View Single Post
Old 02-20-2015, 04:34 PM
med.3012's Avatar
med.3012 med.3012 is offline
Gold Member
Join Date: Nov 2012
Location: Algeria
Posts: 1,059
some practical aspects

to measure the resonance frequency of the E-TBC there is a need for frequency generator plus an oscilloscope, but if a frequency generator is absent there exist a way to do this without frequency generator,

just build the following simple Colpitts oscillator which in turn based on LC tank circuit, close C D connections in your E-TBC, connect it as shown from A B and X point ( x = CD closed ).

i tried this circuit with two different E-TBC and it gave a nice result showing the frequency of 3.2 MHZ and 1.4 MHZ , the objective is to achieve a manageable frequency up to 17 MHZ so the quarter wave length will be

143/ 2x frequency in MHZ if f=17 MHZ the quarter wave will be = 143/2x17 = 4.2 meter .

4.2 meter will be the length used to wind our L2 coil, it's important to wind it with space between adjacent turn. more space is needed in the edge of the twin coils due to the fact that the voltage has a maximum value in these two points, doing so will avoid the interference between points with higher voltage and the rest of the coil, this help the wave to see the length of wire instead of seeing the length of the coil .

Attached Images
File Type: png buffered_colpitts_oscillator_schemat1ic copy.png (97.3 KB, 932 views)
File Type: jpg efhw_06.jpg (42.1 KB, 346 views)
Reply With Quote