Martin,
Two things:
1. The antenna does not become "useless" when the loops are longer than 1/4
wave. It just won't work as a DHDL, but may still be useful as a low noise
RX antenna.
2. The DHDL is actually two loops, and each loops should be shorter than 1/4
wave. Note that there is nothing special about the dimensions. You could
make it smaller, to make it more suitable for 80 and 40. The dimensions
originally published were set to maximize the signal output on 160.
One thing that's important: the two loops should be exactly the same size
(within a couple of inches)! You can easily achieve that my moving the
central crossing to the exact center.
73,
George,
AA7JV
On Sun, 30 Jun 2019 18:03:23 +0200
Martin <dm4im@t-online.de> wrote:
Topbanders,
just read a few articles about DHDL antennas. One article states, the cut off
frequency where the antenna becomes useless is when the overall length of wire
reaches a 1/4WL. In my understanding the original dimensions , 2*7.5m vertical
plus 22m horizontal plus 2*13.3m sloping wires equals 63meters, which is
already a lot longer than 1/4WL on 160m. What did i miss?
--
Ohne CW ist es nur CB..
73, Martin DM4iM
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