Anyone who has owned various Icom or Kenwood rigs which utilize a 455KHz IF may have encountered one of these beasties if the rig's covers were ever removed for servicing or upgrades:
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This particular filter is a 6-pole unit and is spec'd for a 6dB B/W point of ~2.4KHz. It's also rather small, which comes in handy for what follows.
The IC-R7000 receiver uses a 455KHz IF strip, and employs three Murata 4-pole filters on the IF/Detector Board: One with ~15KHz/6dB B/W, one of 6KHz/6dB B/W and one of 3KHz/6dB B/W. The latter (F16 on the IF Board schematic) is used for SSB reception:
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Good, but not optimal. SSB sounds a bit "hissy" and if you use the receiver on a crowded band (say, 10M during a 'phone contest) stations adjacent to the desired frequency can create a noticeable amount of interference.
I freed up a couple of K5s recently when I installed FL-44As in two of my R-71's accessory SSB filter spots. The '44A is also a 2.4KHz B/W unit but its shape factor is a good deal better than the K5...which (of course) is a good deal better than the plastic cube unit. At least, on paper. It is also shielded, whereas the OEM unit is not.
If one is willing to get creative with a solder sucker and a Dremel tool that has a very small dental burr installed, one can remove the OEM filter and modify the IF Board so it will accept the K5 or another K-series filter of identical form factor. There is just enough room to accommodate the larger filter. A couple of components must be desoldered and relocated to the foil side of the board, where they are reattached.
Pics of the finished assembly to follow, and when I rework the next IF Board I'll take "before" and "in-process" photos.
I might try to locate a narrower K-series filter. While an improvement as far as the R-7000 is concerned, the K5 is not the equivalent of its larger 8-pole cousin. But there's not enough room to mount one of those, either.