Design of broadband transformers. Scheme, description

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Design of broadband transformers. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Knots of amateur radio equipment. Filters and matching devices

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In an article devoted to the design of broadband transformers (SHPT) on ferrite rings for transistor KB power amplifiers, it is noted that the cross section of the ring should be 0,25 cm² for every 100 watts. The winding inductance is calculated by the formula Lmin[MKrH]=4R/(27pf), where R is the resistance of the circuit in which this winding is connected [Ohm], af is the lower operating frequency of the SHPT [MHz]. So, for f=1,8 MHz and R=50 Ohm Lmin=18 µH.

Design of broadband transformers
Ris.1

Ris.2

Figures 1 and 2 for this example show the circuits of transformers 1:4 and 1:9, respectively. The first of them is wound with four wires put together, with the condition of obtaining an inductance of one winding of 4,5 μH, and the windings are connected according to Fig. 1. The second SPT is wound simultaneously with six wires with an inductance of one winding of 2 μH.

Author: Zoltan Jabot (HA9PN); Publication: N. Bolshakov, rf.atnn.ru

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