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High Performance
25 Watt Mast Mounted
Amateur Preamplifiers

mast mount preamplifier Features:

• Low noise figure
• Automatically switches off during transmit
• 25 watt through power capability
• No transceiver modification necessary
• High immunity to overload
• Completely shielded
• Rugged custom weatherproof enclosure
• Mounts to 1-1/4” - 3-1/4” diameter masts

Series MSPXXXVD, MSPXXXVDA and MSPXXXVDG preamplifiers have been designed for the most demanding amateur, commercial and military applications. This series of preamplifiers are specifically designed for mast mounting. Locating the preamplifier close to the antenna reduces feedline losses ahead of the preamplifier lowering system noise figure. Each preamplifier is housed in a rugged, weatherproof custom aluminum enclosure. An aluminum and stainless steel clamp assembly facilitates mounting of the preamplifier to masts of 1-1/4” through 3-1/4” diameter. This clamp assembly may be removed for in station mounting. Female N coaxial fittings are provided for the input and output rf connections. DC and control functions are made through an MS military type connector. A mating connector for the control line is supplied.

Several models of preamplifiers are available for most frequency ranges. Selection of the most suitable model for a particular application will depend primarily on the noise figure and overload characteristics required. Preamplifier models using dual-gate MOSFET and bipolar transistor devices (part numbers with suffix VD or VDA) are suitable for most scatter, tropo, satellite, ATV, repeater and radio telescope applications. Gallium-arsenide FET (GaAsFET) preamplifiers (part numbers with the suffix VDG) provide the lowest noise figures and highest immunity to overload of any preamplifier types. These preamplifiers would be well suited for very low signal level work, either terrestrial or earth-moon-earth (EME) communications, or in areas where strong signal levels are normally a problem.

MSP series preamplifiers use rf sensing to detect the presence of transmitter power and immediately switch the preamplifier out of line. The relays used in the preamplifier will handle 25 watts of rf power. In systems where higher power amplifiers are used, the preamplifier may be installed between the driver and final power amplifier. MSP series preamplifiers may also be hard keyed with a GND to transmit command. If hard keying of the preamplifier is planned, we recommend the use of a sequencer such as the TRS04VD. Review the TRS04VD instruction sheet for more detailed information.

All preamplifiers are designed to be powered by a 10 - 16 volt dc source with a current consumption of 100 mA. Low power consumption along with the small size make these preamplifiers ideal for installation within existing equipment or systems, or for remote mounting at the antenna. Mounting the preamplifier at the antenna will provide the best system noise figure.

For mast mount applications, power for the preamplifier can be supplied via the output coaxial cable - consistent with the capabilities of some newer transceivers. Alternatively, a “dc injector” can be installed in the transmission line at the transceiver. A suitable dc injector is part number DCINJ-N-PWR. When ordering a preamplifier, specify that the optional “choke” be installed for applications where power will be fed via the output coaxial cable. For example, part number MSP144VDG-25-choke.

Specifications

Model



MSP28VD-25
MSP28VDG-25
MSP50VD-25
MSP50VDG-25
MSP136VD-25
MSP136VDA-25
MSP136VDG-25
MSP144VD-25
MSP144VDA-25
MSP144VDG-25
MSP220VD-25
MSP220VDA-25
MSP220VDG-25
MSP432VD-25
MSP432VDA-25
MSP432VDG-25

Freq.
Range
(MHz)

28-30
28-30
50-54
50-54
136-138
136-138
136-138
144-148
144-148
144-148
220-225
220-225
220-225
420-450
420-450
420-450

N.F.
(dB)


1.2
0.55
1.4
0.55
1.6
1.1
0.55
1.6
1.1
0.55
1.9
1.3
0.55
1.9
1.2
0.55

Gain
(dB)


15
24
15
24
15
15
24
15
15
24
15
15
24
15
17
16

1 dB
Comp.
(dBm)

0
+12
0
+12
0
0
+12
0
0
+12
0
0
+12
-20
-20
+12

1 dB
Bandwidth
(MHz)

2.5
2.0
5.0
4.0
8.0
8.0
7.0
8.0
8.0
7.0
10
10
12
40
40
40

Device
Type


DGFET
GaAsFET
DGFET
GaAsFET
DGFET
DGFET
GaAsFET
DGFET
DGFET
GaAsFET
DGFET
DGFET
GaAsFET
Bipolar
Bipolar
GaAsFET

Price



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Supply voltage: 10 - 16 Vdc
Supply current: tx - 10 mA, rx - 100 mA
Weight: 10 oz.
Through mode VSWR: 1.25 max
Through mode attenuation: 0.5 dB max
Minimum power to rf switch: 0.5 watt
Dimensions: outline drawing

Prices shown for standard N connectors
For custom frequency ranges see
Special Frequency Ranges or contact factory

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