Dear LF Group,
The antennas at Rugby and Criggion have had some modification
over the years - the original designs both used 8 wire "sausages"
slung between the masts for the top load. Now both have a sort of
horizontal spider's web filling the whole area between the masts.
Rugby still has the original 12 guyed masts, which are 820 feet
according to the paper. Criggion originally had 3 x 600 foot self
supporting masts; these were all that was available during the war,
and were not considered enough, so the station was sited adjacent
to a cliff, and one side of the top load is anchored to the top of the
cliff. Since then, 3 x 700 foot guyed masts have also been added
to the antenna.
Rugby was also used experimentally for early trans-atlantic
telephone services, using ssb on about 60kHz. For this purpose,
the main antenna was divided into two sections, the smaller part
carrying the telephone signal.
Both VLF antennas also have various smaller L and T antennas for
LF slung lower down the masts. Rugby has a whole forest of what I
presume are HF antennas, across the road from the VLF/LF site.
Originally, Criggion had several HF Rhombics too, but these are
now gone.
As far as phase control goes, the 1926 paper describing Rugby
mentions that the frequency was derrived from a valve maintained
tuning fork. This apparently had a tempco of 100ppm/degC, and
was regarded as a major advance in transmitter frequency
stability, and neccessary because of the increasing use of the
spectrum. By the time Criggion was built 18 years later, crystal
oscillators with 1 in 10e7 stability over a period of months were in
use.
If you visit either site, it is worth taking a pair of binoculars, since it
is hard to see much detail from ground level (but be prepared for
funny looks from the site staff!). I heard that the telegraph poles
and cables over the road at Criggion are there to support the top
load when it is lowered for maintenance.
Cheers, Jim Moritz
73 de M0BMU
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