Aloha,
Just finished a chat with the engineer in charge out at Manoa
at WWVH. He is actually beginning planning for new antennas;
was looking in the ARRL Antenna Book, how about that!
Present verticals are Rohn towers, with center insulators!!
Rohn evidently will no longer quote these for 1/2 wave vertical
application. On site antennas were supplied and installed
back in 1971, the year Kauai became the new home for
the station which was moved from Maui. His notes, left
by the engineer from some 27 years ago refer to the
present set up as a "Franklin Design". Meant nothing
to me.
The engineer said he climbs the towers and Rohn is afraid of
doing the center insulators, one on each of the three legs,
as one or two are in compression while the third might be
in tension. That is the part they are frightened about, hi.
But the center insulators are, of course needed to form
the two tower array of 1/2 wave antennas, one tower fed
90 degrees out of phase with the other.
I asked how high up the feed points were on 5, 10 and 15 MHz;
he replied, as he recalled, at least 3/8ths wave, but seemed
a little uncertain. The tallest tower is about 200 feet, but it
is also a 1/2 wave vertical, center fed, for the 2.5MHz omni
coverage, 5kW for local coverage here in Hawaii and the
near by areas of the Pacific. 1/2 wave at 2.5 MHz is 196.6
feet.
He is quite concerned because of the lack of a source for
new, center insulated towers. Said he had about decided
to put out an RFQ for a professional engineer to come out
to give him a hand in planning for a new antenna set up.
Is quite concerned about radial needs if he is forced
to go to 1/4 wave verticals. Does not want to loose
field strength over in the Philippines, and other areas
of the far Western Pacific. Would require a sea of
radials beneath seven towers!
His other problem is the transmitters; they are all by
manufacturers' no longer in business: AELabs and
AlcomPower, or some such. So is having to investigate
that aspect of the station's upgrade also.
Will be interesting to follow this project.
So, that is the info about WWVH.
73, Jim, KH7M
On the Garden Island of Kauai
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