[TowerTalk] VERY simple 40m antenna help

[corneliuspaul@gmx.net]

Hello Herb,

as Tom already pointed out, a vertical is what best fits your description
and very easy to make. For 40m it is about 30 foot high.
Your 20 foot pole is a bit too short, but you can easily put a little fiber 
glass (fishing) rod on top to make it about 30 foot overall length. 
Connect a wire to the top of the metal pole and run it up the fiberglas rod.
If you dont want to do this, try top loading your 20foot pole. That means,
connect at least 2   10foot wires to the top of the 20foot pole and let
them slope
at an angle of 45 degrees or more (angle between the wires and 20ft pole).
attach the rope to these wires thru an isolator as the end of the wires
will carry high voltage!! be careful so nobody can touch them!!
In either way, you can control the resonant frequency of this antenna by
cutting the wire(s) to the proper length. If the antenna resonates too high
in frequency your wires are too short. if it resonates too low, they are too 
long. how do you find the resonance? use a swr meter and your 100w transmitter
at 5w output and tune for best swr --> there is the resonance. anyway,
with the approx dimension given in the text above you even dont need to
worry about
the exact resonance, just use a tuner and you are fine.

here comes an important point: you need to isolate the base of the 20ft pole 
from your chimney mount. for a quick-and-dirty  approach, just wrap several
layers of plastic foil/tape around the pole before you install it into the
chimney mount. no high voltage at this point, so the plastic will be
sufficient.

About the radials: although 30 radials are fine, you will already have a
good signal
with 10-15. Add as many more as you like. Dont worry about exact length,
cut them to 21meters length and run them out from the base point of the
20ft pole.
If the roof is not flat, but slopes down, thats ok too. This will give the
antenna a higher radiaton angle but still low enough. It also increases
the impedance of the antenna, which normally is around 35 ohms. With the
sloping
radials you might end up with 50 ohms, so you have a 1:1 SWR to smile about.

Connect all the radials together at the base point of the antenna. Connect
them 
directly to the outer sleeve of the coax cable. Connect the inner wire directly
to the (isolated!!) pole. Put some waterproofing around this connection so no
water leaks into the coax cable.

Have Fun! CU in the CQWW Contest!!
This antenna will work the whole world if the propagations are at least
regular.

73 Con DF4SA 
(hopefully to be CS7T in the Contest)







At 16:25 13.11.01 +0000, you wrote:
>
>Hello all,
>
>First of all, I have absolutly no experience building antennas. I tried 
>making a dipole once, but it never really worked. I would like to put 
>something up for the CQ World Wide Contest coming up. I will only be able to 
>operate at night, so it will have to be a 40 meter antenna. Im looking for 
>some advice on what type of antenna would be very simple to build and put 
>up, that will be effective on my very small city lot. I know I probably wont 
>work all the long haul stuff, but if I can work most things that I can hear, 
>and work some stations from Japan, that would be great. I have a 20 foot 
>metal pole that I can put on a chimney mount, and can probably get my hands 
>on a tuner. I also have an SB-200 (120v)that will give me maybe 300w. Any 
>help would be great, as I will use it to learn, and possibly become more 
>confident in building my own antennas.
>
>Thank You..
>
>

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