this is my first post in your forum and really when i have seen this forum i was interested in some topics but now i have a huge problem and i hope some one solve it for me

i am a student at the last year in the communication and electronics department in the faculty of engineering

a task was demanded from me to design an AM transmitter on aprinted circuit board

i have found many designs on the internet but before i i implement any of them i have to get the output on any simulation program

i am working on workbench i tried many circuits on the program but neither of them gave me an output i really need your help

i will put some images for the circuits and its outputs and also i will put 2 files for the workbench files it self and i hope helping at the nearest time

first this is a pdf file for the first circuit

4shared.com - document sharing - download AM_transmitter.pdf

this is the circuit on the work bench

this is the output after the diods or for any one who will read the pdf file its the chopped output voltage and this stage was successfully out and this is its image

also who will read the pdf will notice that this output must be the input of a transistor connected to another circuit to be able to obtain the AM SIGNAL but unfortunately this was the output so i need some one to tell me what is wrong with my circuit

second this is the second design but also this is a word document for the design before my circuit

4shared.com - document sharing - download (2) AM TRANSMITTER.doc

this is my circuit on workbench

and this is the output

and for illustration i have not found any of the variable components values and the problem was not in the variable resistance but it was in the variable capacitance and inductance in the program because who will read the word document will notice that the variable inductance is 100 uH and the capacitance is 500 pF. the greatest value for the variable capacitance in the program is 350 pF and also the is 100pf and 30pf so i tried a parallel combination between them to get close to the requested value and the same case in the inductor i have found that the greatest value and the only value for a variable inductor with micro henry is 10uH variable inductance so i tried a series combination of 10 inductors but with no result

i hope u will help me in the nearest time because i need to get a result before next monday please

thanks alot