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The Tiny SA Ultra is a 0-6GHz (18GHz with reduced accuracy) RF spectrum analyzer as well as a calibrated level signal generator. The latter is most useful, since you can check receivers by setting the mode, AM/FM and then entering the output level in -dbm values. There's a simple demodulator mode *slope detection" that can be used as a basic monitor for AM/FM signals. Just plug in a set of STEREO headphones to the 3.5mm jack socket. It's good enough for basic use. I've used it to listen to BBC Radio 4 on 93.5MHZ or as an AM RX on the 7Mhz band. Traces can be saved to an SD CARD that is provided. The performance of the device is superb. I have used plenty of HP / Agilent / Anritzu / Marconi stuff in the past that used to cost £10000 etc, and this little £150 device really is as good. Don't be fooled. Resolution bandwidth is a 200Hz minimum. A USB charging / data transfer cable is supplied so that you can charge or update firmware, as well as SMA patch cords for using the self calibration features. If at any time you use a 3rd party USB cable then ensure it is a proper 4 wire version to allow data transfer. 2 wire cables only allow charging. Maximum input level to the analyzer is +6dbm (under 4mw!). The Tiny SA Ultra also has a 20db LNA usable to 4GHz.
Users have reported excellent accuracy beyond the accepted calibration specifications, such as being able to view and measure signals signals at 10GHz to within a few db of accuracy. The signal generator appears to be fully functional up to the 5Ghz range. A review of the user forum does however reveal that some users can misunderstand some basics though. For a start, an SA is NOT a frequency measurement device like a frequency counter. Setting a marker for example, depending upon resolution bandwidths etc will sometimes appear a few Khz different to the actual transmission frequency, all perfectly normal on any spectrum analyzer. Spectrum analyzers are spectrum analyzers, and frequency measurement devices are frequency measurement devices !
To use the basic inbuilt demodulator you need to have a sensible resolution bandwidth (RBW). For narrow band AM/FM use that might be 10Khz, for broadcast FM 88-108Mhz that would be 100Khz. FM demodulation is by what is known as slope detection. You tune slightly off the carrier frequency to achieve demodulation, a technique use on many basic consumer receivers found in boom boxes, regenerative receivers etc.
This article refers to the model now known as the ZS-405. As of Jan 2025 there also exists official variants as the ZS-406 and ZS-407.
Specifications are here -
The ZS405 as reviewed here - TinySA4.Specification
Comparison chart between models - TinySA4 Model Comparisons.
The device comes with a simple telescopic sniffer antenna (for basic monitoring and sniffing out signals). For proper measurements you should be using proper input attenuators or RF samplers. My photo shows that I've added a 30db SMA attenuator and a screen stylus, since the screen is touch sensitive. It is a resistive screen, and not capacitive. Use the correct stylus.
I thought it would be interesting to show some screenshots of my local RF environment to show what the spectrum anaylzer can show from my location in Whitstable, Kent,UK.
Below - an old Baofeng UV5R from about 2012 showing the harmonic output at 145MHz and 435Mhz bands (5w level). It's the original version, basic LCD display, and not one of the many variants sold as higher power etc. The test setup was the Baofeng UV5R followed by the 10w 40db attenuator followed by a 2w 30db attenuator and then connected to the spectrum analyzer. Remember that the 10w attenuator should be at the TX end ! Harmonics on 2m are typically 50db down and on 70cms appear to be better than 60db down. (I made no tweaks to the spectrum analyzer to see if I could see below that level).
Next is the UK PMR446 band and 8 hours of band occupancy. The spectrum analyzer was left on the top floor bedroom window with a small vertical antenna in order to replicate a typical handheld, and left during the day for 8 hours on max hold settings. Note in the UK/ EU the PM4 446 band is a general public use walky talky band, 500mw ERP. NOTE, 70cms UK ham and is 430-440Mhz unlike other parts of the world. There are 16 channels or use, analogue or digital, licence free, anyone can use it.
Have you ever tried transmitting via the wrong LPF ? Here's an example of what harmonics are present on a U3S TX if you try transmitting the 7MHz band via the 28Mhz LPF. Note that this a basic off air measurement. The TX on 7Mhz fed a quarterwave wire via a T Match ATU (CLC high pass type), with me in the garden and the sniffer antenna just to get an show that high level harmonics were present. Inserting the correct 7Mhz LPF solves the harmonics.
And here's a view of the local FM broadcast band.. The spectrum analyzer is simply using the 50cm or so telescopic whip to simulate a typical consumer FM broadcast receiver. 89.1Mhz is BBC Radio 2 from Wrotham, 96.7Mhz is Radio Kent, Wrotham TX. 102.8Mhz is Boughton, about 5 miles away called Heart FM, 106Mhz is KMFM from Canterbury, about 6 miles away. Freq list here.
Here is the 40m band in the UK. The analyzer shows the difference is ham band signals versus broadcast signals in the evening time, December 2023 via a tuned quarter wave wire. Note the appalling high noise floor -70dbm caused by local broadband internet fed down local telephone lines (copper landline]. Noise floor is just over S9 = bad! Normal atmospheric noise should be about -106dbm on this band. You can use my spreadsheet to calculate natural noise floor levels by frequency here. Save the file and open it in your favourite spreadsheet software. Don't use the Google online system, it's not friendly. The trace (50Khz per division) clear shows that once you hit 7.200Mhz where the broadcast band starts that the signal levels are much different.
Here's a recent view of the 28Mhz band during a CW contest. Almost the bottom 150Khz is full of signals and the SSB / phone portion has few signals. Noise floor about -100dbm. Antenna is a tuned full wavelength horizontal wire.
And now a crude look at the HF spectrum during the day. The analyzer is fed with a 33 foot wire direct to the input with no matching. in the winter of 2023. The maximum signal levels equate to about S9+20db.
Here's a quick test looking at the signal strength of BBC Radio 4 on the long wave band 198Khz. You can also see a second peak below in frequency that is the French TDF transmitter. The antenna is an unmatched 10m wire. You could gain up to 20db more signal with a matching circuit. BBC Radio 4 on 198Khz AM is due to close in 2024. Power is listed as 500Kw and is several hundred miles away from my location in Whitstable,Kent. TDF used to transmit AM programmes but now only radiates a time signal. Side note - my Tecsun PL880 signal meter shows a max field strength of 32db/uv using it's internal ferrite rod. That's about -75dbm into 50R, or -86dbm into a 600R load.
I seem to recall, but I cannot find the source that closing down the 198Khz would save half a billion pounds in energy. In the last week or so, Dec 2023 I did a bit of research as to what energy production costs in the UK, I considered a 50% efficiency for the TX and came up with a figure that matched half a billion pounds to run that transmitter. So I'm satisfied that the claims are true for savings, That's a lot of money compared to the BBC income. As of Feb 2025 the service is still running. I listen to it most days for the news when I wake up. Latest news as of August 2025. The BBC have set a date of 26th September 2026 for the 198Khz service to close down. Apparently employees of Arqiva who maintain the transmission facilities have been informed.
Here is the AM Medium Wave broadcast band with a basic untuned 10m wire fed against earth. Remember that markers are approximate. 648Khz is Radio Caroline in Orfordness. 693/909Khz is BBC Radio 5, 1053/1089Khz is Talk Sport, 1242Khz a commercial station in Kent The unmarked peak on the left hand side is 603Khz based in Kent. Freq list here. Radio Caroline reads on my Tecsun PL880 as 38db/uv on it's internal ferrite rod. That equates to -69dbm into 50R or -80dbm into a 600R load. If I remember correctly, I thought the input impedance of the PL880 and others in the series were 600R but I cannot confirm this. Apart from the UK and Spain, Europe abandoned all AM broadcasting stations some time ago. In the UK, it's pretty much just UK / Spanish stations at night and the odd Dutch station, since Holland allows a few private AM licences. Otherwise the AM band is dead. The last few years have seen mass abandonment of AM in the UK too. How much longer will the old AM band survive ? AM can actually be quite good. The problems is the very crappy receivers on the market. But a decent quality AM receiver is actually very good if you get one, batteries last forever, no telescopic aerials to get bent and broken, long distance coverage,simple receiver design circuitry etc.
You MUST be very careful not to break your analyzer, it can easily be destroyed ! If you wish to take high quality measurements of your transmitter harmonics you MUST use suitable attenuators. You CANNOT simply connect your HF rig for example directly to the input. DESTRUCTION IS ASSURED.
PLEASE ENSURE THAT YOU CALCULATE THE CORRECT ATTENUATION REQUIRED.
Switch off the LNA. Here's an example, you wish to look at a 5w rig, maybe an FT817, an HT or a homebrew rig. Now firstly you need to consider what level you can send into the Tiny SA input, AND be at a level that doesn't cause internal intermod products in the Tiny SA itself, oterwise you get false results. It's recommended that the fundamental needs to be no more than -25dbm, that 3.162 microwatts. So now we calculate the difference between 5w and 3.162 microwatts. And that equals 62db. So for a 5w rig use say 70db of external attenuation to be safe. Also note that some transmitters can overshoot upon initial keydown, and produce slightly hower power, so having a little more attenuation than required is good practice. Typically the attenuators used would be a 10w rated 40db attenuator folllowed by suitable 2w rated ones. You can buy these cheaply enough online. Caution - don't exceed the wattage ratings. If you use a 10w rated attenuator then treat it a a 5w rating and never ever go above the 10w. These style DC-3Ghz etc items usually use ceramic chip resistors that can fry easily with a small amount of over wattage. For transmitter measurements DO NOT use the internal attenuator it's an active device, and could introduce it's own problems, and do not use the internal LNA.
FIRMWARE UPDATES.
The Tiny SA Ultra does occasionally receive firmware updates that enhance some capabilities. Remember that the product was launched in early 2023, so enhancements are coming fast and are worthwhile. It's easy to to. Go here and download the .bin file and use DFU command line updater if you use Linux. Or if you purchase from the UK from Mirfield Electronics then they supply their units with any new firmware as standard within a few days of the firmware being available. I don't know if other outlets do the same. Do not buy clones, use approved dealers only. Cloners often use substandard RF parts, no good at all for our sensitive work.
I use DFU Util either on my Linux or Raspberry Pi. (Your Linux repo will have it).
1 - Download latest .bin firmware from the official source or my own backup .
2 - Rename the file to tinySA.bin
3 - Navigate in the Linux terminal to where you have saved the .bin file.
4 - Connect your Tiny SA Ultra to your PC with the USB cable.
5 - Hold the jog button down and switch on the Tiny SA (screen is blank, looks dead),
6 - Use the command dfu-util -a 0 -s 0x08000000:leave -D tinySA.bin (the latter depends upon the filename you saved the file as).
7 - You can see it updating etc on the terminal screen.
8 - Unit will reboot. Now re-enable Ultra Mode in the menu using 4321 as a password.
9 - Connect an SMA to SMA cable to the ports on the Tiny SA Ultra.
10 - Use the menu system and run the SELF TEST and CALIBRATION options (for below 6Ghz)
11 - Finished!
Please read the official website and the groups.io user group for info.
I also include a simple update script in my Raspberry Pi image, suitable for Pi Zero's to Pi400's, (tested and compiled a a Pi3B+), updated occasionally when I feel that there's enough new functionality to warrant an update, but it's dead easy to see how things work if you REALLY want any up to the minute firmware updates. You can't "brick" a Tiny SA Ultra with firmware updates, it either accepts it or it doesn't. Pi image is meant to include useful ham radio software mostly for QRSS users, WSPR, and general data modes etc. Includes a working Nano VNA Saver app and stuff for other VNA's etc.
THE SIGNAL GENERATOR FUNCTION.
And now a few words about the signal generator function that is built in. The signal generator is a calibrated level output AM/FM type. You can set the output level, for example -80dbm or whatever and test your receiver sensitivity. You can choose an AM modulation depth in percent or an FM deviation and a modulation tone like 1000Hz etc. It works well. It's been interesting to check out out rigs like the Baofeng UV5R down to -130dbm, or consumer grade FM broadcast receivers down to about -90dbm. (The latter can be quite deaf). The UV5R FM broadcast receiver achieves -110dbm, the best I've seen for a broadcast FM receiver.
The Tiny SA Ultra's signal generator's minimum power level with calibrated accuracy is -115dbm. For measuring lower levels you need to insert an external attenuator. Prior to Jan 2024, the firmware allowed a setting down to -121db, but it could be a few db in error. To prevent potential confusion, firmware from 10th Jan 2024 onwards now only allows a setting down to -115dbm. Frequency resolution is 44Hz, so although the signal output level is calibrated,the actual output frequency is not. It runs in 44Hz steps. Not of any consequence for normal daily usage. If you need a calibrated frequency reference then you should go out and get one instead. Jan 2025 - I did a quick test on the signal generator. I calibrated my favourite frequency counter using a GPS disciplined QRP LABS U3S source as well as a 198KHZ BBC Radio 4 locked generator, the 198KHz TX being Rubidum locked. I then chose three frequencies to observe.
50.000003 (dialled frequency was 50.000MHz - an apparent 3Hz error)
28.000011 (dialled frequency was 28.000MHz - an apparent 11Hz error)
10.000018 dialled frequency was 10.000MHz - an apparent 18Hz error)
All within the 44Hz specification.
Please learn how to use your spectrum analyzers and your VNA's properly. It's too easy to destroy them, even a professional $/£100,000 is not immune to untrained users.
USEFUL TIPS.
Never remove the SD CARD in the Ultra when the power is on. Make sure it is OFF. The SD CARD will probably become corrupted. Many software utils for repairing SD CARDS are not perfect. But I think I have found the most reliable solution, your cell phone ! The SD CARD formatters in cellphones appear to know a lot more about resettable bits, presumably because there is closer industry collaboration. The SD CARD industry must rely greatly upon this market, and are probably a bit more open to cellphone manufacturers, who both need each others reliability to maintain sales. If the consumers had widespread unreliability issues with cards or cellphones that use them then it would be bad press all around, if that makes sense. Carefully remove your cell phone SD CARD, insert a corrupt card and you should be prompted to format it.
Also take care when removing or inserting an SD CARD with the Tiny SA. Note the physical gap around the SD Card connector, and ensure that the SD Card is inserted only into the connector.
Use a DC block. Some equipment that you may wish to measure, like old boat anchor receivers can have high levels of DC on the antenna socket ! The Tiny SA Ultra can only handle 5v, so beware. A DC block is no more than a high quality capacitor, suitable for the maximum frequency that you intend to measure with almost no loss. It's best to always keep one attached regardless to prevent static discharge from your body, especially if you are touching the telescopic sniffer antenna. At UHF for example, a high quality SMD capacitor with only about 50pf could be used, or for alignment of an old AM broadcast receiver at 1Mhz a simple 1000pf "audio grade" capacitor would do. A bog standard 1000pf or 1NF disk ceramics for a few pennies is all that you need for LF/HF connections.
Also remember that a long length of coaxial cable becomes a capacitor, and it can store electrical energy in it's own right. Ensure that any coax is discharged too.
Want to save a screen capture ? Use STORAGE / SAVE CAPTURE option. Other options can be confusing and may end up with only a .CSV file being saved. Using the SAVE CAPTURE option ensures that you have a .BMP file saved just like the screenshots used on this web page.
Keep the battery charged. The indicator should be green. There are reports that performance such as some odd close by spurs about 28Khz away from the carrier can be exhibited with low battery voltage. Or just make sure that you power the device from an external 5v PSU. Quite natural. Any device that is run outside of it's intended voltage will perform out of specification.
To view GMSK and other signals like WIFI you must select the PEAK HOLD function and turn off the SPUR REDUCTION option. Otherwise you'll see nothing.
Working below about 600Khz ? Use the LNA otherwise you see a high noise floor. Here's a YT video from the designer himself. https://www.youtube.com/watch?v=cSuj8E77lz0
More useful videos from the designer himself are here -
https://www.youtube.com/playlist?list=PL5ZELMM2xseNkwVBtyAG00uZevwWUdVIg
Finally, many users of these devices are often ex professional users who tend to be familiar with test and measurement techniques, and understand how to use Spectrum Analyzers correctly. This webpage is not a complete how to use these devices, and so it is assumed that some test and measurement experience has taken place. I suggest that anyone new to test and measurements read and explore other online material. There are excellent guides for free from major manufacturers of professional (and highly priced) equipment to learn from, or Youtube guides. These are not toys for newbies, but are meant for those who have proper experience in the field of radio frequency measurements.
Electrostatic prevention. Things like Nano VNA's and Spectrum analysers are VERY sensitive to electrostatic discharge. Your antenna could easily be charged with 10,000 volts of static (seriously) and you'd never know. So before connecting it, touch the outer and the inner to a nearby ground to discharge it just in case. Also if you wear what I call "safety boots", you could be charged up too. Discharge yourself in the same manner just in case you end up sending lots of volts up the input. And never operate a spectrum analyzer into a large antenna when there's a nearby thunderstorm. Food for thought here.
SMA ATTENUATORS AND DC BLOCKS.
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