Tuesday, December 31, 2013

Inverted L antenna

With about a 70 ft radiator (intentionally cut long to be able to prune later and with 460 feet of radials, I have the following results.

It looks like I have to prune it to move the sweet spot 100 Hz to the right for the dip to occur at 3627 Hz which gives me a range of 3500 Hz to 3740 for a 2:1 bandwidth.  It looks like 30m will be OK with this pruning as the 30 meter portion of the band is small and relatively broad banded.  This assumes a velocity factor of 0.66 for RG-213 which checks out to a precision dummy load.

These are the only bands which will be resonant.  It looks like 17m, 12m and and 10m are tuneable - with 10 m in the phone portion only.  See full sweep below:

I plan to lay down another 1000 feet of radials to improve gain about 1 dB over what I have now and improve radiation efficiency.  I will prune it after laying down the radials..

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