EMRFD Message Archive 12998

Message Date From Subject
12998 2016-07-05 17:00:29 cwfingertalker Question on page 3.18 Figure 3.31 crystal filter.


I have crystals from some old heath-kit HW12, 22 and 32's from the IF part of the heath receiver.  Looking at the schematic diagram of the heath-kits they show a resemblance to Figure 3.31 on page 3.18.  The heath-kit schematic shows a bifilar transformer and capacitor but have four crystals within the filter.  Two of the crystals are slightly above 2305 kHz and two slightly below 2305 kHz.  Here is a diagram of the heath filter.

I would like to recreate the transformer/capacitor circuit and use the old heath-kit crystal filters in future receiver projects.  

I assume, correct me if I am wrong, the bifilar transformer and capacitor resonate at the crystal/filter frequency.  In the case of Figure 3.31 that would be 5 mHz and for the heath filters 2305 kHz.  If this is true it should be reasonably easy to recreate the heath bifilar transformer and capacitor.  

Anyone that can shed some light on this subject please jump in.  


Bill N7EU

13000 2016-07-05 17:35:04 cwfingertalker Re: Question on page 3.18 Figure 3.31 crystal filter.

The schematic did not come through the message format.  I loaded the schematic into my folder in the Files section under N7EU.

Bill N7EU