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.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.