[TowerTalk] 80M attic loop

[Bill Turner]

On Wed, 3 Sep 2003 16:51:36 EDT, Dinsterdog at aol.com wrote:

>Thinking of putting up a 80M attic loop.  Just want to cover the DX windows 
>from 3.500-3.800MHz.  Can anyone suggest a design?......I plan on running my 
>Alpha 99 with it- Curious as to what the 2:1 band width might be as I want to 
>avoid a tuner and also if any thing can be done to make the angle more favorable 
>for DX

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Firstly, I don't think this belongs on TowerTalk since no tower is
involved.  But since you asked...

I did that once years ago and it worked pretty well.  Make the loop as
large as possible (run part of it outside the attic if you can) and
spend some time getting the matching network right.  

You can't avoid a tuner of some kind - maybe not a "real" tuner, but
some kind of matching network will be needed.  No loop, big or small,
resonant or nonresonant will be 50 ohms of pure radiation resistance.
The laws of physics are agin' you.

As a rule, the smaller the loop, the narrower the bandwidth.  There
are so many variables, it's hard to say what the bandwidth will be.
Count on it being small and you probably won't be disappointed.  If
the bandwidth is suspiciously high, look for some unexpected loss
somewhere.

The DX angle is mostly a function of height above ground.  If you want
to try some manipulation of that and other factors, download a copy of
EZNEC and try them out.

Have fun!

-- 
Bill, W7TI