开云体育

I posted the below to the QRP Tech group just now:

To be sure, you are right, I get these CYMI for a great price! One big reason why QRP Labs kits are such low cost is because I work hard on finding the best pricing for all the components. It all adds up. When I make the BPF kits I make 3,000 at a time... which means 6,000 trimmer caps... it does help with bringing the price down :-)?

I can make some inquiries and see if I can get a smaller quantity. How many do you need? The lettering on the top of the capacitor shell reads "CYMI" and under that, "FS".

I found these capacitors to be decent quality and very reliable, though of course you can always melt something by over-heating during soldering, but generally I have never had that problem.?

During the development of the BPF kit I first tried this style of capacitor:

In my opinion they were horrible...?

1) they melted very easily during soldering

2) they were not easy to adjust with a standard screwdriver - I guess some special tool is preferred

3) You cannot see what is going on inside that small blob of plastic - so making adjustments is horrible

The latter point is important. With the CYMI capacitors used in the BPF kit you can physically see the angular displacement of the fixed and movable sets of plates. The reason this is important is because often in the circuit you have other components all with tolerances, particularly inductors - which have quite some variation depending on how you wind them etc. When everything is installed, and you peak the BPF or try to adjust the VFO limits or whatever - if the capacitor plates are fully open, or fully closed, you know something is wrong. Likely it is necessary to add or remove a turn of wire on a toroid inductor somewhere. I give this advice on all my kits. With the CYMI capacitors you can SEE what capacitance it is set to (approximately). If it is at either the two extremes, you know things are not optimally adjusted, and have to take other remedial actions, on the inductors.?

Those tiny 6mm encased plastic trimmers are cheaper. But they didn't match my idea of what quality I wanted for the BPF kits. That is why I chose the more expensive CYMI ones.?

73 Hans G0UPL