Kevinr,
I have an inverted-L on 630m (that is 475 KHz) and is simply a
vertical section with one horizontal section. A quarter wave
vertical for 1.8 MHz would be 137-foot high so 80 foot is going to be
short. The horizontal wires add capacitance to the top end of the
vertical effectively shortening the length needed for resonance.
My inv-L is only 43-foot high (1/4WL= 524-feet) so its not very
efficient and requires a big loading coil in series to resonate. If
you have four top-hat wires that may work better to shorten the
needed vertical. But probably still need a loading coil. Use EZNEC
to model it and it will provide a close est of the antenna Z. I
modified my MFJ-269B to operate 400-800 KHz and directly measured
mine; adjusted coil to reach resonance.
Also do not forget it also needs ground radials (more the
merrier)! I only had a 100-foot square patch of ground for my inv-L
so radials are very short as well. But my signal has been heard
4,000 miles away with 4w EIRP (100w output from amp). Antenna is
currently down.
73, Ed - KL7UW
http://www.kl7uw.com
Dubus-NA Business mail:
dubus...@gmail.com
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