On Sun, Oct 05, 2008 at 06:30:40PM -0400, Dan Zimmerman N3OX wrote:
> What do YOU guys use to determine which antenna works better or if you've
> > made an improvement in gain, null, signal strength, etc. during the
> > daytime, -and- how far away does this source have to be? (I don't like the
> > thought of driving a mile down the road, installing a 30' vertical antenna
> > on my analyzer (so it can be heard a mile away), then leaving it unguarded
> > for someone to swipe, HI HI !)
I have come up with a method that seems to work pretty well for adjusting my
parasitic array.
I built a noise generator circuit. First, I bought the one from Elecraft, but
it really doesn't have enough power to do the job. I ended up building about
10 gain stages using a single transistor (who cares if it has a bad noise
figure) and finally got a few volts of output. Found I could just use my
own zener to make the noise. Has a transformmer on the output to get from
about 1K down to 50 ohms. I can hear this about 1/2 mile away. Putting it
through a 160 meter bandpass filter keeps it from QRMing AM radio stations.
Then I built a small TTL sequencer to step through the antennas or directions
with about 2 or 3 seconds on each step. With this - I go omni, pointing one
way and then pointing the other. And one of the states is OFF so I can tell
which step I am on.
I bought a used DFing receiver that covers 160 meters. You can find them on
ebay for about $25 - and this one is powered by six C cells. It even has
a nice sensitive relative signal meter. Of course, you could use a ham rig
as well hooked up to a wire.
I drive 1/2 mile or more away and tune around and see where my gain is best
and where the F/B is best.
This system is really a time saver.
Tree N6TR
tree@kkn.net
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