G5rv configuration and performance problem

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KE0BXN, Mar 9, 2018.

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  1. KE0BXN

    KE0BXN Ham Member QRZ Page

    I have a g5rv with 300ohm twin lead tv line and a balun with about 75’ of coax attached. I have a majority of the coax is coiled and tucked into the termination box outside. I have also had some problems with static build up at one point (high enough it was arcing between the pl259) which I remadied as soon as I noticed the problem. The peek is at about 48’ with the ends at ~12-15’.

    I have noticed recently that I just don’t seem to be getting out like I used to. Is it possible that the coax dialectic broke down due to the static? Could the coiling be preventing it from being as efficient as it could be? I guess I’m just not sure what I can do to test things.

    I did put the analyzer on the antenna and I am getting mostly 3.5:1 or less on most bands with the exception of 40 and 15 where I am ~4.5:1.

    Any guidance would be appreciated!
  2. G3YRO

    G3YRO Ham Member QRZ Page

    If you're worried about your coax, check it by putting a dummy load on the end and looking at it with your SWR Meter or Analyser.

    Is your 300 ohm ribbon the correct length, 34 feet?

    I personally hate the G5RV . . .

    In my opinion, a much better multiband dipole is a W3DZZ . . . and about the same length.

    Unlike the G5RV, it's actually RESONANT on the main bands from 80m - 10m, so you feed it directly with co-ax, and there are far less losses.

    Roger G3YRO
    AK5B likes this.
  3. AI3V

    AI3V Ham Member QRZ Page

    Static so strong it arced a pl259?

    I don't think so.

  4. KF4ZGZ

    KF4ZGZ Ham Member QRZ Page

    The G5RV ..... some people swear by them .... other people sear at them!
    I would imagine the problem is coming from the coiled up coax in the box.
    Thats a lot of stress .... depending on how tight the coils are .... and if it gets hot enough the center conductor migrate through the insulation.
    Another place to look is the junction of the twinlead and coax. Corrosion, bad connections etc.

    I personally prefer simple ladderline fed doublets. They work.
    TV twinlead, 450 ohm, 600 ohm homebrew ...... they work.

    Matt - and yes ..... I've seen static discharge across 450 ohm ladderline.
  5. KE0BXN

    KE0BXN Ham Member QRZ Page

    Seriously...during a blizzard I walked into my shack hearing a squeal and pop. Not believing it was the coax, I grabbed it by the PL259...big mistake! It didn’t feel good at all!!!

    It has permanent coax and twin lead to the balun :/ (non removable)
  6. KE0BXN

    KE0BXN Ham Member QRZ Page

    The coil is fairly loose...it is coiled so it fits in a ~12”x12” box.
  7. W5DXP

    W5DXP Ham Member QRZ Page

    Rege, I can tell you haven't lived through central AZ dust storms. The P-static can get so bad that the arcing on a PL259 sounds like a machine gun.
  8. N8CMQ

    N8CMQ XML Subscriber QRZ Page

    A friend of mine, before he passed away, used to keep the disconnected ends of his coaxes in glass jars. Occasionally, the static buildup from storms would cause arcing across the PL-259 connectors.
    The antennas were all on his 50 foot tower, which also lit up with Saint Elmo's fire, or corona, at times.

    When I was at the top of the tower, I could see where lightning had struck the ground in his back yard. That part of his property was always damp and very conductive. He moved away from that location to get away from the problem...
  9. G3YRO

    G3YRO Ham Member QRZ Page

    Yes but you have a fault !

    And you want to find what is causing the problem, right?

    So disconnect the far end of the coax . . . connect it to a Dummy Load . . . and do a test.

    Also do a simple resistance check.

    Roger G3YRO
    KC8VWM likes this.
  10. AI3V

    AI3V Ham Member QRZ Page

    Video of all this static arcing or it never happened.

    A static discharge big enough to see -across a pl259 no less- would instantly destroy a receiver.


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