Quote:
Originally Posted by things_green
what he said ;-)
Presumably the Lower freq unit is for the C45/B48 ?
Chris.....are the same 3x radials (top guys) utilised on both antenna or have they got specific lengths of the steel wire for the slightly different ranges?
Brent.
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Yes, the C45 and B48 used the lower frequency aerial kit.
The radials are specific to the antenna, and the setup is apparently quite critical - you can get a mismatch and potentially damage the set if not erected correctly.
<Fetches "book of words">
Elevated Antenna (LARKSPUR)
Characteristics
Essentially a vertical splayed dipole, elevated above ground to minimise
ground effects.
The top part of the dipole is a telescopic rod, adjustable for frequency.
The bottom part of the dipole is formed by 3 splayed wires, incorporated
into the mast stays.
Construction
Issued as a kit in two versions, 23-38 MHz and 36-60 MHz.
The telescopic rod is adjusted exactly to the working frequency and is mounted on the top of a mast.
The top of the mast is supported by three stays containing the splay wires (length 2.9 m (9 ft 6 in) for 23-38 MHz, and 1.5 m (5 ft) for 36 - 60 MHz). They must be equally spaced around the mast 120 degrees apart, and make an angle of 30 degrees to the mast in the vertical plane. (The stay pegs must be 4.5 m (15 ft) from the foot of a fully extended Mast, Telescopic 8 m (27 ft).)
Any variation from the correct lengths and angles of the splay wires would cause:
Mismatch, possibly with damaging amounts of powerreflected back into the radio set.
Change in the direction of radiation away from the horizontal.
The base insulator of the mast must NOT be fitted.
The ATU is not used
Masts higher than 8 m (27 ft) can be used and will give increased ranges, but the orientation of the splay wires MUST be maintained at 120 degrees apart and 30 degrees to the vertical.
Radiation.
Mainly space wave. The range will be about twice that obtained from a 2.4 m (8 ft) whip
Vertically polarized.
Omnidirectional.
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Elevated antenna (CLANSMAN)
Characteristics
A broadband (30-76 MHz) omni-directional antenna intended for use at permanent stations where speed of erection/dismantling is less important.
The design is a sleeve dipole.
Construction
The antenna is constructed from 3 basic component parts, an upper radiating element comprised of 2 x 2 m rods, a lower radiating element consisting of a coaxial sleeve, and a base unit. The latter item contains a number of resistors designed to absorb reflected currents, thus matching the antenna to the set over its working frequency range.
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(Note: the base unit contains beryllium oxide in the resistor pack, so messing with it is inadvisable. Also, the unit heats up when in use to the point of being detectable by night vision equipment, potentially giving your position away if the enemy can get suitable bearings on it. (My informant said they used to set up with a hill between themselves and the opposition, which reduced both the direction finding risk and the infra-red signature.)
Chris.