Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Attic antenna idea's for HT to reduce lighting ris  (Read 614 times)
KD5OMC
Member

Posts: 7




Ignore
« on: January 16, 2003, 10:08:39 AM »

I am looking for ideas on an antenna I can build to place in my attic, to improve RX/TX on a Kenwood TH-G71. (5W output)  I currently have a cushcraft AR-270 dual band mounted on my roof that I use for base station operations, but when thunder storms approach I always disconnect the feed line on the outside of the house, leaving me with only the rubber duckie antenna on the HT.   I can usually hit the 2 repeaters that I use during skywarn nets while im outside, but while inside the house its a stretch.

So I guess this is a two fold question.  

1. What is a good antenna that I can build for the HT and mount in the attic to improve performace over the rubber duckie?   J-pole, ground plane?

2. How much safer (aware that the risk is still present) is an attic mounted antenna over the roof mounted antenna during times of high lightning?

Another thought that just occured to me.  I also have a Kenwood D-700 in my truck.   Would it be possible to use the repeater function of that radio to TX/RX to and from net control using the HT inside the house?   (just a thought)

All suggestions and comments welcome.

Thanks
Tim - KD5OMC
Logged
N8VCL
Member

Posts: 15




Ignore
« Reply #1 on: January 16, 2003, 12:09:06 PM »

Lightning stikes the highest object.  It is not attracted to antennae.  So if your vertical isn't above all the trees and other buildings in the immediate area, you should be OK.

You could use the RPT function on your mobile, but that would kill your battery, no?

FWIW
Scott
Logged
WB6BYU
Member

Posts: 13027




Ignore
« Reply #2 on: January 16, 2003, 04:07:15 PM »

I'd suggest you build a quarter wave vertical with
radials and set it on the floor of the attic - it
should still get out well enough, but there will be
enough taller things around (like the vertical on your
roof!) that the chance of a direct hit on it is very
unlikely.

Depending on the size of your attic, you can even put
yagis or quads up there if there is a specific
direction of most interest.  Because the antennas are
sheltered from the weather, quite simple construction
is adequate:  I usually use pieces of aluminum wire
stuck through holes in a piece of PVC pipe.

Just about any antenna in the attic will beat the
rubber duck.  That will allow you to maintain the same
coverage with lower power, which translates to longer
operation from the battery.  Quite a good thing in an
emergency!
Logged
KD5OMC
Member

Posts: 7




Ignore
« Reply #3 on: January 16, 2003, 04:45:14 PM »

Thanks for the ideas.   BTW, my roof mounted vertical IS the tallest thing in the near area.   There are no trees nearby, and it is mounted atop a mast that houses my weather station gear.  Even so, I think lightning will choose the shortest (best) path to ground, not necessarily the tallest object.  Both items are grounded quite well, and I'd prefer not to be holding the "mic" end of the coax should lightning decide to strike it for whatever reason...lol

Also, I figure this is a good time to learn how to construct an antenna.   There is plently of attic space to work with, so depending on suggestions I get, I might try building 2 or 3 different antenna's just for the experience and choose the one with the best results.
Logged
KE4DRN
Member

Posts: 3714




Ignore
« Reply #4 on: January 16, 2003, 10:14:36 PM »

Hi,

Here are two links for you:

http://www.softcom.net/users/kd6dks/quad.html

Quad beam antenna with drawings to help construction.

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

This is the half square, you can build it for a few dollars and use it indoors when a bad storm hits.
A wealth of info on Dr. Cebik websit.

73 james
Logged
WA4PTZ
Member

Posts: 528




Ignore
« Reply #5 on: January 17, 2003, 07:34:26 AM »

I hate to burst your bubble, but lightning does not
have to strike to destroy an object, especially if
the object is solid state electronics. Do your
homework gang, EMP.....Electromagnetic Pulse, which
is usually associated with a nuclear event is also
present in a lightning strike. Perhaps not the band-
with as the nuclear but just as destructive. This is
why so many experienced HAMS say "Disconnect and
ground all unused antennas and coax." It is also why
so many antenna switches ground the unused ports.
73 - Tim
Logged
K1RDD
Member

Posts: 213


WWW

Ignore
« Reply #6 on: January 22, 2003, 09:26:02 AM »

I have a dual band Comet with a mag mount on a 4' x 4' piece of sheet metal on the rafters of my attic floor. Although I usually use it with my 706, I have connected it to my TH-F6A and run 5w thorugh it. I always get great signal reports, both into the repeaters and on simplex.
Logged
NA4IT
Member

Posts: 870


WWW

Ignore
« Reply #7 on: January 26, 2003, 07:30:10 AM »

If you are not handy in the homebrew department, any mag mount antenna on a 19" X 19" sheet metal plate will do pretty good. If you have the height for 5/8 wave antenna, so much the better.
Logged
KB8ASO
Member

Posts: 71




Ignore
« Reply #8 on: January 26, 2003, 07:04:51 PM »

Get a mobile mag mount antenna 1/4 to 5/8 wave and stick it on the top of your refrigerator.  You may be suprised at how well it will work.  If it is still not good enough, mount it on at least a 19" X 19" piece of sheet metal in the atic.  Unless you are in an RF hole the fridge will get the job done and you will not have to climb into the atic.  I have used this type of antenna off and on for years and I get very good results.  

Randy AB9GO
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!