[hackpgh-ham] Re: Loop Antenna Build 1
- From: Matt Stultz <matt@xxxxxxxxxxxxxxxxxx>
- To: hackpgh-ham@xxxxxxxxxxxxx
- Date: Sat, 11 Dec 2010 14:57:59 -0500
I hate you Ed.
I played around with a lot of calculation tools and it's hard to get a loop
that is good on 40-30 it seems.
I wonder what just taking it outside would do.
On Dec 11, 2010 1:11 PM, "Ed Paradis" <legomaniac@xxxxxxxxx> wrote:
Friday night after the presentation, Tim and I built a wire loop
antenna with some parts I brought up.
The antenna was a square, 7 feet on each side. We used a coupling
loop instead of a gamma match and only used it for receiving.
We could tune the capacitor to peak the noise on 40 meters, 30 meters,
and 20 meters. We didn't try any other bands, but I didn't tune
around some of the short wave stations between 40 and 30 meters.
Notes:
- a 7 foot square is a huge freaking antenna. It fit inside, though.
- reception was very spotty and we heard no amateur activity at all on any
band
- we did receive some shortwave pretty well
- there was far less interference than the random wire and in general
it was a pretty 'quiet' antenna.
- we could show the expected directivity of the antenna on some
French-language station, moving it from S8 to S0 with a 90 degree turn
- some way to tune the capacitor remotely and very slowly is critical
if you don't want to go nuts, though we did come up with a clever way
of doing so with a big stick and a piece of thick copper wire
Conclusions:
- because we could show the directivity, I think we can legitmately
say it was a loop antenna and not just a big random chunk of metal
- a 7 foot square is really large compared to the designs I saw online
but I thought bigger would be better. This might not be true
- the general "deafness" of the antenna leads me to believe that we
won't get anywhere until we get our antenna "out of the basement"
Future plans:
- Modifying this antenna to be a multiturn loop would be simple
because we used wire. I'd like to try that
- we need a long piece of coax on the antenna so we don't have to sit
right next to it (though we didn't seem to be picking up any birdies
from our radio)
- I'd like to come up with a clean remote controlled variable
capacitor. I've seen some gear motors that would be perfect online
for $7.
- I'd still like to go through with the copper pipe antenna, even if
it ends up being fixed on 20 meters
Make thanks goes out to Tim for his help putting the antenna together
and everyone else in the shop with putting up with another night
filled with radio static. I'll get some headphones up there soon, I
promise.
Ed
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