If you must use FT240-61, then in a single layer about 18 turns of RG58 would fit, which should give you ~600 Ohms on 1.8 MHz. That would be very good for a dipole, but for a Beverage a much higher impedance is needed. Try to fit as many turns as possible, until there is no more room in the center of the core.
Alternatively, use RG174. In a single layer you should be able to put ~32 turns, which will give you a respectable 2000 Ohms on 1.8 MHz. But in this case take care to make all coax joints (RG174 to RG58) completely shielded, eg. by using a copper foil. 73, Sinisa YT1NT, VE3EA ----- Originalna poruka ----- Pošiljalac: JC <n...@comcast.net> Datum: Ponedeljak, Oktobar 12, 2015 15:40 Tema: Re: Topband: Commond mode choke for Beverage Primalac: 'Filipe Lopes' <ct1...@gmail.com>, 'topBand' <topband@contesting.com> > Hi Filipe > > Zero , you should use material #31 or #77 , The core you > have is not good > for low bands. > > JC > N4IS > -----Original Message----- > From: Topband [mailto:topband-boun...@contesting.com] On Behalf > Of Filipe > Lopes > Sent: Monday, October 12, 2015 8:46 AM > To: topBand <topband@contesting.com> > Subject: Topband: Commond mode choke for Beverage > > Hi guys, > > I am about to add a common mode choke to isolate the antenna > from its > feedline to each of my beverages and I only have FT240-61 > ferrites. My > question is how many turns should I do on the ferrite using RG58 > (all my > bevs are fed with RG58). Also should I put the choke near the > 9:1 balun or > near my bev switching box? > > Thanks in advance. > > 73's Filipe Lopes > CT1ILT - CR6K > F4VPX - TM3M > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband > > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband