Yes that is correct and the five times rule is marginal at best - even for fifty-ohm feed point antennas. Here are a couple of URLs that have good papers on the subject and the reasons that the choking impedance should several times greater than the five time rule. http://www.ifwtech.co.uk/g3sek/in-prac/inpr1005_ext_v1.pdf and http://audiosystemsgroup.com/RFI-Ham.pdf 73, Danny, K6MHE On 07/01/2010 10:09 AM, Brian Cake wrote: > That rule of thumb does not apply to off-center-fed antennas, such as > the C pole, where the common mode potential at the feedpoint can be high. >> 73 >> Brian KF2YN > ----- Original Message ----- > From: "Roy"<royanjoy at ncn.net> > To:<Antennas at mailman.qth.net> > Sent: Thursday, July 01, 2010 12:47 PM > Subject: Re: [Antennas] RG-178 balun turns count >>>>> About: >>>> "I have a 2" diameter coil form. How do I calculate/test for the number >> of turns required to be an effective choke at 14MHz?" >>>>>> The old rule is to aim for five times the reactance in the coil than the Z >> of the load....5 X 50 = 250 ohms. >>>> 73, Roy K6XK >>>>>>>> ______________________________________________________________ >> Antennas mailing list >> Home: http://mailman.qth.net/mailman/listinfo/antennas >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:Antennas at mailman.qth.net >>>> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >>>> __________ Information from ESET NOD32 Antivirus, version of virus >> signature database 5243 (20100701) __________ >>>> The message was checked by ESET NOD32 Antivirus. >>>> http://www.eset.com >>>>>>>>> ______________________________________________________________ > Antennas mailing list > Home: http://mailman.qth.net/mailman/listinfo/antennas > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Antennas at mailman.qth.net >> This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html >>