Using the "138MHz-4.4GHz USB SMA Source/Signal Generator/Simple Spectrum Analyzer" for TV/CATV/SAT

[vma]

Hi,

The "138MHz-4.4GHz USB SMA Source/Signal Generator/Simple Spectrum Analyzer" can be purchaed cheap at eBay from Chinese sellers. It costs around 60 Euro, but comes with an unsuitable software.

I have written a new alternative software that is tailored for this exact device.

Take a look here:

More info and download at my blog: VMA's Satellite Blog

Regards,
vma

 

[battenfan]

Nice job!

I assume it's equipped with an ADF4350 and an ATmega8L. Is the Atmel chip doing the AD conversion? I wonder if there's a chance of accessing the firmware of this device.
I don't think I will buy one as it seems slow. So this is not a feature request, just a tip:
If it was me, I would make it possible to save a spectrums as a csv files to import them in Excel or similar. It would make it possible to use one as a baseline and a second to easy compare differences to the first. You could check out how Ear To Ear Oak has solved it by even having a compare option within the program:
RTLSDR Scanner | Ear to Ear Oak
Great feature to have when noise generators and/or directional couplers aren't linear.

Happy programming!

 

[vma]

Hi,

Sorry for the late reply.

The original NWT hardware used a PIC, not sure what mixer was used.

This cloned version uses one ADF4350 (a ADF4351 version is available, also, at higher price, covering 35MHz-4.4GHz). It uses an Atmel controller, programmed to behave like the original NWT. I haven't even tried to extract the firmware, as I assume it has obviously the lock bit enabled.

Regarding the AD conversion: I am not sure, but it is likely that the Atmel takes care of it.

It is a bit slow, but then, not that slow: I have professional field meters which are much slower than that.

I considered CSV export, just haven't had time to implement it. If you want to do comparisons, you can for the time being use the TRACE functionality and render MIN, MAX, AVG traces together with the LIVE trace.

The thing is: as soon as you are able to save the trace, you want to be able to load it in again and then there is a huge problem: what if you load a trace from a different frequency range, than the one being rendered live? Should the loaded one be shown partially or should the live one adjust to the frequency range of the saved one? It is easier to implement the latter one.

It is definitly on my list.

The other HUGE issue: calibration! This is IMHO the real deal breaker, as my software does not provide any calibration. Truth is that a spectrum analyser is not so much intendend for accurate power measurements - there are dedicated power meters for exactly this purpose and they are EXPENSIVE! The probe alone can cost over 1000 Euro... But still, the accuracy of the SMA Spectrum Analyser could benefit a lot if some calibration would be implemented. I am still considering it, but have no final idea on how to implement it.

Regards,
vma

 

[jeallen01]

Just ordered one of those Chinese knock-offs from Hong Kong, which should be here in a few weeks, and with Vitor's (vma) kind help I have down loaded his s/w package and activation code - hope it all works!

PS: the units have SMA connectors on them, and so people will probably also need a couple of SMA to F connector adapters (possibly like these from China and they should arrive about the same time as, or hopefully before, the unit itself).

 

[Anonymous_1]

Thanks VMA for this great tool and a very cheap price

and it's not so slow ! very interesting, I will test 'deeper'

 

[jeallen01]

F..D..
Have you done a scan of a feed from an LNB on of your many (!) dishes to see what that looks like as I/we would be very interested to see that?

 

[jeallen01]

The SMA to F connectors adapters arrived yesterday, which was quick, and look well-made - maybe the actual unit will get here earlier than indicated (which was 4-28 Nov)?

 

[vma]

Guy's,

To use the SMA Simple Spectrum Analyser for satellite bands, don't forget to purchase a DC Blocker!

The LNB voltage is enough to fry the ADF4350 RF mixer and receivers normally do not block the voltage on the Loop Through connector.

These DC blockers are cheap. Search eBay for: "sat dc blocker"

I published a new version today: it now supports the ADF4351 (35MHz-4.4GHz) and has a new optimized GUI layout, with all controls on the right side. This allows use of the software on screens with less vertical resolution.

Regards,
vma

 

[jeallen01]

vma

Had no idea of that but it sounds entirely reasonable - will get that blocker PDQ!

 

[jeallen01]

Have now ordered a DC blocker - but not from ebay but from Amazon, and even then it was not "cheap" (£13.68 delivered from Germany) because that was cheaper for UK delivery - see here if you want one.

Edited:
VMA
Just took another look at your blog page and you say that an attenuator is also needed to reduce the input voltage to the S/A to avoid killing the i.c. - how much attenuation would you recommend (I already have a couple of attenuators, but I might need to buy another one)?

 

[Anonymous_1]

New GUI loaded, great job VMA !

 

[jeallen01]

vma

BTW, if I download your new s/w then will I need a new activation code (having already used the existing one to have a look at the existing version)?

Thanks in advance.

John

 

[vma]

Hi,

@jeallen01: The activation code is always the same, regardless of the version. See my blog for expiry dates and renewal policy (it's free).
@jeallen01: I am not using any attenuator for DVB-T/C/S. The attenuator is important if you hook up a tranceiver directly or have one transmitting very close to your antenna. Take a cheap Baofeng radio: it transmits up to 5W!!! Hold its antenna close to the RF Input of the SMA device and you easily kill the ADF4350 IC if it is not protected by an attenuator. I have several F-type attenuators with 5dB attenuation, each. For my Siglent SSA3021X I purchased a switchable attenuator 1db-90dB.
@Feedsat: You get a much better view, if you reduce the upper and lower dB range! The above picture would be much nicer if displayed from -50dB to -90dB

Cheers,
vma

 

[jeallen01]

vma

Many thanks for the info

 

[Anonymous_1]

Hi,
@Feedsat: You get a much better view, if you reduce the upper and lower dB range! The above picture would be much nicer if displayed from -50dB to -90dB
vma

just tested with weak data signals @ 7°E ;)

much precise than other PC card tools

 

[vma]

Cool! Nice pictures!

I have on my TODO list allowing to show the SAT frequency by adding the LOF. That would make it easier to read the frequencies. Not sure how to implement it for Low/High band, though...

Regards,
vma

BTW: Some did not know this - if you click on the small graph (with the waterfall), you exchange the spectrum window with the waterfall window!

 

[Anonymous_1]

F..D..
Have you done a scan of a feed from an LNB on of your many (!) dishes to see what that looks like as I/we would be very interested to see that?

This SSA tool help me to understand why I was not able to get the same result of scans in blindscan .

This frequencies are not always active (few minutes and few minutes off, it depends, confirmed by the waterfall (I already seen it in Xband @ 12.5°W, some GS frequencies "pop up" and leave)

34.5°W 11120 11122 11124 11127 V 1700 & 11129 V 500 GS streams, not very interesting for most of the people but not for me
This is exactly a good usage of the waterfall.

 

[Anonymous_1]

after a couple of minutes:
11120 11127 always "on"
11122 active frequently
11124 not often active

 

[vma]

Cool!

It makes me happy to see that the software is useful!

Tip: once you have the frequency set as desired, click on the CLR button within the trace group.

If you later on want to see the MIN, MAX or AVG spectrum, you can just turn those traces on: they are being recorded continously since the last CLR press or frequency range change.

So, if you suspect that a transponder has been turned on or off, just activate MIN or MAX, accordingly!

Regards,
vma

 

[vma]

I published a new version today. It allows saving a spectrum and loading it back as an overlay.

Regards,
vma