# Stray capacitance -- how to calculate formula...

1. Jun 22, 2017

### michael1978

Hello,
i am reading one book over the "tenichians radio receiver handbook", but there was a stray capacitance

can somebody help me, how to calculate stray capacitance?
of what arethe standard value of stray capacitance

thanks.

YES do you see the circuits
the stray capacitance is 7pf and 320pf main and trimmer 21pf

Last edited: Jun 22, 2017
2. Jun 22, 2017

### tech99

Can you please give more details of which stray capacitance you require? For instance, is it the capacitance of a coil, or wiring, or that of a tube.

3. Jun 22, 2017

### michael1978

yes do you see i edit look the circuits, me i dont understand how come in 7pf cstray i dont have idea

thnx

4. Jun 22, 2017

### marcusl

Please write in complete sentences, and use correct capitalization and punctuation. That's the rule here at PF.

5. Jun 22, 2017

### Tom.G

Hello @michael1978

Stray capacitance is "extra" capacitance that usually can not be exactly calculated. It is the sum of the capacitance of the coil, of what the circuit is connected to (maybe a transistor or a vacuum tube), and the capacitance of the wires and of the components to other nearby things. The capacitance of the coil can be indirectly measured, of a transistor or tube can be found in the datasheet, of a wire can be not-very-well calculated (for an example see: https://www.emisoftware.com/calculator/wire-over-ground-plane-capacitance/ ). A wire with plastic insulation laying flat on a metal chassis has a capacitance of 1 to 2 picofarads per centimeter of length.

6. Jun 23, 2017

### michael1978

thank you ....now i understand.

7. Jun 23, 2017

### michael1978

sorry but my english is not good....ihope you understand me.