SA vs SDR

[peterx]

Hello

My interests are HF experimentation.

i've started to spec equipment as follows:

• SDR Ettus B210 SDR 70 Mhz to 6Ghz
• Antenna AOR DA600 70 Mhz to 6Ghz

Would run GNU Radio on Meerkat PC running Linux, Ettus prefers native not virtual.

I've considered getting measure and test equipment which I do not have experience with.

One option is USB multi purpose type scope (Pico, Digilent, NI),
the other option is stand alone equipment (scope + PS + DMM + FG).

But in reading a post recently, I read that a Spectrum Analyzer performed (better)
the same function as an SDR. Aside from price, what are the pros and cons.
I would assume higher resolution, cleaner signal on SA...

Thanks in advance for any guidance.

[tkamiya]

You can think of a spectrum analyzer as a receiver that constantly scans.  You can also scan zero span and demodulate AM and FM signal on some models.  A major con I can think of are, you really don't want to keep an antenna connected to SA at all times.  If you get static coming in, it is so easy to blow the input section, and that is a majorly expensive proposition to repair it.  Also, demodulation is limited to AM and FM.  You can't demodulate SSB.

Pro, of course is speed and bandwidth of scan.  You can scan an entire spectrum range in one sweep on SA, where as with SDR, it is typically limited to 50MHz or less at a time.  With SDR, prices tend to be lower, and it is designed to be a receiver, so having antennas connected is not typically a problem.

Which is better totally depends on your purpose.  There is not much justification to go the spectrum analyzer route if all you want is to receive a single signal at a time.  If you need quantitative measurement, then SA would be more appropriate.

Hope this helps

[peterx]

Thank you. Very helpful explanation of the pros and cons.

I eventually will want quantitative measurement, but an SDR is more appropriate now.

Deferred gratification... 10 week back order for the SDR!

[NiHaoMike]

Modern spectrum analyzers pretty much are SDRs, main difference is that the local oscillators are optimized to constantly sweep while most SDRs are designed to have the local oscillator set to a certain value and only occasionally changed. Thus a general purpose SDR might not yield reliable data when the local oscillator frequency is changed until it stabilizes at the new frequency, since the frequency shift behavior is not characterized.

[peterx]

HenHaoMike

Thanks for the feedback...  I'm using this project to kick start my ee education.
Forgive any erroneous assumptions on my part.

My interest is in HamSci projects (like Space Weather Station) rather than contesting.
I've read having a disciplined LO is an important component, and I've looked into GPSDOs.
I liked Ettus B210 specifically because it comes with an input for clock or time reference.
There's also an out-of-the-box GPSDO option.

The more I've read about GPSDOs, the more I see 1) I can build them using projects available
from other contributors and 2) they are extremely ambient temperature sensitive.

This is link from another eevblog post that I found very interesting.
https://www.paulvdiyblogs.net/2020/07/a-high-precision-10mhz-gps-disciplined.html
And there are a few other notable efforts on the blog.

Many rabbit holes to go down!

So back to the original question, because I was going to invest in high end SDR, I wondered about
putting that towards a piece of lab equipment (SA) that I'll eventually want anyways.