Mosley Mini 32A giving weak signal

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by WU0B, Sep 19, 2017.

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  1. WU0B

    WU0B Ham Member QRZ Page

    I just put up a previously owned Mosley Mini 32A and am having a peculiar issue with it. When plugging the coax feed line from the antenna into my antenna tuner, I can hear signals with no problems when only the center conductor is inside the SO-239 connector. When the shielded part of the coax touches the outside of the connector, however, my received signal strength drops dramatically, often to the point where I can't hear any signals or even normal static noise at all.

    The antenna is mounted on a steel mast at approximately 25ft. I coiled 5-6 turns of feed line at the feed point of the antenna per the assembly manual to create an RF choke. I've checked for a grounded center conductor from my shack all the way to the antenna and haven't found anything. I changed out my feed line with a different one, but the problem persisted. I can transmit into the antenna without much difficulty...the SWR peaks out around 3:1 on the band edge.

    I've been comparing the received signals to those I get on my 80m horizontal loop and the Mosley's received signal is significantly weaker. Sometimes an S9 signal on the loop will only be an S1 or S2 on the Mosley, even with it pointing directly at the received signal. This is only with the outer shield connected, however. When just the inner conductor is connected the signals are comparable. The loop hasn't exhibited this effect at all.

    I've wondered if it could be a grounding issue, but my station ground is only about 5ft from my shack and the antenna mast is also grounded.

    Does anyone have any idea why this may be happening and what could be done to fix it? Any help would be greatly appreciated!

    Hans WU0B
  2. WU0B

    WU0B Ham Member QRZ Page

    I should also note that I previously used a homebrew spider beam about 10ft off the ground which didn't exhibit any of these effects, usually outperforming the loop on 10-20m receive. I would have kept it, except it won't fit at my new QTH.
  3. W1VT

    W1VT Ham Member QRZ Page

    When you just connect the center pin, it allows the feedline to act as the antenna. You could verify this by disconnecting the feedline to the antenna and taping it in place, and then listening when you repeat the center pin connection experiment.
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    When what is described happens, the coax is shorted somewhere (usually at a connector, but could be at the antenna or almost anywhere).

    Check it with an Ohmmeter.
  5. N0YPD

    N0YPD Premium Subscriber QRZ Page

    Sounds like a short somewhere to me also. Do the continuity test.

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