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Review: TTi PSA2702T handheld spectrum analyzer

-February 24, 2014

One thing that I find handy is a small hand held spectrum analyzer for use in troubleshooting EMI issues. As I travel a lot in my job, I like to take the minimum amount of test equipment possible. Unfortunately, most good quality analyzers are large, heavy and expensive. About ten years ago, I ran into the Thurlby Thandar Instruments (TTi) PSA2701T and have used it extensively since then. During that time, I reviewed it several times (see References below). In May 2013, TTi completely redesigned and repackaged this analyzer and released it as the PSA2702T. This is a review of the new PSA2702T, which I have used for several months now.


Figure 1 - The Thurlby Thandar Instruments, model PSA2702T. Photo courtesy TTi.

Overview
Much if the functionality and specifications remain the same as the older model. The PSA2702T covers 1 MHz through 2.7 GHz and includes three resolution bandwidths: 15 kHz, 280 kHz and 1 MHz. They sell a lower-cost unit, the PSA1302T, which is similar in specs, but has an upper frequency limit of 1 GHz. There are two markers that can read out amplitude and frequency, as well as delta. Limit lines may be defined and the unit may be programmed to beep, stop the sweep, log the sweep, or provide an output pulse if the limit is exceeded.

The unit can display amplitudes in dBm, dBuV, mV or uW and there are two reference levels: 0 and -20 dBm. There is a simple video filter (on/off), but it also includes averaging and “peak hold”. Amplitude and frequency accuracy is reasonable for a unit this size and are fine for general troubleshooting purposes. However, you'd want to move to a lab-grade analyzer for the most accurate measurements or compliance testing. Setup configurations may be saved and recalled and the screen may be captured and stored in internal memory or USB thumb drives. At this point, not all thumb drives are supported, however. Only ones that conform to the USB Mass Storage Class (MSC) and have capacities from 32 MB to 32 GB will work. I had to try a handful before I found one that would work for me. Further details on this are included in the manual.

I love the clean design of the newer model. The previous model (PSA2701T) was based on a Palm TX PDA and while completely useful and actually rather clever, obviously had a limited lifetime due to a lack of supply of the PDAs. The new model has a large 5.5 by 9.5 cm (4.3-inch) backlit TFT LCD display with a useable waveform display area of 5.5 by 5.5 cm (2.25-inch square). The remaining portion of the display is devoted to status indicators and a three-tiered menuing arrangement. I like the fact the nested menus are always visible and I rarely have to guess where to find a function. The display is clear and easily readable. The new model also comes with a hinged protective cover that can snap off and remount to the rear to prop up the unit. The Li-Ion battery seems to last for weeks. I’ve only had to charge mine about once a month to top it off.

The unit even includes AM/FM demodulator circuitry and an earphone jack at the top for evaluating potential commercial ambient signals.There are a few key hardware controls for markers, presets and run/stop, but most are touch-sensitive soft-keys. There are two USB connections - A host controller (type A) port that will accept flash drives and a mini USB (Type B) that will allow a connection to a PC for running the PSA-Manager software (requires option U01). This software allows the PSA2702T to be operated remotely by the PC and to display and capture the screen waveforms. A very nice feature is that the unit may be user-upgraded as new firmware is released. Be sure to register your unit, so you’ll be notified of upgrades.

PSA Series II RF Spectrum Analyzers key specifications:
  • 1MHz to 1300MHz (PSA1302T) or 2700MHz (PSA2702T) frequency range
 
  • Resolution bandwidths of 1MHz, 280kHz or 15kHz
 
  • -96dBm typical noise floor at -20dBm reference level
 
  • Trace modes of normal, single, peak hold and average
 
  • Zero span mode with AM and FM audio demodulation
 
  • Live, View and Reference traces in contrasting colors
 
  • Twin markers with readout of absolute & difference values
 
  • Measurement in dBm or dBuV, mV or uW
 
  • Smart marker movement with selectable peak tracking
 
  • Auto-find automatically sets sweep parameters for the
 highest signal found
 
  • Unlimited storage for waveforms, set-ups and screens
 
  • User assignable file names, file stamping from real-time clock
 
  • USB interfaces for flash drives and PC connection
 
  • Comprehensive status and context sensitive help screens
 
  • 4.3" color backlit TFT display with touchscreen
 
  • More than 8 hours continuous operation from a charge (international charger included)
 
  • Smaller and lighter than other spectrum analyzers
 (weight only 0.56 kg)
Additional features with option U01
 
  • Limit lines and limit patterns with limits comparator
  
  • Data logging of peak values, complete traces or screen
 images from timer, external trigger or limits comparator
 
  • Sweep triggering from external trigger or limits comparator
 
  • Compensation tables, fixed offsets and 75R compensation
 
  • Capability to show screen contents on a PC


Figure 2 - The PSA2702T with screen protector flipped up. The protector may be removed and added to the back to prop up the unit.

Troubleshooting
Troubleshooting with the PSA2702T and attached probe is fast and easy. No heavy instruments to lug out to the measurement chamber or open site and no line cords to plug in. Just turn it on and go! I found I can quickly zero in on an emissions issue, even during characterization or pre-qualification testing. Oftentimes, a wide-band preamp is unnecessary, especially when using the 2-turn Beehive probes, however, for some signals, such as a current probe, additional amplification may be required. I use the low-noise Mini-Circuits ZX60-3018G-S+ amplifier module. This module covers 20 to 3000 MHz with a gain of 18 to 23 dB and noise figure of 2.7 dB.

By attaching a near field probe directly to the analyzer, you have the perfect hand held emissions detector. While the unit lacks the standard EMI bandwidths (for example, 120 kHz), I don’t find this to be a limitation during the troubleshooting process. What you’re typically looking for is “how much leakage is there now, and how much is there once I apply this fix?” Once the fixes are implemented, that’s when it’s time to measure your product in a chamber or OATS with the proper measurement equipment as specified in the appropriate standards.

Emissions can be recorded via screen shots (bmp format) or tables of comma-delimited (or separated) variables (csv), which may be saved and imported into your favorite spreadsheet. What I especially like is the unlimited number of instrument setups I can save. Favorites of include 1 to 30 MHz for conducted emissions, 30 to 200 for low-frequency emissions, 100 to 500 MHz for a lot of my typical troubleshooting and 2.4 to 2.7 GHz for Wi-Fi and Bluetooth sniffing.


Figure 3 - Screen capture showing a Wi-Fi signal on channel 6 with interfering a wireless telephone FHSS signal.

Issues and Anomalies
During the time I’ve had to use the analyzer, I’ve noticed some operational issues and firmware bugs. None of this should prevent you from purchasing the unit, however, my hope is that TTi will release updated firmware to incorporate improvements.

The most blatant bug is that during File Operations, the “PageDown” button is really a “PageUp” function. All other file commands operate as designed. Because there are Up and Down keys, this is not critical.

Once a screen capture is saved to the thumb drive under a particular name, you cannot re-save the file under the same name and you will get an error popup. There ought to be an “Are you sure you want to over-write?” option. In addition, the “Save All” command will fail with duplicate file names.

Some unsupported flash drives will “Verify” forever. The only way to stop it is to pull out the drive. My wish is that a future firmware upgrade will allow all common USB flash drives to work.

Summary
While the PSA2701T does not offer the typical EMI bandwidths or quasi-peak detection, it does include a number of very handy features for general EMC troubleshooting. Things like markers, peak search, averaging, peak hold, waveform memory, amplitude scale in dBm or dBuV, screen capture and instrument setup memory - not to mention the portability - are very powerful tools for the EMC engineer. Using this low-cost instrument to perform the initial troubleshooting prior to moving the product out to a compliance test facility will save both money and time. This truly handheld spectrum analyzer may be purchased for about the monthly cost of renting a bench-top analyzer. I would recommend purchasing the PSA2702T-USC, which includes a protective carry case, option U01 and a 12V DC power cable. The U.S. distributor is Newark Electronics and it sells the above package for under $1,800. Highly recommended.

References:

TTi PSA2702T spec sheet

Review of the TTi PSA2701T analyzer

Troubleshooting Roundup: Low-cost spectrum analyzers

U.S. distributor (Newark Electronics)

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