Radio W4KAZ

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Inverted-L Matching

The 160 Inverted-L is about 160 feet of wire.  To get a good match there is a series capacitor in line with the wire.  The bandwidth for any useful value of capacitance is about 40kc.  The object is to use a set of relays to switch in or out additional capacitors.  That will allow the antenna to be tunable across most of the band – from 1800kc to 1930kc.  There is also a 1.5:1 unun at the feed point, followed by a coax cable choke.  This lowers the SWR to a very nice 1.1:1 over the useful range.  The rig is very happy at resonance, and a good match will be a dial click away.

Currently the capacitance in the system gives a nice 1:1 SWR at 1825kc.  Using the autotuners, either radio [K2, FT-920] can work from 1800 to 1875.  The goal is to be able to turn off the tuners and feed the antenna directly.  Maybe I’ll pick up a few extra QSO’s with a good match on the antenna end of the feedline.

After several other projects using relays and the 3kv Panasonic capacitors for the band pass filters, enough extra parts are in the parts bin to make it happen.  So, why wait?

A handy nearby line previously shot into a nearby biological antenna support provides an opportunity for expansion.  The line seems well placed to add an INV-L element for 80m.  One additional relay for switching bands.  Judicious choices for the capacitance values may allow the sharing the capacitor banks for either antenna.  Being able to cover the CW segments is most important, so the minimum value used would ideally resonate each wire near the bottom of either band.  Hmmmmm.  Time to pull the 80m wire up and start tinkering.

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