Quasi-Random Wire Results

Following up on last week's post regarding good random wire lengths, we now have a weekend's worth of experimentation to discuss and results to report for the 75' wire.  Also, if you need more background, here's the related Wikipedia article.

The first step was to set up the wire in the side yard nearest the shack, and connect in to the radio gear with 25' of LMR-240 coax cable.  The 9:1 unun was protected by a quart zip-loc bag; coax in through the zipper side, wire out through a small slit in the other end.  This made for comfortable, dry operation on a rainy Saturday afternoon, for both the unun and the operator.  The coax was entirely suspended at 4' to 6' off the ground, and grounded at the shack end.  The radiating wire was suspended roughly horizontally at heights varying between 4' and 7'.  R, X, SWR, reception, and transmission measurements were made both with and without the ~30' counterpoise attached to the ground leg of the unun.  The feedline was routed through a two-position switch, which was also attached to an existing MFJ-17758 loaded dipole.  This allowed for convenient A/B performance comparisons.  The dipole is relatively low-mounted for NVIS work, configured in a shallow inverted-V, from 18' at the feedpoint to 5' at each end.

R, X, and SWR were all within useable ranges across all ham bands from 3.5–10.2 Mhz.  80m in particular benefited from the counterpoise, with SWR dropping from 6 to 2.  60m was relatively unaffected.  40m, without the counterpoise, had an SWR in the 1.4-1.7 range and, as with the dipole, did not require an antenna tuner.  This fortunate coincidence allowed direct comparisons between the two antennas on 40m, without the need to re-tune.  With the counterpoise on 40m, the SWR increased to 2.7-2.3, necessitating the use of the tuner.  30m performance was slightly improved by the counterpoise, with SWR dropping from 2 to 1.4.

The main performance results were that, without the counterpoise wire, noise levels were approximately 18 dB higher relative to the dipole, while signal strengths were approximately 6 dB lower.  With the counterpoise wire attached and draped across damp grass, noise levels were approximately 12 dB higher than those from the dipole, while signal strengths were roughly 3 dB lower.  The handful of QSOs made with each antenna show a similar 3–6 dB decrease in transmitted signal strength.

In other words, there ain't no such thing as a free lunch.  The random wire did work, but it has serious performance drawbacks relative to a dipole.  It's an interesting trick in the toolbox however, and it is much easier to deploy than a dipole.  Experimentation relative to the 21' mini-W3EDP is in store for the next camping trip.

Well, that was also dry as dust.  Again, "just the facts ma'am" fits here.  But, having gotten to the bottom of this mass of data and (hopefully) useful conclusions, have another enjoyable song.