RIGOL DSA 815 TG

[kurnia putra]

Hi everyone,

I am planning to buy this RIGOL SPECTRUM ANALYZER, but rather confused how to use this equipment and don't know
exactly the advantages of this Spectrum analyzer.

I need this equipment especially to measure the antenna also coaxial cable.

I am planning also to buy RETURN LOSS BRIDGE.

Can anybody help me or give me a recommendation  what kind of RETURN LOSS BRIDGE  I have to buy? 

How often must we calibrate the Rigol Spectrum Analyzer or Can we calibrate its RIGOL by My self ?

Thanks for helping me

'73

[jimeagle]

Check out my videos about the Rigol DSA815-TG at https://www.youtube.com/jimeagle1 and you will be able to see demonstrations and evaluations of the Spectrum Analyzer and Tracking Generator.  I use a Mini-Circuits Directional Coupler to measure Return Loss in several of the videos.  The attached Photos are of measuring a Band Pass Filter, Pass-Reject Cavity Filter, and measuring coaxial cable loss as some examples of how this unit can be used.

Jimeagle1

[Velund]

Interesting question - is tracking generator of 815-TG useful as a general purpose signal generator? Can it be set to zero span mode to get CW signal of specified frequency from TG output? If so, is it stable enough to test receivers with narrowband filters?

I understand that there will be no modulation anyway and external attenuator must be used to get signal to microvolt range, but it would be nice to be able to tune up 23 cm transverter and check sensitivity of receivers above 1 GHz.

[olsenn]

Interesting question - is tracking generator of 815-TG useful as a general purpose signal generator? Can it be set to zero span mode to get CW signal of specified frequency from TG output? If so, is it stable enough to test receivers with narrowband filters?

I understand that there will be no modulation anyway and external attenuator must be used to get signal to microvolt range, but it would be nice to be able to tune up 23 cm transverter and check sensitivity of receivers above 1 GHz.

The DSA815-TG has a RBW (minimum) of 100Hz, so if using the tracking generator as a signal source it will be sweeping between 50Hz below your center (desired) frequency and 50Hz above it. This is usually acceptable if your center frequency is large (such as 1GHz) but can be problematic with low frequency use, unless frequency stability is not very important. There is no zero-span output.

The amplitude of the TG output is configurable from within the device; 22.36mV RMS is the lowest setting, but this is when you have a 50-ohm termination. Lower valued impedance on the receiving end will act as potential divider giving you whatever voltage you need... as long as it isn't below the noise floor.

[jimeagle]

If the Sweep is set to the Same Start and Stop frequency, the output should be CW at a single frequency.  However, when I tried this while listening to my 2M SSB receiver (IC706MKIIG) the Tracking Generator was definitely sweeping between two 'tones' about 100 Hz apart.  This sounds very much like FSK or RTTY tones with 100Hz shift or so.  The Start Frequency listed is 144.19995 and Stop Frequency is 144.20005 as indicated by Olsenn.  The Sweep Rate will, of course, affect whether this is heard as distinct tones or swept tones.

However,  when I pressed the 'Zero Span' button, I got a nice, clean single frequency.  Thus the unit should be useable as a signal source for various purposes. 

I did not check how much leakage might be present coming from the unit radiated through its plastic case.  There is a significant cast aluminum shield inside the unit to prevent this, however, and my roof top antenna heard nothing from the DSA815-TG until I placed a Quarter Wavelength whip antenna on the Tracking Generator output.  At that point the roof top antenna provided an S9+35dB signal with the TG set to -20dBm and with a Mini-Circuits 10dB attenuator pad between the TG Output and the Whip.

By the way, when I disconnect the whip antenna and place a half-inch long piece of wire into the output side of the Mini-Circuits 10dB attenuator, the signal to my roof mounted antenna provides only an S-3 signal (with the IC706 Rx Preamp "On") thus I would think that reasonable control of levels should be possible using an external Step Attenuator.

In the 'Zero Span' mode the step attenuator can be placed between the TG Output (or in my case the 10dB pad output on the TG Output) then it can be connected to the DSA815-TG analyzer Input to check the conducted signal level. 

Since you can adjust the BW/Det to 100Hz, you should be able to confirm levels down to where the internal leakage between the TG and SA input becomes the primary signal factor rather than noise.  This is about -102dBm on my particular unit when the TG is 'On' but only -125dBm or so on noise peaks when the TG is 'Off'.  Also note that you will probably see 'beat notes' between the input signal connected to the SA and the internal leakage signal.  These will be peaking about 6dB above the internal leakage level alone.

Bottom Line:  You can provide an accurate and stable signal source using the DSA815-TG Tracking Generator output.

OK, that was the 2nd from Bottom Line.  See https://www.youtube.com/jimeagle1 for an example of narrow Xtal filter sweeping.