ad: elecraft

Tuner problems

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by K0DT, Feb 11, 2018.

ad: L-HROutlet
ad: l-rl
ad: MessiPaoloni-1
ad: L-MFJ
ad: Subscribe
ad: Left-2
  1. K0DT

    K0DT Ham Member QRZ Page

    I have an LDG IT-100 tuner and an Alpha Delta antenna switch connected to a G5RV and a 20m dipole. When I use a jumper cable longer than 1ft between the tuner and the switch, the tuner won't tune the dipole less than 2:1. But it tunes the G5RV fine, regardless of the length of the jumper. Any ideas? Thanks in advance!
     
  2. WA7ARK

    WA7ARK Ham Member QRZ Page

    Bad jumper? High resistance connection inside the PL259? I use my carbon-pile 500A 12V battery tester and a 12V car battery to pass about 100A through coax cables, tit-to-tit, and shield-to-shield. Run the current for about 15sec, and then feel the PL259s. I have found several bad coax jumpers over the years. Some of these came from hamfests, some I screwed up myself...
     
    WB5YUZ likes this.
  3. K0DT

    K0DT Ham Member QRZ Page

    I thought it might be a bad jumper, but I've tried several different ones and keep having the same problem. Driving me crazy!
     
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Try a length "a lot" longer than one foot, like 20 feet, and see what happens.
     
  5. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    What is the SWR range of the dipole on the frequencies of interest with the tuner in bypass?
     
  6. KX4OM

    KX4OM Ham Member QRZ Page

    Common mode current?

    Ted, KX4OM
     
  7. K0DT

    K0DT Ham Member QRZ Page

    At 14.220, the swr is 3 in bypass. (It was a pre-made dipole and I just threw it up without tuning it. Too cold at the time.) The tuner gets the swr down to 1.3.
     
  8. K0DT

    K0DT Ham Member QRZ Page

    So I lengthened the jumper between the tuner and the radio to 3ft. Now when I use a 3ft jumper between the tuner and the switch, everything seems to be ok. I wanted to keep the jumper as short as possible between the radio and tuner because I have them both in a Go box. But I guess something's going awry when the jumper is too short between the radio and tuner, and not between the tuner and switch.
     
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    There's a reason for that. Think about it, and do some research about conjugate matching via transmission lines.

    A 3' jumper of RG8X can be coiled in 3" diameter and stuffed into a shirt pocket easily, so you're not sacrificing much portability.
     
  10. K0DT

    K0DT Ham Member QRZ Page

    I meant to say I have to keep the jumper between the tuner and the switch as short as possible (no more than 1ft). It doesn't seem to matter how long the jumper is between the radio and the tuner. Thanks for everyone's help. Steven, I'm going to have to read up on conjugate matching.
     

Share This Page