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Author Topic: J-pole or Ground plane in the Attic?  (Read 7488 times)
KD0PBO
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Posts: 67




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« on: December 11, 2011, 09:40:25 PM »

I've been looking at getting either an Arrow brand j-pole or ground plane antenna to place in my attic so I can set up a simple 2m base using my mobile rig. So my question is this; What would radiate better from the attic?? J-pole or Ground plane? Also any tips on running coax down from the attic to the shack, or in my case my bedroom?

Short. Sweet. To the point.  Grin

Thanks,
KD0PBO
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ONAIR
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Posts: 1735




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« Reply #1 on: December 12, 2011, 11:37:54 AM »

I've been looking at getting either an Arrow brand j-pole or ground plane antenna to place in my attic so I can set up a simple 2m base using my mobile rig. So my question is this; What would radiate better from the attic?? J-pole or Ground plane? Also any tips on running coax down from the attic to the shack, or in my case my bedroom?

Short. Sweet. To the point.  Grin

Thanks,
KD0PBO
  I used to run a home brew 2 meter ground plane in my attic with very good results!  You might want to try making one before you make a purchase.  Any chance of getting an antenna up outside your home or on the roof?
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WB6BYU
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Posts: 13028




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« Reply #2 on: December 12, 2011, 12:41:32 PM »

Theoretically both antennas are virtually the same performance (especially if the ground plane
radials are sloping downwards.)  So my answer would be, "which ever is easier for you to build."

In practice both antennas are prone to common mode currents on the feedline, so actual
behavior will depend on a number of factors including the length of the coax and what is
attached to the shield at the far end (including power supply ground cables, etc.)  I've had
good luck with a ground plane design that was supposed to reduce common mode currents
(18" whip with 24" radials):  I haven't actually confirmed that it works any better, but it
allows me to cut two whips out of a 36" length of brazing rod.


How to get the coax to your shack?  I just made a small hole in the ceiling and ran it down
to the rig.   Dropping it into a closet and then through a wall plate looks a little nicer.
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W7ETA
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Posts: 2528




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« Reply #3 on: December 12, 2011, 04:28:22 PM »

Making a gp using an chassis mount for a PL259 is easy.

You can use the same connector to make a dipole.

73
Bob
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KD0PBO
Member

Posts: 67




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« Reply #4 on: December 12, 2011, 06:41:17 PM »

  I used to run a home brew 2 meter ground plane in my attic with very good results!  You might want to try making one before you make a purchase.  Any chance of getting an antenna up outside your home or on the roof?
[/quote]

I've thought of making a homebrew to add with my 2m 2el yagi I constructed on a day off awhile back. I was satisfied with my results with that so a J or GP wouldn't be too difficult. My only grief about homebrew is finding the time to make it. I haven't had too many days off with Christmas coming up (work in retail!  Roll Eyes) so spending the $40 on a new antenna is more of a plus for me than a drawback. There is a chance of putting something up on a chimney pole but the neighbors already seem a bit annoyed with my procupine of a truck sitting in the driveway.  Undecided

KD0PBO
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NA4IT
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« Reply #5 on: December 12, 2011, 08:18:25 PM »

Here is a little ground plane (dual band) you can build...
http://www.qsl.net/na4it/dbgp.html

de NA4IT
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ONAIR
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Posts: 1735




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« Reply #6 on: December 13, 2011, 11:01:04 AM »

  I used to run a home brew 2 meter ground plane in my attic with very good results!  You might want to try making one before you make a purchase.  Any chance of getting an antenna up outside your home or on the roof?

I've thought of making a homebrew to add with my 2m 2el yagi I constructed on a day off awhile back. I was satisfied with my results with that so a J or GP wouldn't be too difficult. My only grief about homebrew is finding the time to make it. I haven't had too many days off with Christmas coming up (work in retail!  Roll Eyes) so spending the $40 on a new antenna is more of a plus for me than a drawback. There is a chance of putting something up on a chimney pole but the neighbors already seem a bit annoyed with my procupine of a truck sitting in the driveway.  Undecided

KD0PBO
[/quote]    It's usually pretty easy to hide a 2 Meter or 440 Jpole or ground plane outside.  Stick it inside a PVC pipe, an upside down bucket, a flower pot disguised as a plant, a "flag pole", etc!  The sky's the limit.  Never let those evil neighbors win!!!  Smiley
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W7ETA
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Posts: 2528




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« Reply #7 on: December 13, 2011, 09:32:11 PM »

You can cut and strip the wire, wrap it thru the 4 pre drilled holes on the SO239 while you sit on the john.

73
Bob
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KA5N
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Posts: 4380




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« Reply #8 on: December 14, 2011, 07:28:11 AM »



 There is a chance of putting something up on a chimney pole but the neighbors already seem a bit annoyed with my procupine of a truck sitting in the driveway.  Undecided

KD0PBO
[/quote]

Do your neighbors pay your rent or utilities bills?  A 2 meter gp is paractically invisible.  Of course if
they are so finicky you might put a tail on the gp and tell you neighbor kids flew their kite onto your
roof and you just haven't gotten around to removing it.

Allen
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ONAIR
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Posts: 1735




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« Reply #9 on: December 14, 2011, 07:35:35 AM »

Ventenna?
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N4NLQ
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Posts: 55




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« Reply #10 on: December 16, 2011, 06:14:31 PM »

Ventenna?

Mounting antennas on your plumbing vent pipe is not a good idea.  Antennas will move a bit in the wind which makes the pipe move also.  The pipe's movement can loosen the seal that keeps the rain out and your roof may start leaking.

If your house wiring is done in the attic and not the basement, you have a way to drop your coax into almost any room.  Since interior walls are not usually insulated, you have hollow spaces in which to run wire.  Pick a wall outlet you want your coax routed to and TURN OFF THE BREAKER.  Drop your coax down the hole in the header plate next to the house wire and fish it out beside the outlet box.  If the outlet is hidden behind furniture, just snap a corner off the cover to allow the cable to exit the wall beside the box.  If the outlet is in plain sight, move to the other side of the hollow space, cut a hole in the drywall and set a new box.

Hope this helps.

Allan - N4NLQ
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N7TEE
Member

Posts: 39




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« Reply #11 on: December 17, 2011, 02:29:30 PM »

Rather than running the coax down the wiring hole I would drill another hole one stud on either side of the house wiring.  That way you will not take any of the insulation off the wire where it goes through the header.  That way you could make it three quarters of an inch and drop the fitting and all down rather than just the coax.

Dave
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K9MHZ
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Posts: 393




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« Reply #12 on: December 19, 2011, 06:50:51 PM »

All good suggestions above!

Say I'm wondering though, do yo have any height to work with in your attic?  Even a modest gain commercial antenna won't be very big, but will provide quite a bit more performance than a ground plane.

I think HRO has a nice antenna comparison page in their catalog.  (No, I don't work for them)

FWIW,

Brad, K9MHZ

 
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ONAIR
Member

Posts: 1735




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« Reply #13 on: December 20, 2011, 09:28:00 AM »

  You may want to look at the Jetstream JBT2 or JBT3 antennas.  Heard some really great reports about them, and I think they are only around 50 or 60 bucks!
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KD0PBO
Member

Posts: 67




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« Reply #14 on: December 20, 2011, 12:22:40 PM »

Say I'm wondering though, do yo have any height to work with in your attic?  Even a modest gain commercial antenna won't be very big, but will provide quite a bit more performance than a ground plane.

Brad,
At the peak I've got at least 6ft. Thats not an exact measurement but a good guess since when I go up during the spring to uncover and hook up the attic fan I can stand no problem and I'm 5'6". Plenty of room to mount a 5/8 wave 2m Wink

I actually just got an Arrow Jpole in the mail today from HRO as a surprise gift for Christmas so I guess my mind was made up for me! Haha!

73 fellas
KD0PBO
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