Topband: Non-resonant receive antennas

[John Kaufmann]

A few years ago, I put up a low, non-resonant dipole, about 150 feet long
and 10 feet high for use as an auxiliary receiving antenna on 160.  My main
receiving antenna was and still is an array of short verticals.  What I
found at my W1 location after I installed the dipole is similar to what N5IA
described at XZ0A.  

If the band was open before my local sunrise (not always the case!), the
verticals would always outperform the dipole by a large amount.  However, as
soon as we hit sunrise, the dipole would suddenly start equaling and then
outperforming the verticals.  The transition would take place in a matter of
a few short minutes.  Past sunrise, DX signals would drop into the noise on
the verticals but would continue to hang in on the dipole.  The dipole would
sometimes extend the opening for me by 5 to 15 minutes, allowing me to make
some contacts (mainly JA and VK, if the band was open in those directions)
that would not have been possible with the vertical array.  Sometimes the DX
would be virtually inaudible on the verticals but Q5, although not strong,
on the dipole.

What is rather interesting, however, is that in the winter seasons of
2012-2013 and 2013-2014, this dipole advantage became non-existent.  The
dipole was never even close to the verticals, either before or after
sunrise.  It caused me to go outside a number of times to see if the dipole
had fallen down, but that was never the case.  Evidently the propagation
mechanisms at work around sunrise have changed from a few years ago, at
least at my QTH.  So far in the 2014-2015 season, the dipole has still not
provided any receiving advantage around sunrise.

I generally don't operate much around local sunset, but I have never seen
any dipole advantage at sunset.  

73, John W1FV