Quick Reference Guide
Vaisala Telemetry Antenna
RM32
0611-035
Figure 1 RM32 Antenna Assembly
PRODUCT OVERVIEW
This Quick Reference Guide yields a general description of the
Vaisala Telemetry Antenna RM32 used for receiving radiosonde
signals in the 400 MHz meteorological band.
General
Vaisala Telemetry Antenna RM32 is an antenna system intended
to be used with Vaisala DigiCORA® Sounding System. It is
well suited for fixed installations, but it can also be used in
portable systems where feasible.
RM32 has two antennas which have been selected to optimize
the performance in all elevation angles, both near the horizon
and at the zenith. The sounding system selects the antenna with
the best reception through a two position antenna switch.
Construction
The Vaisala Telemetry Antenna RM32 consists of
•vertical antenna (1)
•helix antenna (2)
•Antenna Amplifier and Switch RAA111G (3)
•tubular antenna mast, tube branch and antenna cables.
The numbering above refers to the figure on the cover page of
this Quick Reference Guide.
Vertical Antenna
The vertically polarized omnidirectional antenna performs best
at the low elevation angles when the radiosonde is near the
horizon. The maximum gain of 5dBi is just below zero elevation.
Helix Antenna
The helix antenna is an omnidirectional antenna with
approximately hemispheric coverage with a maximum gain of 3
dBic at the zenith.
Antenna Amplifier and Switch RAA111
All the amplifier parts are housed in a watertight box at the base
of the antenna mast. The amplifier runs on +12 VDC voltage,
supplied by the UHF receiver.
Antenna Mast and Tube Branch
The vertical antenna is installed on top of a tubular mast, and the
amplifier box is mounted on the base of the mast.
The helix antenna is attached to a flange in the tube branch.
A mounting sleeve is provided for mounting the whole antenna
on top of an external mast.
INSTALLATION
Select an installation site that is open, in other words, clear of
obstacles such as buildings, dense forests, or high metal masts.
1. Fit the Antenna Amplifier and Switch RAA111G on
the tubular mast.
2. Attach the tube branch to the tubular mast using the
clamp included as shown in Figure 2.
0611-037
Figure 2 Attaching the Tube Branch to the Tubular Mast
The distance between the antennas in the system is
optimized to minimize mutual interference. Set the
distance as shown in Figure 3.
0611-038
Figure 3 Distance Between the Vertical and Helix Antennas
3. Connect the vertical antenna with cables
(DRW214802) to the ANT1 and the helix antenna to
the ANT2 connector in the Antenna Amplifier and
Switch RAA111G. Direct the cables through the holes
in the antenna mast and the branch as shown in Figure
4.
