this is the first of 3 excellent posts on this topic from this list:
----- Original Message -----
From: "Lloyd Rasmussen" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, January 17, 2012 8:59 PM
Subject: Re: requesting help with math question
>I won't beat this to death. I promise!
>
> I looked at Mike's version of the formula, and I understand the rationale.
> For RF circuits, the component values are usually stated in microhenries
> and
> picoFarads (or micro-microfarads in the olden days).
>
> So the resonant frequency of a 1 pF capacitor and a 1 uH coil (the micro
> symbol is the Greek letter mu, so people sometimes write u for it) is 1
> over
> the quantity 2 times pi times the square root of ten to the minus 6 times
> ten to the minus 12, end square root, end fraction. 1 over 2 pi is about
> .159. Ten to the minus 6 times ten to the minus 12 is ten to the minus
> 18.
> The square root of ten to the minus 18 is ten to the minus 9. The
> reciprocal of ten to the minus 9 is ten to the 9 or one billion. So the
> resonant frequency is 1 gigaHertz times .159, or 159 megaHertz. So
> raising
> the capacitance, the inductance or both will lower the frequency.
>
> We get into a whole nuther discussion when we make the inductor and
> capacitor non-ideal, meaning that they have some resistance, so that the
> resonant circuit doesn't have an infinite Q factor nor an infinitely
> narrow
> bandwidth. There are formulas for these things, also.
>
> I hope this helps somebody. If not, I'll QRT.
> 73,
> Lloyd Rasmussen, W3IUU, Wheaton, Maryland
> Home: http://lras.home.sprynet.com
> Work: http://www.loc.gov/nls
>
>> -----Original Message-----
>> From: For blind ham radio operators
>> [mailto:[log in to unmask]]
>> On Behalf Of Scott Howell
>> Sent: Tuesday, January 17, 2012 6:00 AM
>> To: [log in to unmask]
>> Subject: Re: requesting help with math question
>>
>> Mike,
>>
>> I see how this works, but one question is where does the 159 come from? =
>> Just curious and hey if it works that is fine by me. Any other tips? =
>> grin
>> Like I said, math is my weakness and something I have always wanted to =
>> understand. I used to be afraid of math which seems pretty silly, but I =
>> really find the subject fascinating now and wish I had the same attitude
>> =
>> when I was younger. I'm not really sure where I went wrong in my study =
>> of math and why I never learn to appreciate the value of subjects like =
>> algebra. Probably just did not have the right teachers when I was young =
>> and impressionable. grin
>>
>> 73
>> Scott/N3BYY
>> On Jan 17, 2012, at 12:20 AM, Mike Cozzolino wrote:
>>
>> > hello scott, i tried to follow your formula, but the way you wrote
>> it=20=
>>
>> > i couldn't follow it. anyway scott, why don't you use the formula
>> >>=20=
>>
>> > f=3D159 over the square root of l times c <<. first you multiply the =
>> l=20
>> > times c and then you get the square root of that answer. then you=20
>> > take the 159 and devide that by your answer. the answer i got
>> > using=20=
>>
>> > the values you gave, 50 microhenries and 200 pico farads was 1.59.
>> i=20=
>>
>> > left the values at their original values picos and=20
>> > microhenries. thats the formula i always use for resonance of a=20
>> > tuned circuit. 73 bl c u mike w6quv
>> >=20
>> >=20...
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