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Author Topic: Indoors 2 mtr. ant. ideas?  (Read 376 times)
KY7R
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Posts: 5




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« on: January 01, 2008, 11:29:05 PM »

I need the most efficient indoor ant. for abt. 146.7 mhz? Tnx alot,ans pse.  from Gary C
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ONAIR
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Posts: 1747




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« Reply #1 on: January 01, 2008, 11:44:02 PM »

    2 meter antennas are relatively small!  You can easily stick a mag moint on top of an air conditioner, or make a coaxial bazooka dipole and hang it out a window.  Lots of ways to make it stealthy too.
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W7ETA
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« Reply #2 on: January 02, 2008, 12:01:39 AM »

Efficient?  Wattage in vrs wattage radiated?

Can't beat a dipole.

73
Bob
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VA7CPC
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« Reply #3 on: January 02, 2008, 02:44:50 AM »

I agree with Bob.

Two wires, each 19.25" long, taped to a wall or window (vertically oriented if you're working FM), makes a decent 2m antenna.  Fairly inconspicuous.   Works fine if there's no metal in the wall.

Or, two lengths of self-adhesive copper foil (available in craft shops) for a "more professional" look.

Do you need a "gain antenna"?  If so, you'll be looking at collinear verticals.

   Charles
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KB9CRY
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« Reply #4 on: January 02, 2008, 03:45:33 AM »

Minimum 6 element yagi beam mounted on a camera tripod in the middle of the living room.
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WA3SKN
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« Reply #5 on: January 02, 2008, 04:33:02 AM »

"the most efficient indoor ant."... probably a dipole made from copper pipe. (power out / power in x 100).
But, your terminology is probably off... did you mean the most gain? Just how much room is available?

-Mike.
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N1LO
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« Reply #6 on: January 02, 2008, 05:48:56 AM »

Hello Gary,

 What antenna are you using now?
 Do you want to build or buy?
 Who are you trying to communicate with: repeater, simplex, and distance ?

Mark
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AC5E
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Posts: 3585




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« Reply #7 on: January 02, 2008, 07:51:38 AM »

Yes, the most efficient antenna is a resonant dipole with large (low RF resistance) conductors. Such an antenna usually radiates more than 98 percent of the RF power applied.

"Gain" antennas are usually much less efficient because they use re-radiation and cancellation to "beam" more signal in a specific direction. Canceled radiation is lost energy. Of course, a dipole in a dish can be very efficient and very directional but that's another story.

But you left the most important part of the question out. What do you want to do with your indoor 2M antenna?

73  Pete Allen  AC5E
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AC5UP
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« Reply #8 on: January 02, 2008, 01:49:18 PM »

Here's something to consider...

Remember the thread about using an incandescent lamp as an HF antenna? Sure, you were concerned about variations in the load resistance and the challenges that might present to the finals with an amplitude modulated mode like SSB, but... In this thread we're talking steady carrier FM. Aren't we?

Near constant voltage, near constant current independent of the modulation.

Hmmmmmmmmm.

Let's take this a step further. Visit any home handy guy store and in the lighting section you'll find a nice assortment of both incandescent and compact fluorescent lamps. Read the packaging on the CFL's and you'll find that a 15 watt fluorescent produces about as much light as a 60 watt incandescent lamp. That's a 4:1 ratio or 6 dB worth of lumen gain. A full optical S-Unit for the same input power - and - it's omnidirectional.

Apply the same theory to this situation and I'm thinking a nice, big, chubby CFL on a stick wired to the 2-Meter rig could be the ticket to many, many illuminating Q's.

Wink
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Never change a password on a Friday                
N5YPJ
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Posts: 642




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« Reply #9 on: January 02, 2008, 02:10:14 PM »

Hmmm. I might be wrong on this one but nobody has mentioned anything about RF exposure risks to the folks in the room / apt. / house.
Years ago I used a 2 el. quad built inside 1/2" PVC pipe. After later reading about rf exposure concerns I hung it out the window when qsoing.
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AC5E
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« Reply #10 on: January 02, 2008, 02:21:12 PM »

Chuckle: The problem with using a CFL as a dummy load is the stepup transformer built into the base. According to the General, this 100 Watt equivalent GE's impedance at 3.75 mHz is more than 4,000 ohms. It would take some pretty fancy matching to light that bulb up.

73  Pete Allen  AC5E
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KE4DRN
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Posts: 3734




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« Reply #11 on: January 02, 2008, 06:20:11 PM »

hi gary,

take a look at this 2m antenna, the half square
you can build it for a few dollars worth of pvc pipe
and use #14 or #12 copper wire, direct fed with coax.

hang it on the wall or put it in the attic.
it is directional and has gain over a dipole.

http://www.cebik.com/vhf/hs.html

73 james
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K9YLI
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Posts: 876




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« Reply #12 on: January 03, 2008, 06:34:28 AM »

look up his call sign.  explainesd a few things. .
where  the antenna will be, restrictions. etc.
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