Re: Some BCI Filter Notes
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Chuck,
Now that I have the QRPme BCI Filter kit in hand AND the Preparation T kit in hand, based on your observations, would it be ideal to wind two toroids for this kit? I intend to use it primarily on 40 - 20M, I do not see myself deploying much on 80M for portable operations. Would there be any noticeable visual/audible dB enhancement or build AS-IS? Later today I will have both kits in-hand according to the latest USPS estimates. I haven't compared yet to see if the caps are of similar values between the two kits. I know Dan built many prototypes until his Chinese gear was effectively rejecting the AM broadcast stuff. I will make a chart between the two kits to understand any differences other than just the connectors. While the grandbabies are taking a nap today perhaps I can wind a couple toroids unless of course if I won't be joining myself if I stare at the charts too long, LOL.
I am not smart enough yet to put my Rig Expert to good use for this task ...
Fun stuff,
Davey - KU9L
On Tuesday, April 11, 2023 at 05:57:46 PM EDT, Chuck Carpenter <w5usj@...> wrote:
The filter being considered was from N4ELS, Nelson, using readily available parts and no toroids to wind. Chokes aren't really all that good so best to use toroids. The Elsie design plot looks like this:  The important marker data are Transmission Loss, Return Loss/VSWR and Real R values. The filter looks good for 40 meters up.? The filter was done before nanoVNA so no sweeps, yet. I may have one around someplace to do a VNA check with. K9BPs HPF is really nice and, just looking at the pictures, worth the money.? I ordered one. I believe I figured out the Elsie design and the plot looks like this:  Note the blue impedance line. That is really good; hugs 50 Ohms from one end to the other. The marker data show just how good the can be. I won't disclose the design values used for the plot.? Buy the filter and determine them for your own amazement. I'll know how close I came in a few days.? Fun Stuff...
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David Knapp