Encyclopedia of radio electronics and electrical engineering / Civil radio communications
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A diplexer is a device for adding or separating two signals. It is convenient to use it to operate one multi-band transceiver (receiver) over one drop cable for two antennas or two single-band transceivers for one multi-band.
The scheme of the diplexer is shown in fig. 1. It consists of a low-pass filter L1C2L4C5L6C7L8, a high-pass filter C1L3C4L5C6L7C8 and a notch circuit L2C3. It provides addition (division) of signals in the ranges of 144 and 430 MHz. During its development, attention was paid not only to the required frequency response, but also to obtaining the required input impedance (50 Ohm), i.e., minimizing the SWR.
The inductors have: L1 - 4,5 turns (winding length 12 mm), L2 - 2,5 turns (length 10 mm), L3, L5, L7 - 1,5 turns, L4 - 5,5 turns (length 15 mm ), L6 -4,5 turns, L8 - 2 turns. All of them are wound with PEV-2 1,2 wire on mandrels with a diameter of 5 mm. Capacitors are applicable types KD, K10-17.
The input impedance of the diplexer with XP50 and XP1 outputs loaded at 2 ohms in the frequency ranges 100...160 and 400...500 MHz is 49...51 ohms. The main characteristics of the diplexer: the transmission coefficient in the passband -0,59 ... 0,65 dB, in the stopband -75 dB (145 MHz) and -64 dB (435 MHz), SWR was 1,11 and 1,23, respectively . The frequency response of the 144 MHz channel is shown in fig. 2, and the 430 MHz channel - in fig. 3.
The dependence of SWR on frequency is shown in fig. four.
Structurally (Fig. 5), the diplexer is made in the form of a metal box 1 with a lid, on one wall of which an RF socket 2 (XS1) is installed, and two sections of the RF cable 3 and 4 with plugs at the end are led out through the other side. In the middle, the box is divided by a metal partition 5. Installation is carried out by a hinged method, capacitors are used as support posts in the low-pass filter, and inductors are used in the high-pass filter, while the leads of the capacitors and cable are made as short as possible. The braided cable is soldered directly to the metal case of the diplexer, for this it is desirable to use a cable with a fluoroplastic insulator.
Author: Igor Nechaev (UA3WIA), Kursk
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Boris
I repeated the diplexer, set it up, it works fine, but from 100 watts the coils burn out at 144. 50 watts, no longer pulls [roll]
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