Re: Failure to get a sufficiently high BPF Peak #qcx #bpf #alignment #40m

Jim Mcilroy


If you have access to an LCR meter I suggest you measure the toroid windings.

I’ve built one (QCX40) and I had to take off a couple of turns. From my notes I reckoned it was around 0.1uH/turn.

It also depends on how ‘elegant’ the windings are. I.e. loose v tight. That will change readings a bit. 

Try this. You won’t break anything.



On 18 Nov 2019, at 02:27, william.wallace1@... wrote:

Hello and greetings, 
My name is Will Wallace and my class mate Joe Corbin and I are building the QRP Labs QCX 5W CW Transceiver as a part of a class. We are both students studying engineering at Ottawa University, up to this point the project has been going extremely well, but once all of the hardware was installed, and we ran power through the device into a dummy load and began the alignment process, we could not get a BPF Peak of over four. Does anyone have any insight as to how we can go about fixing this? I am sure its an improperly installed hardware component, but with the both of us being so new to this neither of us are entirely sure which components need to be tested. 
Thank you, 
William Wallace

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