# Resonance

Discussion in 'General Electronics Chat' started by mollie, Apr 21, 2008.

1. ### mollie Thread Starter New Member

Apr 21, 2008
2
0
Hi
I am new to this forum,registered a few minutes ago,so please bear with me if my protocol is lacking.All about circuits is very informative and useful to my research.On the (tank circuit) resonance page f=1/2pi rootLC

OR----LCproduct=1/2pifsquared
OR----LCproduct--proportional to--resonant frequency.
Any number of individual values of L and C will give the same LC product.
Is there a specific value for L and for C (the product giving the resonant frequency) which will provide the maximum gain in a receiving parallel or series LC circuit?---generally.
The frequency I am particularly interested in is 198kHz

Best wishes, mollie.

2. ### thingmaker3 Retired Moderator

May 16, 2005
5,072
6
Resonance occurs when XL = XC. Best transfer of power occurs when input impedance = output impedance. Choose a value for Z which gives you maximum gain, and calculate either L or C to match. Then calculate the remaining component.

3. ### mollie Thread Starter New Member

Apr 21, 2008
2
0
Thank you for your reply thingmaker3. I dont know the impedance of my exciting source and can make the load impedance of any reasonable value.I am planning to construct one of those carrier powered radios which were popular in the 1970's. Powered by a strong local station but able to receive other stations.It must be portable however without an antenna or ground.I think I stand a bit of a chance because my house is just 4.5 km or 3x wavelengths from the 500kW 198kHz BBC transmitter at Droitwich! I have worked out the LC product @198kHz to be 646 x10to the -15. Which L and C values will give me the best coupling?
2mH and 323pF, 4mH and 161.5pF,------------323mH and 2pF---etc?

Best wishes mollie

4. ### Caveman Active Member

Apr 15, 2008
471
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They all work, but read up on Q. It defines the bandwidth of the tank circuit and leads to how much L and C you need.