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Saturday, 31 December 2016

What is the resolution of the ADF4350/ADF4351 devices? People asked and I verified...


Some people using the VMA Simple Spectrum Analyser Software asked me about some strange signal shapes and in the past I thought they were simply looking at Double Sided Amplitude Modulation (

But as the inquiries increased, I sat down and did some simple tests.

First off, here are the specs as published by the Chinese sellers on eBay:

  • Output frequency range: 35MHz - 4.4GHz
  • Stepping: 1kHz
  • Output power (for reference):
    • 150MHz -3.2dBm
    • 250MHz -3.4dBm
    • 500MHz -3.4dBm
    • 750MHz -2.8dBm
    • 1000MHz -3.4dBm
    • 1500MHz -3.6dBm
    • 2000MHz -4.0dBm
    • 2500MHz -2.8dBm
    • 3000MHz -1.8dBm
    • 3500MHz -3.6dBm
  • Spectrum of the input frequency range: 35MHz - 4.4GHz
  • Frequency Accuracy (after calibration): +/- 1KHz @ 1GHz
  • Low-noise input signal amplitude:-70dBm @ 0.5GHz
The alone means, that the device cannot "look" at anything under 1KHz of resolution.

Here are some pictures, to show what happens:

Picture 1: This shows an analogue TV transponder. The right peak shows the video carrier, the second peak the audio carrier. The modulation is of course AM - Amplitude Modulation (, so there shouldn't be the inverted spikes in the middle of the peaks, as in Sideband Modulation (!

Picture 2: Is it a problem of the VMA Simple Spectrum Analyser software? I guess not, as WinNWT, the original software for these devices, shows exactly the same spectrum!

Picture 3: Fortunatly I own a Siglent SSA3021X spectrum analyser, so I fed the same signal, using the same parameters. This is how the transponder looks like. Quite different!

Picture 4: Zooming into the video carrier, we can see the video carrier exactly how it should look like in a spectrum analyser.

Picture 5: Zooming into the the same video carrier with the VMA Simple Spectrum Analyser, we see a totally different picture. Clearly we are beyond the resolution capabilities of the device! When it is sweeping, it will use a too wide RBW - in fact we can only change the sweeping steps, but not the RBW.

Picture 6: If we select a combination of span and samples, so that the (equivalent) RBW is 0.1MHz, we get a correct representation of the spectrum.

Picture 7: Same spectrum settings as in previous picture, but using the Siglent SSA3021X. This confirms that at 0.1MHz (equivalent) RBW the ADF4350/ADF4351 devices are showing a good representation of the spectrum.

Conclusion: Do not expect to resolve higher than specification of the ADF4350/ADF4351 with the VMA Simple Spectrum Analyser software, even though you can input the relevant settings!

This problem results from the requests I had to implement three decimal points to all frequency input fields - before the software only used 1MHz resolution. This opened the door to usage beyond the hardware capabilities. Nothing wrong with that, just always question what you are measuring!

Hopefully future SMA/NWT devices will come along with higher resolution.


Friday, 30 December 2016

Performance demonstration of ADF4350/ADF4351 based devices with the VMA Simple Spectrum Analyser software


I just published this video on Youtube, to show the performance of ADF4350/ADF4351 based devices with the VMA Simple Spectrum Analyser software:

The main interest of this video consists in showing the refresh rate of the live spectrum using the 35MHz/138MHz-4.4GHz "USB SMA Source/Signal Generator/Simple Spectrum Analyzer" or NWT4000-1/2/3 devices with my software.

Attached to the device is a sinal cable featuring the NOS (TVCABO) CATV service from 138MHz to 750MHz.

During the video, I change from 500 samples to 250, 200, 100 and 1000 samples, back and forth. Notice the relevant RBW.

At the end of the video I zoom in by reducing the frequency span. This shows how high a resolution on can achieve.

For a device you can purchase for as little as 60 Euro, this is quite a performance!


Friday, 23 December 2016

VMA Simple Spectrum Analyser - Zero Span


Most spectrum analysers have a functionality called "Zero Span". What this does is to show the centre frequency in time domain, as opposed to the frequency domain of the spectrum: the result is similar to an oscillocope.

There are two ways to activate the zero span function:

  1. Just enter 0 MHz in the span frequency box
  2. Click twice on a given frequency, so that Marker 1 and Marker 2 have the same frequency value. Now select MARKER in the "Frequency Preset" group
Picture 1: I clicked twice on a transponder so that Marker 1 and Marker 2 are on the same frequency

Picture 2: The software recognizes the zero span entry and switches into time domain view on centre frequency

Before you get too excited, let me tell you that this function is rather useless... Why? Because the sample rate is much too slow for any useful application. Capturing 500 samples takes around 150ms, which equates to about 3000 Sample/s. The very popular hobby oscillocope Rigol DS1054Z has a sample rate of 1GS/S, that is over 300.000 times more!

The other problem is that the zero span serves to look at the signal modulated on the given frequency. However, the way the SMA/NWT devices work, they only offer 8 bit resolution for the whole signal, leaving little resolution for the modulated signal, itself.

So why did I implement this function? Here are my reasons:
  1. Doing so has allowed me to learn a lot about Zero Span in spectrum analysers!
  2. I consider that the VMA Simple Spectrum Analyser software is a great learning tool: if you learn how to use it, you will be able to use a regular spectrum analyser, so it does make sense to add this function, even if it's implementation doesn't allow a practical use.
  3. If future hardware devices of this family support a higher sampling rate, this function may become more useful.
  4. While the sampling rate is definitly insufficient to look for instance at analogue TV scanlines (a single scanline only takes 64ns!), there might be other applications where the current sampling rate is actually enough (if so, please let me know).
Other new features I implemented:
  • The Signal Source tab has now programmable preset buttons!
  • The frequency input is now verified - if you enter a frequency which is out of range or doesn't make sense, it will be ignored, instead of crashing/freezing the software.
Merry Christmas everyone!


Sunday, 18 December 2016

VMA Simple Spectrum Analyser: Three updates in one day...


Today I uploaded three updates of my software. All minor stuff and bug fixes.

From all the improvements, there is one I am especially happy about: the grid lines are now drawn as dotted lines.

This may seem a ridiculously insignificant thing, but believe me, it looks so much better and makes reading the relevant information much easier. Also, no more disappearing of the horizontal lines in advances measurement modes!

Head to the download page at to download the latest release!


Vintage Instruments and Tools: SCHWAIGER SAP 100 / SPG 101 / SSI 028


I would like to present you with a series of loose blog entries showing some of my vintage test instruments and tools.

I start with the Schwaiger SAP 100 "Satellite System Test Set". I own one complete set and then a second SPG 101 unit. Both were purchased second hand some years ago at eBay for little money.

The core of the set is the SPG 101 unit, which is a neat little device: it is fed by just one single 9V battery and has an ON/OFF switch. What it does is simple: it emits a test pattern composed of a grid at exactly 11.288 MHz. Point it at an LNB and you can receive this fake analogue transponder with any analogue receiver or field meter.

The goal is to test if the LNB is working properly or not. Clever!

Picture 1: The test set comes in a small case.

Picture 2: Inside the case is the SPG 101 ("satellite testing generator"), the SSI 028 ("satellite voltage indicator"), two cables, adapters and the 9V battery

Picture 3: The SPG 101 front view

Picture 4: The SPG 101 rear view with specs and picture of the test pattern

Picture 5: The SSI 102 "satellite voltage indicator", which allows to see if voltage is present and which polarity/band is currently selected

Picture 6: Page one of the included English instructions

Picture 7: Page twoof the included English instructions

Picture 8: Test setup with the SPG 101 facing the LNB. The LNB will pickup the test signal from distances of up to 5 metres! Here I am using the Deviser S7200 TV Signal Analyzer, which is fully digital, so it cannot show the test pattern...

Picture 9: Which is why I grabbed my good friend, the Satlook Digital Color

Picture 10: The test signal is at 11.287 MHz (+/- 1 MHz is perfectly acceptable!)

Picture 11: The Satlook Digital Color has a build-in analog receiver, so it can show the test pattern - a simple grid

Picture 12: Inside view of the SPG 101

The main components of the SPG 101 are these two IC's:

  • ZNA234E: This IC is a pattern generator. It can be used to produce crosshatch, dot and greyscale test patterns. Datasheet HERE.
  • HFC4011B: This IC is a Quad 2 Input NAND Gate. Datasheet HERE.
Interestingly, this device should be easily hackable to circumvent the ZNA234E and feed a direct input of composite video, thus transforming it into a video upconverter/modulator.


C-Band LNB test using 2x VMA Simple Spectrum Analyser


Inspired by John at [Click here to go to relevant thread], I tried out a setup to test if a C-Band LNB is working properly.

Being a bit lazy, I just used a Deviser S7200 field meter to power up the LNB (I could have used a regular receiver or even a plain power source for coax, which I do have - I just didn't felt like searching for it, unboxing it, etc.). Connected the LNB is a simple 1-IN, 2-OUT 2-way splitter.

One output connects to the Deviser S7200, the other, USING A DC BLOCKER, connects to the SMA device #1.

The SMA device #2 connects to a basic antenna, pointed to the C-Band LNB.

Starting two sessions of the VMA Simple Spectrum Analyser (side by site on my desktop, thanks to two 22" FullHD monitors), I obtained these results:

The spectrum is inverted (and thus shown mirrored) and the frequencies are displayed, accordingly. For this I set a negative LOF of -5150 MHz, used by my AMERICAN BIRD GCF-D11C LNB. The "-" sign indicates that the spectrum is to be inverted.

Notice that you can set the "Min. Bandwidth" for transponder recognition to values smaller than 1 MHz!

Hope this inspires new ideas!


Friday, 16 December 2016

History of the SMA Simple Spectrum Analyser devices


Sometimes I get asked about the origins of the SMA Simple Spectrum Analyser, the NWT-4000, etc.

This is what I found out so far:

The NWT devices where originally developed in Germany by amateur radio addicts. At one point this was featured in the magazine

The software (WinNWT and LinNWT) was written DL4JAL for this magazine and is documented on his web-seite:

The initial devices were the FA-NWT, up to the NWT500, NWT7 and HFM9. They can offer a lot of extra functionality, like software controlled attenuator, etc.

The Chinese radio amateur BG7TBL cloned the design and used the ADF4350 chip for an increased frequency range. Other models followed up. They are all compatible with the original design, because they rely on the WinNWT/LinNWT software. Sadly, the Chinese selling the cloned hardware include the WinNWT/LinNWT without any authorisation, causing the author DL4JAL a lot of problems with people asking for help.

He does not reply, because a) he has nothing to do with these cloned devices and b) most support questions come from the cheaper models featuring only one ADF4350/ADF4351: they cannot be used for SWR measurements and hence the WinNWT/LinNWT software is not of great use.

It is to be expected that more and more models will follow up, as new synthesizer chips become available, which offer such increased frequency ranges.

The more expensive NWT4000-1/2/3 models are either sold with or without a case. Bear in mind that you definitely need a case! If you don't have one, don't just buy the PCB version. It will not be immune to interferences and chances are that you will destroy it sooner or later, by touching some traces with a cable connector.

Price range goes from around 60 Euro up to 350 Euro. You can buy these devices on


VMA Simple Spectrum Analyser - Download the latest version here!

VMA Simple Spectrum Analyser

Please read the whole contents of this page before sending any e-mail!

Feature List

  • Sweep Spectrum Analyser supporting ADF4350, ADF4351 and MAX2870 based devices 
  • Free selectable span range
  • Two markers
  • 8 user defined predefined spectrum settings
  • Automatic amplitude adjustment
  • Min/Max/Avg live spectrum traces
  • Line/Shaded spectrum rendering
  • Waterfall display
  • Save/Load spectrum mask
  • Record/Play spectrum
  • GPS and time stamp for on the road measurements
  • Frequency logger from live or recorded spectrum at desired freqeuncy
  • Trigger function with user defined mask and automatic alarm e-mail message
  • Google Maps rendering of logger files
  • Signal source
  • Sweep generator
  • Power meter
  • Special measurements
    • Marker 1&2 bandwidth
    • Marker 1&2 power difference
    • Bandwidth Measurement
    • Channel Power Measurement
    • Transponder Frequency Measurement
    • Math functions applied on traces
    • SWR Measurement
  • Satellite Identification through transponder pattern recognition

Current software download link:

Version 2017-05-30


Link does not work? Please write a comment!

Current manual download link:

Version 2016-12-27

Link does not work? Please write a comment!

Change log:

2017-05-30: Added "Wait" parameter, which allows to set a pause between capturing each sample
2017-02-28: Added initial support for AD9951 and AD9858 synthesizer (FA-NWT and NWT500)
            NOTE: AD9951 and AD9858 are used by FA-NWT and NWT500,
            but as it turns out, these device do not work with my software.
            I will remove the respective options in next release.
2017-02-27: Assed 10 Markers for Math Trace
2017-02-26: Added CSV export for Traces
2017-02-25: Bug fixing and improvents on SWR Measurement
2017-02-23: First experimental SWR Measurement implementation
            Further improvement on Math Operations functionality
2017-02-21: Added Math Operations for LIVE trace
2017-02-19: Added Channel Power Measurement in Automatic Bandwidth Measurement mode
2017-02-18: Added support for MAX2870 synthesizer (i.e. NWT6000)
2017-02-13: Added Automatic Bandwidth Measurement in inverted spectrum (negative LOF)
            Several minor bug fixes
2017-02-12: New function: Automatic Bandwidth Measurement
2017-02-11: Direct frequency input for marker 1 and 2 added
            Fixed bug in center frequency when changing span value
2017-02-10: Additional bug fixes due to 10 Bit resolution upgrade
2017-02-09: IMPORTANT BUG FIX! Increased Amplitude Resolution from 8 Bit to 10 Bit
            Fixed error on AVG Trace
2017-02-03: Added current frequency display in Sweep Generator
            Fixed START/STOP buttons in Signal Source
2017-01-10: Added a STOP button on the Signal Source tab - it will stop any
            signal output
            Bug fixes:
            - Step value of sweep generator could not be changed
            - Centre frequency was wrong when increasing/decreasing span beyond
              frequency range
            - RBW was displaying only integer valures, hence often just a zero appeared
2017-01-03: Implemented variable curve thickness according to selected sample rate
            Fixed small bug with minimum frequency input and maximum span
2016-12-29: Finished implementation of input form for all input fields, including
            on Setup tab
            Switched to x86 binary (should make it compatible with Windows XP)
            Activated new style GUI
2016-12-28: Improved GUI: orange fields cannot be edited, blue field can be edited
            All numeric input fields (except in Setup tab) are now input through
            input form and values are validated/checked
            Corrected centre frequency input
            Implemented COM-port verification - software does not hang if wrong
            port is selected
2016-12-25: Fixed broken Log on Maps function
            Implemented user selectable MAC Address for licensing
2016-12-24: Increased size of mouse frequency box and change tool tip to box style
2016-12-23: Implemented Signal Source Preset Buttons
            Implemented frequency input check
2016-12-22: Implemented Zero Span functionality2016-12-20: Decimal places setting now
            stored in registry
            If decimal places switched off, frequencies are rendered in bigger font
            Tooltips shown for better readability on frequency settings and presets
2016-12-19: Bug fixes for Satellite Identification on C-Band
            Moved LOF input field from Frequency Presets group to Marker
            group, thus allowing LOF to be changed during playback
2016-12-18: User configurable SR treshold for Ku- and C-Band Satellite
            Identification in Setup Tab
            Fixed bug: Satellite Identification was not working when
            playing back recorded spectrum log
            Grid lines are drawn with dashed lines, improving readability
2016-12-17: Improved satellite identification speed and added support for circular
            polarisation in C-band
2016-12-15: Added keyed input on frequency input form
2016-12-14: Added frequency input form, allowing frequency input in KHz or MHz - this
            fixes unverified user input crashing the software
            Frequency is now shown in MHz with 3 decimal places
2016-12-13: Satellite identification shows missed transponders in red
            Added colour map with 256 colours for Log on Maps
2016-12-12: Improved automatic satellite identification
2016-12-11: Added automatic satellite identification
2016-12-10: Added transponder pattern recognition
2016-12-05: Added e-mail alarm alert on trigger
2016-12-04: Added TRIGGER functionality
2016-12-02: Added PRINT SCREEN button to print the entire Form to the default
            printer (only available on the Spectrum Tab)
            Added PRINT MAP button to print single frequency signal power map
            on LOG ON MAPS tab
2016-12-01: Added time stap and GPS position to recorded spectrum
            Frequency log can be created from recorded spectrum, including GPS data
            Enhanced GPS functionality
2016-11-29: Frequency log with GPS position and display on Google Maps
2016-11-28: Initial GPS functionality added
2016-11-27: Added recording and playback of the whole spectrum
2016-11-25: Added MINIMIZE button to hide main window, while spectrum keeps running
2016-11-23: Added Min, Max & Avg measurement with optional horizontal line display
2016-11-22: Corrected Power Meter calculation
2016-11-13: Implemented Auto Scale in Y
2016-11-10: Fully implemented inverted spectrum - if a negative LOF is entered,
            the spectrum is drawn inverted
            Inverted the changelog - new changes on top for better visibility
2016-11-09: Small bug fixes:
            Frequency of mouse position now without negative sign for inverted
            Spectrum load window only shows *.ssa files
2016-11-08: Increased preset buttons to a total of 9
            Implemented option to have frequency grid with 3 decimal places
            Implemented new field to show the frequency at mouse position with
            3 decimal places
2016-11-06: Implemented LOF configuration for frequency grid and marker
2016-11-05: Implemented 6 user configurable frequency preset buttons
            Implemented functionality to save and load spectrum, allowing the
            overlay of a saved spectrum
            Optimized screen width
2016-10-30: Changed screen layout, mainy for use with smaller resolutions
            Added ComboBox to select between ADF4350 and ADF4351 variants
            (138MHz-4.4GHz or 35MHz-4.4GHz)
2016-10-12: Added user defined CENTER FREQUENCY field
            Added user defined SPAN field
2016-10-10: Converted small graphic window to new graphics engine
2016-10-04: Implemented new graphics engine - best fit curve instead of line
            Implemented line/shaded spectrum option
            Corrected waterfall diagram colour map
2016-10-02: Added RBW information
2016-08-31: Removed single spectrum run
            Removed single marker dBm measurement
            Implemented improved graphics engine
            Implemented new markers: circles instead of vertical lines
            Implemented dBm indication at marker 1 & 2
            Implemented Delta dBm between marke 1 & 2
            Cleaned up source code for easier maintenance and speed
2016-08-30: Corrected dBm calibration for improved precision
            Implemented new function: Powermeter - not sure if it is correctly
            Implemented new graphics engine
            Spectrum/Waterfall in main image can be saved as PNG
            Introduced change log
            Cleaned up GUI (Setup screen)
            Cleaned up some code
            Added a SET button on Sweep Generator (less prone to crash due to
            open RS232 port)
2016-08-22: Fixed bug in activation routine
2016-08-21: Implementation of activation routine

Minimum hardware requirements:

The bottleneck is the SMA device itself! The software works well on any fairly modern computer, laptop or tablet. No matter if Intel Atom or Intel Core i7, expect a good performance. No special graphics card is needed.

You do need to have one free USB port to connect the SMA device! 

Operating System requirements:

The software only runs on Windows 7, Windows 8/8.1 and Windows 10.
No installer is used - just uncompress the archive to a folder and run the executable.


The software is closed source and requires a license. There are two types of licenses:
  1. Free temporary license - exiry date always set for the closest of these dates:
    1. March, 31st,
    2. June, 30th,
    3. September, 30th
    4. December, 31st
  2. Permanent license, provided to donators (10€, 10£ or 10US$ - instructions inside the software and in the manual)
New temporary licenses can be requested for free after expiry for free.

One user can request several personal licenses (free or permanent) within a reasonable amount, to allow running the software on PC, laptop and tablet.

Supported SMA devices:

  • 138MHz-4.4GHz USB SMA Signal Source Signal Generator Simple Spectrum Analyzer
  • 35MHz-4.4GHz USB SMA Signal Source Signal Generator Simple Spectrum Analyzer
  • 23.5MHz-6GHz USB SMA Signal Source Signal Generator Simple Spectrum Analyzer
  • NWT4000-1 138MHz-4.4GHz Sweep Simple Spectrum Analyzer Signal Generator
  • NWT4000-2 35MHz-4.4GHz Sweep Simple Spectrum Analyzer Signal Generator
  • NWT4000-3 50KHz-4.4GHz Sweep Simple Spectrum Analyzer Signal Generator
  • NWT6000 25MHz-6GHz Sweep Simple Spectrum Analyzer Signal Generator
The first two are low-cost models (60-70 Euro) featuring only one ADF4350 or ADF4351 synthesizer chip.
The third one is a low-cost model (110-130 Euro) featuring only one MAX2870 synthesizer chip.
The NWT4000 models (160-350 Euro) have two  ADF4350 or ADF4351 synthesizer chips.
The NWT6000 model (300-350 Euro) has two MAX2870 sythesizer chips

These devices can be purchased on eBay - search for "SMA Source/Signal Generator/Simple Spectrum Analyzer", "NWT4000" or "NWT6000".

Note: Currently the software only supports a maximum frequency range of 23.5MHz to 6GHz.

Archived versions download link:

Updated 2016-12-29


Link does not work? Please write a comment!

Thursday, 15 December 2016

VMA Simple Spectrum Analyser - Frequency input changed and support for frequencies in MHz with 3 decimal places (= KHz resolution)


Again a new update! This time I finally changed the way frequencies are input. Instead of allowing the user to virtually type anything in the frequency text boxes and often crashing the software in doing so, the software now opens a new frequency input form, when you click on a relevant frequency box.

Frequencies can be entered as MHz or KHz and the frequency value is accepted when you click either of these two buttons. It is really straight forward, I think.

With this new feature, it became obvious that I had to change the way frequencies are handled internally. Instead of using only a MHz scale with the smallest frequency resolution being 1 MHz, I changed the software to having 1 KHz as the smallest resolution. This should make those people happy, who use the software for non TV/SAT related applications.

Frequencies are displayed in MHz with three decimal places. Implementation is not totally finished, so expect a few oddities here and there (mainly in the frequency boxes for the marker 1 and 2).

IMPORTANT: For the software to work properly, Windows has to be setup to use the point (".") as the decimal symbol! If you use any other character, the software will not work correctly and in best case all frequency values will be handled as integer values (= 1 MHz being the resolution). In worst case, the computer might start to smoke...

Please go to "Control Panel", "Region", "Additional Settings..." and change the "Decimal symbol:" to ".":

The lates software version can be downloaded here:


Tuesday, 13 December 2016

VMA Simple Spectrum Analyser - Update: transponder match visualization through colour and improved GPS Log on maps rendering


Here is an updated version with two changes:

1) The satellite identification function shows matched transponders in orange, while unmatched transponders are shown in red. This allows to better understand which transponders are being missed. The reason is an outdated *.ini transponder list or the discovery of a brand new transponder or feed!

2) When rendering the GPS single frequency log on the embedded Google Maps, the measured signal power is now rendered with 256 different colours. The colour squeme is the same as the one used in the waterfall diagram.

Download the latest version here:


Sunday, 11 December 2016

VMA Simple Spectrum Analyser: Automatic satellite identification - UPDATE!


Here is an updated version of my software. I improved the automatic satellite recognition feature.

After spending literally hours figuring out where I had a bug that caused i.e. some bands of Hispasat not being recognized correctly, I found the mistake...
...the stupid satellite transponder lists I had downloaded were outdated/wrong!

This version uses different lists from:

Further improvements:

  • The satellite name is now shown inside the spectrum graphics area
  • There is a new "Sensitivity" option: this will specify the tolerance around the centre frequency for transponder matching against the transponder list

Download here:


Just found a stupid bug, which caused satellite identification errors. Please use this version instead!


VMA Simple Spectrum Analyser: Automatic satellite identification


A new milestone has been reached! My software is now able to automatically identify the current satellite, even before the signal is good enough for a receiver to lock any transponder.

If you read my previous posts, you will know that I am identifying the satellite through a transponder pattern recognition against known satellite transponder lists, stored in a folder.

This satellite transponder lists can be generated and downloaded from different websites, like and are included in the transponder_lists folder.

The results are impressive and actually better than I expected: the software identified all satellites I tried without any error and without any learning process. All I did was to download the current satellite transponder lists.

How does it work? Without going into deep, the software first determines the frequencies of the transponders in the live spectrum. Then it tries to find the satellite list, which contains the most matches to the identified transponders of the live spectrum. The satellite list with the most matches wins.

The percentage next to the satellite name shows the score: 100% would mean that all transponders in the live spectrum have been found in the winning satellite list. Mind you, a score of 50% is pretty good and will accuratly predict most satellites.

Here a few example pictures:

Picture 1: Astra 1 (19.2E) - Identification score of 93%

Picture 2: Badr 4/5/6/7 (26.0E) - Identification score of 69%

Picture 3: Astra 2 (28.2E) - Identification score of 78%

The identification score can be improved if the treshold is fine tuned: it represents the horizontal line, where transponders are identified. However, 60% is a pretty good default value!

Notice that the satellite identification tells you what band you are tuned to: VL, HL, VH or HH.

The name of the satellite takes about 1-2 seconds to be displayed and it just isn't quicker due to the fact that it takes about 3 seconds to refresh the live spectrum with 500 samples.

Interested in trying it out? What are you waiting for - download the latest release here:


Saturday, 10 December 2016

VMA Simple Spectrum Analyser: Transponder pattern recognition in development


I am in process of implementing a transponder pattern recognition.

It allows to automatically identify the frequencies of transponders. This is the ultimate blind scan, as the signal doesn't even need to be locked and frequencies are determined instantly on the whole frequency range!

The next step is to match the frequency pattern against a database of known transponders, i.e. satellite transponders. This allows signal (satellite) identification much before the signal can be locked.

Of course, I need to clean up this functionality and include an export function to save the transponder list.

Here are some pictures of the current state:

Picture1: Transponder identification on Astra 28.2E

Picture2: Digital transponder identification on CATV (NOS - TV Cabo)

Picture 3: Digital transponder identification on UHF, showing local DVB-T and two LTE transponder

The treshold value controls the position of the horizontal line, which is calculated as an average dBm value from all samples - thus moves up and down according to reception quality. This has to be set accordingly, for best results, though the default value of 50% works quite well.

The bandwidth field will filter all transponders with less bandwidth than the specified one. This is important, for instance in CATV, where there are a lot analogue channels, which may not be of interest.


Uploaded the first demo video on Youtube:


Monday, 5 December 2016

VMA Simple Spectrum Analyser: New trigger function available!


I finished the implementation of the trigger function. You can now use trigger masks, which can be edited within the software or externally with any bitmap editor.

The trigger will look for events where a given frequency is higher than the MAX treshold or lower than the MIN treshold.

When an alarm occurs, it will be added to the log and optionally an e-mail can be sent!


Picture 1: This is how the spectrum normally looks like. So I set a trigger mask.

Picture2: After a while I receive an alarm e-mail. The transponder at 611MHz triggered the MAX alarm.

I updated the manual, accordingly, and here is a request: please do read the manual. The software has got so many functionality, some not that obvious. Let me know suggestions to improve the manual.

Here is the download link:


Sunday, 4 December 2016

VMA Simple Spectrum Analyser - New name and new trigger function!


I am implementing the next item on my list and it is almost done: the trigger function.

A modern spectrum analyser has to feature a trigger function, which serves the purpose of alerting the operator whenever a given frequency exceeds a pre-defined treshold value.

Newer spectrum analysers, like the Siglent SSA3021X will actually allow the user to draw lines, which act as treshold values across the setup frequency range.

Naturally, I had to do something even better! The problem with defining a set of line segments to draw the power treshold for an alarm is that it takes ages to define a complex treshold mask.

Also, most spectrum analysers will only alarm if the signal power is greater than the defined treshold, not offering any alarm in case the signal power is lower than a second treshold.

I implemented something slightly different:
  1. The user saves a bitmap of the current spectrum (using the "SAVE PICTURE" button).
  2. The user opens said bitmap with Paint (or any other bitmap drawing tool) and draws the upper limit as a blue area and the lower limit as a red area.
  3. This new bitmap acts as a trigger map.
  4. Once loaded, the software will extract the exact upper/lower treshold contour and starts monitoring the live spectrum.
  5. Should any frequency have a higher or lower signal power than specified with the current trigger map, an alarm is issued.
  6. In the present state, the alarm is shown as a red or blue status message and the individual alarm is put with time stamp and description on a list box.
The following pictures show the process:

Picture 1: Just draw blue (MAX) and red (MIN) areas to define the trigger treshold mask. Don't worry about the remaining picture of the original spectrum screen shot, as the software will only extract the blue and red areas!

Picture 2: Once the trigger mask is loaded, it is rendered over the spectrum, so that the user can check the live spectrum agains the trigger mask. Note that the trigger mask is static: changing the spectrum amplitude or frequency range will NOT change the trigger mask!

Picture 3: Any alarm will be shown in the SPECTRUM TAB as a red/blue status alarm and listed in the TRIGGER LOG tab on a list box with further information, including time stamp and frequency value

This version will be made available, soon. I need to finish a few oddities.

Future functionality may include automatic e-mail with spectrum image upon alarm - stay tuned!

Regarding the name change: the software was initially called "SMA Simple Spectrum Analyser", since it was developed for the "138MHz-4.4GHz 35M-4.4G USB SMA Source/Signal Generator/Simple Spectrum Analyzer" device.

However, the software works with the NWT4000-1 and NWT4000-2, too (or at least I think so, but I did not test it, since I don't have such devices).

This made the "SMA" a bit silly, as it refers to the input connector format...

Because I do use my initials often enough, I just changed the name of the software to "VMA Simple Spectrum Analyser"...


Sometimes I excel myself (*cough*) and get actually surprised on what I did (joke):

I just tried out what happens if the trigger mask is drawn with just incomplete blue and red lines...

This picture says it all:

Note: The image in Paint is drawn at 50% scale, so that both screens fit the window.


I ended up implementing a simple "Trigger Mask Editor", but Paint can still be used:


The VMA Simple Spectrum Analyser is now sending TRIGGER ALARM e-mail messages with embedded picture of the offending signal:

Still needs a few polish up until the next release, but it is working!

Now you will never again miss that sporadic feed, the intermittent signal or the annoying random signal loss - even when away from your computer...


Great GPS app for Android - compatible with SMA Simple Spectrum Analyser software!


I finally got time to test the "Bluetooth GPS Output" app for Android phones.

What it does is to transform your smartphone into a Bluetooth GPS receiver, compatible with NMEA standard, which is exactly what you need to operate my SMA Simple Spectrum Analyser software on the road.

Instead of having to purchase a dedicated BT GPS receiver (around 60 Euro from eBay), you can use your existing Android smartphone (provided it has a GPS receiver, of course)!

Head over to:

The app is free, but has a 10 minute time limit. This is enough to test the functionality and even for some single frequency signal power mapping.

The good news is, that the full license costs just 1€!

Here you see the app in action on my Samsung Galaxy Note 3:

My KUBO tablet (running Windows 10) connects without issue to this app, recognizing a regular BT GPS receiver. And my SMA Simple Spectrum Analyser software is happy with the NMEA data:

This solves the problem I was having with the Asus BT-100 GPS receiver: I had to uninstall and reinstall it every time I wanted to use it, because neither tablet nor laptop would manage to reconnect to it.