Fw: Re: [HBR] transformers or capacitors

Thu, 25 Apr 2002 11:35:51 -0500

I can imagine 300 turns each on several toroids would burn you 
out. I think I'll stick to the slug tuned cores ... I think the mid 50s 
article uses TV horizontal osc coils. 

Anyone ever suceeded in making a homebrew toroid winder ?

73s  Kees K5BCQ 

--------- Forwarded message ----------
From: Helmut Usbeck <[email protected]>
To: <[email protected]>, <[email protected]>
Date: Wed, 24 Apr 2002 23:45:34 -0400
Subject: Re: [HBR] transformers or capacitors
Message-ID: <20020425154640.FTAA25781.out004.verizon.net@gemini>

>Some questions. What are the pros and cons of IF
>transformer coupling vs capacitor coupling (2-3pf)
>of tuned circuits ? Ray N3XZV pointed me towards
>an article in a mid 50s ARRL Handbook which touts
>some pretty sharp passbands using the latter (several
>stages).
>
>I think it's great to read an article which discusses
>"L1" .... with inductance, number of turns, and coil "Q".
>That's doing it right.
>
>73s  Kees K5BCQ
>************************************
>Visit the HBR Receiver Web Site with over 100 pictures of receivers
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>
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>http://mailman.qth.net/mailman/listinfo/hbr
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>
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To me, the first thing about using shunt inductors with coupling caps 
was always, seems to be easier to build one own's coils and IF 
strips.  Also changing the coupling cap value is one way of varying 
the selectivity.  I don't think there's a selectivity advantage of 
one over the other.  I built a 50 khz IF strip once using 3 inductors 
which then fed an LM-1350 ic.  It worked on the bench and had a 
bandwidth about 2 khz.  The coupling capacitor between the coils was 
a 3 gang variable capacitor.  Increasing the capacitance (and 
coupling) between the coils brought the selectivity out to 12 khz or 
so.  Never used this thing in a receiver.  The inductors were 300 
turns of #28 on 1 inch toroids I pulled out of a switching power 
supply.  It took about a week and a half to wind the coils.  I hate 
winding toroids now.
Chapter 26 in the Radiotron book has a lot about if transformers 
along with the math, Q, selectivity and such.  Only thing it  about 
shunt inductors is that they're not used too much.
-- 
Helmut Usbeck, WB2ADT [email protected] on 04/24/2002
"You mean you can build something like that!?"

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