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<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>MUNIN
needs an impedance transformation 1:16 or winding ratio 1:4 of the output
transformer. Since almost 40 years my friend Helge O. Granberg (Motorola
principal staff engineer) recommended to the designers that the primary
impedance at low cut-off should be at least 3 times the load impedance or<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>
2 pi Lp Fmin > 3 R<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>With
R=50 ohms, Fmin=500 kHz: Lp = 47,8 µH<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>It’s
correct that you can multiply the L by factor 6-7 when moving from type 61 to
type 43 of the core material. But it’s not trivial to employ such
transformer now over 7 octaves instead of the current 5 octaves. New
compensation efforts on the upper cut-off will probably be necessary, thus I
would suggest a tailored amp for 470 kHz.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>73,
Helmut, DC6NY<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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color:#1F497D'><o:p> </o:p></span></p>
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<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>Von:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Hpsdr
[mailto:hpsdr-bounces@lists.openhpsdr.org] <b>Im Auftrag von </b>FRANCIS CARCIA<br>
<b>Gesendet:</b> Dienstag, 6. Dezember 2016 23:49<br>
<b>An:</b> hpsdr@lists.openhpsdr.org<br>
<b>Betreff:</b> [hpsdr] 630.<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<div id="yui_3_16_0_ym19_1_1481063715593_11964">
<p class=MsoNormal style='background:white'><span style='font-family:"Helvetica","sans-serif";
color:black'>All,<o:p></o:p></span></p>
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<div id="yui_3_16_0_ym19_1_1481063715593_11964">
<p class=MsoNormal style='background:white'><span style='font-family:"Helvetica","sans-serif";
color:black'>I'm looking at the output transformer. At 50 volts you would need
16uH so at 12V it is down around 4uH. Changing from a type 61 core to
type 43 core the permeability is about 7 times higher. That should yield enough
reactance. BN 43 7051 or the Fair Rite equivalent should work at 12 volts. I
measured the inductance of 1 turn at around 8uH. I had them in my big amplifier
for a while and 2 turns primary worked fine at 50 volts on 160 meters. I only
changed them out for mechanical reasons. BTW I'm using type 43 material on 6
meters with no heating issues but my flux density is under 10g. <o:p></o:p></span></p>
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<p class=MsoNormal style='background:white'><span style='font-family:"Helvetica","sans-serif";
color:black'>Frank,<o:p></o:p></span></p>
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<p class=MsoNormal style='background:white'><span style='font-family:"Helvetica","sans-serif";
color:black'>WA1GFZ<o:p></o:p></span></p>
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