Paul,
An alternative which works great for me is to start a quarter wavelength of
wire out a few feet, insulated from and up about 50 feet on your 160m shunt
fed tower. Run it down at an angle so at about 20 feet out from the tower the
wire is about 10-15 feet off the ground, put a loop in the wire and use small
rope to tie it down to a big rock. Then have the remainder turn back to the
tower with the bottom next to the tower. Use the same radials and series feed.
Move the rock to make it tight.
73… Stan, ZF9CW
Sent from my iPhone
> On Dec 30, 2021, at 5:05 AM, N1BUG <paul@n1bug.com> wrote:
>
> Hi Towertalkers,
>
> I spent much time this summer rebuilding after storm damage last winter. As
> part of that I upgraded from inverted V's at 90 and 105 feet for 30m and 40m
> to an OptiBeam OB1-4030 at 108 feet. I expected improvement but Wow! I wasn't
> prepared for what I observed! The old antennas on another tower were left up
> for a few weeks to make comparisons. Unbelievable. I now consider "inverted
> V" roughly synonymous to "dummy load".
>
> So... 80m is now my worst performing band, still using an inverted V there. I
> can work stuff with a shunt fed tower on 160 that I cannot work on 80. I'm
> thinking a quarter wave vertical for 80 would probably be an improvement and
> surely no worse. Plus it would eliminate a set of ropes that are somewhat in
> the way of other projects. But I don't want to have another guyed structure
> for reasons I won't get into for now.
>
> I looked at the DX Engineering self supporting 80m verticals. Nice, but they
> won't fit the budget any time soon.
>
> So here is a question: Would 30 feet (real height 28 feet) of Rohn 25 be OK
> freestanding with a 35 foot whip on top? I have a 30 foot whip made from
> aluminum tubing, tapering from 1.5" down to 1/2". It could be extended to 35
> feet with a section of 1.75" OD 0.120 wall tubing I have laying around. I'm
> confident this whip would be fine, but not sure the Rohn 25 would be OK self
> supporting with this on top. A 1992 Rohn catalog says 6.4 square feet of
> antenna with no ice, dropping to 2.5 square feet with 1/2" ice. That is for
> 70 MPH wind and assumes one 5/8" feedline on each tower face. There would be
> no feedlines and being sheltered by trees this thing would never see 70 MPH
> winds. 50, maybe. Any experience or wisdom on this?
>
> My main concern is not that this thing would come crashing down, but that
> every Rohn 25 tower I have ever taken down that did not have guys on the
> topmost section had seriously elongated bolt holes. I'm not sure what the
> deal is there since Rohn seems to be saying they should be OK with small
> antenna loads.
>
> Another option might be 28' of tower, air wound loading coil, and somewhat
> shorter whip.
>
> Base insulators could be a problem (budget-wise) but I see no reason not to
> ground and shunt feed a 1/4 wave vertical. I wonder if it might even cover CW
> and SSB by adjusting the shunt feed capacitor without needing to move the tap
> point on the vertical? Comments?
>
> Happy New Year to all and thanks in advance for any comments or suggestions
> regarding my vertical thoughts.
>
> 73,
> Paul N1BUG
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