Topband: Signal source and distance from antenna?

[Tree]

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 at kkn.net