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Author Topic: 20 and 40 meter inverted V's  (Read 3350 times)
SWMAN
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Posts: 547




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« on: August 08, 2010, 08:20:02 PM »

 Hi ereryone, I just received my Tech license 6 weeks ago. I hope in a month or 2 I with be a general, I hope. I wanted to start making my antennas soon. I live in a small lot, 50 ft by 100 ft. So I don't have much space but I want to make some dipoles. I want to make an inverted V on the rooftop. I have a 10 ft piece of EMT conduit mounted at the center of my one story rooftop. The center of the inverted V will be mounted at the top of the conduit and the ends will be mounted to the opposite rooftop corners, this will be my 40 meter dipole. My question is, can I mount a 20 meter inverted V dipole just below the 40 meter dipole a foot or so lower. Both antennas will be almost parallel with each other but a foot appart on the EMT. I am hoping that this will work, I don't have much room and no good trees to anchor to. Hope someone will know from experience if this will work or not. I will be using only one antenna at a time but will the other one interact with the one being used at the time ? Thanks and 73 Jim KF5HRN.
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K7AAT
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« Reply #1 on: August 08, 2010, 08:41:01 PM »


  Yes, Jim,  that should work fine.   I assume you realize that you can feed both Inverted V antennas with the same coax ..... just solder or connect per your plan  both antennas to the coax.   The non resonant one will have negligible effect on the one you would be transmitting on.  You might consider running the two antennas perpendicular to each other,  but I don't believe it is very important that you do so.

Ed   K7AAT
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K5CQB
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« Reply #2 on: August 08, 2010, 09:15:41 PM »

http://www.hamuniverse.com/multidipole.html
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W7ETA
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« Reply #3 on: August 08, 2010, 09:27:51 PM »

You can buy wooden dowels, two for each leg.  Drill a hole large enough to pass some insulated solid conductor wire thru--18 gauge should be fine.

Cut 3-4 inch to run thru the dowel, wrap the ends around the antenna wire to hold the dowel in place.  Run string from the end of the 20 meter dipole to the 40 meter leg and tie it off. to hold the 20 meter away from the 40 meter.

73
Bob
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SWMAN
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Posts: 547




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« Reply #4 on: August 09, 2010, 03:38:26 AM »

 Thank you for the replys. I never really thought about using just one coax for both inverted V's. But I already have the 2 coaxes run. Would it be better to use 2 seperate ones or better to use just one coax for both ants. Since I already have coax there use both or just one ? Thanks again, 73 Jim KF5HRN
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KF5AHV
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« Reply #5 on: August 09, 2010, 07:53:20 AM »

you can use one coax to feed both of those dipoles and use the other for a antron99 or imax2000 or something to get you on 10/15 meters as well. one of those will mount nicely on the conduit.
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W4VR
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« Reply #6 on: August 09, 2010, 08:24:47 AM »

It does not matter if you use one coax to feed both antennas or one coax to feed each antenna, you will have to prune the wires, especially the 20 meter legs, to get a reasonable SWR.  I do this all the time, feed two antennas with one coax, but I keep my legs at least 45 degrees apart to minimize interraction.  What you could do is rather than putting the legs of the 20 meter dipole directly under the 40 meter dipole is to put them at right angles to the 40 meter legs and tie the ends at the front and back of the roof edges.  Good luck.
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WA3SKN
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« Reply #7 on: August 09, 2010, 01:35:45 PM »

If you have two separate coax runs, go ahead and use them.  It is much easier to trouble shoot problems, if they occur!  You can always re-use them for other bands later.
73s.

-Mike.

ps: STAY AWAY FROM POWER LINES!
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SWMAN
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« Reply #8 on: August 09, 2010, 05:34:31 PM »

 Thanks guys for the good info as usual. I think that as long as I already have the coax already there, I will use one coax for 40 and the other for 20. I also have an
A-99 tuned for 10 on a 3rd coax. Thanks again and 73. Jim. KF5HRN
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