EMRFD Message Archive 6945

Message	Date	From	Subject
6945	2011-12-04 05:42:47	john	Collins Mechanical Filter
I have an old Collins Mechanical Filter on a surplus board. I know it is an AM filter with a 6 dB BW of 6.0 KHz. The source and load Caps are 150 pf. each. What I am trying to find out is what the source and load resistance is for the filter. The filter's markings are as follows: F455 FC 60 6714 and 526 9522 003. I have tried the Rockwell Collins website and also searched the Internet but can not find any hits that will provide the source and load resistance for the filter. Any suggestions or help is appreciated. Thank you, John K5IRK
6949	2011-12-05 08:49:13	nm0s_qrp	Re: Collins Mechanical Filter
From the Collins filter catalog: "THE DESIGN OF CIRCUITS employing Mechanical Filters is relatively simple, since no special matching networks are normal]y required. Being internally terminated, the filters need only a high-resistance terminati
6950	2011-12-05 09:10:25	William Carver	Re: Collins Mechanical Filter
Note that that the Collins info is oriented toward TUBE circuits where pentode output resistance and grid resistances are very high. A FET gate has high input impedance at 455 KHz and a common base bipolar have high input/output impedances. A common-emitter transistor or JFET typically have an output impedance well under 30K. For solid state circuits you might prefer to SERIES resonate the internal transducer. The series resonant corollary would be drive it from ZERO impedance, or into zero impedance. Those can be well approximated by common base bipolars as a load, or low-output Z feedback amps. But be aware a feedback amp can/(will!) oscillate with a reactive load. W7AAZ On Mon, 2011-12-05 at 16:48 +0000, nm0s_qrp wrote: > > > >From the Collins filter catalog: > "THE DESIGN OF CIRCUITS employing Mechanical Filters is relatively > simple, since no special matching networks are normal]y required. > Being internally terminated, the filters need only a high-resistance > terminati
6957	2011-12-05 21:15:56	john lawson	Re: Collins Mechanical Filter
Bill to you and everyone else, many thanks for the guidance and thoughts. John K5IRK ________________________________