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Our
single tuned dipole is ideal for the beginner who wants to get on air
fast within a limited price budget. The dipole has a built-in
transformer to match the 72 ohm balanced terminal impedance to 50 ohm
unbalanced (balun) feeder cable. This will provide an SWR of 1.5 or less
and the correct termination to the transmitter.
The entire dipole system is truly plug and play and INCLUDES 10m of
RG58 feeder coax cable with a PL259 plug fitted and a
mounting clamp, this allows the dipole system to be plugged straight
into a transmitter without the need of any additional connectors or
soldering. Normally the dipole system clamps in a vertical position as
high off the ground as possible to a mounting pole (1" to 2"
Dia) which you need to provide yourself.
Only two frequency types of dipole are required to cover the entire FM
broadcast band 88-98 MHz and 98-108 MHz. 50W MAXIMUM POWER
HANDLING (this dipole is not suitable for use with the 100W power
amplifier)
PLEASE STATE WHICH FREQUENCY TYPE YOU REQUIRE ON ORDERING
STACKED
BROADBAND DIPOLES
PROFESSIONAL RANGE
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Power...... |
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The
double stacked dipole has the benefit of 3.7dBi of gain and broadband
operation. This is achieved using a specially designed splitter box to
feed each dipole antenna with the correct RF signal phase. Providing the
antenna is mounted correctly the SWR is less than 1.8 across the whole
band from 87.5 to 108 MHz. This antenna system never needs tuning, just
put your transmitter on any frequency from 87.5 to 108 MHz and switch
on.
Normally the dipole system clamps as high off the ground as possible to
a mounting pole of at least 4 meters in length and 50mm in dia which you
need to provide and engineer yourself.
The RF field strength directly below this antenna is lower than that of
a single dipole. The built in balun provides a truly unbalanced input
and prevents any RF currents traveling down the outer of the feeder
cable. This combined with the low field strength below the antenna
reduces the chances of audio and TV interference considerably and
maximises RF power to the horizon.
Coaxial line losses can be considerable at 87.5 - 108 MHz. For long runs
use a good quality cable such as RG213 or equivalent for connecting the
antenna system to the transmitter.
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3.7dBi
Gain at Band Centre, 2.3 times Effective Power Increase |
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SWR less than 1.8 from 87.5 to
108 MHz |
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20 MHz Bandwidth |
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Aluminum and ABS Construction |
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50 ohm unbalanced input (SO-239
socket) |
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ANTENNA
ACCESSORIES
PROFESSIONAL RANGE
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RG58 50 OHM COAX CABLE
Low cost 50 ohm cable suitable for short runs at VHF frequencies.
External diameter 5mm, Loss per 10m 2dB at 100MHz.
PRICE PER METRE
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RG213 50 OHM COAX CABLE
High quality 50 ohm low loss cable recommended for long runs at VHF
frequencies.
External diameter 10mm, Loss per 10m 0.68dB at 100MHz.
PRICE PER METRE
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SWR METER
Easily tune your transmitter up to maximum RF output power or check your
antenna match with this 50 ohm SWR meter. The design specification
allows measurements at VHF 88-108 MHz. Construction is a steel case
fitted with two SO239 sockets.
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PL259 PATCH LEAD
Short length of RG58 pre-terminated with PL259 plugs for general use
with SWR meters, power amps and dummy loads.
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PL259 PLUG
The industry standard RF plug used on most VHF equipment. Two versions
of the plug are available with 5-6mm or 9-10mm cable entry Suitable
cables are RG213 and RG58 available from Veronica Kits. State 6mm or 9mm
when ordering.
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SO239 CHASSIS SOCKET
Usually chassis mounted on RF equipment. Ideal for the antenna output on
transmitters fitted into case's.
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SO239 STRAIGHT ADAPTER
Two SO239 sockets back to back forming a barrel type connector allowing
two PL259 plugs to be joined. Ideal for antenna extension cables.
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FM
TRANSMITTER POWER
AND RANGE
TECHNICAL INFORMATION
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In theory the range of a transmitted
radio signal is infinite regardless of power used, basically it goes on
and on forever until it encounters an obstruction. More power helps to
penetrate any obstructions. Given this, when engineering and planning a
station it is always better to consider the issues that limit the range.
Range is limited by:
a) How far the transmitting antenna can effectively see. If you stand
where the antenna is mounted and look out with a pair of binoculars,
wherever you can see it is possible to transmit to. This can sometimes
be up to 20, 30 even 40 miles if you are looking out from a mountain
top.
b) Other sources of interference or other stations operating on the same
frequency. For example the antenna may be able to see 20 miles, but if
another station is on the same frequency 20 miles away, it will
block/interfere with the signal.
c) Transmission power. If the antenna can see 20 miles, but say 1 Watt
ERP of power used, it's very likely that about 1 mile of range will
result. This is quite simply because there is not enough power to
propagate the signal 20 miles. If 50 Watt ERP is used, it's very likely
that 20 miles of range will be achieved. This is because 50 Watt ERP is
ample power to propagate a strong signal 20 miles. If 1 Million Watts of
power is used, it is very likely that signal will only propagate just
over 20 miles. This because the range is limited as described in point
a) above.
Assuming the antenna has a clear view, the frequency is clear and an
average quality portable receiver is used, typical transmission power
ver range figures are as follows:
Watts
ERP
1
2
4
8
16
32
64
128
256
512
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Range
Miles
1.5
2.1
3.0
4.2
6.0
8.6
12.0
17.0
24.0
34.0
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