Simple Spectrum Analyser / Signal Generator 25MHz - 6GHz

[tlg]

Hi All

I recently purchased one of these "Simple Spectrum Analyser / Signal Generator 25MHz - 6GHz" from eBay:
     http://www.ebay.com.au/itm/NEW-25M-6G-signal-source-signal-generator-simple-spectrum-signal-source-tracking/263004176910

I am using it with the VMA application running on Win7.

The performance above 3GHz for both Spectrum Analyser and Signal generator seems to be quite poor.

Specifically the output in the Signal Generator mode appears to be around 0 - 3dBm up to 3GHz, but it then drops fairly dramatically to less than -20dBm. This is true for both sweep and fixed frequency modes.

So I am wondering if anyone else has this device and whether if behaves similarly, or whether I have a faulty device.

I see that there are also the lower cost 38MHz - 4.4GHz devices available, so if anyone has experience with one of them I would be interested to hear how flat the signal generator is over that frequency range.

Thanks in advance for any info.
T

[fcb]

You get what you pay for!

Not that helpful I know - but perhaps you should tear the unit down and show what is inside - possibly even post a schematic if you can reverse engineer it.  Could be interesting.

[Bicurico]

Hi,

Over the weekend I will run my SMA (AF4351 - 35MHz-4.4GHz) generating a sweep on both my Siglent SSA3021X (hacked). This will allow measuring the output signal up to 3.2GHz.

I will post the result here.

Regards,
Vitor

[ChristofferB]

I have the 35-4.4G version, and there's also an even cheaper 138-4,4G model. It seems it's the same thing with different but pin compatible RF frontend chips. The SA part is just the rf output fed to a mixer with a simple envelope detector on the IF side. Can't really comment on the performance compared to a bench instrument, as I don't have the latter, but for just mucking around and seeing signals I'm quite pleased for the price. The hardware's just an atmega with an FTDI chip for usb interface, and afforementioned single-chip RF synthesizer. Would probably be pretty easy to mod.

Software's REALLY bad! It's clealy made for a different device, as half the features don't work - you'll have to guess, though, since it's not like they're greyed out, they just don't do anything.
Be wary of the attenuator setting - it does nothing! the original (german ham magazine project I believe) had µcontroller outputs for a digital ATT. this doesn't. Almost cost me a mixer dev board.

[Bicurico]

Chris,
Check out my software for this device. It's on my blog. Click on my profile to see the link.
Regards 
Vitor

[Bicurico]

It's vma-satellite.blogspot.com. The link is accessible if you click on the small globe under my profile picture.

Regards,
Vitor

[ChristofferB]

Chris,
Check out my software for this device. It's on my blog. Click on my profile to see the link.
Regards 
Vitor

I have actually seen it, looks quite nice, but the whole license keys that needs to be updated thing sorta makes it more trouble than it's worth for my fairly simple needs in terms of a SA.

[Bicurico]

Hi,

Here are two pictures:

01 - I used the VMA Simple Spectrum Analyser to run a sweep from 138MHz to 3.2GHz (max. supported frequency of my Siglent SSA3000X).
02 - I set the Siglent with TRACE 1 as MAX MOLD and TRACE 2 as WRITE. The other parameters can be read from the image.

The output of the SMA device (ADF4351 version) is not that bad, actually. For the price it is a bargain, actually.

Regards,
Vitor

[tlg]

Hi Vitor

Thanks, that's quite a nice result which I would be happy with on my unit. 
This makes me think that my device is actually faulty.
The seller has asked me to return the unit - good service really I guess!

For interest here are a couple of photos of the unit which appears to be quite well made and fitted into an extruded aluminum enclosure held in place by the end plates where the SMA connectors are fitted.

In the center of the board you can see the ATMega chip.  The input SMA connector (lower) feeds to the Maxim chip and below that you can see the AD8307 500MHz log amp chip.

T

[tlg]

And here is a plot of the Signal Generator mode output into a log power detector as it is swept from 100MHz to 5000MHz )in 100MHz steps with pause of 100mSec.)

The vertical scale is 10dB per division with the center graticule at +5dBm, and horizontal scale is 500MHz per division.

The output is relatively flat up to ~ 2GHz then drops by 20dB by the time it gets to 3.5GHz.

[Bicurico]

What SSA did you use?

[hendorog]

I'm pretty sure pullup inductors instead of resistors are needed on the MAX2871 for best power out at the higher frequency end.
Although 20dB down seems a heck of a lot for just that so no doubt not the full story.

What is fitted on the board - the image is not quite sharp enough to see.

[tlg]

The forum won't allow a larger image to be attached unfortunately.

My log detector is based on the Analog Devices AD8318 chip.

(http://www.analog.com/media/en/technical-documentation/data-sheets/AD8318.pdf)

[Mosaic]

Those Siglent SSA3021X DSA with TG can be hacked to 3.2Ghz?
GOT a link for that?
What's the noise floor like compared to the RIGOL DSA815 TG.

[Bicurico]

Hi,

There is a whole thread in this forum delicate to the hacking of the Siglent SSA3021X.

Regards,
Vitor

[halfmac]

I just recently purchased one of these units. The CD-Rom does not work so have no software. It would be great someone could give me link to the software. Alan

[Bicurico]

Hi,

This is the software that is ILLEGALLY included on the CDROM: http://www.dl4jal.eu/hfm9.htm

The software was developed for the ORIGINAL NWT500, but chinese sellers include it without the author's authorisation anyway. This explains the total lack of support from him - obvious, as he has nothing to do with the SMA/NWT clones.

This led me to develop my own software, as I did not like the WinNWT software (http://vma-satellite.blogspot.pt/2016/12/vma-simple-spectrum-analyser-download.html), which does not not have spectrum analysis as the prime objective.

Regards,
Vitor

[cleanworkbench]

As said before you get what you pay for.
If it does,nt work as advertised its quite clearly not fit for purpose ie faulty, send it back at no cost and get another one, if the same, contact the trading standards and let them deal with the imports !.

[Bicurico]

If the hardware is working, then there is no need to get into trouble with Chinese seller: this will only take AGES and won't really solve anything, as you would have to ship the product back, before receiving a refund. That is the price you pay for really cheap hardware.

The included software is WinNWT/LinNWT and you can download it from the link I posted in my previous reply.

With this software, the hardware does work, however, you won't be able to do much with it, because the WinNWT/LinNWT was especifically programmed for the NWT500 devices, which have different hardware configuration then the cheap cloned SMA/NWT devices from China.

In my opinion, the hardware is by itself pretty awesome for the price, if you hook it up with a software that makes the most out of it (i.e. use my software or write your own).

Regards,
Vitor

[aandrew]

Bicurico, what is your blog address? You mention that it is in your profile, but when I look at your profile here there is no additional information.

It is possible I am blind though, so I apologize in advance...

[Bicurico]

It's hard to see...

Click on the small globe under my avatar picture.

vma-satellite.blogspot.com

Regards,
Vitor

[jgalak]

Out of curiosity - what's the real NWT500?  Who made/makes it?  Is it still around Googling for it just gets me the dl5jal website and ebay listings for the knock-offs.

[Bicurico]

The original NWT devices (there are further models prior to the NWT500) where developed and published by the German amateur radio magazine "Funkamateur":

http://www.funkamateur.de/

They have an online shop:

http://www.box73.de/

But the NWT series are totally sold out. They were very popular in Germany!

NWT stands for "Netzwerk Tester" - network tester.

Regards,
Vitor