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<blockquote data-quote="battenfan" data-source="post: 966491" data-attributes="member: 239108">I don't feel like buying expensive 50 ohm cable for a toy rtl and a toy coat hanger antenna. For a 75 ohm discone, the cone angle should be reduced.For broadband operation, the best cone angle depends on band-width. Given a frequency band from f1 to f2, the optimum cone angle decreases as the ratio f2/f1 increases. For a nominal 50-Ω antenna, as the design bandwidth increases from one to ﬁve octaves, the optimum cone angle decreases from 47° to 39°, and the peak SWR creeps up. In addition, as the feed point design impedance increases, the optimum cone angle decreases. An interesting implication pursued in some designs is that the cone should be curved instead of ﬂat sided.<a href="http://www.fars.k6ya.org/docs/All_About_the_Discone_Antenna,_QEX,_Jan-Feb-2007.pdf" target="_blank">http://www.fars.k6ya.org/docs/All_About_the_Discone_Antenna,_QEX,_Jan-Feb-2007.pdf</a>I'll probably order some cheap Chinese pre-amps, it would be nice if there were some with balanced input for the qfh.I have to start making up my mind on what frequencies I want to receive.</blockquote>

[QUOTE="battenfan, post: 966491, member: 239108"] I don't feel like buying expensive 50 ohm cable for a toy rtl and a toy coat hanger antenna. For a 75 ohm discone, the cone angle should be reduced. [i]For broadband operation, the best cone angle depends on band- width. Given a frequency band from f1 to f2, the optimum cone angle decreases as the ratio f2/f1 increases. For a nominal 50-Ω antenna, as the design bandwidth increases from one to ﬁve octaves, the optimum cone angle decreases from 47° to 39°, and the peak SWR creeps up. In addition, as the feed point design impedance increases, the optimum cone angle decreases. [b]An interesting implication pursued in some designs is that the cone should be curved instead of ﬂat sided.[/b][/i] [URL]http://www.fars.k6ya.org/docs/All_About_the_Discone_Antenna,_QEX,_Jan-Feb-2007.pdf[/URL] I'll probably order some cheap Chinese pre-amps, it would be nice if there were some with balanced input for the qfh. I have to start making up my mind on what frequencies I want to receive. [/QUOTE]

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