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15 meter low pass filter characteristics #lpf

KI7MWA
 

I'm building the relay-switched filter kit for the Ultimate 3S, characterizing the filters with a nanovna.  The 10 meter looks great, around 0.4 dB down at 28 MHz, falling off nicely to -40 dB at 60 MHz.  The 15 meter filter starts off a little over -5 dB at 21MHz, about -4.5 dB at 21.45MHz.  It falls off after that, though with a second minimum of -9 dB at 36MHz, then falls off nicely to -37 dB at 50 MHz.

Built according to the specs: 12 turns for L1 and L3, 14 for L2.  Squeezing the L1 and L3 toroid windings gave a little improvement.

Curious about others experience with this filter.  Anyone tried additional windings?  Different capacitors?

ajparent1/KB1GMX
 

I made two of those without issues.  That result is really off.
Soldering?

Allison
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Dave
 

I made a number of low pass filters a while ago, during the first few weeks of lockdown.  I found I had to remove turns on my 15m and 20m filters. If I recall correctly it was two turns on the 15m and one turn on the 20m.

As I had lots of room on the toroids I used slightly larger wire, and that might have had a small impact.

Dave


On Jun 29, 2020, at 18:04, ajparent1/KB1GMX <kb1gmx@...> wrote:

I made two of those without issues.  That result is really off.
Soldering?

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due address harvesting