Hi Gary, Earl, Pete, Bob and all,
Thank you for some excellent information. As a result of Gary K9AY's
remarks below and my own practical experiences, I think I will make up some
12" spacers from PVC reticulation tubing instead of using the 3" ones.
Gary's observation about the (very) close spacing affecting the bandwidth
of the parallel antennas is right on the button. On my parallel 160m and
40m inverted vees spaced 3", the bandwidth of the 40m inverted vee is much
narrower than it should be - around 50KHz between 2:1 SWR points from
memory - and is very critical to prune/tune.
The 160m inverted vee bandwidth seemed unaffected by the 3"
spacing/presence of the 40m element.
The 40m inverted vee here is actually made of PVC-covered soft-drawn copper
wire (so if it gets tangled up with the 160m one, it doesn't stop working).
This wire tends to stretch by an inch or so over the course of a year
owing to wind movement/tension. As a result, I have to retune the 40m
inverted vee every 12 months or so, which gives you an idea of how critical
the tuning is!
The parallel inverted vee antenna is going to be changed so there is 12"
spacing between the two inverted vees!
Vy 73,
Steve, VK6VZ
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