Sudden dipole problem

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KD1DDM, Jan 10, 2018.

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  1. KD1DDM

    KD1DDM Ham Member QRZ Page

    Today I was working 20 meters in the morning on my home brew dipole. The balun is also homebrew This afternoon it seemed like the band was dead. I checked the SWR and it was 4:1. I couldn't believe it, what happened? I went outside and disconnected the pl259, screwed on a short jumper and had almost a perfect 1:1 across the band with the analizer. The highest reading was 1:5. Back in the shack I checked the coax with analyzer and checked distance to vault. It read the distance to the end of the line. Back outside and looked at the pl259 on the end of the coax. Very slight green discolor. Got some steel wool, cleaned everything up, coated everything with dielectric and resealed. Back in shack all is good. The point is I can't believe how fast I went from almost a perfect match to 4:1. I thought a problem like that would take time to develop. I had been working DX with no problem in the morning. The weather has warmed up which may have caused some expansion.
  2. K8MHZ

    K8MHZ Ham Member QRZ Page

    If the weather got warmer, it may be that condensation formed on the antenna, which would be cooler. The condensation may have gotten into the corrosion and caused a problem.
  3. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    This will happen even without exposure to the elements. It is pretty much standard maintenance practice in all circles to periodically unplug and then replug connectors of all types to ensure good contact. Even the best ones, indoors, will eventually develop a very thin film of oxidation products between the male and female. Periodic un- and replugging goes a long way to mitigating this problem.
    ND6M and NH7RO like this.
  4. WB3BEL

    WB3BEL Ham Member QRZ Page

    You did not indicate, but it might be that you need to weatherproof the connection better.
    VK2WP and NH7RO like this.
  5. NH7RO

    NH7RO Ham Member QRZ Page

    And I'd go one step further and use silver-plated connectors as much as possible. They are much less prone to deterioration even with significant oxidation.

    If you live in the desert, though you can still get away with nickel-plated brass---but silver connectors are easier to solder and take less time with a high-wattage gun.
    N0TZU, KC8VWM and K3RW like this.
  6. KD1DDM

    KD1DDM Ham Member QRZ Page

    I thought I had it weatherproofed enough but I guess not. Just the slightest indication just a very very light green it wasn't pronounced. The silver color wasn't really shiny. If I hadn't looked closely I never would have noticed. guess I need to reevaluate my sealing of my 259s
  7. VK2WP

    VK2WP XML Subscriber QRZ Page

    Any outdoor connectors are best sealed with a couple of layers of amalgam tape, otherwise known as self bonding electrical tape. Over the two layers of amalgam tape put a couple of layers of good quality insulation tape as a final seal.

    Have seen connectors that have been on communication site for 15 or more years done in that manner which are still in perfect condition.
    N0TZU and ND6M like this.
  8. N8CMQ

    N8CMQ XML Subscriber QRZ Page

    I try to use high quality connectors when they are difficult to reach or change out, then they are less likely to be an issue.
    Name brand connectors can fail, but are less likely to do so, as opposed to no name connectors.

    The location of the connector also determines how much weather proofing I do. When the connector is covered by structure, then I am less likely to cover the connector in any tapes, but if it is exposed without any cover, then I will use the self sealing tape, followed by 3M vinyl 77 tape. If the area is prone to very high moisture, then I use DC-4 or vaseline to protect the internal contacts. I use the same for lamps that are outdoors. It reduces the corrosion of the metal, and also keeps it lubricated so it comes apart when you want it to.
  9. AI0K

    AI0K Ham Member QRZ Page

    I hope you meant you coated the connector with deoxit, not dielectric. :)
    NH7RO likes this.
  10. N1OOQ

    N1OOQ Ham Member QRZ Page

    Ahh... ham radio up north. I'm still getting erratic SWR readings for the first 10 minutes, as the water cooks off my window line and insulators. Big snow storm last week...

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