[Milsurplus] Collins F84Z4 filter - do you know it ?

[Hubert Miller]

So, rooting thru my stuff, I rediscovered these, which I have had since I worked at a surplus store about 45 years ago.

About time to do something with these, right ?

I cannot find any online info on these. We got these in the store with a load of FAA equipment, I think. I saved two

because they were "close" to the IF of a well known mil - surplus LF receiver.



I wonder if anyone has better specs and maybe even a schematic of the chassis. I thought I did, but cannot find, so

maybe I imagined that. These filters are F84Z4  F88Z5. The online lists for these freqs start with Z7 and increase the

Z # from there. The published specs for those that are there are typically like 2.5 or 3 kHz at  0.25 or 1 db down. Not

real useful. But a graph at

http://jptronics.org/Collins/MECH_FILTERS/collins.filter_catalog.pdf

shows them in this family to be about 3.5 kHz wide at -6 db and 5 kHz at -60 db. Pretty good shape.

I wonder if anyone here has a schematic for this chassis.

And/ or, the input - output Z.



It looks like I may have to draw out the circuit. Not that much fun, but the layout is pretty clear and should be just

drudgery, nothing mysterious. There are 2 audio - looking small transformers ( black things ) on the circuit board

I would like to know about, know if they're practically usable. The two chassis are not identical. One has topside

a potted 1500:600 ohm xfmr, and the other has a 1500: 50K ohm and a 27K: 600 ohm transformer. There is a

compression trimmer for "MF TUNE". One chassis has a single tube socket, the other, has two.

I

Seeing as I have no idea of their actual condition after all those years, and being up to my ears in must-do, I am

pretty much abandoning thought of somehow using them in ( hacked ) BC-453 project. Or plug - in IF, if that makes

you feel better. If this is something the reader thinks interesting to pursue, contact me. The actual filter size is

about broomhandle diameter and about 5 inches. I briefly thought, hmmm, my Eddystone 750 has an 85 kHz IF,

hmmm.... but this thing is way too large to elegantly drop in.

thanks- Hue Miller



[A picture containing indoor, wall, electronics, tube  Description automatically generated]










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