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Author Topic: INDOOR VHF/UHF ANTENNA  (Read 1656 times)
N9LCD
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Posts: 166




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« on: February 19, 2012, 01:24:29 PM »

HELP!

I've been through two attempts with professionals to install at least a minimal antenna installation with proper lightning protection on the house.  Both attempts were ultimately torpedoed by rapidly escalating budgets because:

1.  The house wasn't built as drawn by the architect.

2.  The best point for cable entry into the house and lightning protection is next to the gas meter.

3.  You need a 60 foot ladder at about a 75 degree angle to reach the roof

4.  There is no attic.

Those are the major complications.  There's at least six or eight minor ones.

I'd like to keep it fast, simple and CHEAP.

I've been thinking of using a mobile, multi-band VHF/UHF antenna sitting on a metal ground plane on a broad window sill.  The inside of the window frame is wood.  The outside is aluminum clad.  There is a steel lintel above the window.

QUESTION:  What could happen to my transmitted signal under those conditions?  How might the VSWR be affected?

N9LCD

 Huh   
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KI4SDY
Member

Posts: 1452




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« Reply #1 on: February 19, 2012, 01:31:53 PM »

Why don't you just build a VHF/UHF SO239 ground plane antenna for less than $5.00 out of 12AWG copper wire? It will perform very well. It will be small, light weight and allow you to try different locations for the best results. Instructions are all over eHam.net and the internet!  Grin
« Last Edit: February 19, 2012, 01:42:18 PM by KI4SDY » Logged
WB6BYU
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Posts: 13029




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« Reply #2 on: February 19, 2012, 01:51:37 PM »

First question - what size is the window?  That makes a big difference.  In some cases
the metal framing may be resonant.  You also

My current UHF base antenna is a wire ground plane stuck hanging on the office window
from a suction cup.  But the, I have 4' x 6' windows to work with, and could manage
various sorts of 2m antennas on them as well.  (And with a 100-year-old farm house
there are no architectural drawings to work from.)

If you have aluminum siding on your house, getting the antenna near (or outside) a
window is probably the best approach.

I just wrote an article on window antennas for the local ARES newsletter, and it
might show up on the internet some day...

One approach I'd consider is mounting the antenna outside a window - I've seen this
done in apartments, townhouses, etc.  For example, if you can lean out the window
and install a 6" square wood plate against the siding,  window, or whatever, you can
mount a plumbing floor flange to it with a pipe sticking out horizontally, then use
further standard fittings to mount an antenna.  A good choice at that point would be
some sort of side-mount dipole, though they aren't as commonly available commercially
for multi-band use.  For example, a half wave dipole for 2m with a couple parallel
elements would cover both 2m and 440, and other combinations can be invented
depending on the bands you want to work.

You probably don't have to worry much about lightening protection if the antenna is
below the peak of the roof, though I'd try to choose a high window for best coverage.
(And one facing the most important direction.)

Any chance  you can reach the eaves of the house with a ladder and/or long pole
sticking out  top-floor window?  You might be able to find a nail or install a hook
to hang various antennas from that, like a J-pole or ground plane.


There are too many variables to predict the actual SWR and/or radiation pattern, so the
best approach is probably to try it and see.  I'd suggest starting with one of the shorter
antennas - like a 1/4 wave 2m whip with an extra coil for 440.   You can put it on a
cookie sheet or strip of galvanized flashing and set it on the sill of various windows
and see how it works.  In fact, you might even stick it to the steel lintel upside down
(with the coax dressed off away from the radiating element.)
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N0AZZ
Member

Posts: 241




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« Reply #3 on: February 20, 2012, 03:33:55 AM »

I just finished installing some attic mounted antennas for emergency's, outside I have 12 in the air now and 3 towers. The 3 that I mounted were for 6/2/432m all were M2 Loops you can see them on there web site. They are stacked and can be used mobile also with the mount and really are foe SSB and Digital but work fine on FM also in my attic they still give me a 200mi range on 2/6m SSB no problem with just the 100w out of my radio this is ground wave only. All mounted on the mobile mast stacked it is about 5 1/2' tall and the largest loop 6m is about 30" these are square loops 2m 12", 432 5". They could be mounted anywhere you wish from inside to outside the higher and in the open the better. These are quality antennas in every way I have several of them from a 33 1/2 ' boom 2m yagi, 24' 6m yagi.
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