Topbanders
About a year ago I put up a new 3 el SteppIR. It is a sensational antenna. I
did not want to lose low band capability so I put a loop over the top of the
steppIR in the plane of the boom. All matching and connections for 30, 40, 60,
75/80 and 160 are made at ground level so there is no tower climbing. On 160 TX
the loop is driven on one side against a loop radial system in my basement and
the other side is left open. The total length of the loop wire is somewhat more
tha 1/4 wl but it is bent over in the middle so the height is only about 1/8
wl. The pattern is omni to 0.1 dB whereas an inverted L at the same height
loses about one dB
in the pattern and the loop has only one support.
I don't have room for a separate RX ant. so I tried the loop on EZNEC connected
like a K9AY. It didn't work so I tried adding reactance in series with the
loop.That worked. By adjusting resistances and reactances at the load end and
at the source end I could get between 30 and 49 dB F/B with Minninec, high
accuracy, perfect and freespace grounds.
The EZNEC results looked good but I still did not believe the results so I
tried it in the real hardware wold. It works! I measured more than 30 dB F/B
and the loop is big enough so a preamp is not needed.It's nice to have a high
performance RX beam that rotates and is physically the same as the TX antenna.
The whole system worked so well that I wrote an article for QST. It will be in
the Feb. issue coming out now. Take a look.
73
George W6TC
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