楼主所列的都是电压型巴伦。实际按国外测试和看法,还不如两根线并绕的电流型(扼流型)巴伦。两线并线既可以绕出电流型巴伦,也可以绕出电压型巴伦,都可以绕出不同的阻抗比。
最后那个伦是4:1 电流型巴伦,频率1.5 - 54 mhz 可用于双极天线和八木,最大承受功率:3千瓦,价格68美元一个,据说用了特夫龙涂层防止高压打火。要我看,要上大功率的话,就用电缆绕巴伦。
下面一段选自w8ji的文章''choosing the correct balun'',全文在附件中,pdf文档。
电压型巴伦
电压型巴伦迫使输出终端(我的理解是双极天线的最未端)有相同的电压,这有时会在输出端和地之间产生相移(不懂),如果天线两边的阻抗不是完全相等,馈线和负载天线的电流就不是大小相等、方向相反,馈线就产生幅射。
电压型巴伦不提供共模电流隔离,电压型巴伦几乎肯定会产生馈线幅射(同时也意味着馈线参与接收,底噪增大),因为几乎没有完美平衡的天线和完美的电压巴伦。
不同于1:1的电流型巴伦,电压型巴伦总是磁化它的磁环,并且正比于负载(天线)电压,负载阻抗直接影响磁环热度和磁通密度。
电流型巴伦,而不是电压型巴伦,在任何可能情况下都是首选,电流型巴伦提供更好的平衡并且通常有更低的损耗,电流型巴伦,特别是1:1的巴伦,容忍阻抗和平衡的变化比电压型巴伦强,电流型巴伦可以隔离馈线和天线,还可用在不平衡到不平衡的转换(如同轴馈线接长线天线)。
下面列了原文,译得不对和不准的地方请指出,国外的文章仅作参考和讨论资料。
什么是电流型巴伦,两线并绕没有任何花稍的就是1:1的电流型巴伦,下图是几种电流型巴伦。
voltage baluns
voltage baluns always try to force the output terminals to equal voltages. they sometimes introduce phase shift between each output terminal and "ground". if the impedance presented at each terminal is not exactly equal, feedline or load currents will not be equal and opposite. this means the feedline will radiate.
they also do not provide common-mode isolation. a voltage balun almost certainly guarantees some feedline radiation (or reception), because there are very few "perfectly balanced" loads or perfect voltage baluns.
unlike a 1:1 ratio current balun, a voltage balun will always magnetize its core in direct proportion to load voltages. in a voltage balun, load impedance directly affects core heating and flux density.
current baluns, rather than voltage baluns, should be used whenever possible. current baluns provide better balance and often have lower loss. current baluns, especially 1:1 ratio baluns, tolerate load impedance and balance variations much better than voltage baluns. current baluns can also be used as isolators or un-un's.