The Kiwa Shortwave Preamp is a high performance preamp optimized for the SW frequencies. The Preamp is designed to connect between the antenna and receiver to provide additional gain to signals within the shortwave spectrum. Impedance matching to any type of antenna is provided with the high and low impedance inputs. (The low impedance input is ideal for slopers and dipoles while the high impedance input is ideal for long-wires and beverages.) The preamp also includes the Kiwa BCB Broadcast Band Rejection filter at the preamp input. The filter will virtually eliminate any possibility of distortion or interference within the shortwave spectrum from strong broadcast band signals.
The SW Preamp is ideal for receivers that lack an internal RF Preamp. Such a receiver is the Lowe HF-150. Bench measurements of the HF-150 showed that the receiver's Noise Figure is 12 dB. By adding the SW Preamp, the combined Noise Figure measured 6.5 dB. The result is an extremely quiet receiver. Other receivers with their preamps engaged typically measure higher. (The Drake R8 with the preamp engaged measured 9.8 dB, the NRD-525 measured 12.3 dB) Another example of how the SW Preamp can improve the Noise Figure of a receiver is with the Drake R8A. The Noise Figure of the R8A with the Preamp engaged measures 12.8 dB. By switching out the internal preamp and using the Kiwa SW Preamp, the Noise Figure measures 9.3 dB - an improvement in Noise Figure of 3.5 dB.
The receiver's Noise Figure may be improved when using the SW Preamp, especially if the receiver's preamp can be disengaged.
The SW Preamp has excellent signal overload immunity. It typically measures 20 dB better than the average receiver. Third Order Intercept or ICP3 is a measurement of signal overload characteristics. The SW Preamp ICP3 measures +34 dBm. A typical table top receiver measures +4 to +10 dBm. The Drake R8A specifies an ICP3 of +10 dBm with the preamp engaged.
The balanced input allows proper termination to balanced antennas such as a two wire beverage antenna, or T2FD antennas. Kiwa will soon have a phase switching control unit available for balanced beverage antennas. This control unit would connect to the SW Preamp output and the CT-Center Tap connection providing the ability to switch the receive pattern of a two wire beverage antenna. (In one position the receive pattern would be from one end, the other position would switch the receive pattern to the other end.)
Reception below 1.8 MHz is possible when using a long-wire or beverage antenna by connecting the receiver input to what is the 50 Ohm Input. In this configuration the input transformer is acting as an impedance matching device to the 50 Ohm Input and signals are passively coupled to the receiver bypassing the BCB Filter and Preamp.
Kiwa Electronics503 7th. Ave. N.E.
Kasson, MN 55944 USA