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Thread: best antenna

  1. #1501
    Captain abcd567's Avatar
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    Quote Originally Posted by peterhr View Post
    Neat!

    Now if a shot length of stiff plastic pipe was tightly (gled) unto the bottle neck - it would provide something that could be used to fit the assembly to a pole.

    I'm not really thinking of a tower or a mast here - someone who has invested th oney for one of those won't seriously be making a cantenna, this will be for the guy to fix to the top of the TV antenna pole.
    Very good idea. Deserves giving a try.
    Your concept in picture below - Not actually built, assembled in Photoshop, using independent photos of Cantenna, Water Bottle, and PVC Pipe.

    Last edited by abcd567; 2014-08-18 at 16:15.

  2. #1502
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    Quote Originally Posted by abcd567 View Post
    Another of 1001 ways....
    Just a concept...very easy to make, provides rain water protection, but bottle will blow away with wind unless glued to the Coke can.
    Drill some holes in the bottle and the can and pop a cable tie through doesn't need to be tight (what do you call them - zip ties?)

    The open bottom allows ventilation around the amplifier - needed on a warm day - but if you have a foggy day then water could be a problem, so it would probably still be a good idea protect the amplifier maybe by wrapping it in self-amalgamating tape.

    The inverted bottle could cook the amplifier on a sunny day in it's personal unventilated greenhouse.

    If using cable ties to fix the can to the open ended bottle, they could also pass through the short plastic tube to provide a fixing.

    ---

    I now have my can, amplifier, voltage inserter, power supply - need to sort out some connectors and a bottle

  3. #1503
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    Wot no
    Cable ties
    Tie wraps
    Zip ties ?
    Best invention since the hammer.
    Have fun
    Terry

  4. #1504
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    I have replaced pepsi/coke aluminum can (66mm dia) with a larger can (100mm dia). First 1/2 hr run shows some improvement in range. Needs longer, say 24 hrs run to get a clearer picture.

    Since can's circular bottom acts as ground plane, and smaller dia ground plane pulls down the lobe, more planes flying low/on ground are picked up, and long (horizon) range is reduced.

    Increasing dia of can will provide better ground plane, and hence it's lobes are less pulled down. It should therefore theoretically pick more distant planes and lesser low flying/on ground planes.

    I want to see how far my larger dia cantenna's results conform with theory.
    Last edited by abcd567; 2014-08-19 at 12:52.

  5. #1505
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    After about 10 hrs trial run of 100 mm dia cantenna, the maximum range figures are:
    With Pepsi/Coke 66mm dia can = 450 km (250 nautical miles)
    With Large 100mm dia can = 550 km (300 nautical miles)

    Range Plot 100mm dia Cantenna (Amplifier inside the can + 50 ft RG6 Coax between antenna & receiver)
    Very few aircrafts at this hour of night (about 2 AM)


    Last edited by abcd567; 2014-08-19 at 06:18.

  6. #1506
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    All this does make me wonder just what we would be able to do with the magmount antenna that comes with the dongle, by:
    * tuning it's length (trial and error)
    * feeding it to an amplifier
    * sticking it on a 100mm (or bigger) can with a dongle and RasPi inside(using POE)
    and so on.

  7. #1507
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    The 100mm dia Cantenna With Amplilifier inside.
    While taking this photo, the 66mm dia Coke can was kept at left for size comparison.
    The Cantenna was hooked to receiver & desktop located in another room, using 50 ft (15 meters) of RG6 Coax.


    The can's circular bottom is made of tin (steel sheet), and the cylindrical wall is made of cardboard with aluminum foil lining inside. I checked continuity, and found the aluminum lining is electrically connected to the can's circular metallic bottom. I have checked many other cardboard cans, but they did not show electrical continuity between foil & bottom, or even between two points on the foil, possibly because their foil lining was plastic film coated.

    Last edited by abcd567; 2014-08-19 at 13:09.

  8. #1508
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    Photo of my cantenna. It is a 70mm baked bean can and installed in a Ginger Beer bottle. I managed to fit the bottom half of the bottle inside the top piece then ran a bit of insulating tape round the joint. I'm sure it will fall apart at the first drop of rain!

    cantenna.jpg

    It gets a max range of 170nm but does pick up helicopters on the ground from my local aerodrome which my Franklin doesn't.

    Following ab cd's idea of going larger with the ground plane, I spent an hour in the local supermarket with a ruler and magnet. I resisted the temptation to buy a load of tinned stuff I don't need. I did, however, find a metal container of coffee from Gaggia which has a 100mm diameter base.

    Coffee anyone?
    Last edited by trigger; 2014-08-19 at 18:57.

  9. #1509
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    I've been playing with making a Franklin from 3mm copper wire. I took the Earth wire out of some 30 amp cable and twisted it with a drill to make it a bit stiffer. This is the result.
    3mm Franklin.jpg

    I found that the stubs opened considerably when it was hanging up due to the weight, so I popped some small cable ties round them.
    Franklin stub.jpg

    Testing from the ground shows it works but not as well as the one I made from solid 1.5mm wire.

    I've also had a thought about the kinking problem with 5mm tube. How about this?
    5mm pipe loop.jpg
    Cut the tube to 138mm straight lengths and solder the pieces together. The problem I see is that the wire is 3mm diameter and the tube is 5mm diameter. What that will do to SWR and Gain I don't know.

  10. #1510
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    The stub gaps are related to diameter of wire/tube of which the stub is made. The gap bcomes smaller with smaller dia wire/tube.

    Dia of vertical limb's wire/tube has little influence on stub gap.

    As crude rule of thumb the impedance matching stub's gap lies between 1.5 x dia of wire/tube and 2 x dia of wire/tube.

    As crude rule of thumb the phasing stub's gap lie between 2 x dia of wire/tube and 3 x dia of wire/tube.

    Optimum dimensions are by simulation.
    Last edited by abcd567; 2014-08-19 at 22:23.

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