Saltwater and Plastic Antenna

Discussion in 'Amateur Radio News' started by G4TUT, Sep 21, 2019.

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  1. W1YW

    W1YW Ham Member QRZ Page

    No one is complaining about that. Some are dubious as to the value of the 'technology', but specifically this embodiment.

    Anyone familiar with invention would describe this as 'obvious to anyone skilled in the art'. We know how to do arrays ( some RDF arrays look just like this BTW), we know salt water antennas are antennas. Therefore....

    Even if the concession of 'new'ness is addressed, the real issue is: what is the VALUE? What problem does it solve? Why is this a better solution than others? What new avenues of approach does it open up?

    BTW...your CALLSIGN is....?
    NN4RH likes this.
  2. K4AGO

    K4AGO Platinum Subscriber Platinum Subscriber QRZ Page

    I use a tree sprayed with antenna spray every field day. The last can of antenna spray I purchased has lasted almost 20 years.
  3. W4HM

    W4HM XML Subscriber QRZ Page

    I have on 160 meters using a 100 foot pine tree. I drove a long copper nail into the tree through the sap. I fed it with 75 feet of RG-213U. I used a home brewed matching network at the feed point and an RF choke at the shack end.

    The RG-213U was sitting on the ground surface and covered with dirt. I was reasonably sure that the coax wasn't radiating any signal.

    It radiated really well as in working DX in Europe, Africa, the far east and Australia New Zealand.

    I used 100 watts and CW.
    Last edited: Oct 2, 2019
  4. W1YW

    W1YW Ham Member QRZ Page

    Many years ago, there was an article in NATURE on VLF resonance in trees. I suspect that they are not very efficient down there, and the obvious potential for fire exists at high powers. I am sure a 100 foot pine tree could be used for 160m (MF), but probably a 100 foot adjacent copper wire, vertically, works far better ;-)
  5. VE9DAN

    VE9DAN Ham Member QRZ Page

    All kidding aside ...
    If you live near saltwater (and I do) here are my comments:
    1) There is no need to use Plexiglas. 1/2" common Poly Pipe should work equally well. In Canada it costs $30 for either a 50' or 100' roll (the online source doesn't say what the length is). We'll assume 50 ft (worst case) ... so the cost is $30/50 per foot... = $0.60/ft CDN = $0.45/ft USD.

    2) OK ... that is not so bad. If I tied one end to the top of a tree in a 'sloper' fashion, I could now have a potential antenna. I'll use the salty marsh for a ground plane.

    3) So how do you tune it? I would use a pump and a pressure sensor connected to say a Raspberry Pi to tune to the various bands ... 3 psi (say) = 14.250 MHz ... 5 psi (say) = 10.130 MHz ... 7 psi (say) = 40M etc.

    4) How would you feed it? One of the new VNA instruments that provides a Smith Chart analysis would provide all of that.

    The 'droop' of a filled poly pipe sloper is purely mechanical and can be addressed.

    The actual feedpoint could be a stub inserted into the contained saltwater. The VNA will indicate where you would stand for impedance. Perhaps a 6" stub yields 70 ohms, while a 24.073" stub could yield 50 ohms. Who knows?

    All materials in contact with the salt would have to be stainless or brass.

    This idea is not worth dismissing.
  6. VE9DAN

    VE9DAN Ham Member QRZ Page

    Just a few of additional comments are worthy.

    a) The Rpi would not only relay switch the pump to fill the pipe to a pre-calibrated setpoint, but it would also drain the pipe to accommodate higher frequencies. This would fall within a "Calibration Expert's Dream". A digitized graph (using VNA data) would provide the exact pressure level for each frequency - kind of similar to how a SteppIR works.

    b) I casually mentioned Poly Pipe as the container of saltwater. Perhaps two SCH 80 ABS, verticals, rope supported, and co-phased may be a better option. There is not much wind load on a vertical.

    The original article mentioned 380-450 (?) MHz. There is no reason not to apply the same thought process to HF. I just don't think we are all capable of erecting several verticals to cover all directions, but 2 would be nice.

    If you are not located near a saltwater source, then someone earlier mentioned using salt-licks as their source of salt. That is a good idea but the Rpi would have to pump the expelled saltwater into a storage tank to preserve the salt, as you tuned up in frequency. And, of course, you would also have to address your local Ground Plane.
  7. WN1MB

    WN1MB XML Subscriber QRZ Page

    Or you could:

    1) Run a less expensive and far less unwieldy wire sloper, then feed, and tune it conventionally.

    2) Dismiss the salt water filled poly pipe idea as it should be!
  8. W1YW

    W1YW Ham Member QRZ Page

    OK, here is why you shouldn't waste your time (please read prior posts):

    1) The interface from salt water to coax, no matter how you make it, will corrode. Stainless is a very poor metal to use for RF. Brass WILL corrode, or at least, the water impurities will form a poor-RF layer on it. It will also be a base for crystal formation. That means you will have to frequently keep on flushing the system and scrapping it down;

    2) PVC is a horrible suggestion for HF. CPVC works OK, if you can find it;

    3) Basically if you can put a pipe vertically (in part) on your property, you can run a copper wire up the middle. You can even change its length with a tape measure type system. So why do you need salt water over copper wire?;

    4) Did I say CRYSTALS? Unless TUFA towers are desired, you will constantly be balancing salinity versus precipitation (that is, a change in the water salinity (read: conductivity) from crystal growth).

    So...why is this a good idea?
    Last edited: Oct 9, 2019
  9. WY7BG

    WY7BG Ham Member QRZ Page

    They ought to call it the Slurppir....
  10. G0WXU

    G0WXU Ham Member QRZ Page

    Well What do you know. I'll get one planted and report back in about fifty years or so when it has grown to a sufficient quarter wave in height. May have to get the grandson to do the reporting. I will be more than likely a SK by then. 73 de John - G0WXU.

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