EMRFD Message Archive 4417

Message Date From Subject
4417 2010-03-08 16:44:05 Andy USB spectrum analyzer
Ever since I can remember (well, not quite, but for almost as long as I've
been tinkering), I wanted a spectrum analyzer. At times I wanted one more
than an oscilloscope.

In recent years we've seen the appearance of inexpensive DSO sampling scope
boxes from China that interface to your computer via the USB port.

Well, now there is an RF spectrum analyzer, in a similar compact box that
attaches to the USB port. It covers 1 Hz to 4.4 GHz.

The product is called "Signal Hound" (www.SignalHound.com), and is sold by
Test Equipment Plus, in Washington state. The short manual is online, and
there are a number of short video demos, recorded in America. The product
also says "Made in USA", unlike those USB scopes which aren't. It isn't as
inexpensive as the USB scopes I've seen, but a spectrum analyzer is a
different animal with very different capabilities. I don't imagine it could
compare with a mainframe spectrum analyzer, but I'd bet a ham or hobbyist
could do some useful stuff with it anyway.

Maybe I'm the last one to know this. I only first saw it a couple days ago,
in one of the webclips (one-line ads) that pops up in Gmail.

I believe there are a couple of spectrum analyzer projects you can build.
But if you aren't into that, and would rather use one than build one, this
might be for you.

Now if I could only find room for one in my personal budget... ;-)

4418 2010-03-08 20:57:31 ka7exm Re: USB spectrum analyzer
Hi Andy.

I caught the Signal Hound ads recently as well (I have google mail and apparently it noticed me saying something about a spectrum analyzer....) The box looks neat
4419 2010-03-09 00:08:26 Ashhar Farhan Re: USB spectrum analyzer
the problem with most things that attach to the PC are that the PC is itself
capable of ruining the performance. a few years ago, i had borrowed a
friend's DSO with spectrum display capability. when i connected it to my
project on the bench, i was appalled to see the noise on my VFO. this turned
out to be a false alarm (after re-checking in a professional shop on an
Agilent mainframe). Most of the time, PCs (and laptops) being extremely
noisy, the performance of these boxes gets severely limited.

I even remember seeing some folks use an optical data cable to feed analog
signals (digitized in the external box) to the PCs. recently, i have had a
similar experience with a respected brand's HD camera. The audio noise
shoots up the moment I connect the USB cable.

- farhan

4420 2010-03-09 00:56:57 drmail377 Re: USB spectrum analyzer
If 1.3GHz is high enough for you, then I would suggest the DG8SAQ VNWA vector network analyzer (VNA). For roughly half the price of the signal hound you get a real VNA and a spectrum analyzer. I don't own a VNWA, but plan on getting one.


There's an active VNWA Yahoo Group. Ask there for comments regarding the spectrum analyzer functi
4442 2010-03-11 13:31:48 Paul Re: USB spectrum analyzer
Maybe a dumb question, but how do you use a VNA as a general spectrum analyzer?

Is this something particular to the DG8SAQ analyzer, or could I do this (at HF frequencies) with my N2PK?

A VNA seems perfect for some SA functions, like when you use a tracking generator to plot the response of a device.

But for some functions, like checking for the spectral purity of a transmitter, how do I do that with a VNA?

Maybe I'm missing something really obvious, but if I just sweep the detector over a range and plot the output, how do I control resolution bandwidth? Doesn't a "real" spectrum analyzer have a narrow post-mixer filter to control this? I always thought that the VNA didn't need such a filter since it was detecting a signal that was ultimately from its own generator and thus at a "known" frequency.

I'm by no means an expert
4443 2010-03-12 06:41:06 Craig D. Smith Re: USB spectrum analyzer
I'm also considering an inexpensive USB based spectrum analyzer. Appreciate
the pointer to the Signal Hound device. With an external reference to
enhance the phase noise performance, it would appear to offer a fair amount
of utility for the $$ except for the lack of a tracking generator option. I
would encourage anyone who has one to post their experience with it to this

Another interesting possibility is the Perseus SDR, which has a spectrum
analyzer function. But I've been able to find out relatively little about
it. The specs and on-line demos are oriented around the SDR application as
one would expect with little concrete information about the spectrum
analyzer function, either in terms of hardware specifications or user
software interface. I've been following the Perseus list lately, but there
again not much in terms of using it as a spectrum analyzer. So if anyone
has used it as a spectrum analyzer I would be very interested in hearing
about your experience.

73 Craig AC0DS
4444 2010-03-12 07:17:15 Brooke Clarke Re: USB spectrum analyzer
Hi Paul:

When you look at the HP 8411 Harmonic Converter for the 8410 VNA, or the
Tek S-6 Sampling module or the front end mixer in a SA they all look
very similar. The thing that's different between a VNA, SA and sampling
scope is what you do after the front end.

In the case of the HP 4395A you get a VNA and SA all in one box that
covers 0 to 500 MHz with a true RBW of 1 Hz that also is an impedance
analyzer. It has a 12 MHz IF after the front end and uses I&Q sampling
of the IF to feed a DSP. This means the SA can display the true
magnitude of the signal, not just a peak detector like in analog SAs.
See: http://www.prc68.com/I/4395A.shtml

Have Fun,

Brooke Clarke, N6GCE
4447 2010-03-12 13:26:21 Roelof Bakker Re: USB spectrum analyzer
Hello Craig,

I own a PERSEUS SDR and use the analyzer function for testing active

Some examples of the range 0-40 MHz can be found here:


This is how I receive from 0 to 40 MHz.

I have also used it for low pass filter evaluation using a wideband noise

This receiver is more like a piece of test gear than a receiver as it
features a true level meter accurate to 0.1 dB.
Unfortunately the absolute value is not calibrated, but using a known
source as a reference, one can still make accurate measurements. The
bandwidth in receiver mode can be set as low as 5 Hz, so it can be used as
a selective level meter.

Roelof, pa0rdt
4448 2010-03-12 23:15:12 Kerry Re: USB spectrum analyzer
My VNWA kit is "in the mail".

I have an N2PK VNA; a lovely instrument but I wanted a greater frequency range.

The VNWA has a spectrum analyser function; I look forward to trying it.
4462 2010-03-15 20:49:06 Ivan Makarov Re: USB spectrum analyzer

I'd say keep your HP 8558B for now. Spectrum analyzer function on
mixer-based detector kind of VNA is rudimentary. Also, special software
routine has to be written to realize the function (if you try using VNA mode
to display spectrum, you get garbage). Providing you have that, on N2PK VNA
you control resolution bandwidth by changing ADC speed. Even with all this
the dynamic range is limited and the user has to understand what is being
measured. Slow scan speed is another issue. Overall, this mode is not a
substitute to a real SA hardware. I wrote an SA program 2 years ago for N2PK
VNA but gave up. It is all limited by the hardware.

If someone has a different experience and can present practical measurement
results using VNWA or N2PK VNA, I'd be happy to discuss. Yes, I have done


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