STEVE,

The Random Wire Antenna using a Magnetic Longwire Balun
(MLB) a 9:1 Un-Un "Matching Transformer" and Coax Cable
Feed-in-Line on the Roof will work OK.

Here are a few ready-made 9:1 MLBs:
- Palomar Magnetic Longwire Balun
http://www.palomar-engineers.com/MLB-1/mlb-1.html
- RF-Systems Magnetischer Langdraht Balun (MLB)
http://www.thiecom.de/mlb.htm
http://www.universal-radio.com/catalog/antsup/1484.html
- Universal Magnetic Balun UMB (9:1) by Wellbrook
http://www.wellbrook.uk.com/UMB.html
- WinRadio Long Wire Adapter (BNC Connector)
http://www.winradio.com/home/lwa.htm
- ICE-180A/182A Matching Transformers for Random/Longwire/Beverage
http://www.arraysolutions.com/Products/ice/reconly.html#Beverage%20Matching
http://www.arraysolutions.com/Products/ice/1.html
Here is some reading on the "Magnetic Longwire Balun"
- 'Not Really a Balun' by John Doty
http://www.hard-core-dx.com/nordicdx...d/magbal2.html


Here are a few things to consider before you start building:
- First take a 'portable' SW Radio and Check around the
Top of the Roof for any 'noise' generating sources. Place
your Antenna away from these 'noisy' areas.
- Try to locate a good Grounding Point on the Roof to
use as your Antenna's Ground. Must large/tall buildings
with Flat Roofs have some metal object/pipe/panel that
is a good ground.
- In general buildings have an RFI/EMF "Noise" Envelop
that can extend for several feet from the building. So
your idea of having the Wire Antenna Element above the
Top of the Roof is good. Do It !

The SHAPE of your Antenna:
- Run the Wire Antenna Element near the center of the
Roof so it can not be seen from the street.
- Run the Wire Antenna Element along the Side of the
Roof so that it is out of the way. This can be End-Fed
or Off-Center-Fed like a Windom Antenna.
- You may wish/need to run your Wire Antenna Element
along one side of the Roof and then turn a Corner and
along the another side of the Roof to make it longer.
- You can also start at a corner and use a single
Antenna Wire Element that runs out along two sides of
the Roof at a 90 Degree angle. These two legs do not
have to be the same length and are like a bent Windom
Antenna.

What To Do - When You Start Building:
- Plan, Located, Meassure and Draw-Out your Antenna,
Ground and Coax Feed-in-Line System.
- Establish the Antenna, Ground and Coax "Junction Point".
- Establish your Roof Top "Grounding Point" and Ground Wire.
- Establish your Antenna Supports. Consider using two
or more pieces of 1.5" x 10 Ft PVC Pipe as 'supports'
for your Wire Antenna Element and Rig the wire between
them.
- Route your Coax Cable from your Radio Shack to the
Roof and over-to the MLB Location that your have
established. This is the Junction of the Coax, Ground
Wire and Wire Antenna Element.
- Mount your MLB at the Junction Point usually about
One Foot above the Roof's Surface.
- Connect your Ground Wire to the MLB.
- Connect Your Coax Cable to the MLB.
- Route your Wire Antenna element and Connect it to the MLB.
Go down to your RadioShack and Connect the Coax Cable to
your Radio.
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REMEMBER: "The AM/MW and Shortwave Antenna is 55.5% . . .
of the Radio/Receiver and Antenna/Ground Reception Equation"
http://groups.yahoo.com/group/Shortw...na/message/288
A Shortwave Antenna is "Equally" Important for Good Reception [.]
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iane ~ RHF
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Some Say: On A Clear Day You Can See Forever.
http://groups.yahoo.com/group/Shortw...na/message/502
I BELIEVE: On A Clear Night . . .
You Can Hear Forever and Beyond - The Beyond !
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= = = *m (Steve) wrote in message
= = = . com...

When people talk about the 'clearance' of an antenna,
they seem to mean how high the antenna is suspended above
the earth and surrounding objects. It also seems to be
agreed that, at least with most types of antennas, the more
clearance you have, the better.

If I were going to put a random wire antenna on the roof
of my five story building, would the elevation resulting
from its rooftop location be a plus even it's only six
or seven feet above the rooftop itself (assuming there's
not a lot of rfi up there from power lines, the apartments
below, etc.)?

Second question: I'm thinking the random wire should
attach to a balun which should then attach to a coax
feedline. (My understanding is that, if the wire isn't
cut for a particular band, I'll need to use either a
balun or a tuner-- and it would be nice to avoid having
to fiddle with a tuner all the time.) But how does one
determine what sort of balun to use? For example, how
does one decide whether to use a 4:1 vs a 9:1 balun?
Can anyone recommend a particular balun that they've
found to work well with a random wire antenna?

Thanks, Steve
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