what does it mean when the antenna tuner goes to bypass automatically on 10 &15 meter

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KN6JVS, Aug 10, 2020.

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  1. KN6JVS

    KN6JVS XML Subscriber QRZ Page

    Hello everyone , as the question implies , I'm a newbie @62 years old . I know I have not tunned the AV-680 properly , but have notice that on 10 meters and 15 meters when I press the tuner button on the IC-7300 , the LDG AT-100pro II tries to tune but goes to bypass and the light indicator stays on .

    I just bought a Rigexpert aa55 and have lmr-600 coming that is shorter than the 100' of 213 coax the unit is using now.

    I also noticed something that seems a bit odd , but the swr changes from day (heat ? ) and night .

    thank you for your answers

  2. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    The AV-680 is a multi-band trap vertical that if adjusted correctly for each band per the instructions should NOT need a tuner - at all! Possibly if you wanted to work the CW end and you had set it for SSB end on one band or another - but that would be a minor adjustment that your tuner could handle.

    The whole point of the traps and adjustments on the antenna are to put it at resonance in the band segments you choose during assembly, thus not requiring any external tuner

    It sounds to me like something is way off in the adjustment of the antenna itself.

    Trap verticals can be fussy to adjust - every adjustment affects every other one.

    KF5KWO and AK5B like this.
  3. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Probably either common mode current on the feedline or simply RF overload causing the tuner circuits to trip.

    -How much power?
    -How far from antenna to shack?
    -Do you have a Current Mode balun/isolator or coax grounding point directly at the shack entrance? If not start there.

    Also, some general houskeeping in the shack:
    -Separate coax and signal and power cables.
    -Coil them up.
  4. W6MK

    W6MK Ham Member QRZ Page

    A common beginners' error with modern transceivers is to use both the internal transceiver tuner and an external tuner like the AT-100.

    One or the other should work. Both together can create problems if you don't understand how each works separately and how you intend them to work together.

    And as already pointed out your antenna, if properly set up, is unlikely to need ANY tuner.

    Start with your new Rigexpert and tune your antenna properly. Go from there: if you need minor retuning across a single band, use the internal transceiver antenna. If you want to try to use the antenna on a band for which it is not designed, you may want to use the external tuner alone or in conjunction with the internal tuner.
  5. KE5MC

    KE5MC Premium Subscriber QRZ Page

    Root cause could be water in traps. Heat of day burns it off and they work as intended. Night time cooling and condensation gets inside messing thing up. No experience with construction of AV-680 so comment may be way off the mark.
    KF5KWO likes this.
  6. N4MU

    N4MU Ham Member QRZ Page

    I agree with HCP. I use a 100 with a FT857 and get the same results occasionally. My solution is to reduce power to 50 watts and try to tune. Also, RF could be getting into the situation at only certain frequencies. Note the comments about the trap vertical...I would "forget" the tuner(s) and tune that baby first for optimum performance...THEN see if and where you need a tuner.
  7. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    There seems to be some misunderstanding here. The AV 680 doesn't use traps; it uses stubs and a set of parallel-fed matching coils to tune the radiator to an electrical 3/8 wave length, then a 4:1 broadband matching transformer to match the 3/8 wave radiator's characteristic impedance (which the manual gives as "in the order of a few hundred ohms") to 50 ohms. It also has a built-in current balun designed to suppress common mode currents on the feedline. (although how effective that balun might be is beyond my ability to determine just from the instructions).

    It still shouldn't need a tuner, and still has to be adjusted, and I would strongly recommend following the instructions and tuning it before trying to decide if there is a problem of some kind or not:

    Last edited: Aug 10, 2020
    KA0HCP likes this.
  8. KE5MC

    KE5MC Premium Subscriber QRZ Page

    Oh my... I seemed to have stubbed my toe. :)
  9. W4HWD

    W4HWD Platinum Subscriber Platinum Subscriber QRZ Page

    Auto tuners go into bypass mode when the SWR is acceptable and the tuner is not needed to provide a match. My KAT500 stays in bypass mode against the R6000 on segments of 6, 10, 12 and 15M cuz the tuner likes what it sees.

    As for changing SWR - my R6000 did that on 20m in the rain until I drilled another drain hole in the 20m trap cap. Doesn’t do that anymore.
  10. KN6JVS

    KN6JVS XML Subscriber QRZ Page

    As it was explained to me, the 4 hole plug on the back of the 7300 and the cable I bought at HRO , connects to the Autotuner and when you press the tuner on the 7300 it automatically activates the external tuner(and it does ) . so that should not be the issue . When I bought the whole rig I bought a Radiowavz OCF dx 80 , that's why the auto tuner was purchased . have not had good luck with that piece of wire and my property settings.

    Yes I am aware of the AV-680's abilities(sort of, plus there's always hype for every antenna), and am working to remove the tuner soon.

    As I understand from HY-gains web site's photo of the " black black box" it has a 1: 1 and a 4:1 , so common voltage feedback " should not " be the problem .

    the 213 coax is grounded temporarily with a aligator clamp on the shielded nut (is this the problem ? I'm grounding the shield ? ) .

    For the time being I am using 100' of 213 from the tuner up to the antenna 45 feet up in the air, but I do have some shorter pieces of LMR 600 coming and have a transi-trap that will be hooked up to the 8 foot grounding rod (right now using a piece of rebar I sunk in that spot for the TV antenna 40 years ago. all they had at Homedepot and Lowes was a 21 foot ground rod ? I wonder if Los Angeles county electrical code was adjusted from when I put in a 200amp main electrical box 20 years ago (did it myself and back then all I had to put in was a 8 foot rod under the main box )

    again thank you for any more advice on any of my mistakes like the grounding of the coax ?

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