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ATU OK, but SWR very high when transmitting ?

Teijo OH1TSMTeijo OH1TSM Member
edited June 6 in SmartSDR for Windows
Sorry this poor beginner question... 
I am very experienced DX-listener. But this is my first transceiver and first transmitting antenna...    :/

When I use ATU, it says SWR is OK / Bypass. But when I transmit CQ from WSJT, the SWR is over 3 (max) and Flex cut the transmission power very low.

I am using:
Flex 6400 (+ATU) with Alinco DM-330MW power supply.
Antenna is HyEndFed 8 band antenna (from Holland), 40 meter long at 17 meter height with Ecoflex 10 coaxial cable.
HyEnd Line isolator in the coax, near receiver.
Two grounding rods and one point grounding for: Flex, power supply and coaxial cable cover.
SmartSDR v3.1.8 and WSJT-X.

CAT operates OK.
DAX operates OK.
WSJT Test CAT is OK.
WSJT Test PTT is OK.

Here is picture:



  • Bill W2PKYBill W2PKY Member ✭✭
    edited March 15
    The ATU software in 3.1.8 can stop trying before acquiring a low SWR. When you click the ATU button watch the SWR indication. If it stops but the SWR is high keep clicking the ATU until a low SWR is achieved. Hope this helps.
  • Brian HemmisBrian Hemmis Member
    edited April 23
    This has been a known issue for some time. Apparently downgrading to a previous software version will fix it. Sure wish Flex would fix it. I’m in FL operating remotely back to OH and run into the same problem every time I try to use the rig. It can’t be fixed remotely so I’m stuck till I get back up there.
  • Bill W2PKYBill W2PKY Member ✭✭
    edited March 15
    Hello Brian-
    Try re-clicking the ATU continuously until a low SWR is achieved
  • Teijo OH1TSMTeijo OH1TSM Member
    edited March 15
    This is not the reason, I think. This antenna should work even without tuner. https://www.hyendcompany.nl/antenna/m...
  • Brian HemmisBrian Hemmis Member
    edited March 15
    Eventually- sometimes it can take 20 or more attempts it will tune. Sometimes it tunes after a few tries. Sometimes it just won’t tune at all. Frustrating.
  • bobbybobby Member ✭✭
    edited March 15
    It works first time everytime on version 2.4.9 which is the latest version it worked on before it was updated so now the tuners about useless and its been about a year and still not fixed kinda like profiles also.
  • AlanAlan Member ✭✭
    edited March 15
    One way to find a failure point in a feedline/antenna system is to use a dummy load.   Start with the dummy load at the antenna end of the system and try transmitting at full power.   If you get anything other then a low SWR, move the dummy load one connection closer to the transceiver and "repeat".   Keep moving towards the transceiver until you isolate the problem.

    If you had a low SWR on the dummy load, when it was connected at the end of the feedline (in place of the antenna), then the suspect problem is the antenna itself.

  • Brian HemmisBrian Hemmis Member
    edited March 15
    Flex giveth and Flex taketh away.
  • WX7YWX7Y Member ✭✭
    edited June 6
    If you have a Antenna analyzer then use it so you don't cause RFI if not the with a external Watt/SWR meter with the TUNER in bypass hit the tune button and see what the SWR is on 75 Meters (40 Meters 1/2 Wave wire).

    Not familiar with that brand of Antenna BUT I am very familiar with the END FEED 1/2W antenna 
    I would bet it's your counterpoise/ grounding and or constant mode choke or combination which is VERY Important on this type of Antenna. Don't believe everything the Antenna manufacture tell you because your ground is different, Height above ground, or Coax your feeding it with etc.

    Here are a couple of very GOOD videos that may help you understand END Feed 1/2W antenna that are VERY educational and really show how to properly load this great Antenna if done right.


    hope this helps your problem and you track it down. 


  • KD0RCKD0RC Member ✭✭
    edited April 7
    How much Tune Pwr are you using?  Sometimes you need more like 20 W than 10W to make it work.
    Len, KD0RC
  • PatrickPatrick WH6HI Member ✭✭
    edited June 2
    A couple of points:

    1) what happens into a 50 ohm dummy load?  Will it tune? (Will go into bypass if senses 50 ohm match)

    2). Depending on how the antenna is mounted, could be expressing an SWR greater then 3:1.

    3) SWR’s above 3:1 will not tune as it would be out of the range of the antenna tuner of the Flex.

    4). I use v 2.6.1. No problems with tuner on my 6500....

    you need to start trouble shooting from a good reference point.  Use a known good dummy load.  Test at radio, then at end of feed line.  Make sure all is good there.  If both those measurements are ok,  and you can tune the dummy load ( it will automatically switch to bypass, indicating it is measuring the load properly, which is an indication that the tuner will load a proper antenna with 3:1 or less SWR) 
    The additional references to the antenna being used indicates a multi band antenna, if so pick another band and measure the SWR in bypass, if less then 3:1 then try tuning it.  If this fails then open up a ticket with FRS.  
  • Teijo OH1TSMTeijo OH1TSM Member
    edited March 15
    Problem solved. My antenna connection number 1 have failure. I put antenna to the number 2 and it works now.

    Thanks for your support ! 73s Teijo OH1TSM
  • Teijo OH1TSMTeijo OH1TSM Member
    edited March 15
    Steve Ellington’s theories are familiar to me. - Respect !
  • edited March 15
    In my opinion, you should place the Hyendline isolator just below the  HyEndfed  aadaptor at the top  of the antenna. Why? Because you are trying to tune 2 different antennas.

    One of them is the cable of the EndFed acting as half wave on  80 meters (40 meters lenght and the other one is he outside of your coaxial cable, acting in conjuction with the cable of the antenna and the inductance of the HyEndFed adapter, all of the the three items resonanting in another freqiuency as a halfwave on another  multiple.

    That explains that your tuner tunes a SWR  1:1 that is not the real SWR  that is in the inside of the cable, but instead  it tunes a mixed one and hen you have actually a good percentage of reflected power..

    Placing the HyEndline isolator just near the antenna will destroy this ressonance, and will leave the cable of the antenna as the onluy one resonanting on the pretended resonanting bands.

    Luis EA3OG. 
  • Steven WA8YSteven WA8Y Member ✭✭
    edited March 15
    Why can't you select ver. 2.6.1 on startup?
    edited March 15
    Yes Flex, It works the first time everytime on version 2.49. Can you please FIX it in out next update ? coming after 3.18?? most of us have been having issues with the ATU on SSDR 3.18. What good is a remote when your ATU has to be pushed 20 times to achieve a reasonable SWR???.. Please Add this fix to our next update. Anyone else wanna weigh in on this? After all, we paid extra for the ATU option correct? We pay for updates correct? So Flex needs to get on this soon and make this hardware work correctly with a software fix. We all love our Flexes but, why have an ATU if you gotta keep pushing it more then 3 times. And I have tried it on a dummy load. It works when it wants too.  I do love  my Flex. Please fix this issue. Thanks for reading. And this I post with respect. I got an email from Flex and  some Flex guys have time off because of the Corona virus. This would be a great time to try and fix it. Just try for us please. Thank you Flex.
  • Steven WA8YSteven WA8Y Member ✭✭
    edited March 15
    How much power are you sending in Tune? Anyway, try WSJT-X at that power level. If it works, then you have a bad connection, like a lose PL-259 or wing -nut at the balun.
  • Brian HemmisBrian Hemmis Member
    edited March 15
    It's not a good word of mouth advertisement for Flex when a group of hams I talk with regularly know of the issues I have trying to get on the air all due the AT / software issue. The most disturbing thing is it wasn't fixed in an update as soon as it was seen to be a problem. 

  • Paul - K6HRPaul - K6HR Member
    edited March 16
    Hello Teijo,

    In the screenshot it shows your ATU is in bypass.

    I have seen this before, where after tuning, it ends with the tuner in bypass.

    I find that if you engage the MEM button (next to the ATU button) then tune again, once tuned, it will show 'Success' above the ATU button and the ATU button will remain blue, as will the MEM button, which will have the word 'mem' showing above it. You will then have the ATU engaged while you TX going forward.

    Try this on your ANT 1 connector before seeking service.

  • KC2QMA_JohnKC2QMA_John Member ✭✭
    edited March 15
    Overall version V2.49 seems to be the most stable.
  • Teijo OH1TSMTeijo OH1TSM Member
    edited March 16
    Yes, I will.

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