Antenna switch for Yaesu FT-817 transceiver. Scheme, description

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Antenna switch for Yaesu FT-817 transceiver. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Civil radio communications

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DGOZB proposed an automatic antenna switcher for the Yaesu FT-817 transceiver. This transceiver can operate on 12 amateur bands from 160m to 70cm with only one antenna connector. To identify the included range, the author used the BAND DATA output of the ACC connector of the transceiver (Fig. 2), on which there is a voltage that varies in steps of 0,33 V depending on the range (Table 1).

Range, m	Band Data, V	Estimated value, V
160	0,33	0,34
80	0,66	0,69
40	1,00	1,03
30	1,33	1,33
20	1,66	1,68
AM	k.A.	2,03
17	2,00	2,3
15	2,33	2,37
12	2,66	2,63
10	3,00	2,97
6	3,33	3,33
VHF-FM	k.A.	3,67
2 m	3,66	3,67
70 см	4,0	3,98
k.A. - not in the specification

The switch circuit (Fig. 1) is based on the IC of a multi-channel comparator (or quasi-ADC) A277D (analogous to UAA180), which has 12 outputs (pins 4 ... 15), on which 0 V appears relative to - Up, depending on the voltage at input (vyv.17).

Fig.1 (click to enlarge)

For the correct operation of the switch circuit with the FT-817, first set the lower threshold of the comparator, for this, a 2,2 kΩ potentiometer achieves 0,33 V at pin 16 A277D, then when you turn on 160 m in the FT-817, 15 V will appear at pin 277 A4,2D. The upper limit of the 3 V comparator on pin 277 of the A2,2D is set using a second 2 kΩ potentiometer. Power is supplied to the circuit from the transceiver through the same ACC connector (Fig. XNUMX).

Antenna Switch for Yaesu FT-817 Transceiver
Ris.2

The proposed scheme switches 4 antennas, after a simple refinement, it can switch up to 12 antennas.

Author: Knut Theurich (DGOZB); Publication: N. Bolshakov, rf.atnn.ru

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