I'm lazy. Rather than epoxying beads together, I just buy the binocular cores like the BN73-202 or 2873202.
The former is only $.31 in singles from Newark. It makes the best transformer I've measured for Beverage matching - low loss, wide bandwidth. Chuck -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Gil Stacy Sent: Sunday, August 26, 2007 11:35 AM To: Mailing list for the International Radio Club of America Subject: Re: [IRCA] Cable work "What I didn't do is space the toroid so it was centered in the box, nor were the windings exactly opposite to each other on the toroid." A retired electronics pro that I know tested xfrmers with a spectrum analyzer with built in tracking generator and discovered that he had losses above 1000 kc on his transformers with opposing windings on J or 75 mix. His best results occurred with the secondary windings centered on top of the primary, overlapping. His test results were outstanding from LW up. For a transformer, I have followed Gary Breed's (k9ay) method of using two FB77-6301 Ferrite beads epoxied together to make a small bino core. 9 turns of #24 mag wire and 3 turns for the RX side. I saw his note on topband. My buddy tested this core and found MW performance to be very good, but LW had more losses than the 114J or 75 core. While the small twin bead xfrmr did not measure quite as good in the MW band as the toroid core, one would not notice the difference at the headset. These beads are quite small in comparison with the 114 cores and cost $5/dozen. The FT 114J's are $3.75 per. http://www.amidoncorp.com/pricing/ If you are looking for a more compact transformer for strictly MW, the beads are the way to go. 73 Gil NN4CW _______________________________________________ IRCA mailing list IRCA@hard-core-dx.com http://montreal.kotalampi.com/mailman/listinfo/irca Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers For more information: http://www.ircaonline.org To Post a message: irca@hard-core-dx.com
