Tuesday, January 13, 2009

80M Inverted-L

The other night I launched a tennis ball into the same tree my 40M vertical is in, and pulled up a 66-foot wire to use as an inverted-L on 80M:

(can't see it? ha!)
I've "repurposed" the feedpoint of my 40-m droopy radial vertical - the 40m vertical element is still in the tree, just not attached, in case I want to switch back.
So the radial field is the same one I used for the 40 vertical - 6 runs of #18 wire buried in the front yard, asymmetrically (tunneling under the street = not recommended).
My initial observation: this thing is great at receiving the local noise generated from my neighbor's garage. For example, on 3530 kHZ:

Noise floor, noise off, G5RV: S2
Noise floor, noise off, inverted-L: S9

Noise floor, noise on, G5RV: S5
Noise floor, noise on, inverted-L: S9+10dB

My guess is that the inverted-L is just a generally better antenna, so it's just doing a better job of picking up signals, including local noise.

The neighbor garage noise sounds like this. It's pretty regular, in that the time between bursts, the duration of the bursts, and the very loud noise at the end of each burst repeat consistently.

It's odd that the G5RV is much closer to the noise source, yet receives about 30-40 dB less signal. One significant difference between the antennas is their polarization. Could polarization account for that much difference? I doubt it... there must be something else at work here.

Update: 01/15/2009: my first QSO on this antenna was DS1REE in Seoul, South Korea, at about 5am local time.


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Anonymous said...

Nice story you got here. It would be great to read something more about this topic. The only thing I would like to see here is a few photos of any gizmos.
Jeff Kripke
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