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Author Topic: Indoor Antenna Question  (Read 1975 times)
KA4NMA
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Posts: 354




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« on: August 19, 2012, 08:47:17 PM »

Here are some choices for some antennas for my bedroom shack.  I would like 75m-6m coverage if possible.  All antenna's will be either direct connect or ladderline to a sgc239  75m, 40m, state nets, other bands for fun, dx and 'got to get on the air'.
 
Voice, digital, winmore/w2lk, fldigi, nbems...

1. Brass slinky dipole stretched out to about 7-10 ft per leg
2. Random loop made out of speaker wires with both  conductors connected together for Fat wire
3. Same as #2 but connections crossed to make 2 turn loop
4. Window ladder line loop, with second wire using linear loading.
4. Window ladder line loop with wires connected as in 2
5 Window ladder line loop with wires connected as in 3

Should the antennas be mounted horizontal on the ceiling or vertical on the wall?
Before you ask, No way to have outside antennas at this time. I live on the front of duplex by the main street and no nearby trees.

All loops would be the same size - as much room as I can get up.  

Randy ka4nma
ka4nma@arrl.net

PS I know that wiring, ducts, building materials will affect the antenna. I am looking for best guess, ideas, etc when all thevariables are kept the same.
« Last Edit: August 19, 2012, 08:58:23 PM by KA4NMA » Logged
K7KBN
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Posts: 2825




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« Reply #1 on: August 19, 2012, 08:55:01 PM »

One word: experiment.
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73
Pat K7KBN
CWO4 USNR Ret.
KA4NMA
Member

Posts: 354




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« Reply #2 on: August 19, 2012, 09:00:15 PM »

Do to physical limits, it is hard to experement.  I want to experement  but want to try what the gurus consider the better.
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WB6BYU
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Posts: 13458




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« Reply #3 on: August 19, 2012, 09:12:44 PM »

It will depend on the dimensions you have available.  A vertical loop (option #2) should
cover some bands.  A wire dipole tacked to the ceiling, as long as possible with the ends
bent around, may be better on others.

You might consider drilling small holes through the tops of the walls to pass a wire
from one room to the next to allow you to make the antenna larger.

One thing I would recommend is a switch in the ladder line so you can toggle between
two antennas and compare them.  You may find, for example, that a dipole with
loading coils works better on the lower bands, but the vertical loop is better on the
higher ones.


I tried a number of creative indoor antennas in one apartment, and none of them
really worked very well at all.  I ended up running an invisible wire down the roof
and dropped it over the side into my window, and it worked much better.
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KC9Q
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Posts: 49




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« Reply #4 on: August 20, 2012, 05:08:56 AM »

SGC did a bang-up job on the subject.  It's covered in Chapter 6 of this manual:  http://www.sgcworld.com/Publications/Books/stealthbook.pdf.  Don't know if there are units above or below yours, but if there are then I would probably use an outside wall and mount the loop vertically.

73,
Mike
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W5WSS
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Posts: 1772




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« Reply #5 on: August 20, 2012, 08:03:16 AM »

Hello, I have made and experimented with the various indoor types that you described. I have two that worked better, I suppose one could say better with resect to the precise mutual coupling of other conductors an ever changing mixture dependant upon too many variables and antenna type etc but this must be empirically worked. What worked better for me may not for you. In my case The specific height above ground from the ceiling installation is apx 18ft. A horizontally oriented rectangle shape 15ft X 30ft installed at the top of the interior wall to ceiling junction pressed into multi band service worked as good as a quadrant doublet( half of the rectangle). In my case i used a 5ft very short and routed perfectly straight and stood off the wall by 4" length of 300 ohm transmission line connected to a wide range T-match tuner with an internal 1:1 current balun Remember though that the horizontal oriented antenna family of antennas are height sensitive so the dx skywave that arrives at low angles is affected, attenuated etc. closer skywave modes are more compatible with a low percentage of wavelength height above ground.With higher frequency use in mind I built a doublet where one leg dropped downward vertically while the other leg was held in horizontal orientation using the same feedline and tuner etc this antenna was about 15x15ft I center fed it at the junction which I purposely located atop at the ceiling and pressed into multi band service from 17m and up to 10m worked better for lower angle longer dx skywave than the horizontal versions compared from 17m to 10m respectively.
A vertical such as a Hustler mo-1 mast and resonator can fit the usually 8ft space from floor to ceiling I inverted one and placed 4 insulated wire radials on the ceiling mounted to Teflon standoffs the antenna was upside down and the radiation did act as though it was horizontally oriented but the radials were out of the way anyway that approach I condidered to work ok but the horizontal doublets were better with vertical radiation as a design parameter, turning the antenna rightside up and from the antenna base one could place the radials along the floor and probably have a much lower take off angle but I would not install one because of safety and fire potential. All my indoor antenna endeavors were used with very low power not exceeding 20 watts pep. and urge you to be aware of the high potential voltage that can manifest on a radial set, at higher legal power levels be very careful.
Good luck and hope you are successful in your efforts. 73
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KF6RDN
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Posts: 39




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« Reply #6 on: August 20, 2012, 02:00:39 PM »

I'm in a condo, the only antenna I've ever been able to make contacts from inside is a magloop.  Both homebrew and the MFJ versions.

Hit teh googles for info on it, there is plenty out there.
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KA4NMA
Member

Posts: 354




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« Reply #7 on: August 21, 2012, 05:26:22 PM »

First I mentioned the wrong tuner. It will be an SGC 237.   The total loop length will be about 554- ft depending on how I run it.

ka4nma
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