#QDX LPF and Bandpass values for 40 20 10 ? #qdx
Bruce
Good day all. My QDX V3a (kit) worked phenomenally “right out of the box.” Thank you, Hans! I am now building a V4 QDX for 40, 20 and 10 meters. (Arrived in 11 days, from Turkey.)
On 40 and 20, the values for the LPF will be as in the standard QDX version, in the current 80 and 40 positions.
For the 10 meters LPF, what C values are others currently using? These would be in the positions of C7, C11, C14, and C20.
For 10 meters, what values (nanoH) are others using? These would be in the positions of L4 and L10.
I am assuming all fixed 47microH inductors would remain the same.
The band pass filter is a little tricky for me to understand right now. It SEEMS winding 19, the first tap should become about 11 (?) and then the additional taps would become 19 and 30, and the finish would be at winding 36. Is that correct? What would (looking left to right on the board) C30, C28, C31, and C29 become?
Thank you in advance for sharing your insights and experiences!
~ Bruce K3BAB


Bruce
Perhaps this was TMI :) Anybody have their QDX on 10 meters? Values?
K3BAB ~ Bruce 

ferrettoss@...
Hi Bruce,
Hans gave some values for 10m in this thread: https://groups.io/g/QRPLabs/topic/94801691 Ciao /Claudio 

KEN G4APB
Hans, does going to T3710 make a significant difference? I used T376 types from an LPF and get 5 watts at 21MHz but 3 watts at 28MHz (different no.of turns too).
73 Ken g4apb 

Hans Summers
Hello Ken It makes SOME difference, I am not sure how much. It could account for the difference between my 4W and your 3W (6 toroids). On Sun, Nov 27, 2022 at 11:15 AM KEN G4APB <lfoofui.nbz42@...> wrote: Hans, does going to T3710 make a significant difference? I used T376 types from an LPF and get 5 watts at 21MHz but 3 watts at 28MHz (different no.of turns too). 
