Knut,
I did what Don suggests to match my MARS NVIS Loop which is fed with 450 ohm ladder-line and has a ten foot 450 ohm ladder-line stub diagonally opposite the fed corner, but added 75 ohm coax rather than 50 ohm. I made three lengths of RG11, 6.5 feet, 6 feet and 9 feet. With those three lengths you can try 6.5 feet, 12.5 feet, 15.5 feet and 21.5 feet to test with. After testing I ended up with 15.5 feet which I coiled up between the 4:1 balun and the 50 ohm coax feeding the KAT500 and KPA500. I used an AIM 4170 analyzer and looked at SWR and Rs readings. When you do that you compare the SWR and Rs value at a given frequency and if the SWR is > Rs you divide SWR by Rs looking for a value of < 10 If the value is < 10 the KAT500 can tune it at high power. On the other hand if the Rs is > SWR you divide the Rs by the SWR also looking for a value of < 10. When you have value at each of the frequencies within desired range of less than 10 The KAT500 will tune them. My loop has 388 feet of wire in it and will tune with the KAT500 from 3.5 to 10.5MHz, except close to the K3 IF frequency, which can't be used anyway. Good luck with your antenna trimming! 73, Tom Amateur Radio Operator N5GE ARRL Lifetime Member QCWA Lifetime Member On Fri, 07 Dec 2012 20:00:24 -0500, Don Wilhelm <[email protected]> wrote: >Knut, > >You might try adding or subtracting feedline at the shack end of the >feedline to bring the SWR down on those bands. I would suggest >experimenting with an antenna analyzer rather than the tuner - you will >be able to see which way to go for making improvement. > >The fact is that the feedline with SWR will act as an impedance >transformer, and it will be more of a transformer on bands with high SWR >than on the bands that are better matched. > >Some experimentation may be in order. > >73, >Don W3FPR > >On 12/7/2012 5:52 PM, ab2tc wrote: >> Hi, >> >> Still can't manage to get any improvement doing this. Anyway, right now the >> tuner is doing a great job to my G5RV on all bands except 15m and 80m. For >> those bands the raw SWR is above 12:1 so is outside the design parameters >> for the tuner. These are screen shots for the bands where the tuner is >> finding a good match: >> >> http://ab2tc.getmyip.com/g5rv_10m.png >> http://ab2tc.getmyip.com/g5rv_12m.png >> http://ab2tc.getmyip.com/g5rv_17m.png >> http://ab2tc.getmyip.com/g5rv_20m.png >> http://ab2tc.getmyip.com/g5rv_40m.png >> >> I'll continue to work on the 15m and 80m to see if I can improve it. >> >> AB2TC - Knut >> > >______________________________________________________________ >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 ______________________________________________________________ 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
