500MHz spectrum analyzer
| This is a spectrum
analyzer which I made several years ago. I could observe
the frequency element of the signal of 0-500MHz using
this. I used the satellite TVRO tuner unit sold cheap in
the junk store for 1stLO and 2ndLO. This unit contains
VCO of the variable range of 500-1000MHz to change 430-930MHz
into 70MHz IF. I am changing the signal of 0-500MHz into
1stIF of 500MHz by sweeping this VCO by the ramp wave OSC.
And, I used the IC for the mobile radio of JRC for the
logarithm amplifier of 3rdIF. This IC contains the IF
amplifier which has the very wonderful logarithm
character of 90dB. I input a ramp wave and the output of
the log-amplifier to the X-axis and Y-axis of
oscilloscope, and make it indicate wave shape. I am using
BPF of LC-type for the 3rdIF filter which I decide
resolution band width (RBW). RBW is about 300kHz. I tried
a crystal filter so that I might make RBW smaller, too.
But, I couldn't get a good character with the general
filter for FM and one for SSB.
|JG1EAD's Home Page Top (English)|