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## Re: [Amps] Asynchronous coax matching transformer

 To: Ian White GM3SEK Re: [Amps] Asynchronous coax matching transformer Larry Benko Sat, 01 Aug 2009 09:59:05 -0600 mailto:amps@contesting.com>
 ```Hi Ian & Carl, Actually given only 50 ohm and 75 ohm coax and not paralleling any coax you can match all resistive impedances between 50 and 112.5 (75*75/50) ohms. e.g. 50 ohms ---- 29.3 deg. 75 ohm coax ----- 29.3 deg 50 ohm coax ----- 75 ohms (as shown by the 1/12 wave match) 50 ohms ---- 40.5 deg. 75 ohm coax ----- 23.8 deg 50 ohm coax ----- 85 ohms 50 ohms ---- 58.3 deg. 75 ohm coax ----- 14.9 deg 50 ohm coax ----- 100 ohms 50 ohms ---- 90.0 deg. 75 ohm coax ----- 0.0 deg 50 ohm coax ----- 112.5 ohms (std 1/4 wave match) Also many reactive impedances are also easily matched e.g. 50 ohms ---- 42.6 deg. 75 ohm coax ----- 10.3 deg 50 ohm coax ----- 75 - j20 ohms For a matching over a small range of frequencies transmission lines work well. 73, Larry, W0QE Ian White GM3SEK wrote: > Carl wrote: > >> Does anyone remember the formula for matching 50 to 75 Ohms with 2 very >> short lengths of coax? >> If I remember it used a 75 Ohm section at the output of the amp, and a 50 >> Ohm section to the CATV hardline. Frequency dependent of course. >> >> Its been about 25 years since I built one. >> >> > > http://www.tuc.nrao.edu/~demerson/twelfth/twelfth.htm > > By paralleling two lengths of 50 or 75 ohm line, it can also match to 25 > or 37.5 ohms; or to even lower impedances by paralleling three lengths > of the same line. > > > _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps ```
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