Collins mech filter help - numbers

[John Kolb]

On Mon, 23 Oct 2000, N5AIT  Allan Stephens wrote:

>      So far have figured that Collins part number 526 xxxx xxx
> is a mechanical filter, and the last three indicating (I think)
> the filter bandwidth.  What I need is the Collins part number
> for filters that will fit the 75A-3 (looking for narrow - CW -
> filter).  How does a 526-9764-020 pan out? right IF (455) and
> bw (200 cps) (I think) - but would it fit?

Collins filters are identified by both a part number and a type,
although filters are sometimes seen with only one or the other
of the two. P/N's start with 526, except for some old filters
starting with 522. Type numbers are of the form F455FA-21,
starting with F, then three digits which are the carrier freq.
(center freq for AM or CW filters, carrier freq for SSB filters)
one or two letters which often identify the case, (F455FA-21,
F500B-60), and then a two or three digit number indicating
the bandwidth in 100's of Hz. So F455FA21 is 455 kHz center,
FA case, 2100 Hz wide, F500B60 is 500 kHz center B case,
6,000 Hz wide. Among the exceptions are filters with Q or
Z following the freq. Z filters are for SSB, and the following
number seems to be the order in which the filters were designed,
certainly not the bandwidth.

I have a list that says the 526-9764-020 is a 455 kHz center,
0.19 kHz @ 3 db, 2.40 @ 60 db, in a "V" case. I would expect
the 75A-3 to need a larger case size than that. The "V"
is a metal case, almost identical to the common "FA" case,
except 0.2" longer.

John  KK6IL