Re: [Elecraft] K3s 400 Hz filter differences...
Yep... here it is right here, wayyyy back on
"Matched filters are optimal...."
______________________ 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. billOn 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... 73 ______________________ Clay Autery, KY5G (318) 518-1389