Appendix; Licensing; Antenna; Transmission Range - Simrad HT50 Manual

3 Appendix

3.1 Licensing

Prior to use check the national licensing requirements for the operator.
In the UK license applications and queries should be made to the following authority -
Ship Radio Licensing
Tel - 015394 34662
A set may only be operated by, or under the supervision of a holder of a Certificate of
Competence and Authority to Operate. This involves a simple examination and an annual
license renewal fee. The VHF only certificate is administered by the Royal Yachting Association -
Royal Yachting Association
Hants, SO5 4YA
Tel - 01703 629962
Holders of the Restricted Certificate of Competence in Radio-telephony (which covers
MF/HF SSB etc), do not need a separate VHF certificate.
In all other countries, please contact your regional authority for information.
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Wray Castle
PO Box 5
Ambleside
LA22 0BF
RYA House
Romsey Road
Eastleigh

3.2 Antenna

The antenna for the radio is fitted to the unit via a robust screw fitting to an M6 threaded socket
on the top of the radio. This system is more rugged than a traditional BNC connector, so the
radio's drop-proof integrity is not compromised by the antenna fixing.
While the radio is drop-proof and very robust, damage to the antenna such as bending or kinking
may adversely affect the transmission efficiency of the unit, which may lead to overloading of the
power module. Damaged antennae should be replaced immediately.
Replacement antennae can be purchased from authorised Simrad Service Agents. Please refer to
section 3.7 for more details on spare parts and accessories available.

3.3 Transmission Range

Because VHF signals travel in a straight line and are not reflected back off the ionosphere as lower
frequency signals are, the range of VHF signals is limited to 'line of sight', beyond which the other
vessel passes behind the curve of the Earth. Therefore, the range will increase greatly the higher
above sea level the antenna is, as Fig 3.1 illustrates (assuming maximum transmission power is
used):
Cherbourg
30 m/
100 ft
Mast
Endeavour
Fig 3.1 - VHF transmission range
Therefore, the typical range of a handheld radio such as this one used at sea level will be approx-
imately 8 Km (5 Miles). This will increase as height above sea level increases, or if the other radio
user's antenna is at a greater height - note that the range between the yacht with the antenna
mounted on a 9 M (30 Ft) mast and the handheld user increases to 13-16 Km (8-10 Miles).
Isle of Wight
87 km / 65 M
20 km / 12 M
9 m/
30 ft
8 km / 5 M
Mast
Niton
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