Just do what you can do. If 60' is the maximum vertical length you can
have, then do it. It should work fine. Just adjust the horizontal length
for best SWR. You will probably end up with a total length of about 135 to
140' (vertical plus horizontal). Just put out the most radials you can.
Even short ones help and they don't all have to be long, or straight, or any
particular length. I have a lot of mine across walks and the driveway by
using the expansion joints in the concrete. Also, don't let anyone tell you
the antenna necessarily requires a matching network. Just feed it with
50-ohm coax, with the braid going to ground at the antenna. By adjusting
the length (prune or lengthen the far end) you should end up with an SWR of
about 1.5-to-one, or less, at whatever frequency you are centering it on.
This is well within reason. Trying to match it for 1-to-1 is a pointless
exercise that will only waste your time and delay your fun on 160, and it
won't help your signal a bit.
The idea of making the antenna a little too long (160' or so) is so you can
tune it with a series capacitor. This would only be necessary if you wanted
to make some unusually large frequency excursions. As long as you operate
between 1.800 and 1.900 or so you should be able to prune the length for
best SWR at around 1.85 and be fine. I would try it the simple way first.
If you need something more exotic then worry about that later. Matching
would only be necessary to help your radio put out full power. In fact,
even with a 2-to-1 or 3-to-1 SWR your radio's matching circuit might do the
job. Matching a 160M inverted-L at the antenna will not affect your signal
one iota (unless the radio would otherwise not produce any power) and is
usually not necessary.
Wes N5WA
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