Hello Everyone

Referring to my message:

https://groups.yahoo.com/neo/groups/Electronics_101/conversations/topics/87771

Something went the opposite way than I expected. Holding L at the same place (0.44874 MicroHenrys in my 11-6 meter I.C. receiver circuit), I found that a tuning cap of a HIGHER pF rating gave me a LOWER frequency- I expected the opposite to be true.

Thinking of this, I remembered that the 365pF tuning cap took us down to the BCB in kiloHertz range (at about 540 kilohertz to 1700 kilohertz), but with a different coil).

I used: http://www.1728.org/resfreq.htm

And got the following results (if you can stand the headache of reading my notes):

Given INPUT MegaHertz (I used highest frequency for this project -i.e. 56 MegaHertz)

INPUT Picofarad 18

Find Inductance:

4.4874e-7 Henrys, or 4.4874e-4 MilliHenrys, or 0.44874 MicroHenrys.

This is where the 0.44874 MicroHenrys came from.

Okay. I set about finding the frequency for a higher 36 pF rating as the tuning cap:

The answer is (I THINK) Frequency = 39.598 MegaHertz. RATS!

This is a LOWER frequency than the 18pF tuning cap!

I tried again with a LOWER rated (LESS than 18pF) tuning cap and got:

Find frequency with:

INPUT Picofarad 10pF

Inductance 0.44874

Frequency= 75.132 MegaHertz!

The lower tuning cap value gave me a HIGHER frequency.

I was sure that a higher rated tuning cap would give me a higher frequency.

Now my head hurts A LOT. I'm going to let it rest.

Ideas? Am I THAT lost?

Thanks

Patrick

p.s. NOTE: NO TYPO CHECK WAS DONE HERE; please forgive any that are present.

- The math doesn't change with the passage of time or specs. What does change is the ability to measure/predict all of the parameters. Mutual inductance, distributed capacitance, circuit impedances, all are rather difficult to measure/predict. So, they hang a little trimmer capacitor on the tuning capacitor to allow for matching to the display and the inductors will often have a tuning slug.That's one of the cool things about LTSpice (or any other Spice for that matter): We can get the wrong answer to several significant digits.Richard