UHF Amplifier AMP1-10
AMPUS/1 106/98
UHF Power Amplifier Model AMP1-10 MK2
Overview
This amplifier is designed to increase the operating range of an already correctly installed
system. In such a system the need for a well sited transmitting aerial should previously have
been addressed. The amplifier is not intended as a substitute for an indifferent, poorly located
aerial. In this context, we would strongly advise not to connect a simple quarter wave antenna
directly to the ‘N’ type output connector, as this will inevitably produce a strong local radiated
field, which is quite capable of causing interference to other equipment in the vicinity.
Note! This system requires a valid Radiocommunications Agency licence for operation in the
UK. It is the user’s responsibility to apply for this licence on form RA5.
Warning! Alteration or modification to any part of this equipment, without the prior written
consent of the manufacturer, will invalidate all Approvals and Warranties attaching to the
equipment. Further liability for the operation of the equipment, under the applicable law, will
pass to the user, who will absolve the manufacturer of any further responsibility for it’s correct
operation and use.
Installation
The output from the amplifier should be fed, via good quality coaxial cable, to a dipole or
beam aerial mounted high on a mast and clear of local obstructions. A minimum cable
specification is RG213 or UR67, and for runs longer than ten metres, helical membrane
(Heliax) cables are worth considering. At high frequencies, poor quality cable and associated
plugs and sockets incur high losses, and quickly negate the theoretical improvements in system
performance which a power amplifier might otherwise bring.
The following example is presented as an illustration of potential system losses. At 460 MHz
standard RG213 or UR67 cable loses 1 decibel -approximately 20% -of the incident power
for every 5 metres of length, and 15 metres (50 feet) loses 3dB. This means that if you start
with 10 watts out of the amplifier, you will get only 5 watts at the far end of 15 metres of
RG213 cable! These loss figures apply only to cable in a new, dry condition. Note that word
dry, because once moisture is allowed to enter the ends of the cable it will corrode the copper
conductors, particularly the outer braid, and thereby raise the loss to the point where the cable
looks like a reasonable dummy load, soaking up most of the transmitter power. It follows that
only good quality watertight, ‘O’ ring sealed connectors should be used. Unsealed crimped
connectors are a false economy and will result in the system failing in the longer term.
At radio frequencies signal currents flow only very near to the surfaces of electrical
conductors, a phenomenon which is known as skin effect. This means that the surface
resistivity of the cheaper nickel plated and chromium plated connectors makes a significant
contribution to the losses. For this reason we would advise to use the better quality silver
plated N series connectors.
