SunSDR2DX PA50WV amplifier

This kit includes a SunSDR2DX transceiver and a PA50WV VHF power amplifier. The amplifier extends the transceiver’s capabilities on the 2 m band by increasing transmit output power to 50 W. A built-in low-noise amplifier in the PA50WV is available for weak-signal reception. The kit is intended for operators who want to complement their HF/VHF transceiver with a more powerful transmit chain on the 2 m band.

The PA50WV 50 W VHF power amplifier (hereinafter referred to as the Amplifier) for the 2 m band is designed for linear amplification of high-frequency signals. Externally, it uses the SunSDR2PRO transceiver enclosure and a heatsink and fan from the SunSDR2DX.

This amplifier will be of interest to operators making long-distance contacts on the 2 m amateur band. One possible application is installation in a vehicle together with a SunSDR2PRO transceiver.

A Mitsubishi RA60H1317M amplifier module is used to deliver 50 W of VHF output power. Active broadband components eliminate the need for adjustment or tuning throughout the operating frequency range. Active cooling allows continuous-carrier operation for extended periods at full output power. The amplifier uses a conventional single-ended circuit and supports all modulation modes.

Features

50 W

PA50WV provides clean signal amplification up to 50 W over the 136–174 MHz range.

The amplifier can operate continuously for extended periods, including in digital modes.

Two input levels

The input-power setting can be switched between 1 W and 5 W.

Compact size

The amplifier measures 185 × 165 × 83 mm including the cooling module and weighs 1.7 kg, making it suitable for DXpeditions.

Built-in LNA

To improve reception, the amplifier uses a low-noise amplifier with a gain of +19.5 dB. It is enabled by the “LNA” button on the front panel and operates only on receive: power to the LNA is removed automatically when switching to transmit.

What the LNA delivers in practice

The measurement was made with a SunSDR2PRO transceiver at 145.1 MHz in CW, with a 500 Hz receiver bandwidth and an input signal level of −110 dBm.

The signal increased by 18.3 dB, while the receiver noise increased by only 2.1 dB. The signal-to-noise ratio improved by 16.2 dB: a station that was barely intelligible can now be received clearly.

LNA off: signal −112.2 dBm, noise −122.4 dBm

LNA on: signal −93.9 dBm, noise −120.3 dBm

The improvement depends on the antenna, feed line and noise conditions at the operating location: the lower the receiver's own noise, the less an external preamplifier will contribute. These figures are the result of a specific measurement, not a guaranteed specification.

Transmit control

The amplifier switches to transmit in response to an external control signal from the transceiver through the “TX” connector. PA50WV has no RF detector: an input signal alone does not switch it to transmit, so the transceiver must provide a PTT control output.

Output power and drive

The “Pin” button selects an input level of 1 W or 5 W; nominal output power is the same in both settings: 50 W. The amplifier is linear, so output power follows input power: in the 5 W setting, an input of 2.5 W produces approximately half the output power. There is no separate power control on the enclosure and ALC is not used; power is set in the transceiver.

Important. Set the drive-power limit in the “Power correction” menu of the transceiver control software. This sets the maximum output level in the firmware and strictly limits spikes that could damage the amplifier. Never apply an input level above the selected setting.

Enclosure indicators

“FWD” — the amplifier is transmitting

“REF” — reflected power; lights when SWR exceeds 3:1

“LNA” — the low-noise amplifier is enabled

“PWR” — power

The REF indicator is a warning for the operator, not automatic protection: the amplifier does not switch off by itself, so the operator must respond to the indication.

More about the PA50WV power amplifier (VHF, 2 m)