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Author Topic: 2 meter/ 70 cm antenna: indoor vs outdoor.  (Read 4488 times)
KG4WXP
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Posts: 165




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« on: December 16, 2012, 04:53:37 PM »

I've been using an old dual band mobile 5/8 wave magnet mount antenna for a while now... its magnetic base is in my closet about 7 feet off the floor (which means maybe 10 ft off the ground, accounting for crawlspace area). Most of it sticks up into the attic. The ground is a small metal square. With it connected to my baofeng uv-5r it seems to 'get out' about 15 miles to get into repeaters.

If I put it out on the back deck, with the base on a metal bbq grill (way more metal as ground) as ground, and with the magnetic base being about 8 feet off the ground, would it be able to work farther away, since it's outside? Or would it lose a height advantage?

Thanks!
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M6GOM
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Posts: 876




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« Reply #1 on: December 16, 2012, 05:19:22 PM »

The difference in gain from being outside compared to being indoors would outweigh the height differential. A couple of feet difference in height isn't going to be noticeable.

What is the guttering of your house made of? If it is metal then get a gutter mount for the antenna and clamp it to that. Personally I'd be inclined to get it on the roof or on the top of the gable end on a small bracket.
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KE4VVF
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Posts: 61




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« Reply #2 on: December 16, 2012, 08:03:26 PM »

2m and 70cm radio waves are attenuated by the walls/roof of your house.  Be glad you don't have aluminum siding like I do, LOL. 
You need an external antenna like a 1/4 wave ground plane or a J pole, both of which can be made to dual band.  Put this antenna as high as you can. 

Arrow Antenna sells these antennas - http://www.arrowantennas.com/osj/j-pole.html  and http://www.arrowantennas.com/gp/gp146.html

N9TAX (2way Electronix) also has a roll up dual band J Pole that might interest you.  You can haul it up into a tall nearby tree. http://www.2wayelectronix.com/Dual-band-2m-70cm-Slim-Jim-Antenna-dual-slim.htm

I don't recommend a high gain Yagi for your UV-5R.  It doesn't have good enough off frequency signal rejection and gets overloaded by erroneous signals like weather broadcasts on the 162 Mhz.  My UV-5R freaks out when attached to an antenna with 2 m gain higher than 6 dbi, but it does play well with my Jetstream JTB4 vertical.

73,
Tony KE4VVF   
« Last Edit: December 16, 2012, 08:05:46 PM by KE4VVF » Logged
K5KNE
Member

Posts: 65




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« Reply #3 on: December 16, 2012, 10:52:37 PM »

I recommend you get an outside antenna.  Houses have a lot of wiring in the attic.  It is not practical to use an inside antenna except for very local repeaters.  The higher and clear of other objects the better.  That is why hams usually have outside antennas.

Good Luck.  Walter K5KNE
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ONAIR
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Posts: 1735




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« Reply #4 on: December 16, 2012, 11:09:34 PM »

For 2 Meters or 440, you can easily home brew antennas yourself!  Check online for simple ground plane designs, and mount them on a mast or a 2x2 outside.
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K7KBN
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Posts: 2765




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« Reply #5 on: December 17, 2012, 08:42:33 PM »

I've been using an old dual band mobile 5/8 wave magnet mount antenna for a while now... its magnetic base is in my closet about 7 feet off the floor (which means maybe 10 ft off the ground, accounting for crawlspace area). Most of it sticks up into the attic. The ground is a small metal square. With it connected to my baofeng uv-5r it seems to 'get out' about 15 miles to get into repeaters.

If I put it out on the back deck, with the base on a metal bbq grill (way more metal as ground) as ground, and with the magnetic base being about 8 feet off the ground, would it be able to work farther away, since it's outside? Or would it lose a height advantage?

Thanks!

Why not try it and SEE FOR YOURSELF how much difference there might be?  And while you're at it, add a few decent size radials (1/4 wave on 2M; they should work on 70cm just fine).

In a situation like yours, nobody but YOU can answer the question of how much difference this will make, although just about any antenna outdoors will beat the same kind of antenna indoors.
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73
Pat K7KBN
CWO4 USNR Ret.
W8JX
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Posts: 5485




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« Reply #6 on: December 17, 2012, 08:56:06 PM »

I used a vertical dipole in attic for 2m made out of set of old TV rabbit ears for many years as a backup antenna during severe storms. It worked surprisingly well, it still up there 25 years later too.
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K2OWK
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Posts: 1041




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« Reply #7 on: December 17, 2012, 09:18:03 PM »

The ground plane would be made up from a Mag-mount on a paint can lid using 8 radials (4 for each band) drooped at 45 degrees and soldered to the paint can lid (as per the article in QST). It would be mounted outdoors on my roof at about 30 or so feet.

The "J" Pole would be made from the website  www.alpharubicon.com/elect/jpolejaden.htm  with the onldifferencece being instead of using copper, I would use 1/2conduitet with the joints welded. The hight and mounting would be the same as the ground plane.

I hope this helps to answer my question better?

73s

K2OWK
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WB6BYU
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Posts: 13033




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« Reply #8 on: December 17, 2012, 10:12:22 PM »

The difference between 8' and 10' is probably less important than getting it
outdoors, but that depends on the desired direction and the building material
used in the house.  If you want to work a repeater on the opposite side of
the house from your balcony, the signal has to pass through two walls instead
of one when it is outside.  If you have stucco (with a layer of chicken wire
inside), foil-lined insulation or concrete in the walls, that won't help your signal
much.

On the other hand, in directions where the antenna doesn't have to radiate
through the walls, it will work much better outside.
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KC4MOP
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Posts: 729




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« Reply #9 on: December 18, 2012, 07:47:06 AM »

AND at those VHF and UHF freqs you must watch for RF exposure a lot more closely than HF freqs.

Fred
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K0JEG
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Posts: 638




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« Reply #10 on: December 19, 2012, 06:03:39 AM »

Don't forget about a collinear vertical if you're going to the effort of putting up an outside antenna. Good gain and still omni-directional. Most are dual band 2M/70CM as well. I had one up about 20 feet at my old QTH and could hit repeaters 60+ miles away easily.
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SWMAN
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Posts: 548




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« Reply #11 on: December 19, 2012, 07:54:55 AM »

 I made a 2 meter/440 vertical dipole that W7LPN sort of designed and it works great. Real easy to make, you can google it for easy instructions. I had it inside near a window in a single story house. I put it outside in the yard only 10 feet off the ground and it works 10 times better now. About the same height outside as in the window but much better outside.
Nice , easy antenna. check it out. good luck and 73, Jim   W5JJG
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KD8NGE
Member

Posts: 35




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« Reply #12 on: December 27, 2012, 04:11:53 PM »

KE4VVF speaks truly:  the roll up J-pole can be hoisted into a tree (mine is an oak) and it's so far and away better than when it was indoors!
Height is might.  Could I hoist mine another twenty feet in the air I would.  It's up as high as it will peacefully go and does very well.
I know the roll up J-pole has come in for its share of criticism, but for my purposes it works very well indeed.
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