Re: [Elecraft] K3s 400 Hz filter differences...

Clay Autery

Yep... here it is right here, wayyyy back on v5.33:

* DIVERSITY WORKS WITH MISMATCHED MAIN/SUB RX FILTERS:  Diversity mode in the K3S (or a K3 with the KSYN3A installed) now works with any combination of main/sub RX crystal filters. They can have different bandwidths or offsets, and it's not necessary to have an equal number of filters in each receiver. Note: Matched filters are optimal for diversity, but non-matched filters will still perform well.

"Matched filters are optimal...."

End of discussion as to IF I will get matched filters....  Now to decide between the "in-house" 6-pole I just bought, or an INRAD #701 that matches the one I bought with my MAIN Receiver...


Clay Autery, KY5G
(318) 518-1389
On 01/14/20 11:16, Nr4c wrote:

I think you’ll find in the release notes that main/sub filters no longer need to be matched.  

However, I think I’d be happier with two alike, either 2 8-poles or 2 6-poles. 

Sent from my iPhone
...nr4c. bill

On Jan 14, 2020, at 7:18 AM, Clay Autery <KY5G@...> wrote:

The 400Hz filter on my Main RX is an Elecraft (by INRAD) 8-pole filter in a Faraday cage and no offset.
The 400Hz filter I just received for my SubRX  is an Elecraft (by Vibroplex?) that is a 6-pole filter with no Farady cage AND it has a -0.71 kHz offset.

I called support when I saw the obvious differences, and they said, "Don't worry about it.  Enter the SubRX offset exactly as on the crystal (no averaging with the [supposed] 0.00 offset on the 8-pole filter), and let the new Synthesizers do the heavy lifting." or words to that effect.

I hear what was said, and I don't want to come off like I don't trust what I was told....  But something simply is not sitting right with me on this.... a 6-pole "matched" with an 8-pole?  No offset averaging?  What about the difference in the skirts between a 6-pole and an 8-pole.... Aren't the cutoffs and cutoff rates different?  I realize that things change, and that perhaps the instructions for averaging the offsets is not applicable here... (though I don't yet understand why)

Can someone clear this up for me so even I can understand it.

Seems to me that I either need to get a matching INRAD-made 8-pole, or buy another of these new parts and try to get it matched.

Want to move on this, because IF I am going to have a hope in getting a "matching" 6-pole (new stock) 400 Hz filter, I need to try and do so from within the same batch that the one I just bought came from.
The prospect of finding an "by INRAD" 8-pole available on the market seems much less likely...

Obviously, I am operating on a number of assumptions here... which is why I am asking...


Clay Autery, KY5G
(318) 518-1389


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