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Author Topic: STACKED WIRE ANTENNA QUESTION  (Read 635 times)
KC2TGP
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Posts: 12




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« on: July 29, 2010, 06:30:24 AM »

I have a G5RV running north/south over my house, and an Alpha Delta DX-CC running East/West over the house as well.  Each are fed into my shack with separate RG-8 coax, and I can switch between both antennas depending on the band and propagation.  Is there a way to join both antennas into one feed line to get the best of north/south/east/west propagation, without switching between antennas?  Is there any downside?  -  Steve  -  KC2TGP
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WX7G
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Posts: 6214




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« Reply #1 on: July 29, 2010, 06:38:53 AM »

You can build a circuit that allows the adjustment of signal amplitude and phase to each antenna. Or, it can be as simple as connecting both antennas in parallel using a TEE connector. Give it a try.
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WA3SKN
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Posts: 5526




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« Reply #2 on: July 29, 2010, 06:39:41 AM »

Keep them separate, with separate feed lines.  You will be better off.
What little directivity you have can be put to use.
73s.

-Mike.
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PD2R
Member

Posts: 131




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« Reply #3 on: July 29, 2010, 07:18:50 AM »

Or you can go the expensive way and buy a stack match like the ones WX0B makes (Array Solutions). Then you are able to switch between the two and combine them.

But like I said, that's going the expensive way...
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WB6BYU
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Posts: 13486




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« Reply #4 on: July 29, 2010, 10:57:50 AM »

The downside is that half your power goes into each antenna, so stations that are off the end of one
antenna are half as strong as they would be on the favorable antenna, while subject to QRM picked
up on the other antenna.

There are a number of other technical issues as well.  With two dipoles, simply connecting them in
parallel does NOT give an omnidirectional pattern:  you still get a standard dipole pattern with nulls,
but they are rotated in azimuth as if you had a single dipole intermediate between the two.  The
only way you can get an omnidirectional pattern is to feed the two antennas 90 degrees out of
phase - you can do this with the right feedline lengths, but that only works on one band.  With
relatively random lengths of coax (and the fact that you need a tuner for the G5RV throws an
additional random phase shift into the works) it would be difficult to predict the resulting pattern.

And that is just for dipoles - the G5RV when used on 20m or higher has a multi-lobed pattern, and
maximum radiation may not be broadside to the wire.  So now you're combining two antennas with
very different radiation patterns.


You can connect the antennas in parallel using a T connector and see what happens.  It might be
better on some signals, it may not on others.  If both antennas are 50 ohms, the result will be 25 ohms
( 2 : 1 SWR ) so you may need a tuner, but for reception there shouldn't be a problem.  If you
add a length of coax into one of the lines, the pattern likely will change.  It certainly would be a
learning experience, but might not be something that is of much advantage in actual operating.
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