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High insertion loss / early rolloff 6m LPF

 

I've assembled and tested the LPF kit from 160m to 6m. All the filters work as expected without adjustment except 6m.

The 6m filter starts to roll off very early and has a high loss in the 6m band (over 4db at 52Hz).?

I've checked for solder bridges and cold joints, continuity is good through the inductors and all the pads that should be connected. I can't find any shorts anywhere.

Any thoughts?

- Justin, AI6YM
 

Mine does the same, but not as bad as yours. It starts to fall off a little early but is only?-0.5dB at 50Mhz. My measurements were much worse when I first tested using croc clips etc so I soldered SMA sockets on to the board. That made the measurements more consistent, but not ideal.

Sorry, no solution Justin. Just my observations.
 

Here's a more close up image, with CH0 VSWR included...
 

Hi,
I suppose you have all the right turns and capacitors at right places according to the LPF Manual.

9Band C1 C2 C3 C4 L1/L3 L2 Toroid
6m 22 82 82 22 7 (165nH) 9 (265nH) T37-6 (yellow)

I think in this case you have no possibility to spread the turns more around. You could possibly just make one turn less (and not cut the wire yet).
But looking at the graph I would say the capacitances are not ok or there is one turn too much.
--
73 Bojan S53DZ

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