Aha! Well, at least it didn¡¯t come down to me making mistakes during building. I¡¯ve been very careful but mistakes can still be made¡?
Maybe I should just go and see how it performs and truth be told, I¡¯m looking at using it (for now at least) on 10m only.?
73
Sander?
Yes, you're measuring it correctly from the sounds of it.?
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What's wrong? The receive BPF on the QDX HB is shared between 20m and 17m, so compromises had to be made. On this model, the BPF sometimes has problems spanning both 14 and 18 Mhz, and there may be some interaction with the board, stray capacitance, etc around 14 MHZ as well, I suspect. So others have seen that 20M on the HB QDX often is less sensitive on receive.? It was discussed in some previous threads here... one of them:
/g/QRPLabs/topic/102685749?
Your options? First thing would be to try and squeeze windings on the BPF toroid, especially the 17/20M portion...you may see some improvement. You could try and add turns to that "last" portion as well. You might try and mess with capacitors if you want and have some on hand. Another option if you NEED 20m to receive very well is to bypass the BPF in that slot, but that comes with risks. There's also a possibility there's some LPF interaction that feeds into this, so bypassing the BPF may not solve it entirely.
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I attached pics from my QDX HB build, which came out the same as yours on 20m, built as instructed BPF-wise. In my case, I can use 17m-10m on this QDX, and have a low band QDX cover 80-20m, so I didn't worry about trying to optimize the BPF on 20m, so I'm not sure how easy/difficult it may be on the high band.?
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-Nate
N8BTR
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