1001 uses for a NanoVNA

Recently, I pried open my wallet and plunked down the sum of $150.00 for one of these little devices. Now, to be certain, this is not a replacement for a real VNA, especially at a high power broadcast site. However, it can be used for basic trouble shooting and I have had a good deal of fun fooling around with it.

First, a few quick specifications:

  • Type: SSA-2N NanoVNA V2.2
  • Frequency range: 50 KHz to 3 GHz
  • Power output: -50 to +10 dB
  • Measurement points: 201 (or 1024 with software and computer)
  • Measurement types: S11, S12 and S21
  • Screen Size: 4 inch touch screen
  • Traces: up to 4
  • Battery: 3000mAh Lithium Ion
  • Software OS (VNA-QT): Win 7, Win 10, Linux, MacOS

The unit I purchased came with a small carrying case, calibration loads and test jumpers. The software is downloadable and is easily configured.

What I really like about it is the internal battery and the touch screen.

So what can it be used for?

  • Test a coaxial cable
  • Measure the length of a coaxial cable
  • Figure out what frequency an antenna is designed for
  • Tune a 1/4 wave stub to make a notch filter
  • Measure the characteristics of a crystal/holder
  • Measure a capacitor
  • Measure an inductor
  • Tune a parallel resonant LC circuit to make a notch filter
  • Tune a filter can
  • Test a high pass, low pass or band pass filter
  • Sweep an antenna (Simple AM, FM, RPU, STL, WiFi)
  • Check isocouplers for proper circuit functioning
  • Etc

Pretty much anything you need to know about RF antennas, filters and transmission lines can be learned with a VNA. One thing to keep in mind; the measurement points are limited, especially in the stand alone mode. Thus, the smaller the frequency span, the better the measurement resolution will be.

What is this antenna for?
Antenna under test, 659 MHz center frequency

While this is a very inexpensive device designed mainly for Amateur Radio, it can be useful to diagnose antenna and transmission line problems. Would I depend on it to make precise measurements? No. Especially things required by the FCC like base impedance measurements on an AM tower or channel filter measurements for a TV station. Would it work at a high RF transmitter site with multiple AM/FM/TV transmitters? No and chances are you might burn out the front end. Those types of things are best done with professional equipment that has much better accuracy and resolution.

It is a pretty good little tool for basic troubleshooting. One can look at the individual components of an AM ATU for example, or measure the input impedance to see if there has been a shift (should normally be 50 ohms). It is small enough that it can be included in a basic tool kit. It is self powered. Not bad at all for the price.

Resurrection of a different sort

I just finished a full alignment of my Kenwood R-2000 receiver and tonight I am treated with the pleasing tones of “Jazz from the Left,” on WRMI. Jazz from the left means the west coast sound, aka Smooth Jazz as I am given to understand. I spent some time on the west coast and beyond. I have fond memories of those years.

It is amazing to me still, that a simple AM receiver demodulating +/- 4.5 Khz audio bandwidth from 1,057 miles (1701 km) away can sound that good. That is being received directly; no Internet Service Provider, no satellite service, just a transmitter and a receiver.

There is an art to all this, which is being forgotten. A few minutes with a manual, a volt meter, a tone generator and a non-conductive screw driver can bring something that was neglected back to life sounding as good as the day it left the factory 35 years ago. Try that with with your very expensive iPhone 10,000,000x! Of course, you will need those tiny pentalobe tools to get the screws out. Apple would rather you return your expensive i device to their expensive i store so that their i geniuses can fix it for you.

I don’t know, maybe I am an old fart. Perhaps the right to repair the appliances that I purchased and therefore should own is an old fashioned point of view. After all, all of these corporations have my best interests at heart, right?

I recommend you support your not so local shortwave stations by listening and supporting their programmers. Even in 2021, there are still many shortwave broadcasts that are worth listening to!

Attention K-mart shoppers…

During the impending doom that is/was Hurricane/tropical storm Henri, I decided to bust out the old Kenwood R-2000. This venerable radio has been in my collection since 1989, when first purchased at the AFEES on Andersen AFB, Guam. Over many a year, it has given me lots of great service. However, last time I tried it a few years ago, the frequency tuning was all haywire and it seemed to be inoperative. I set it aside, as I always seem to have something important to work on. Not so much today.

As I discovered, there were two problems; first being a dead lithium battery and the second being the dirty pots on the VCO stepper, which are common failure modes for these units. I unsoldered the lithium battery and ordered a new one (CR 2032 with leads). The VCO stepper issue was corrected with a few slight turns of a small screw driver. There are a couple of Youtube videos on this procedure. Truth be told, the entire unit needs an alignment, which I will do once the replacement battery arrives. The service manual is available from several sources on line and it gives very good directions on how to perform an alignment.

Tuning around the Shortwave bands, I heard the normal things; some hams sending CW, some good some bad. A few messages from the Air Force Global HF network. On the broadcast side of things, Brother Stair seems to have multiplied… Then I came across an interesting signal on 9395 KHz. KMRT was broadcasting the K-Mart shopping sound track from the 70’s – 90’s, interspersed with spoof adds for “Plummet Mall.” As the story goes, these cassette tapes were saved from the rubbish bin by a store manager in 1992. Now, they are being broadcast for everyone’s enjoyment on the short waves. I can say, I felt like I was pushing that shopping cart down the very narrow isles looking for a pair of Adidas.

This is via WRMI, Okeechobee, Florida.

This was a lot of fun.

I will finish the alignment/repairs of the Kenwood R-2000 and put it back in service in the upstairs equipment rack. Enough of these software driven dongles, it is nice to just listen to the radio without having to boot up a computer.

The future of Broadcast Engineering

Nature abhors a vacuum.

There has been a lot of hand wringing and ink spilled recently on the titled subject. The problem seems to be particularly acute when it comes to RF knowledge. I agree with those concerned that there are very few new (read also as young) people entering the field. There are a number of reasons for this; competing technical fields that pay more and are generally easier to work in, the very broad knowledge base required for Broadcast Engineering, and the lack of awareness by major stake holders.

It seems obvious that for as long at there are radio and television stations, there will need to be those people who install and maintain the transmission systems. The question is, how to attract new people into that field. In order to answer that question, a follow on question would be, what exactly does a Broadcast Engineer do?

This can be broken down into three very broad areas:

  1. Conversion of the art into electronic form. In other words, capturing sound and video with cameras and microphones. What are the various analog and digital formats, how are those signals routed, edited, stored, retrieved and transmitted. What are the various bit reduction (e.g. compression) formats. How these live streams and stored files are mixed to generate the final program material.
  2. Transmission of the program material. Meaning moving the program to the transmitter site and broadcasting it for public reception. This would involve knowledge of Studio To Transmitter (STL) systems which can vary greatly but often include satellite distribution, public internet, fiber, RF wireless microwave systems, etc. Next step is the actual transmitter, filters, combiners, transmission line and antenna. Knowledge of all regulatory (in the US, FCC) obligations including EAS, Tower lighting and marking, transmitter operations; power level, interference, etc.
  3. Physical plant systems. Broadly speaking; HVAC, electrical power, emergency generators, towers, fire suppression, etc.

These work categories can be further broken down into three functions; installation, maintenance and replacement.

Since I have been more involved in the management side of things lately, I find that most of my problems are people problems. What may be a surprise to some, Broadcast Engineers are people. What may be even more shocking; people have interests. Those interests are the reason why they chose to work in a technical field. Forcing the IT guy to go to the transmitter site to see why the generator won’t start is not a good use of resources.

Looking at the very large skill set that a competent Broadcast Engineer needs to function in a modern broadcast facility, the first part of the answer becomes obvious; more specialization. Break down these broad categories into separate skill sets. Since it seems that many things are headed toward the IP domain, Broadcast IT should become a thing separate from office IT. While the two are similar, Broadcast IT requires more knowledge of physical wiring, switch architecture, VLANs, subnets, IP streaming protocols, audio formats, video formats, transport streams, etc.

RF infrastructure has its own set of rules, including personal safety requirements. A solid electronics/engineering background is required to understand how transmitters work, what various failure modes are and what can cause them.

Physical plant work, most often can be contracted out to various vendors. However, that work needs to be supervised by a competent station representative.

The next item is the thing that nobody wants to talk about; the all importance of work/life balance. This means not utilizing a broadcast engineer as a piece of equipment to be worn out and discarded when the performance level drops below expectations. I have know several broadcast engineers who have left the industry because of this. Worse still, there are those who have died of heart attacks or committed suicide. Work/life balance also includes proper compensation, so those people can afford to pay for essentials, have a reliable vehicle, healthcare, etc.

Of course, many smaller operators cannot afford to hire a RF specialist and a Broadcast IT specialist plus pay contractors to do physical plant maintenance. This is where contracting can fill in the vacuum. If contracting becomes the new normal, then how does the next generation of Broadcast Engineers get trained? Broadcast transmitter manufacturers have some training courses available as does the SBE. However, there is no substitute for hands on experience. While many Broadcast Engineering evolutions are similar, no two situations are the same and thinking on your feet is a job requirement. How are new people coming into the field get the necessary experience? The situation is not untenable, however it will require some creative thought.