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Radio Set AN/PRC-521 (RT-5113) (NSN 5820-21-911-5982) Modified Installations

INTRODUCTION

The purpose of this documentation is to explore the undocumented modified installations possible for use with the Canadian Forces radio set AN/PRC-521 (RT-5113).   Please note that the information presented in these pages concerning these modified installations are unauthorized modifications and unauthorized installations. There are no advantages of using a PRC-521 in a vehicular installation other than to make use of the embedded COMSEC in the PRC-521.  Since the PRC-521 does not provide any ECCM capabilities, compatibility with field deployed PRC-521 can be achieved with the use of an RT-524 or a PRC-25/77 set.

The first possibility is the integration of the AN/PRC-521 in a vehicular installation.   A vehicular installation can be accomplished with minimum efforts.  With a few simple adapters and some extra parts, the AN/PRC-521 can be employed in a radio station vehicle and achieve an acceptable transmission range.

CONFIGURATION #1
In the first example, we will look at a basic configuration employing existing equipment that is specified in the ECL for a VHF radio station vehicle.

The parts required are:

1. Radio Set, AN/PRC-521 with battery BB-521/U and headset microphone H-5034/U.
2. Antenna, Ground Plane, AS-5162/VRC with coaxial cable of suitable length.  The antenna and its associated installation parts are encompassed in the Antenna Group, OE-5025/VRC kit.
3. Antenna adapter, BNC jack to TNC plug (see parts list below for p/n).

Installation:

1. Assemble and frequency/crypto fill the AN/PRC-521 radio set per standard procedures.
   When selecting frequencies for the  PRC-521, take in consideration the 3 operating frequency bands of the AS-5162/VRC antenna. Band "A" 30 MHz to 37 MHz (radiating element fully extended) band "B" 37 MHz to 44 MHz (top down) and band "C" 44 MHz to 76 MHz (fully retracted).
2. Install the antenna AS-5162/VRC as per standard procedures making sure that the top antenna element is adjusted to the proper frequency band that the AN/PRC-521 has been frequency filled to.
3. Remove the antenna from the AN/PRC-521 and install in its place a BNC jack to TNC plug adapter.  Do not over tighten the adapter in position or it will be very difficult to remove it later due to the limited "finger room" available to grip the adapter and unscrew it out of the radio's antenna jack.
4. Connect the AS-5162/VRC antenna system to the AN/PRC-521 radio set antenna connector.

Notes:

1. The use of the AS-5162/VRC ground plane antenna kit provides an increase gain level (+dBi), an overall uniform omnidirectional radiation pattern and an increase in total antenna height above ground with the use of the mast kit.  These characteristics will allow communication ranges of well over several km using the AN/PRC-521.
2. Do not substitute the battery on the PRC-521 for a power supply or power adapter.  The radio set, AN/PRC-521, only offers minimal internal electrical protection at the battery contacts which are unsuitable for use with vehicular DC power or from power supplied by AC adapters and installations connected to a generating set.   Any external power supply should be (a) appropriately fused, (b) filtered against RF ripple that may be introduced in the DC and (c) must protect from voltage spikes.   Additionally, the DC supply must be well regulated.  A good power alternative is to use heavy duty, external 12 Volts DC batteries which are isolated from the vehicle DC supply.  You can have one battery on charge and a second operating the radio.  Alternatively, the use of a BA-5590 Lithium non-rechargeable battery (NSN 6135-01-036-3495) with both internal 12 VDC battery packs connected in parallel and a AN/PRC-521 electrical DC cable plug adapter (NSN 5995-21-913-2633) will yield excellent results.   The BB-590/U (NSN 6140-01-063-3918) is the Nickel-Cadmium version of the BA-5590 and can be recharged with the TCCCS/IRIS battery charging system PP-5417/G (your PRC-521 battery charger).  If you are considering using any of the batteries mentioned above you will require a mating connector for the battery which can be demanded as NSN 5935-01-096-8047.
3. Electrical power to the radio must be constant.  Do not forget that the radio will zeroize 90 seconds after loss of power.

Figure 1.  Block diagram of installations.

CONFIGURATION #2
In this second example, we will substitute the ground plane antenna in configuration #1 for a broadband vehicular antenna system.

The parts required are:

1. Radio Set, AN/PRC-521 with battery BB-521/U and headset microphone H-5034/U.
2. Antenna, VHF Tactical, Vehicular Broadband Model 4242-MK2-N (NSN 5985-01-316-8424).
3. Antenna adapter, BNC jack to TNC plug (see parts list below for p/n).
4. Antenna adapter, BNC jack to N plug (see parts list below for p/n).

As most users will not be familiar with the 4242-MK2 antenna, now is a good time for some background information on it.  The 4242-MK2 is a broadband, centre-fed, dipole antenna.  The antenna base is physically identical to that of the MX-6707 for the exception that it utilizes broadband circuitry that does not require any mechanical nor electrical tuning mechanisms.  The frequency coverage of the 4242-MK2 is from 30 MHz to 88 MHz.  This antenna offers no relative gain.  For the most part, it is -1 to -3 dB below reference for the exception of the band area between 74 MHz and 84 MHz where the antenna exhibits a 0 to +1.8 dB gain with the peek being at 80 MHz.   Despite this, tests with this antenna has yielded excellent results with the added advantage of not having any requirements for electrical "tuner" connections and making the antenna fully compatible with the AN/PRC-25/77, the RT-524 and the AN/PRC-521 radio sets.  Furthermore, its broadband design and its power handling capabilities of 100 watts also makes it compatible with ECCM radio system such as the AN/PRC-116 (JAGUAR-V).   Other enhancements include EMP protection, the upper section of antenna affords protection from electrocution in the event of powerline contact and, the overall design of the antenna makes it suitable for shipboard, shelter and fixed-station applications with no requirements for a ground plane.  The only recommendation that I make is that the user physically mark the lower and upper fiberglass antenna elements of the 4242-MK2 as they closely resemble and can be confused with those of the AS-1729/VRC (MX-6707) antenna elements (AS-1730/VRC and AT-1095/VRC) but are not interchangeable.

Installation:

1. Assemble and frequency/crypto fill the AN/PRC-521 radio set per standard procedures.
2. Install the antenna 4242-MK2 as you would any regular (AS-1729/VRC) MX-6706 AMU.
3. Install the BNC jack to N plug adapter (UG-201A/U) on the 4242-MK2.
4. Remove the antenna from the AN/PRC-521 and install in its place a BNC jack to TNC plug adapter.  Do not over tighten the adapter in position or it will be very difficult to remove it later due to the limited "finger room" available to grip the adapter and unscrew it out of the radio's antenna jack.
5. Connect the 4242-MK2 antenna system to the AN/PRC-521 radio set antenna connector.

CONFIGURATION #3
In this third example, we will explore the "ultimate" installation.

The parts required are:

1. Radio Set, AN/PRC-521 with battery BB-521/U.
2. Antenna system (any of the 2 discussed above) with appropriate accessories.
3. Antenna adapter, BNC jack to TNC plug.
4. Amplifier, Audio Frequency, AM-6747/V (NSN 5895-01-056-4553).
5. Audio adapter cable (manufactured locally).

In this configuration, we will add to the basic AN/PRC-521 installations mentioned above the capability for an operator to have an amplified audio output to a loudspeaker and the ability to connect standard North American audio accessories to the radio set.  Since the radio set utilizes U.K. Clansman Standard audio connectors it is necessary for the user to fabricate an adapter cable that will convert the Clansman audio connector on the AN/PRC-521 to one that can be utilized with North American Standard military audio connectors (U-183/U and U-229/U).

You will require the following parts to manufacture the audio cable adapter.

1. Audio connector for the AN/PRC-521 (NSN 5935-99-721-6448)
2. Audio connector, North American 5 pin in-line jack U-228/U (NSN 5935-00-929-7082)
3. Suitable length of audio cable (NSN 6145-00-484-8981)

Assemble the cable as follows:

Figure 2.  Audio connector adapter assembly.

Now that you have an adapter cable, you can connect any standard audio accessories to the AN/PRC-521.
Since the PRC-521 only has about 400 mWatts of audio output, which is unsuitable for use with the LS-454/U loudspeaker, we will use the AM-6747/V audio amplifier/loudspeaker to boost the output of the radio set to an audible level.  Connect a suitable cable from the audio connector (J2) of the AM-6747/V to the locally manufactured PRC-521 audio adapter.  Then, connect either a H-250/U handset or M-80C/U microphone to the AM-6747/V's handset connector (J1).  Apply power to AM-6747/V from the vehicular system's 24 VDC supply.

PARTS LIST

Revised: June 08 2017
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