[hpsdr] 630.

[Helmut]

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

                                                         2 pi Lp Fmin > 3 R

With R=50 ohms, Fmin=500 kHz:    Lp = 47,8 µH

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.

 

73, Helmut, DC6NY

 

 

Von: Hpsdr [mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von FRANCIS
CARCIA
Gesendet: Dienstag, 6. Dezember 2016 23:49
An: hpsdr at lists.openhpsdr.org
Betreff: [hpsdr] 630.

 

All,

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. 

Frank,

WA1GFZ



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