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So I pulled the bottom cover off my newly acquired FT-847 to check if it had the optional filters installed. (it did not)
I see the open space for the CW filter, 4 pins on each end.
I also see the Murata SSB (stock) filters installed, 4 pins on one end and 3 pins on the other. They appear to be identical.

My question is this - Are the SSB filters called '7-pole' because they have 7 pins to connect them? Will a Collins 8-pole SSB filter work there?

Also - What is the difference between the Collins filters and the Inrad? Inrad apparently has stopped manufacture and is pretty much out of stock, so a used filter is probably my only option here. Which filters fit/work for SSB? Can I install an 8-pole filter in the 2 spaces (TX & RX)?

Thanks in advance
Micky K1XH

Hi Micky,

I can answer one of your questions.? My understanding is the difference between the Inrad and Collins filters is that the Inrad being a crystal filter has a much steeper skirt at the passband edges, thus a much sharper cutoff.? I think they also have a couple more bandwidth options.? And i've seen mentioned a couple of times that the Inrad filters are a bit larger and must be tucked off to the side inside the rig.? See:

I don't have the SSB filters yet but do have a Collins XF-115C cw filter on the way.? What i'm curious about is if two SSB filters are needed. Can one get away with just one in the RX slot?

after I install my newly found stock filter (better for FT8 and other digital modes)
I will have a 2100Hz Inrad to rehome??
it currently is in the TX side as that wont bother much for FT8/JS8call and others??
wish there was a 3Khz available

Is there a market for the original stock muRata filters?? I recently thought I found a Collins YF-115S-02? ssb filter, sent the money, got the package today and found that someone had substituted the Collins filter with the muRata one.? :^(

well till a couple weeks ago I needed one??
now I have to get rid of a 2100Hz Inrad
or maybe i will just keep it in the radio disconnected
till some day I want to sound tinny??