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Thread: I am looking for plans for a 20m Isotron antenna

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  1. #11
    Join Date
    Jan 2008
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    St. Mary's County Md since 2000
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    7,965

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    KA7BSA You can make anything you want for personal use, if you sell it is another matter. Thank you for your thought less comments.!!!
    Sure, you can build anything you like. I've thought of this myself. I already an Isotron 80m. So, get off your duff and do it!

    But it takes a lot of nerve to get on a national forum and ask other hams to help you undercut an honest long-standing ham vendor!

  2. #12

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    You have your right to your opinion, that is what America is all about. I am not undercutting anybody with my question, first of all I am not planning on purchasing a commercial antenna when I can figure out how to make one. If, you do not want to help other Ham operators then I suggest you find another hobby. That is what the hobby is about helping others, and figuring out how to make things RIGHT? Great inventions start with someone else's ideas that are improved upon.
    73's

  3. #13
    Join Date
    Jan 2000
    Location
    Belmont, Michigan
    Posts
    927

    Question Plans for an isotron?

    Quote Originally Posted by KA7BSA View Post
    You have your right to your opinion, that is what America is all about. I am not undercutting anybody with my question, first of all I am not planning on purchasing a commercial antenna when I can figure out how to make one. If, you do not want to help other Ham operators then I suggest you find another hobby. That is what the hobby is about helping others, and figuring out how to make things RIGHT? Great inventions start with else's ideas that are improved upon.
    73's
    As you have just experienced, you've been punked because no one really knows the answer to what you want, mainly because that particular design antenna is not efficient or popular. If it was such a great design people would be swapping their pictures of how they homebrewed one... for example: The hex beam (by Traffie Tech) is being made by hams and pictured in a Yahoo Hexbeam Group. Many are homebrewed, but other companies are making all the parts you need to build them better than the original Traffie design. But no one is making parts to build your own home rolled isotron. Hmmm must be a reason not involving lawsuits.

    Most people consider the isotron as an antenna of LAST resort or abject desperation. The suggestion about using a light bulb on the end of a piece of coax and elevating it up in the air would probably work as well. Actually you could feed that light bulb with coax or open wire feeder with about as good results. You could improve its efficiency by adding a couple wires attached to each side as a dipole.
    73 de w8nsi/nnn0uzw jim

  4. #14
    Join Date
    Jul 2009
    Location
    Hurricane, WV
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    192

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    Having owned one for 40m and 80m all I can say is they were both a coil of wire in between two aluminum plates. Look at the pictures on the website and break out the resonant frequency formulas... shouldn't be too hard to come up with a "workable" design. I'll not go into how good they do or do not work, only say that in the absense of available space they do work better than nothing and will get someone on the air. I only considered them for those 2 bands as I had enough roof space to put up a dipole for 14 through 30 mhz and dipoles do work well.
    Never do anything you don't want to explain to the ambulance technicians.

  5. #15

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    Quote Originally Posted by KB5HAB View Post
    ... they were both a coil of wire in between two aluminum plates.
    It is a low-Q resonant tank circuit connected to the end of a transmission line. The multi-turn coil is the inductor and the aluminum plates are the capacitor. It is a lot like a multi-turn loop antenna which is known to be notoriously inefficient.
    73, Cecil, www.w5dxp.com
    Can CO2 emissions save us from the coming ice age?

  6. #16

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    Being a fairly new to the hobby this antenna looks interesting to me. I like to make things, being a machinist triggers my need to make and learn at the same time. I really want to thank you all for the suggestions and information. My plans are not to purchase any commercial antennas not because I am cheap, it's I want to understand how they work. I would love to make my own towers only if I had a shop big enough to do that.

  7. #17
    Join Date
    Jan 2000
    Location
    Near Boston
    Posts
    3,586

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    I don't believe the patent is still active. Likely off-patent. Worth checking.

    The 20M isotron is not a poor performer. If you can get it up very high(say 60 feet or more) it will work well for DX. About the same size as a mag loop for example. A 20M dipole at that same height will work much better, by about 6-10 dB. If you can only raise a dipole to much less than 1/2 that height, and/or have covertness issues, the isotron is a fine antenna.

    Isotrons for 80M, or 160M, for example have very low radiation resistance and are not good performers, IMO.
    73,
    Chip W1YW

  8. #18
    Join Date
    Jan 2000
    Location
    Near Boston
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    3,586

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    Quote Originally Posted by W8NSI View Post
    As you have just experienced, you've been punked because no one really knows the answer to what you want, mainly because that particular design antenna is not efficient or popular. If it was such a great design people would be swapping their pictures of how they homebrewed one... for example: The hex beam (by Traffie Tech) is being made by hams and pictured in a Yahoo Hexbeam Group. Many are homebrewed, but other companies are making all the parts you need to build them better than the original Traffie design. But no one is making parts to build your own home rolled isotron. Hmmm must be a reason not involving lawsuits.

    Most people consider the isotron as an antenna of LAST resort or abject desperation. The suggestion about using a light bulb on the end of a piece of coax and elevating it up in the air would probably work as well. Actually you could feed that light bulb with coax or open wire feeder with about as good results. You could improve its efficiency by adding a couple wires attached to each side as a dipole.
    Actually the isotron sells pretty well. I used two, 30M and 20M, manyyears ago. The light bulb suggestion is a poor one and fraught with danger as a fire hazard.

  9. #19
    Join Date
    Jan 2000
    Location
    Near Boston
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    3,586

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    Quote Originally Posted by W5DXP View Post
    It is a low-Q resonant tank circuit connected to the end of a transmission line. The multi-turn coil is the inductor and the aluminum plates are the capacitor. It is a lot like a multi-turn loop antenna which is known to be notoriously inefficient.
    Cecil:-) ALL antennas are tank circuits. Slosh slosh:-)

    73,
    Chip W1YW

  10. #20

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    Juergen DL7PE did a pretty good analysis of the Isotron design and includes some design formulas and stuff here:

    http://www.dc4fs.de/microvert.pdf

    I think this was all published in Antennex years ago.

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