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Sommer T-25 assembly help

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by WX5O, Jun 7, 2021.

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  1. WX5O

    WX5O Ham Member QRZ Page

    I recently came in to the possession of a Sommer T-25 vertical. I think it supposed to handle 80-10m... The one I have has the 4 radial kit on it. I'm pretty sure I have all the pieces, but several of the wires are broken and it's not obvious to me how they go back together... So, I was wondering if anyone has the assembly instructions they'd be willing to scan or can talk me through it. It would make a really good Field Day antenna.



    ARS WX5O
    AK5B likes this.
  2. AK5B

    AK5B Ham Member QRZ Page

    No idea, offhand, Dave---but I bet the wire(s) with the dogbone insulators are for parallel (fan) elements space some inches from the main radiator. Hopefully W9GB will chime in with all the pertinnent info soon.

    GL & 73,

  3. WX5O

    WX5O Ham Member QRZ Page

    Thanks... I'm fairly certain that white wire is run through the insulators on the radiator and is held taught by a spring at the base, it then connects to the end of that coil/transformer attached to the base... I'm unsure if the length of that wire is critical. Where I'm really confused is how does the second coil/transformer on the assembly you attach the radials to gets connected in to the mix.

    I'm going to have to straighten that bottom section a little bit. Also, the mechanical connection for the radials back to the main antenna is a bit wonky (technical term) that might need to be addressed if the antenna is going to be left up for any length of time.
  4. AK5B

    AK5B Ham Member QRZ Page

    If the second coil is already attached to the radials then that's probably all that need be done. Try assembling it after straightening it and pulling the vertical wires taut, laying out the radials (elevated, perhaps?) and see where it has resonance (zero or very little reactance if you have the means to do so).

    For the mechanical connection---apply plenty of Noalox before joining, and a Scotchbrite (not steel wool) scrub is also in order.


  5. WX5O

    WX5O Ham Member QRZ Page

    Sorry... I should have updated this a while ago.... I did get the antenna assembled and mounted, but the SWR is a bit off... 1.9:1 pretty uniformly across all bands...

    I've also included a closeup of the wiring.... I'm thinking there is something wrong with the T1 transformer... but it will take a bit more time than I have at the moment to investigate.

    Sommer-T25-installed.jpg Sommer-T25-detail.jpg
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Did you not find this?

    It includes a photo that I believe looks different from what you've arranged; however what's shown is the T-25/S which does appear to be slightly different and does not include the separate vertical wire -- the aluminum tubing is fed via the upper transformer:

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