40 meters ATU shows "tuned" but "TUNE" still shows more than 3:1 SWR

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  • Updated 9 months ago
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6300, end-fed antenna that shows less than 1.5:1 SWR on 40 meters on RigExpert AA-230 antenna analyzer. . All other bands 80-10 are fine.  On 40 meters, ATU grinds for a few seconds, shows GREEN "tuned" light, but when checking by manually transmitting carrier only at 10 watts, SWR meter on 6300 shows greater than 3:1.  Is there a part of the 6300ATU that could have failed? Or is this some kind of antenna issue I'm not acquainted with? Tried this with 2.0 version software and others down as far as v1.10.
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Bob Hinkle

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Posted 9 months ago

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Jim Gilliam

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End fed antennas need a counterpoise just like a vertical. If you don't have an adequate RF ground just about anything can happen and most readings will be erratic.
(Edited)
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Bill W2PKY

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What is the VSWR on the 6300 without the tuner engaged? I have seen differences in the VSWR between my AA-54 and the FLEX meter as well. Try adding a few feet of coax to the feedline. If you have several coax jumpers, try various lengths for the best results. A coax choke at the antenna might help as well. Finally, end-fed antenna usually have a 9:1 balun and counterpoise, do you have that? How long is your coax? This antenna type usually requires 60-70 feet of coax to work properly.
Hope this helps.

Check out Balun Designs for info in end fed antennas: http://www.balundesigns.com/content/Wire%20Lengths%20for%204%20and%209-1%20ununs.pdf
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Bob Hinkle

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Thanks Bill... this is the “MyAntennas” 80-10 replacing their 40-10 model.... no problem matching that one. Feedline is about 40 ft from the 9:1 balun... tried it with and without counterpoise (manufacturer manual suggests no counterpoise). AA-220 shows swr as 1.6:1 at 7.06 mhz. Ideas?
(Edited)
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Bill W2PKY

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Your feed line is probably too short. What does the FLEX SWR meter show without the tuner engaged?
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Bob Hinkle

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3:1  is as high as the 6300 goes and it zips up way past that, Bill... just tried a common mode choke module on the feedline just before it goes into the outdoor antenna switch, and added 6 feet to the feedline.  The IC-73 tuner fast-tunes like there's no SWR at all.... 
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Bill W2PKY

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If not using a counterpoise then the coax is the counterpoise so if using an in-line common mode choke make sure there is at least 50 feet of coax after the choke towards the antenna wire. The antenna was designed to have 50 or 100 feet of feed line. 
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John - K3MA

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The MyAntenna EFHW 80-10 has a 49:1 balun.  Does not need a conterpoise.  At my station works fine with or without the tuner.
(Edited)
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Bob Hinkle

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Thanks guys......i added i feet of coax to the feedlinevand installed an in-line coax choke.....not perfect, but it helped a great deal! Tomorrow I’ll play with longer coax and the filter and add clamp-on ferrite beads on verious non-rf carrying leads – pwr, speaker, etc. once again, the generousity of the flex community offers solutions and suggestions....thanks everyone! De KK8ZZ
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Ken - NM9P, Elmer

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Good luck, end fed wire antennas are notorious for allowing common mode RF interference into the shack unless the feedline is extremely well decoupled with chokes at the feedpoint and often other places along the way. But they can be mastered with work.
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Bob Hinkle

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Thanks, Ken.... by adding 205 more feet of feedline and an in-line choke, I've conquered the beast. Never had any problems with its 40-10 predecessor.... regardless, I seem to be up and ready for my upcoming adventures in shoulder replacement and "living" in a reclining chair and being left handed for 3-5 weeks.  I'm determined to see if I can do WAS and DXCC while I'm...ummm... encumbered !   Thanks to everyone who shared their experiences, thoughts and recommendations with me on this topic.  The Flex Community is GREAT, as always !   Cheers... Bob KK8ZZ