Friday, 30 March 2018

40m Inverted vee success

It's been unusually calm this week, with light winds and some warm sunshine.

I decided to have a go at a 7MHz inverted-vee antenna, which is very useful in only needing one support.
40m is go!

Initially, the wires were cut at 10.1m per leg, which proved to be too long, as expected.

With the apex at about 8.5m, and the dipole wires sloping down to about 4m above ground, the correct length of each leg proved to be 9.7m, yielding a SWR no greater than about 1.2:1 SWR across the whole band, as the following (much too wide) scan with the SARK-110 shows:

There were not so many stations active mid-afternoon on 7MHz, but I did work a very strong PA station that was using 500W to a dipole (easily defeating a damned tuner trying to interrupt proceedings):

I also ran about 20 minutes' worth of 200mW WSPR, just to get a quick idea of relative performance.  The plot shows my 200mW was doing better than the comparison station's 5W into a half-size G5RV, which is very pleasing.

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