I tested the idea tonight, and got some surprising results. I attached the XG1 to a 12 foot dipole, which I taped to the center of my 52 ft. loop (16 X 10 ft.) opposite the feedpoint. I used insulated wire, so there was not an electrical connection from the XG1 to the antenna, just wanted the dipole to couple with the loop. I could distinctly hear the 1 microvolt tone at 7.040 MHz. Weak but clearly there. So I turned it up to 50 microVolt to get a better signal to noise ratio, and hopefully highlight the differences between the two feedlines. I cranked the RF on my K2 all the way up, but left the audio at 9 o'clock to keep the signal from being too loud. I measured 9 millivolts AC at the speaker output. I then swapped out the 3/8 inch copper ladder line and attached 450 ohm "window" ladder line. I re-tuned the tuner to get a perfect match. I then re-attached the XG-1 (I left the two wires taped onto the loop, so there isn't a variable there) and turned it on. I was surprised to get a higher reading, 23 millivolts AC. That wasn't what I expected. I turned the XG1 down to the 1 microvolt setting and listened, and it was clearly louder and with a better signal to noise ratio than what I heard with the fat ladder line. So I swapped lines out again and tested the fat ladder line again. It was back down to the 9 millivolt AC level again...
So, what did I conclude? Well, first of all, my fat ladder line wasn't run the same way as the original "window" ladder line was run. So when I swapped out feedlines, and re-routed the feedline, I changed two variables, and I assumed that my noticeably louder signal was because of the new fat feedline. When I did the test tonight, I routed the window line the same general way as the fat ladder line. Maybe my homemade ladder line, which I'm sure isn't 450 ohm, does not provide the tuner as efficient a match, since I'm measuring both feedline losses as well as the associated tuner losses when matching the antenna. And the total system is what really matters. So, I'll ponder this, and re-install the window ladder line, but with the new routing. My wife will be happy, as she wasn't thrilled to see the bigger hole in the (guest) bedroom ceiling, with two copper pipes running out down to my tuner. Over the past few years she has come to accept black window ladder line dangling from a hole in the ceiling. And I learned that the XG1 can be a useful tool to test a feedline/tuner setup. Vic KG4HTT On Tue, 19 Apr 2005 22:47:44 -0700 wayne burdick <[EMAIL PROTECTED]> writes: > The XG1 can be connected to virtually any load without being damaged. > However, if the load doesn't look like 50 ohms at 7.040 MHz, what it > puts out may not be exactly 1 or 50 uV. > Whether you'll hear even the 50-uV signal at any distance remains to > be seen. Let us know how far away you can get and still hear it! > > 73, > Wayne > N6KR _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
