Can a Long Wire be too long?

SDRPlay Independent Community Forum Forums SDR Antennas Can a Long Wire be too long?

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  • #1764
    FlamingHedgehog
    Participant

    Hi All,
    Space at my apartment is limited so loops and verticals are the norm but I do have a window of opportunity to shoot an end fed across the property to a tower.
    It’s 30M (100′) away and a far stealthier, easier and cost effective choice over a massive vertical.
    My question is, with RX antennas does there reach a point of saturation where after the longer you go it will make no difference to pulling signals?

    Cheers,
    Michael 🙂

    #1770
    Andy2
    Participant

    There are so many variables with random wires it’s hard to say. Generally, the longer the wire, the better it will be at low frequencies. The effect at higher frequencies is harder to predict as the radiation pattern will change drastically with frequency. Really, the trick nowadays is to minimise noise rather than chase more signal, which is why more people are going for loops rather than wires.

    #1776
    TekBoss
    Participant

    Michael, a VERY long time ago I built a Heathkit receiver and stuck a 100′ copper wire up on the roof. Even without propery grounding the thing brought in everything. It was amazing. I took it down so I could properly add lightning protection and properly ground the input and ended up in the Air Force before I got a chance to really set it up properly. However my experience leads me to believe you will have great results as long as, like Andy2 says, you make sure to minimize the noise by properly grounding the antenna input.

    Do me a favor and let me know how this works out if you decide to go for it. I am getting back into radio and am considering doing the same thing, properly this time.

    #1777
    FlamingHedgehog
    Participant

    Hiya Boss,
    I too am only getting back into radio after a 30 year absence. Mainly due to the advent of good SDRs, software and moving to the country.
    Sure I’ll post the results. Going to try a couple of grounding options. The usual rod earthing to the planet but also wondering about using the long steel roof gutter beneath the wire as a counterpoise as it is mounted to wood and the drain pipes are pvc making it somewhat isolated. Also going to test earth ground using a spike in a live tree as I can’t find any literature on this idea (maybe because it’s stupid?) Still waiting on the magnetic loop, 9:1 baluns (well ununs really) and telescopic fiberglass poles being shipped by Continental Drift Express on the back of a sea turtle for making a 7m long helical vertical end fed and a 7m long vertical G4NSJ Flowerpot coaxial dipole for comparison. Would love to get hold of an antenna analyser but living in rural Australia borrowing one from a local HAM is a day trip and a packed lunch affair… Have invested in high quality coax and professionally fitted connectors, always amazes me how many people spend big money on radios and antennas then join them with Chinese ebay garbage making the whole thing deaf.
    What I’m really interested in is the natural noise floor of these different setups. Living where I do there are no high power transmitters for over 200km and only one low power cell phone tower in the Ghz band and being next to the ocean should make for some good testing.

    #1836
    JethTran
    Participant

    Hi….A long wire is a helpless decision for a particularly wide inclusion territory. As called attention to, the radiation comes increasingly more off the finish of the wire as the wire turns out to be longer as far as frequency.

    The way that your wire shifts bearing most likely weakens this impact, yet it likewise causes less addition.

    I have, for very nearly twenty years, utilized two bi-directional long wire recieving wires, about a similar length as yours. They work alright in the ways they are pointed (Europe and North Africa, Central and South Africa, Australia, and New Zealand) and not so well somewhere else.

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