Tiny SA Ultra Spectrum Analyzer And Calibrated Signal Generator
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. I did try a set of earphones that were the three ring type, officially known as a TRS, but only a four ring TRRS (NOTE THE EXTRA "R") would work. 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!).
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.
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 is a crude one using the sniffer antenna on the SA. A 144MHZ quarter wave is used, that will also match on 70cm with about 1db of directivity. Freespace coupling loss needs to be taken into account when viewing the harmonics from the 144Mhz TX at 433Mhz. That equates to about 10db. So the 3rd harmonic of the 144Mhz TX is actually about 10db worse. You could be radiating 5mw on your 3rd harmonic. But it's in our own ham band anyway, and in a portion that no one really uses in the UK.
These Baofengs just about scrape about 31db harmonic suppression at the worst,. Not the best but it's good to be aware of them. The 70cm band is excellent, barely anything at all. Technically the UK ham licence is rules are not broken if you read the UK licence.. If no QRM is reported to other users then no enforcement. Other countries are far more restrictive. Hint - a 5w HT on 144Mhz (assuming a quarter wave whip, that is 1 metre away from a Tiny SA sniffer antenna, will give a field strength of +21dbm, and the SA has a max input level of +6dbm. So use the internal input attenuator at 30db, or add an inline attenuator.
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 198hz 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. 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. So I doubt we can save the 198Khz service. Sad but true. But there's still an element of doubt about it's closure. It's not over until it's over. Personally I tend to prefer using the 198Khz service, easy to use on a basic RX and no long floppy telescopic antennas to get broken on an FM receiver. But even I know that I'm in the minority here. The 198Khz TX was also financed by the power industry who used it for controlling energy controllers called Economy 7. They no longer require the service with GPS now, and the UK Maritime Service no longer supports the need for meteo broadcasts that were sent as Shipping Forecasts. That only leaves us old guys using it as a frequency standard, or us listeners that have decent AM receivers. So we're doomed and need to accept it, sigh. [Update Feb 2024, personal view only, I'm not convinced yet that the 198Khz TX will go QRT for various reasons, but we'll see.]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.
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, often totalling 70-80db. You CANNOT simply connect your HF rig for example directly to the input. DESTRUCTION IS ASSURED. An RF sampler is also another way to do it, such as described here - https://sites.google.com/view/andy-g0ftd/rf-tap-experiments
PLEASE ENSURE THAT YOU CALCULATE THE CORRECT ATTENUATION REQUIRED.
The example in my above website shows a basic 40db attenuator, suitable for driving a frequency counter with a 5w dummy load included for direct power measurements, but this will be insufficient for a 5w handheld rig or a 100w HF rig. You could either using the table provided work out a suitable value resistor for a tap off point, or add an inline SMA attenuator to boost the attenuation suitable for your application. This also ensures a constant impedance system too.
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 which has the latest 10 Jan 2024 FW.
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.
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 - Re-enable Ultra Mode in the menu using 4321 as a password.
12 - 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.
In general the Tiny SA Ultra is a great way for testing receivers, especially home made QRSS receivers and transmitters, and. The most recent firmware update as of Dec 2023 adds the ability to transmit CTCSS tones on the signal generator function. The 10th Jan 2024 update fixes a few user interface bugs, including the signal generator function at lower signal levels.
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.
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.
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.
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.
SMA ATTENUATORS AND DC BLOCKS.
I hope to add more to this webpage during 2024, please check for updates.
Last update = 17th Feb 2024.