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40M BPF alignment T1 and C1 #qcx #bpf #alignment

Bill Wrbican
 

I've completed a 40M QCX (built the 20M last year). Doing the BPF alignment, I could only get max signal with C1 nearly fully meshed (at a power of 10), so I removed 5 turns from T1 (which was easier than I thought). However I still get the same issue. A power of 10 seems way higher than others I've seen, and I wonder if I should stop messing with it and just continue, or if there is something with C1? Through one complete turn of C1, the scale moves several bars, but never leaves the 10 scale (it was this way prior to removing the turns as well).

Bill
KA3BMU

 

Fully meshed C1 would seem to indicate too low inductance on S3. Removing turns is the wrong way to go. 
Are you sure C5 is correct value? I.e. not too small?
--
> I finally got it all together...now I can't remember where I put it<

VY 73,
Wes

AE6ZM

Sierra Vista, AZ

 

Bill Wrbican
 

on another reading of the manual, I seem to have misread it. Rats. OK, I'll have to add some wire to the winding, in addition to what I removed. 

I'll check C5 while I'm at it.

Thanks!

James Daldry W4JED
 

Hi, Bill

Sorry to rain on your parade, but if peak comes at full mesh of C1, that means you are using the capacitor to compensate for insufficient inductance. You need to either (a) add turns (which either means make it ugly or rewind the big winding) or (b) add a capacitor across C1. The added cap should be either NPO or silver mica.

Jim W4JED

On 2/3/19 10:21 AM, Bill Wrbican wrote:
I've completed a 40M QCX (built the 20M last year). Doing the BPF alignment, I could only get max signal with C1 nearly fully meshed (at a power of 10), so I removed 5 turns from T1 (which was easier than I thought). However I still get the same issue. A power of 10 seems way higher than others I've seen, and I wonder if I should stop messing with it and just continue, or if there is something with C1? Through one complete turn of C1, the scale moves several bars, but never leaves the 10 scale (it was this way prior to removing the turns as well).

Bill
KA3BMU

Bill Wrbican
 

I managed to attach and get the connection under the toroid, so I think I'm alright adding the turns. I'll try that tonight. If that doesn't work, I have several values of NP0 that I've been collecting.

73
Bill
KA3BMU