Need to Figure out if this Spectrum Analyzer Works

[Supercap2F]

Hey guys! Hope all is going well for you. Man it’s been a long time since I last posted on here, I’ve been pretty busy with school stuff and getting ready for college. Hopefully in the future I’ll be able to be active on here again though.

So a couple months ago I got quite a score with some test equipment. I saw a listing on craigslist for a guy who was liquidating his dads business’s stock of all sorts of used and surplus test equipment. Really he just wanted to get rid of the stuff so he let it go super cheap. I ended up getting 3 fluke 8050As, a HP 3311A function generator, a Tektronix portable oscilloscope (2MHz I think), a really old HP sig gen, a wavetech function generator and two Texscan 1GHz spectrum analyzers all for around $400. I got some other equipment too, but it wasn’t that exciting. Most of the stuff I’ve been selling off on ebay.

So that brings me to my question. One of the spectrum analyzers that I got I know for sure is broken – I can’t get a trace on it no matter what I do. The second one I think is broken but I don’t know for sure. It turns on and I can get a trace on the screen but my knowledge of spectrum analyzers pretty much ends there. I ran the calibration signal from the front panel to the input, but I can’t get any single tone to show on the screen. It could just be me though. Here’s the setup:


The first picture is with the calibration signal hooked up and the second is without it. The front panel claims that the calibration signals frequency is 54MHz.

Does anything obvious come to mind that I’m doing wrong or is there more that I could do to try and test this piece of equipment?

The model is a Texscan spectre 1050, and the only manual I could find is for the model 1075 here: https://elektrotanya.com/trilithic-texscan_1075_spectrum_analyzer_manual.pdf/download.html

Thanks for your time!
Dan

 

[davenn]

The first picture is with the calibration signal hooked up and the second is without it. The front panel claims that the calibration signals frequency is 54MHz.

so you have the Cal output going straight to the RF input ?

I just ask because of the 2 different types of coax cable

Does anything obvious come to mind that I’m doing wrong or is there more that I could do to try and test this piece of equipment?

well it's not going low enough to get to 50 MHz. the lowest at it's current setting is 150MHz
change the centre freq from 400 MHz to 200 MHz and try again

 

[dorke]

Looks like it is working.
The base line looks a bit high

1. Set the center frequency to 54MHz.
2. Set the Span /div to 1Mhz.
3. You should have the cal signal in the center of the screen with an amplitude of -40dBm.

What do you ?

 

[Supercap2F]

Okay so I dropped the scale down to 1MHz and adjusted the center frequency to 54MHz and I do get a single tone at around -50 dbm. It doesn't look very stable though because jumps around quite a bit in the horizontal direction - I don't know if that's normal or not at lower scales? It seems kinda odd to me too that when you hook the calibration signal up you get so many tones all across the spectrum. I guess that might just be noise?

The cable I'm using is a RG59B bnc.

 

[dorke]

No.it isn't noise,these are harmonics of the main 54Mhz frequency.
It is the way it should be.

Assuming the input attenuation is set to 0dB,and that the cable you are using is good.
The amplitude reading you get isn't correct ,it should be -40dBm.
You should use the calibrator pot(top-right) to calibrate it ,see below.



Addendum,
Before doing the above,without any input signal.
Use the vertical adjust. pot. for setting the "base line" to the lower line on the screen.
(marked blue).