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Wide-band analog VHF military radio
RT-4600 was a modular VHF-L FM military radio set
developed by
Philips Telecommunications Industry (PTI)
in Hilversum (Netherlands) as the successor to the successful
RT-3600.
The radio set was built especially for use by the Dutch Army and was first
introduced in 1984. It was also successfully exported to other countries.
The RT-4600 was succeeded in 2000 by the FM-9000.
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Externally, the RT-4600 strongly resembles its predecessor,
the RT-3600.
It is housed in the same robust enclosure and fits the same vehicle mount.
Most of the accessories are similar to those of the RT-3600. The frequency
range has changed slightly and now covers 30 to 75.975 MHz in 25 kHz 1 steps
rather than 50 kHz steps.
Internally, the radio is completely different however. It has clearly
been designed to save on cost and is far less robust than its predecessor.
The internal wiring has been replaced by a large PCB that acts as a
backplane, which makes the radio far more vulnerable to
vibrations and shocks.
Much of the filtering, that gave the RT-3600 its excellent selectivity
and large signal behaviour, has been left out, and is now located inside the
additional FB-4620 filter unit.
The image on the right shows a complete radio station, consisting of an
RT-4600 transceiver, AF-4620 audio unit, FB-4620 filter unit and standard
vehicle mount.
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The RT-4600 was developed by Philips PTI (later renamed to Signaal)
in the early 1980s as the successor to the
RT-3600 that had become too
expensive to manufacture, mainly because of its extremely robust mechanical
structure. Much of the mechanics were replaced by electronics, which made
the RT-4600 far more sensitive to vibrations, especially when mounted in
a tank.
It never gained much popularity in the Dutch Army, not least because
the RT-3600 wasn't phased out when the RT-4600 was introduced. That said,
it was successfully sold to other countries. The RT-3600 and the RT-4600
remained in use until 2000 when they were replaced by the
FM-9000.
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Versions with a black front panel have a 50 kHz channel spacing.
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Voice and data encryption
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The RT-4600 was suitable for the connection of an external
encryption/decryption device
that could be inserted between the handset
and the U-229 audio socket
of the transceiver. Like on the RT-3600,
the MODE-selector has a so-called X-position, which bypasses the audio
filtering.
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When set to the X-position, both the transmitter and the receiver are
suitable for digital audio signals, allowing a wide variety of digital
voice and data encryption devices
to be used, such as the American
KY-57,
the more versatile KY-99
or the little known
Philips Spendex 10.
The image on the right shows a typical
KY-57 unit.
When used with a digital encryption device, other users of the radio channel
(without access to encryption) will only hear white noise, as if the squelch has
been released. Only users with the same encryption key can hear each
other.
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Philips even developed a small high-end encryption device especially for
the RT-4600, but it was never taken into production. The device was known as
ORTHROS
and was fully integrated with the handset. Although Philips
even won an award for its design, it was not taken into production,
probably because better priced alternatives had meanwhile become available
from other sources. Examples are the
American KY-189 and the
KY-57 shown above,
that was also used with NATO.
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Encryption devices used with the RT-4600
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The RT-4600 is a modular system that allows the radio set to be adapted
for many applications. The standard radio set is suitable for mounting inside
a vehicle, but can easily be converted into a manpack radio by replacing
the PP-4621 power supply unit at the rear end by a battery pack.
Two variants of the RT-4600 are known: one with a 25 kHz channel spacing
and one with 50 kHz channel spacing. The 50 kHz variant can be recognised
by a black front panel. The one featured on this page is the
25 kHz variant.
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25 kHz Green front panel 50 kHz Black front panel
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Remote control set
KL/GRA-3686
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Up to two RT-3600 radios can be controlled remotely
via a 2-wire field line of up to 3 km long, by means of the
KL/GRA-3686 Remote Control Set
shown in the image on the right.
The set consists of two boxes that should be installed at both ends of
the 2-wire field line. The leftmost is connected to the radio(s).
A H-5050 handset can be connected to either box, allowing the radios to
be used in simplex as well as half-duplex (split frequency) mode.
➤ More information
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Frequency 30.000 - 75.975 MHz Modulation FM Channels 1840 Spacing 25 kHz or 50 kHz 1 RF power 2, 10 or 30 Watt Sensitivity 0.2µV / 20dB Power 12V (RT-4600) or 24V (VRC-4622)
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Only on units with a black front panel.
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RT-4600 Transceiver (Transmitter/Receiver), powered by 12V AF-4620 Amplifier/Loudspeaker unit, powered by 24V FB-4620 Filter Box AM-4600 Power Amplifier for 30 Watt output (30 km) PP-4621 Internal PSU VRC-4622 Radioset, consisting of RT-4600 and AF-4620 KL/GRA-3686 Remote control set
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© Crypto Museum. Created: Friday 22 July 2016. Last changed: Sunday, 22 November 2020 - 17:30 CET.
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