very simple spectrum analyzer

[adel_48]

Hi,

I am trying to build a spectrum analyzer with the same construction as a radio receiver but with VCO instead of manual Local Oscillator with the following specifications
1. input signal frequency 0 - 1MHz
2. IF frequency 100KHz
3. VCO operating range 100KHz - 1.1MHz

for the VCO I used a MAXIM function generator IC and for the mixer I used MC1496 but I don't know if this s OK, also for the filter I don't know which type to use a crystal ladder or an active filter.

So can anyone give me some help.

BR
Adel_48

 

[sinatra]

Hello Adel.
It seems the frequency you want to play is quite low for an analog spectrum analyzer.
Why don't you just digitize your signal and then use the pc to do some simple post processing.....
A very cheap adc could be the TDA8708. You can use cache memories form an old PC.... I had donne similar stuff using this ADC some years ago....
This would give you a bandwidth of about 30MHz!

S.

 

[echo47]

For that frequency range, I agree with sinatra. Digitize the signal and do FFT in a computer.

If you really want an analog project, I suggest first changing your IF to 455kHz so you can use common inexpensive 455kHz ceramic filters.

Maybe consider a DDS instead of a VCO. Wonderful frequency stability, agility, and resolution.