People are talking about this super cheap VHF 500W amplifier kits from China, for $35 it comes with the PCB and all components including the LPF, even on-board couplers for SWR! Pretty good deal, isn't it? Is it? Here's the catch, or maybe I should say: "Here are the catches."? First of all, it is a very "simple" design, trying to squeeze a pair of 600W transistors onto board that was originally designed for 170W FM band . It has no thermal compensation to lower the bias in when the amp gets hot, and speaking of bias, there is only one potentiometer for the two MRF300s to share, making adjusting IDQ individually impossible. There is no bias switching circuitry either, unlike other popular amp designs that only supply bias when TX, on this amp the bias will be always on, resulting in warmer transistors. Other things to keep in mind: The bias potentiometer, as the schematics suggests, is placed on the upper side of the voltage divider, which means the bias
Hi~Dear OM 您好! 我姓 連 我的Call sign 是BV2FD 很高興能遇上我們八里在地的業餘電台
回覆刪除我的QTH在八里派出所附近 因目前沒有較大型的短波天線只有簡易的汽車天線
所以很多年沒有上線 通常都在2米守聽 希望有機會能在線上與您通聯 !
73 !
BV2FD
好的,有緣空中相見!
刪除73