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Author Topic: Apartment Antenna  (Read 2595 times)

Posts: 537

« on: December 27, 2011, 12:44:17 AM »

I just moved to an apartment with no place for an outside antenna.  I can run a 40-46 ft loop around by bedroom ceiling to a SGC 237 antenna coupler.  I am interested on dx on 20m-6m and state nets on 75m and 40m.  How will this antenna perform?  Any length of 40-50 ft  better than others?

What is the best way to mount it? Thumbtacks, tape, other?

Randy ka4nma

Posts: 2100

« Reply #1 on: December 27, 2011, 01:53:10 AM »

       You will probably get several speculative answers about performance with this type of indoor antenna ,there are just too many unknown variables (type of building construction,location,wall wiring,ect.,ect.)The only true answer to its performance will be to put it up,experiment with length/coupler combinations and see what works best for your bands of interest.As for hangers ( permanent/removable ) I just use small white screw in cup holders(small holes fill in easy with a dab of paint).Experiment and learn.        Jim

Posts: 7718

« Reply #2 on: December 27, 2011, 05:20:46 AM »

That's not much room for a 75 meter antenna. Fortunately the MFJ 936B loop tuner will do it.

Posts: 17476

« Reply #3 on: December 27, 2011, 06:59:22 AM »

I've mounted antennas to my ceiling using thumbtacks before.  I'd actually recommend using
a short insulator to allow the antenna to hang an inch or so away from the wall - this might be
a piece of string, dental floss, or a strip cut from a plastic milk carton.  White or clear push-pins
are unobtrusive, but just about anything will work if aesthetics aren't an issue.

On 15m - 10m a loop of the size your propose will have maximum radiation straight up, which isn't
very useful since the ionosphere won't reflect such signals back to Earth.  A vertical loop, or
a dipole across the ceiling, is probably a better option on those bands.  On 20m the loop will
be less than one wavelength and will act like a dipole anyway with maximum current in the
portion opposite the feedpoint.  On 6m the loop (at least in free space) is close to 2 wavelengths
in circumference and becomes useful for low angle radiation.

If you are on the first or second floor, height is probably most important, so a dipole across
the ceiling may be the best approach.  On higher floors a loop against the wall may work better
when fed in the bottom center - that's because the bottom wire is further off the ground and
doesn't detract as much from the radiation from the top wire.  A vertical loop that is resonant
around 15m (which will probably require running around two sides of the room if your ceiling
height is lower than the room width) would give mostly broadside radiation on 20m through
10m but probably won't work well on 6m.  (Vertical polarization may work better if you are
on the bottom floor.)

40m and 80m operation will be difficult on such a short loop, and would be better if the loop
were vertical rather than horizontal.  While I'd generally recommend thin wire for the higher
bands, you'll want fatter wire on 40 and especially 80m to reduce losses with the high
currents required to radiate any sort of power in such a small antenna.

You might be able to extend your loop by drilling holes through the tops of the walls and
passing the wire through.  You can pass a drinking straw through the hole and then thread
the wire through it.  With some care you may be able to make a loop the size of the whole
apartment, which would improve performance on 40m at least.

And, having tried such things, I can report that none of them worked very well.  It does,
of course, depend on the building materials used:  stucco has a layer of metal mesh like
chicken wire that isn't particularly transparent to RF, as do some plaster walls.  And
coupling to the electrical wiring in the building makes any antenna difficult to predict.
But give it a try - you may have to experiment with a number of shapes and configurations
to find something that works for you.

Posts: 537

« Reply #4 on: December 27, 2011, 08:30:07 AM »

The walls are to thick to drill holes to extend the antenna size.  The room is about 12x11 ft, located on the ground floor.  Any other antenna suggestions?  I will be using a SGC 237 antenna tuner with the antenna.

Randy ka4nma

Posts: 3591

« Reply #5 on: December 27, 2011, 08:47:39 AM »

The walls are to thick to drill holes to extend the antenna size.  The room is about 12x11 ft, located on the ground floor.  Any other antenna suggestions?  I will be using a SGC 237 antenna tuner with the antenna.

Randy ka4nma
      Screwdriver antenna, mounted on an air conditioner or metal plate?  Something you can put out your window and bring back in after use?

Posts: 5480


« Reply #6 on: December 27, 2011, 09:05:55 AM »

Any other antenna suggestions?

Just about anything outside will work better than just about anything inside.

Your issue isn't an antenna problem, it's a location problem.  Even if you could fit a yagi in the room it would still be an indoor antenna and subject to lots of problems.  A poor antenna in a great location is better than a great antenna in a poor location.  When you dabble with indoor antennas, you get what you get and I can't think of any antenna that will make up for that.

The only way to know is to try something, anything.  You might get lucky and it will work OK, but that is more a matter of luck than skill or methodology.

Mark K5LXP
Albuquerque, NM
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