Jack Bryant, W5FTB wrote:
>Item: worked AA8EB on 20-30-40; he was using 3W to an attic loop
>antenna. I think Mike would do us all a service by telling how he did
>it. He was crummy on 20, but on 30 a solid 589, and on 40 a 579.
Well Jack, since you are interested and so may others be, here's what one can
do. The credit goes to Walter Thomas, WA4KAC, for his informative paper
prepared for the FDIM QRP symposium last year in Dayton.
Put as much wire in your attic as you can run in the shape of a loop. Establish
the feedpoint as high as possible. Use heavy gauge wire to minimize losses. I am
soon to replace my smaller gauge wire with #8 speaker wire. Try to stand the
antenna wire off from the rafters at least by a few inches. I used the longer of
the two stand-offs that RS sells. I have been feeding with twinlead but will
soon replace that with window line. Use an efficient tuner.
There! Nothing unusual or tricky about it. Just the elementary stuff. I have
about 95' of wire in the loop. It tunes easily on all frequencies above 7mHz. I
have been able to work into Central Europe and Africa on 40 meters with 3 watts.
Of course, that only happens when propagation is kinder than it has been to us
lately. The loop will never perform nearly as well as an outdoor antenna, high
and clear of surrounding objects. It does allow my to get on the air from a
location where outdoor antennas are impractical. I make some nice contacts. I
have a lot of fun.
As is typical of loops, there are some deep nulls. To add some variety and
improve coverage in general with the loop, my next step will be to insert a lamp
switch at the point opposite the feedpoint. A long run of lamp cord coming
through the same hole in the ceiling as the feedline and running down to the
operating position will allow me to switch from an open to a closed loop with a
gentle tug. The open loop might not be as efficient but will have a different
pattern of radiation which might allow me to more effectively communicate with
some areas that are in the nulls of the closed loop. If you can get a bit more
wire up in your attic than I am able to hang, the open loop might perform as a
folded dipole on 80 meters.
Don't be discouraged if you are unable to put up a good outdoor antenna where
you operate. I have always wondered what attics were good for. Now I know.
One word of caution. Spouses, it appears, do not take kindly to having large
holes put into the ceilings of their homes with keyhole saws. Be sure you were
very good to your lovey on Valentines Day before proceeding to do that. Maybe
you can get around it by running out the window and back under the eaves.
72
Mike
W. Mike Hansgen AA8EB
Glouster, OH 39.498N 82.088W
102762.1311@compuserve.com
Cqrp #4 ARCI #9156 QRP-L #563
[
QRP-L Archive |
]
[
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000
]