Felipe,
I just now built & tested what you need. I tried 7 & 8 turns, but it resolved too high in freq. Use 9 TURNS on a core-stack of five (5) of P/N 2631803802 cores. That’s the Mix #31 core. For the choke windings, make the windings VERY tight to the core-stack. To do that, you will need 79 INCHES of RG-58/U – for the windings alone. ADD to that what you need for a pigtail and connectors. Here is what I measured after I built the above. As measured on my DG8SAQ VNWA Vector Network Analyzer: 1.8 MHz Zmag = 12,230 Ohms, Rs = 9,201 Ohms, 41.8 dB Common Mode Attenuation 1.9 MHz Zmag = 13,211 Ohms, Rs = 10,831 Ohms, 42.47 dB Common Mode Attenuation 2.0 MHz Zmag = 14,083 Ohms, Rs = 12,414 Ohms, 43.03 dB Common Mode Attenuation Put the choke close to the 9:1 matching device. 1 Foot from the 9:1 will be fine. If you want to, add another choke (9T on 5 Cores) 1 foot from the switch box. If you have any questions, please email me: N3RR (at) erols.com I can email you the frequency plot from my VNWA if you want it. Please let me know how this works for you. 73 & GL! Bill N3RR _____ From: "Filipe Lopes" <ct1...@gmail.com> To: "JC" <n...@comcast.net> Cc: "topBand" <topband@contesting.com> Sent: Monday, October 12, 2015 1:51:43 PM Subject: Re: Topband: Commond mode choke for Beverage Hello JC, Thanks for your answer. I just ordered a few 2631803802 and 5943003801 from mouser. With these ferrites I ask the same question, should I put the choke close to the 9:1 Balun or near the switching box and how many turns? some bevs have the feed point at +- 60m away from the switching box. 73's Filipe Lopes CT1ILT - CR6K F4VPX - TM3M 2015-10-12 15:40 GMT+02:00 JC <n...@comcast.net>: > 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 No virus found in this message. Checked by AVG - www.avg.com Version: 2015.0.6172 / Virus Database: 4435/10802 - Release Date: 10/12/15 _________________ Topband Reflector Archives - http://www.contesting.com/_topband