometer coils connect to the antenna output. I have not been able to find anything useable on the market. SGC tuners are ruled out, they are strictly for long wires and nothing else. They make their money with the UN and other mobile militaries, amateurs are not existent for them. Amateurs use dipoles and ladder lines. No, you can't use an SGC on a dipole. If you do, you are wasting your money. What rermains are MFJ and LDG coax tuners in combination with a 1:4 balanced transformer. Thus the 25 m coax line would see a fine SWR and no losses due to reflections. The coax from the tuner output to the balun input make very short to avoid reflection losses. Very high voltages will oscillate there! What I like less is the balun at the high end, would prefer a symmetric tuner with a balun at the coax input and balanced symmetric output, like the Zellweger tuner does. The MFJ-974HB is also a fine thing. Really symmetrical at the tuning circuits, but manual. 100 Watt are fine, 400 Watt are better. (Maximum in Austria) Can you help me, please? OE8UWW Helmut, All of these replies are right on the mark. There is nothing wrong with SGC tuners, even for your use. I personally have not heard of problems with any tuners currently on the market except for perhaps some limited range tuners built-in to transceivers. Save yourself future update problems. Buy a 1500 watt tuner if you are allowed 1500 watts where you live. Most hams in my part of the Midwestern US use amplifiers. BTW, I share the responders concern here about your criticism on SGC tuners. It was unfounded. I personally own and use a very old Ten Tec 229. It has worked perfectly for decades. Again, read the current QST article about feeding dipoles. It is eye opening. As a youngster might say "600 ohm ladder line rules" :-) |
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