[HBR] Re: [HomeBrew] JW Miller 15-H IFs in series

[Robert S. Stein]

Kees, the best way to tune overcoupled circuits is to shunt the other 
winding with
a resistor to lower the Q.   For example, temporarily connect  a 1k 
resistor across
the secondary and peak the prmary.  Then do the reverse when peaking the 
secondary.
This should give the optimum passband

73, Bob
w6nbi

Sandy and Kees Talen wrote:

>** HOMEBREW REFLECTOR - Please do NOT cross-post messages to multiple mailing lists on the "To:" or "CC:" line of the e-mail message. **
>
>Is there something I'm missing on using IF's in series ?
>
>I connect 2 of the subject, retuned to 100Khz, JW Miller, 
>15-H, IFs directly together and because of overcoupling see 
>a "double hump". This is not necessarily bad because it 
>"flat tops" the passband like a crystal filter. The BW goes 
>up a little from 3.8Khz to 4.2Khz but the -20dB BW drops 
>from 15Khz to 10Khz which is really good.  Using capacitive 
>coupling between the IFs of 5-10pf the waveform is a little 
>distorted and peaked ....and the -20dB BW goes to 8.5Khz. 
>The -6dB BW actually goes up to 4.8Khz.
>
>These are a little more difficult to tune up because it's not
>just peaking (on the capacitively coupled ones) it's also
>passband shaping. The direct (overcoupled) set is easier 
>to tune up because just peaking will get you there.
>
>73s  Kees K5BCQ 
>_______________________________________________
>HomeBrew mailing list
>HomeBrew@mailman.qth.net
>http://mailman.qth.net/mailman/listinfo/homebrew
>