Robin,
At this stage, rather than add turns, why not add some extra capacitance across the trimmer? I would imagine the L/C ratio isn't critical in this instance. As a start, I'd try something a little less than the range of the trimmer itself. I don't have the information to hand but if the trimmer is say 5 to 40pF then something around 30pF can't be too much.
Just tack the cappy on the back of the board at this stage.
Of course you might need more capacitance still, but it's an easy experiment to make.?
Regards,?
John
G4YTJ
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From: robin.travis@...
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[email protected] Subject: [QRPLabs] Winding Tip for 80 Mtr QCX transformer (T1)
Hi Des (again) and others
I just searched this topic and your name came up again.
I had to have 3 attempts to wind the T1 transformer.
On the first attempt, I ran out of 28swg wire to complete the winding having obviously?used generous amounts for the other inductances.
(QRP Labs - please note that a little more wire would not go amiss).
I had some 27swg and 30swg wire and decided to try the 27swg?but trying to wind 83 turns on a T50-2 toroid is no easy task and I abandoned this in favour of the 30swg.
I managed to wind the transformer with quite a bit of overlap of 30swg wire and I presume I have wired it up correctly as I am now hearing stations? reasonably well from continental Europe. Obviously, 30swg wire?is quite delicate but it?is certainly workable if one is careful.
The issue I have is with the alignment: it is starting to peak but I am only achieving a scaling factor of 5 with the plates of C1 completely closed and I now have to add some more turns.
For optimum performance,?is the target value around 9 as indicated in the manual and I am wondering whether it is easier to remove turns rather than add.
In other words, would it be better to add 10 turns rather than 5 turns as suggested in the manual ?
Again input from you or any other would be most welcome.
73s
Robin
G4DNP
