Fw: Re: [HBR] Small 100Khz IF transformers

Sun, 5 May 2002 11:18:25 -0500

I just tried puting the two coils in the 262Khz JW Miller 15-H
in series and you get approx 10mH ....that's expected. This 
and a 250pf capacitor provides resonance at 100Khz. Only 
thing is that with the windings, when connected so they are 
in the same direction, or connected so they are bucking, 
results in a "Q" of 62-64 ......less than the previous measurements. 
I would guess it has something to do with the coil spacing ? 
or the physical design of K-TRAN transformers ? 

All Q measurements are made without any internal/external 
capacitors except for what's in the Q meter and stray 
capacitance to the shield, etc.

73s  Kees K5BCQ  

--------- Forwarded message ----------
From: [email protected]
To: [email protected]
Date: Sun, 5 May 2002 10:06:59 EDT
Subject: Re: [HBR] Small 100Khz IF transformers
Message-ID: <[email protected]>

In a message dated 5/5/02 7:24:14 AM Eastern Daylight Time, [email protected] 
writes:

> Have you given any thought to using two of these 262 coils?
>  Place the windings in series on each and wind yourself a link
>  coil on each, between the windings. Use this link coil as your
>  coupling between the two tuned circuits. If you experiment a
>  bit, you can likely stick a cap across the link to vary bandwidth.

Better yet, try this:

Connect the two coils in series-aiding but leave one end of the winding
free 
(may require destruction of the internal capacitors). Use "bottom
coupling" 
like in the DC-500 receiver to obtain adjustable bandwidth. The DC-500 
claimed bandwidths suitable for AM, SSB and CW from 50 kc. IFs made from
TV 
width coils, whose Q is probably not as good as the Miller IFs. 

>  I've not built this, just a thought. I get them sometimes
>  when it's still early in the AM and I've just had my morning coffee
:-)

Great thought, tho!! Only real problem is getting enough of the 262's.

With 2 IF stages and a single transformer feeding the detector, 5 cans
would 
be needed - 6 if you use one for the BFO. With 3 IF stages the number
jumps 
to 7 and 8, respectively.

73 de Jim, N2EY  
************************************
Visit the HBR Receiver Web Site with over 100 pictures of receivers and 
construction notes...... via http://www.qsl.net/k5bcq/ 

Retrieve reflector archived data via
http://mailman.qth.net/mailman/listinfo/hbr