# Editing RF-Amp

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Latest revision | Your text | ||

Line 154: | Line 154: | ||

* Input Transformer (T1 on Charlie's - T2 on this board) | * Input Transformer (T1 on Charlie's - T2 on this board) | ||

* Need to calculate turns ratio | * Need to calculate turns ratio | ||

− | * 50:80.8 | + | * 50:80.8 Ohms |

* n = sqrt(Zout/Zin)sqrt(80.8/50) = 1.27 turns ratio | * n = sqrt(Zout/Zin)sqrt(80.8/50) = 1.27 turns ratio | ||

* Turns choices | * Turns choices | ||

* Minimum number of turns | * Minimum number of turns | ||

* Rule of thumb - want Xl (coil impedance smallest value) to be least 4-5X the load | * Rule of thumb - want Xl (coil impedance smallest value) to be least 4-5X the load | ||

− | ** Load = 80.8 | + | ** Load = 80.8 ohms |

− | ** 5 * 80.8 | + | ** 5 * 80.8 ohms = 404.2 ohms minimum |

*** More turns = larger capacitance and drops bandwidth | *** More turns = larger capacitance and drops bandwidth | ||

** Toroid is FT37-43 | ** Toroid is FT37-43 | ||

** From [http://toroids.info/FT37-43.php Toroid page] | ** From [http://toroids.info/FT37-43.php Toroid page] | ||

− | *** Xl = 404. | + | *** Xl = 404.4 at 9 MHz is 4.5 turns, round up to 5 |

** Try nearest integer numbers turns ratios | ** Try nearest integer numbers turns ratios | ||

*** 5:6 = 6% error | *** 5:6 = 6% error |