LAPLACE INSTRUMENTS RF200 User Manual - page 6
RF200/500 user manual
6
Fig 2 RF200 stand
This is supplied as a central vertical support fitted with a leg attachment moulding and
three legs.
The legs are a push fit into the leg attachment moulding.
The vertical support has a friction slide fit in the leg attachment moulding so that the
antenna can be adjusted in height over the full length of the vertical support.
The antenna is located on the stand by locating the central support block on the top of
the vertical support in either the horizontal or vertical polarisation position. Nylon
bolts are provided so that the antenna can be clamped in position
If used outdoors in strong wind conditions, the stability of the antenna can be
considerably increased by filling a bag with sand, soil or stones and supporting it by
string tied round the leg attachment moulding.
2.2 RF200 in use
Connect the SA1020 pre-amplifier directly to the antenna output lead and secure the
pre-amp to the central support block with the velcro strips. Ensure that the connection
to the antenna is made to the input of the pre-amplifier. It is easy to get the amplifier
wrong way round!!
Point the antenna, sharp end forward, at the UUT. Note that the antenna is directional
but full sensitivity is maintained over a wide angle either side of ‘dead ahead’.
The reference point for the measurement of EUT – Antenna distance is the central
mounting point, where the vertical pole meets the horizontal main antenna beams.
The height of the antenna can be changed by sliding the vertical support up or down
within the leg attachment moulding. If this friction fit is too slack or tight, slightly
adjust the nylon bolt to suit. Note that antenna height may be a critical factor in
obtaining valid results. See section 4 on Ground Plane.
The main feature of the polar plot of the antenna (i.e. its directional properties) is a
sharp null at 90º on either side. This can be used to null out any strong background
emission for instance from an FM radio transmitter IF using a true open field site.
Note that the null is very sharp and care has to be taken to find the right angle.
Attenuation of up to 20dB is possible under the right conditions. In the presence of
buildings etc., these emissions will be affected by reflections and will not be
unidirectional, making them impossible to null out.