Monday, January 31, 2022

It is in how you figure?

 If I have a 200uh coil and I want to tune 1-5 MHz what value should the tuning cap be?

1MHz     2MHz    3MHz    4MHz     5Mhz

126pfd    31pfd     14pfd    8pfd       5pfd

Now if I mark my dial the scale does not match my Vcap values. Why?

Notice the only place it is close is with the hi value cap. The lower the cap the more the strays effect the circuit.

When the dial does not match we can measure the cap and calculate the inductor value.

1MHz     2MHz     3MHz     4Mhz     5MHz

129pfd    34pfd     17pfd      11pfd     8pfd

196uh     186uh     165uh     144uh    127uh

If we do not account for the strays it appears the inductor is changing value.

Maybe another series of scans with the adjusted values is in order?

No comments:

Post a Comment