Duplexers for 70 cm amateur repeaters

By means of installing the filter at such cavities into the antennas` circuit of the receiver we achieve the complete elimination of the carrier frequency influence from the transmitter. And the filter in the transmitter circuit completely eliminates the irradiation of its own noise outside at broadcasting.

DPRE4-6UL

Frequency MHz
€1131
RXTX

Thus the receiver of the repeater is completely protected against the irradiations of its transmitter.

While using in the repeater two different antennas for reception and for transmission it is usually sufficient to install one filter in each circuit. However in this case the quantity of antennas, feeders and towers has to be doubled. But normally the available space at the roofs of high buildings is limited.

That is why the duplex filters, or duplexers are most commonly applied. These devices allow simultaneous operating of the receiver and the transmitter with one antenna. For the com-plete suppression of the transmitter's signals it is needed to install three cavities in each shoul-der at the receiver's input. By means of using a remarkable feature of the quarter-wavelength converter to transform the impedances from the value corresponding to the "short circuit" into the "infinity" value one can combine both these shoulders into a single common point. And in this case there is no difference for the antenna to receive a signal or to transmit it.

Electrical specifications
Model DPRE4-6UL

Operating
frequency band, MHz 400-440

Insertion loss
(adjustable) not more, dB 2

Frequency separation
TX/RX (min), MHz 1.6

Impedance, Ohm 50

Isolation, not less, dB 90

VSWR, not more than 1.5

Input power, not more, W 300

Temperature range, °C from -30 to +60

Cavity electrical
length 1/4 λ

Mechanical specifications

Model DPRE4-6UL

Diameter, mm (ins.) 116 (4")

Mass, kg 8.1

Connector N-female

Mount to 19-inch rack present

Length/Width/Depth, mm 800x480x265

DPRE4-6UL