6 responses

  1. dan, w5xz

    very nice work.

    it is possible to use a single core. i used a ‘binocular’ core, 43 material, and it works
    very well to share the beverages between 80 and 160 m at W5WMU. for reception only, of
    course..amidon BN 43-202 i think…w8diz has them, very inexpensive.



    the last item; with a 10 turn primary, and 7 turn secondaries, #30 wire. it works f.b. both on
    my miniVNA and in the ‘real world’ of multi-tx contesting. for 50 ohm systems, of course, the resistor should be 25 ohms. our bev. feedlines in La. are RG-6, 75ohms.

    73 from texas; keep up the good work. w5xz, dan

  2. werner, DK8PD

    Hallo Tobias,
    der Artikel ist gut. Leider enthält er auch einen Sprachfehler:
    wounded = verwundet. Richtig muss es heissen ‘wound’ (siehe http://dict.leo.org)

    While the splitter is adequate for most amateur radio applications up to 30 MHz there is room for improvement. Doug Smith, KF6DX gave some thoughts and measurements for high precision splitters in an appendix to his QEX article ‘In Search of New Receiver Performance Paradigms, Part 3′ (QEX March/April 2007, pages 28-34). He used binocular cores allowing small dimensions which is beneficial for the performance at the upper part of the frequency range.

    73 from Monheim. keep on experimenting, werner

    • Tobias

      Hey Werner,
      Thanks for the Information. Sounds good – I always enjoy reading articles from Doug. I’ll dig search for it in the QEX archive.
      Thanks for finding the typo. I already corrected it.
      73, Tobias

  3. Pietro

    Hi Tobias,

    thank you for sharing this nice article ! Already built one as described with two small FT-50-61 for my 2 JRC receiver, just great ! But I have few question:

    – Now I am doing some test measurement with another FT-50-61 toroid with same winding, from the tapping point I connect a 25ohm resistor to gnd and measure it with a network analyzer, wooww I get a nice 20dB return loss …

    – from where you start to calculate the input tri-filar winding ? I checked the toroid data and found matching the real measurement ( each singular winding is about 6,2 uH), and then when coupling them I measure = 6,2 – 24 – 57 uH.

    – but why those figure with the desired band ? 2 -30 MHz ?

    Thank you for any usefull info !

    • Tobias (DH1TW)

      Hi Pietro, just measure one winding. So your 6,2 uH seems absolutely fine to me! The point of the measurements was to check the characteristics of the Splitter… just out of curiosity

    • Pietro

      Hi Tobias,

      thank you ! Maybe I was not so clear about my question … sorry !

      I just wonder why you start calculating your first toroidal core with 3 x 10 trifilar trasformer (tapped at first 10 turns to achieve 25 ohm).

      Is there some law or formula to trasform 50ohm input impedance to 25 ohm to match the input impedence of the second toroidal winding for the band up to 30MHz ?

      I googled around but didn’t found any good answer ….

      BR, Pietro HB9RXC JN45LU

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