Collins/Rockwell mechanical filters are identified by both a part number (P/N), such as 526-9160-009 and sometimes a "Type", such as F455N-40.
The P/N can be broken down as follows: the first three digits, 526, identify the component as a mechanical filter. Some early filter P/N's start 522 or 596. The 522 numbers I've seen seem to be identical filters to those starting with 526 where the following numbers match. The 1954 Collins Mechanical Filters catalog has a picture of the F455B-31 on the cover with a P/N of 596-2924-002. That number does not seem to match any 526 #'s.
The middle 4 digits of the P/N are generally 8xxx or 9xxx. Filters with 9xxx numbers generally also have a type number and appear in filter catalogs. Filters with 8xxx numbers generally do not, so are probably special orders/custom designs for specific customers.
The final 2 or 3 digits usually represent variations of a basic design. 526-9427-00 is the basic filter F455FA-21. 526-9427-011 is the same as the basic filter except F20H and F20L shall be measured and marked on the label. 526-9427-010 is the same as the basic filter with these additions: F20H 456.275 KHz min, 456.475 KHz max. In some custom filters, the last 3 digits represent totally different bandwidths: 526-8477-xxx is a family of 455 kHz xymetrical filters. -010= 0.45, -020= 0.90, -030=1/90 kHz, -040=3.80, etc with other BW variations up to -100.
The Type number, when present, is a useful guide for those without a collection of COllins literature. This number, of the form F455N-20, often indicates the carrier freq, 455 in this case, and the bandwidth in hundreds of Hz. Thus the -20 = 2000 Hz = 2 kHz. The middle letter often indicates the case type. A F500Y-60 is a 500 kHz symetrical filter in a "Y" case that is 6 kHz wide at the top.
Exceptions to this are filters with either a "Q" or a "Z" as the middle letter. A "Z" represents a filter designed for SSB, either LSB or USB. A F455Z-23C is a USB filter. Designed for a 455 kHz BFO freq, the filter passband extends from 455.30 to 458.15, for a minimum bandwidth of2.85 kHz, typical BW of 3.1 kHz. Filter response is more than 20 db down at 455.00 to provide carrier rejection in the output. The F455Z-24C is a LSB filter with the same shape but on the opposite side of 455.00, thus from 454.70 to 451.85 kHz. This filter is in a "V" case. F455Z-4 is a 2.7 kHz LSB filter in a "Y" case, while F455Z-5 is the USB mirror. Z lettered SSB filters generally occur in pairs.
About the only thing that can be said of Q lettered filters is that the type number doesn't seem to mean anything. F455Q-5 and Q-8 are both 0.5 kHz wide. Q-6 is 1.5 kHz, Q-2 is 2.0 kHz, Q-7 is 3.1 kHz, and Q-3 is 40 (yes, forty) kHz wide.
WA3KEY Filter Specifications is a good resource for searching for filter specifications.
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Copyright © 2003 John Kolb Last revised Apr 30, 2003