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LW Antenna -- Cheap and Easy

Discussion in 'Radio and Communications' started by jpanhalt, Nov 24, 2015.

  1. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    Awhile back, I was trying to measure a crystal oscillator's frequency (http://www.electro-tech-online.com/...sure-external-oscillator.145701/#post-1232291 ). Mike's suggestion appealed to me, and I started searching for a suitable receiver.

    A Realistic DX-302 is now on its way to me. Hopefully, it will be a nice Christmas present to myself. I am interested in longwave listening and have found many DX'ing resources. Here is just one example: http://www.am-dx.com/antennas/Ferrite Sleeve Loop Antennas.htm

    The problem, of course, is that the ferrite will cost more than the receiver did. Are there some cheap sources of ferrite or other recommendations for a cheap, easy to make antenna? One use I am considering is to "listen" to the oscillator in an LCD display at about 240 kHz.

    There is a You Tube video of a DIY ferrite made from iron oxide and plaster with no heat treatment. It seems to me that would be a bit too inconsistent product. Anybody have experience with that?

    Regards, John
     
  2. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    Try a random piece of wire, a few tens of ft long. I can hear several aviation NDBs (190kHz to ~400kHz) that are hundreds of miles distant.
    You could also make a receiving loop like this:
     
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  3. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    I will try it. I am anxious to try your method of testing an oscillator's frequency.

    Thanks, John
     
  4. dave

    Dave New Member

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  5. Mikebits

    Mikebits Well-Known Member

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    There is a very well stocked Military electronics surplus store about 20 minutes from where I live. I could take a run by there to see if you can get a big stockpile of ferrite core for cheap. If you want let me know.
    http://www.murphyjunk.net/
     
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  6. JimB

    JimB Super Moderator Most Helpful Member

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    What are you trying to listen to with this receiver?

    If you want to hear low frequency signals from far away - build that ferrite tour de force.

    If you want to listen to an oscillator on the workbench 1 metre away - build a multi-turn coil on the end of a length of coax cable and connect it to the antenna socket of the receiver and place the coil next to the oscillator that you are trying to hear.

    JimB
     
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  7. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    Or even just a clip lead laying near the oscillator, one of which is clipped to the antenna terminal of the receiver.
     
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  8. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    Right now, I am interested in oscillators on my bench. I do have some ferrite rods and coax cable. I even have alligator clips ;) . Mikebits, Thank you for the offer. Actually, there is a decent surplus store in Cleveland too (http://www.electronicsurplus.com/ ). I used to go frequently when it was downtown, but it moved 20 miles East to a newer suburb.

    In the long term, however, I may get into listening to stations. When I was actively flying, I got reasonably good at identifying NDB, ILS, and VOR identifier code. I never enjoyed listening to AM stations, but I would occasionally leave the identifier signals audible just to get used to their unique sounds. Of course, home base was like someone calling my name. It is said the DX-302 will tune to 10 kHz.

    My first project will be the oscillators, and I am relieved things so simple will work.

    John
     
  9. JimB

    JimB Super Moderator Most Helpful Member

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    Yes, that also works well, no problem.

    The advantage of a coil on the end of a coax cable is that when you have a situation where there are several circuits in close proximity, moving the coil allows you to get the most of the signal in which you are interested. This is especially useful when you are trying to sort out the sheep from the goats using the spectrum analyser.

    JimB
     
  10. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    My Dx-302 is currently in FedEx's hands. I may get it as early as next Monday and will certainly post an update, assuming the thing works.

    John
     

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