[SOLVED] wide band am reciever

[newbusofborg]

I'd like to make an am receiver that runs through the normal am spectrum all the way up to 200mhz. I understand there are not normally am transmissions through this portion of the spectrum. Can anyone supply a schematic or tell me how to modify an existing one (with a link to it)?

Oh, I'd like to avoid using any ICs.

 

[D.A.(Tony)Stewart]

You will need more than 300MHz BW to get 1ns rise time. Here is a logic diagram for an obsolete front end amp for UHF High Sensitivity Sensor. You may wish you could buy one.

Frequency range: 10 MHz to 18 GHz
Measurement range: 100 pW to 10 uW (-70 dBm to -20 dBm)

 

[chuckey]

This is an extremely complicated project, definitely not for a beginner. In laymans terms:- You need a filter that that sweeps across the whole frequency range, so you can pick out each signal in turn. This is done by means of a superhetrodyne ("superhet") receiver. The incoming signal is mixed with a local oscillator which produces lots of different output signals, one of which is Foscillator-Fsignal . This frequency is called the Intermediate frequency (IF) and is the one that is filtered out , amplified and detected and finally demodulated and is the output signal to the loudspeaker. So in a superhet receiver you tune the oscillator to get reception of different frequencies.
In your case to sweep 0-> 200 MHZ, you need an oscillator that sweeps from IF to 200+ IF MHZ. Which is difficult. Which leads another point, the IF must be above 200 MHZ, otherwise the receiver will try and receive its own IF frequency which will cause it to oscillate. The choice of IF is also governed by the fact that you must be able to filter the Foscillator-Fsignal out, which means that the IF must be at least 20% away from Fsignal, giving us the lowest IF of 250 MHZ. At this frequency filtering is not very effective, so you must then change the first IF back down to a lower frequency, say 10.7 MHZ, with a second mixer and fixed oscillator.
Do you really feel up to doing this?
Frank

 

[jiripolivka]

Again an ill-defined problem. What means that the receiver" runs all the way through >200 MHz?" The RF spectrum from say 0.1 to 200 MHz is full of signals, modulated AM, FM and pulsed, low as well as high levels.
What is this"project" for? Any other specifications?