Within the last few months, I was recently made the trustee for the NWC
Amateur Radio Club license WX5NWC. I've received numerous queries about
the state of our antenna and the station in general.
The station is quite functional using a vertical antenna mounted on the
roof of the NWC. There is an auto-tuner on that antenna that should
allow its use on any frequency from 3-30 MHz.
After an exhaustive search in our Federal property database, neither the
antenna, mast, or rotator appear to be associated with any Federal
property numbers.
The antenna that is currently up there is a 4 element yagi array, part
number 00204, made by a company called SteppIR, Inc., and will be simply
referred to as "the SteppIR." It is an unique antenna because the
elements you see (two of which have been damaged) are special fiberglass
tubes (radomes) that contain copper beryllium tapes whose length is
adjusted by stepper motors such that the antenna is optimized for the
assigned operating frequency. One of failed element halves has been
found, but the other is lost. This antenna can be used for any frequency
from a bit below 13.9 through 54 MHz, though the forward gain and ratio
of front-to-back gain drops significantly above by 50 MHz. The gain
figures can be enhanced considerably with the addition of two fixed
elements. This antenna is relatively complex and also relatively large.
These antennas are also expensive, at $3000 each. There is an upgrade
kit available for $665 that allows the antenna to be used as a rotatable
dipole for frequencies from 7 MHz through 13.9 MHz. The antenna, along
with all accessories, is designed and constructed to withstand 100 MPH
winds. For its size and weight, it has far better gain figures, and much
less wind loading, than a log-periodic dipole array.
The antenna is rotated using a Yeasu G-2800DXA series rotor. I've been
told that this rotor is scaled to handle our current antenna with a 50%
safety margin. It is an expensive rotor, coming in at about $1500.
Other, more robust rotors are available at appropriately increased cost.
If we do not have one, I strongly suggest purchasing and installing a
Yeasu G-3000 shock absorber to mitigate shock loads imposed on the
system. These are quite inexpensive, at about $140, though installing
one may require raising the mast a couple of inches.
Aside from the two damaged elements, the current antenna system has
suffered an unknown failure of the rotor system. This has precedent in
that happened once in the past and the problem was found to be a shear
bolt within the long mast that connects the rotor to the antenna. The
shear bolt is intended to protect the rotor by failing before the rotor
does, but the original bolt was too soft (grade 5). The bolt was
ungraded to a grade 8 bolt, in hopes of preventing another failure. We
do not yet know what has failed: either 1) the rotor has failed, or 2)
the shear bolt has failed. Regardless of the nature of the failure,
there are several cables that have been severed by the free-wheeling
antenna. These include transmission lines and control cables, both of
which will need wholesale replacement. If the shear bolt has failed, we
will obviously need to replace it, but with something that is more
robust. If the rotor has failed, it needs to be sent to Yeasu for
repair. Either way, we need to determine why the failure reoccurred.
With that preamble, we need to determine how to proceed. We need to who
has purchase authority and then identify a way to execute disbursements.
For example I have located a certified climber though the South Canadian
Amateur Radio Society (SCARS) who will work for $125/hr. I haven't
called him because I don;t have any idea how to write him a check at the
end of the day. We will need to purchase new cabling, possibly repair a
rotor, and likely rebuild the SteppIR. If we choose to replace the
SteppIR, we need to sell it off and purchase another suitable antenna.
How will these decisions be made? How will they be implemented? I'm
happy to accept the responsibility, but I can't execute any action
without also having the authority to do so.
I'm happy to be part of any needed meetings to get things on track.
73,
Kim Elmore, N5OP
WX5NWC Trustee
--
Kim Elmore, Ph
Kim Elmore, Ph.D. (Adj. Assoc. Prof., OU School of Meteorology, CCM, PP
SEL/MEL/Glider, N5OP, 2nd Class Radiotelegraph, GROL)
/"In theory there is no difference between theory and practice. But, in
practice, there is." – Attributed to many people; it’s so true that it
doesn’t matter who said it./
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