Hi Tod! Thanks for the data. I'd like to build up several toroid chokes for 160, 80 and 40 meter use. I looked at the Fair-Rite site, no 31 material. I looked at their vendors and went to Amidon ...amidoncorp.com/items/19
Amidon does have "F Material Ferrite Toroids" " High Saturation flux density at high temperature. For power conversion transfomers. Good noise suppression from 0.5 to 20 MHz." They offer an "F material" core: FT-240-FC ( $20.00 ea ) Inner Diameter 1.4 Outer Diameter 2.4 Height 0.5 Al Value 4107 Is this material suitable or am I barking up the wrong tree? 73 Lloyd - N9LB -------- Begin forwarded message -------- Subject: Topband Digest, Vol 104, Issue 21 Date: 8/29/11 2:00:40 PM From: [email protected] To: [email protected] Send Topband mailing list submissions to [email protected] To subscribe or unsubscribe via the World Wide Web, visit http://lists.contesting.com/mailman/listinfo/topband or, via email, send a message with subject or body 'help' to [email protected] You can reach the person managing the list at [email protected] When replying, please edit your Subject line so it is more specific than "Re: Contents of Topband digest..." Today's Topics: 1. Fabricated common mode chokes and their impedances (Tod) ---------------------------------------------------------------------- Message: 1 Date: Sun, 28 Aug 2011 16:51:14 -0600 From: "Tod" <[email protected]> Subject: Topband: Fabricated common mode chokes and their impedances To: <[email protected]>, <[email protected]> Message-ID: <0E6261DE04D24FDDA95DBC885D2CE12F@g2> Content-Type: text/plain; charset="us-ascii" This probably has a limited audience but I do know that there are some readers on this list interested in fabrication of high impedance common mode chokes for their stations. I built and measured 18 of this type of choke during the past week. There is a write-up on my web site which shows how they were fabricated, how they were measured and the measurement results. I used Fair-Rite 2.4 inch diameter type 31 toroidal cores and small diameter [RG 59 size} coax. I measured the magnitude of the impedance for each of the chokes on the 160, 80, 40, 20, 15 and 10 meter bands. There are also attenuation values for each choke [specific to the 50 ohm measurement circuit]. The results are shown as a series of graphs for two cores, three cores and four cores with 3, 4, 5, 6, 7 and 8 turns on the core bundle. These graphs should provide guidance to those fabricating their own common mode chokes. The site is http://www.k0to.us/HAM/ham.htm The article is under Experiments & Measurements "Measurement of Chokes made using type 31 material cores" My work is an extension of material found in the excellent paper on this subject written by Jim Brown, K9YC, which has been mentioned here before. Tod Olson, K0TO ------------------------------ _______________________________________________ Topband mailing list [email protected] http://lists.contesting.com/mailman/listinfo/topband End of Topband Digest, Vol 104, Issue 21 **************************************** _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
