How to build variable test capacitor of big value

[WM6]

Sometimes we need variable capacitor of big value to establish proper value of capacitor needed for our LC resonate circuit.

Here published schematic show circuit of variable test capacitor, which can change the value of C from about 1pF to 1.111uF.

After finding the true value of C by test capacitor ( we need C meter for such purposes) it is replaced by one or more fixed capacitors to get proper value.

Switches can be 4 x 4DIP switch.

[mikebg]

Here published schematic show circuit of variable test capacitor, which can change the value of C from about 1pF to 1.111uF.

After finding the true value of C by test capacitor ( we need C meter for such purposes) it is replaced by one or more fixed capacitors to get proper value.

WM6, it is impossible with such magazine capacitor to set capacitance below 12pF.
If you don't believe me, please measure it!

[ANDREAS]

Hi WM6 .. We have better solution, i wait the first complet Arado PCB , after i publish my circuit and work fine
best regards
Andreas

[WM6]

WM6, it is impossible with such magazine capacitor to set capacitance below 12pF.
If you don't believe me, please measure it!

This is not for 12pF but to establish bigger capacitor value. If you use C-meter as suggested circuit capacitance is not important.

Sure it is possible, if one wish, by small mod additional switch:

[Esteban]

I design this. Note that you can added another rotative 10 or 12 pos. switch for uF range, but for adjusting coils maybe is not necessary these high values. With the variable cap. closed the switch you can make fine adjustment. When you obtain the capacitance you need, measure with capacitance meter in the jack, because here works also parasitic capacitance. So, with this method you obtain an important instrument for labo. I post this years ago as unregistered, but can't find in forum. I think I posted in General Electronic forum. Was deleted? Go again!

[georgi.g.zhelev]

C variabl

Hi,WM6!C variabl. The idea is good, it will be very easy to select a capacitor (CX) in the coil
RX or TX. How will the switch "C". What kind of keys? Keys 4 x 4 DIP, I think that will happen. C > 555,5 nF, how do you do?
G.L.!

[WM6]

Hi,WM6!C variabl. The idea is good, it will be very easy to select a capacitor (CX) in the coil
!

Hi Georgi

C varialbe between connector you can switch by "small value switch" next to left connector if you wish to tune only with variable capacitor from about 0-100pF (dependent of C var construction).

[WM6]

Hi,WM6!C variabl. The idea is good, it will be very easy to select a capacitor (CX) in the coil
RX or TX. How will the switch "C". What kind of keys? Keys 4 x 4 DIP, I think that will happen. C > 555,5 nF, how do you do?
G.L.!

Hi Georgi

Yes, there will be some of internal circuit capacitance, but this is not problem if you use capacitance meter and establish by meter your Cx.

Yu can use 4 x 4 DIP switch or instead of one 4xDIP 4 single slide switches, as on picture:

[georgi.g.zhelev]

C VARIABLE

OK,WM6. TKS!
G.L.!