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

Tue, 07 May 2002 19:50:59 -0400

Kees-

Did you measure the DC resistance
and is it enough to account for most of the
difference in Q?

-bob

Sandy and Kees Talen wrote:

> 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  
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> 
> ************************************
> 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
> 
> 
> 
> 