My shop works almost exclusively with VHF and UHF conventional and digital two way radio systems. Digital is of course becoming more and more common with each passing day.
We have a need to analyze digital transmitter performance on a regular basis and I don't see this need getting smaller in the future.
We know that we've encountered several digital transmitters that are not modulating correctly and this is resulting in reduced coverage range and generally unsatisfactory performance.
Some manufacturers are frankly doing a very poor job of documenting service, measurement, and adjustment procedures for their digital radio equipment. It's really very aggravating when you end up asking tech support for help and end up telling THEM how their equipment actually works.
My primary need at the moment is to have an efficient way to visualize the digital modulation parameters of NXDN format digital mobile radios. This is a narrowband QPSK formatted signal with 6.25 KHz channel spacing.
I need to know if the Agilent E4406A VSA can be used for this application. Essentially the only thing I ask of the unit is to visualize the modulated NXDN signal as a constellation diagram. If it'll also handle the P25 digital radio format as well, that is a bonus, but it's not absolutely essential.
The prices of the E4406A are now very reasonable. My shop can easily afford to buy a used one now. But it has to be able to do the job or it's not a bargain at any price.
If you have any information for me that will help me to determine if the E4406A will satisfy my requirements, please let me know.
The E4406A is a Vector Signal Analyzer VSA. In order for a VSA to demodulate digital formats, show constellations, etc - the instrument must "understand" the signal it is looking at.
The E4406A had many options that let it analyze a variety of wireless formats standards. I don't believe any of the common two-way radio formats are among the E4406A's capabilities. You can find may brochures and manuals about the E4406A on the Agilent web site to help you examine its capabilities. You might find that you still want one -even if you can't demod NXDN or P25.
It is a very fast instrument and recently KE5FX has added the E4406A to the list of supported instruments for his spectrum surveillance software.
As far as analyzing NXDN - perhaps someone at Agilent has a suggestion. A search of the Agilent web site for "NXDN" does not return any results.
One possibility is a general purpose application such as the Agilent 89600 VSA software which: "...offers a wide range of demodulators for FSK, BPSK,QPSK, offset QPSK, QAM, APSK, and VSB, all with variable filter type and alpha, symbol clock rate, and bandwidth. ...". This is more of a lab application and would require considerable study and configuration in order to accomplish your goals.
There are two products that will meet your needs in the analysis of two-way radio digital formats NXDN, ETSI-DMR, and P25. Those would be the General Dynamics R8000 and the Aeroflex 3920 which are expensive and REALLY expensive, respectively.
I have evaluated the GD R8000 and don't care for it. If I'm to buy a full featured service monitor, it needs to be a full featured unit. The R8000 does not even have any provisions for reading or generating RAN codes or talkgroup IDs or individual IDs. This is totally unacceptable and will not be buying an R8000 until those deficiencies are corrected.
Same goes for the Aeroflex 3920, which I have also evaluated. For the large cost, it does not deliver what I need.
Anritsu's LMR Master with NXDN options, model S412D (now E model) while also strictly a transmitter test device, at least has the benefit of presenting I and Q data in a superior, more easily readable constellation diagram format.
I believe that a properly configured E4406A with customized software should serve my purposes. It only has to decode QPSK data at the appropriate symbol rate. I am guessing it has the flexibility required to do that but as you said, I need to make a phone call and speak to an applications engineer about it.
“…I believe that a properly configured E4406A with customized software should serve my purposes. It only has to decode QPSK data at the appropriate symbol rate. I am guessing it has the flexibility required to do that…” ------------------------------------------------------------------------------------------------
The E4406A might be technically capable of doing LMR formats but as far as I can tell, none were offered as options. As far as customizing an available wireless format, here’s what the Agilent FAQ’s has to say:
"Can I adjust the measurement parameters for the Wireless measurement personalities in E4406A and PSA Series?
Yes, you can adjust many test parameters. For example, you can adjust channel bandwidths and frequency offsets for ACPR measurements. However, you cannot adjust the modulation parameters such as data rate, demodulation filter, or modulation type.
Can I write my own measurement personalities or downloadable programs (DLPs) for the E4406A, PSA Series, or ESA Series Analyzers?
No. We do, however, offer many tools to facilitate remotely interfacing of our instruments to a PC to write custom applications. We do also offer flexible digital demod through the 89601A software."
What you need is what Agilent calls “Flexible Digital Modulation Analysis”. This capability is offered for the PSA as option 241. See:
It is possible that you could use an E4406A as a digitizer for the 89601 software and configure that software to do the analysis, but I think there is a better solution. Look at Agilent’s new N9000A CXA analyzer. This is a reasonably priced instrument with great flexibility.
They have a portable configuration available which makes the unit field friendly. Consider ordering the preamp option. That will give you a great spectrum analyzer suitable for many tasks in LMR. Also get the tracking generator option. That will equip the machine to do alignments of filters, duplexers, combiners, etc.
For software options, Agilent has the W9063A Analog Demodulation Measurement Application which will give you far more accurate results than a service monitor for traditional FM (and AM) measurements.
Last, the 89601 software can install and run on the CXA instrument rather than on a separate PC. Properly configured, that software should be able to analyze the various LMR digital modulation formats.
A little more information: The NXDN format uses 4FSK modulation. Short of decoding to baseband externally and obtaining an E4406A with the baseband option installed, it appears that I can't use that analyzer for this format as it seems that no FSK modes are supported.
The N9000 does look good but it prices out at about 18K with the appropriate software, which is about 10 times my working budget at this time.
My recurrent need for the equipment will preclude renting it. I'd have to rent it too often.