[Test-Equipment] RF spectrum analysis

[David]

My solution is even less expensive.  I just use whatever tunable signal
generator is handy and one of my oscilloscopes.  I tune manually while watching
for the 3 dB, 6 dB, 10 dB, and 20 dB points or whatever I am interested in and
write down the frequencies.  Using two channels on the oscilloscope allows phase
measurements as well.  If I use my DSO which will make automatic level, ratio,
phase, and low resolution frequency measurements, then it takes less time to
write the numbers down than to set up a swept frequency measurement
configuration and calibrate the oscilloscope to it.

Of course this is not very convenient for analyzing filter shape but it will
show ripple, Q, and bandwidth and the frequency resolution is only limited by
the signal source if a frequency counter is available.  If I was tuning filter
shape then a real sweep generator would be faster.

On Mon, 20 Jan 2014 10:58:42 -0600, you wrote:

>Good morning Brian:
>
>If you want to go with very low expenses bear with me.
>
>Buy any signal generator that has FM modulation and an external input for 
>the audio.
>
>Buy a function generator that includes a ramp function.
>
>Buy an Hp 11710 down converter or any other.
>
>Attach the ramp from the function generator to the audio input for FM 
>modulation on the signal generator.  Connect the down converter to the 
>signal generator output.  Now you have a signal generator, a function 
>generator, and a sweeper ----- probably the least expensive way to go.
>
>Before you ask the question:  The down converter is to enable wider sweeps. 
>Most signal generators that have an FM modulation function will limit the 
>modulated bandwidth to a percentage of the carrier frequency.  Using the 
>down converter you can modulate a carrier at a higher frequency enabling a 
>wider sweep range.  Then down convert the output of the signal generator to 
>the desired sweep frequency range.
>
>This is really primitive and I used it many years ago.  As for the marker 
>generator.  The scope has calibration marks.
>
>This whole mess is really as cheap as it gets, and when you are done putting 
>it together and use it you will spend all of your time doing setup.  All the 
>above stuff is what you did in the 60's when you were still starving in 
>University housing.  Today, even if your income is a paper route ---- don't 
>go there.
>
>Now throw the whole idea away and buy the Tektronix 7000 series scope and 
>you will have, at your bench, a system that will do anything that you want 
>it to do except take the dog for a walk and explain to your wife why you 
>stay out late at night.  They are plentiful not expensive.
>
>Good luck Brian --- Kindest regards Jim