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
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
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