Measuring Spurious Emissions of Cheap Handheld Transceivers

If you buy an amateur transceiver cheap enough to make a reasonable grab bag gift or stocking stuffer, you get what you pay for. And if this extensive analysis of cheap radios is any indication, you get a little more than you pay for in the spurious emissions department.

Amateur radio in the United States is regulated by the FCC’s Part 97 rules with special attention given to transmitter technical specifications in Subpart D. Spurious emissions need to be well below the mean power of the fundamental frequency of the transmitter, and [Megas3300] suspected that the readily available Baofeng UV-5RA dual-band transceiver was a little off spec. He put the $20 radio through a battery of tests using equipment that easily cost two orders of magnitude more than the test subject. Power output was verified with a wattmeter, proper attenuators were selected, and the output signal scanned with a spectrum analyzer. Careful measurements showed that some or all of the Baofeng’s harmonics were well above the FCC limits. [Megas3300] tested a few other radios that turned out to be mostly compliant, but however it all turned out, the test procedure is well documented and informative, and well worth a look.

The intended market for these radios is more the unlicensed crowd than the compliant ham, so it’s not surprising that they’d be out of spec. A ham might want to bring these rigs back into compliance with a low pass filter, for which purpose the RF Biscuit might prove useful.

[via r/AmateurRadio]

40 thoughts on “Measuring Spurious Emissions of Cheap Handheld Transceivers

      1. The radios themselves are incredible performers for the $$$. You’re not polishing turds, more like polishing mud for some weird display.

        Putting an after market antenna makes them quite the awesome little bit of gear.

      1. True. And Amazon seems to spend little or no effort “curating” their Marketplace.
        I guess they’re just bowing to The Almighty Buck.

        // this kind of thing (intentional ignorance of regulatory noncompliance) just pisses me off.

      2. True story. I was performing conducted emissions compliance testing on a piece of equipment, and we were consistently failing. We suspected the wall-wart, and used a linear power supply instead. Passed with flying colors. We cracked open the wall-wart to find all of the emissions and overvoltage protection removed to reduce cost. This is my shocked face.

  1. “Careful measurements showed that some or all of the Baofeng’s harmonics were well above the FCC limits.” – well then, why bother putting Pi filters on homemade ham TX at all? I think you can just grab a schematics from 1950s Popular Electronics and be done with it. Some had no filter on the output at all.

    1. So this is not a new thing? Is this a matter of graybeards trying to shoo the noobs off their lawn (again) or are the harmonics emitted legitimately above the noise floor at more than a few meters?

      1. Taking into account the worst of the spurs, I get a theoretical range of 11 miles. (emphasize the theoretical) Whether or not it’s a real problem depends on whether or not someone is trying to conduct weak-signal operations on your third harmonic frequency. A simple work-around is: don’t use your Baofeng to transmit below 144.1 MHz.

    2. Three things:
      1) The transmitter must have been BUILT before 1972, not designed before 1972. Otherwise we could use spark gap transmitters.
      2) It is the operator’s responsibility, regardless of the technology, to ensure that the rig is compliant. Up to now, most of us could have said, “I don’t have access to a spectrum analyzer, so I had to assume the transmitter was compliant when built.” Now that we’ve seen these results, nobody who has read this article can operate one of these without taking action to reduce the spurious emissions.
      3) I think the way they get away with it is that for equipment sold to licensed amateur operators, there is no type certification, and they can just say it’s the operator’s responsibility to ensure the equipment is compliant. After all, passing the licensing tests is supposed to prove that we are proficient in the ways of measuring and reducing harmonic content. At least here in the U.S., and I understand some other countries have more comprehensive license testing.

      1. “I think the way they get away with it is that for equipment sold to licensed amateur operators, there is no type certification”

        Nope. In the US anyway that is wrong.

        A ham is allowed to operate a piece of equipment that has no type acceptance. The FCC had to allow this since it wanted to encourage people to study the ‘radio arts’ up to and including building one’s own equipment. That doesn’t mean you can just sell whatever you want commercially.

        You may sell your non-certified, homemade equipment when you are done with it but this is supposed to be incidental to your practice of your hobby. If you wish to build and/or sell ham equipment commercially you do have to get it certified. To enforce this hobbyist only intent there is a limit of how many non-certified transmitters and/or amplifiers one is allowed to sell per year. I forget the exact details but it isn’t many, I think it is something small like one or two. If you pick up any radio built by the ‘normal’ brands you will find an FCC ID number. These manufacturers would certainly not spend all that money if they didn’t have to!

        Also, amplifiers capable of operating in the CB band either out of the box or with ‘simple’ modifications are automatically turned down for certification. Certified, external 10-meter amplifiers built after the 1970s are hard to find for this reason.

  2. I would say that it differs a lot, and the Baofengs are among the worst, I have used all kinds of chinese brands, and the Wouxun seems to be among the better, and more expensive

    At the moment I have 2 different Wouxung (KG-UV6D and KG-UV8D) and a Baofeng GT3TP, I used to have the Baofeng UV5 and another GT3, but ended up giving them away to newcomers to the hobby until they could afford to buy something better.

  3. This is not a major issue in the real world. Who’s really being harmed? [Crickets…]
    Very inexpensive equipment that is 5X better than what I used to use is a good thing. Graybeards chasing the noobs off the lawn is exactly what is going on. KE4ITI

    1. True, in 99.44% of the cases.

      But, if you live near an airport or VOR, and your Baofeng is producing a spur that interferes with aviation or public safety comms (yes, it happens), the FCC and FAA will drop everything else they are doing to find you. And, when they do, they will NOT be happy. You do not want to meet them when they are not happy. The loss of your license will be the least of your problems.

  4. What about making handheld radios at home then? The radio section which is the most critical part is already available as a pre built uber-cheap module (search for “walkie talkie module” on Tindie, Ebay, Aliexpress etc). All it needs is a small uC and a display+keyboard to operate. Should the module emit too much junk, putting a small pi filter in between its output and the antenna solves the problem in 5 minutes.

    1. Doable. But as long as regulatory agencies turn a blind eye, importers will keep importing unsafe items, to cut costs and make more $. Americans did the same in the $ race until the regulation kicked in (live metal chassis etc.). For example:

      https://en.wikipedia.org/wiki/All_American_Five

      I often repair old equipment, and it is just scary what US and Canadian agencies approved back in “the good old days”: live chassis, flimsy AC cords, AC plugs with covers that fall out and pins that wobble, ungrounded AC outlets, etc.

      People were always trying to make a quick buck.

      1. “… and it is just scary what US and Canadian agencies approved back in “the good old days”: live chassis, flimsy AC cords, AC plugs with covers that fall out and pins that wobble, ungrounded AC outlets, etc.”

        So true, but lets not forget that those were also the days when parents weren’t worried of leaving their kids play down the street. Our entire mindset has changed.

  5. Not surprised, given the price. I mean c’mon, who here really thought they were buying something intended to comply with all FCC standards?

    This statement: “The intended market for these radios is more the unlicensed crowd than the compliant ham, so it’s not surprising that they’d be out of spec.” … North America is not going to be the center of the universe for much longer. Is it possible that these radios were actually made to serve commercially in most of the world where affordability is more important than spectral purity? Not everyone can pony up $300+ for first-world-grade commercial communications gear.

    I bought a UV5R. It’s cute, loads of fun for the $40. Currently I just use it for FM, and marine VHF monitoring. I may licence up and use it occasionally like that.

    Does anyone make a screw-on antenna filter that would bring them into compliance? I smell opportunity…

    1. It’s only an opportunity if anybody cares. The “new” standards for spurious emissions are ridiculous. It makes sense to have them down by 60 dB if you’re cranking out 1000 W, but at 5 Watts, -60 dB is 5 MICROwatts. Who’s even going to be able to pick that up? There could be a market for a screw-on filter if people were getting complaints, but I don’t see that happening.

  6. FWIW, wattmeters such as the one shown (Bird, Cleveland, or their equivalents) are +/- 10% accuracy rated. Wattmeters such as these are excellent for relative readings. But, a spectrum analyzer and a calibrated antenna will get you a much more accurate reading, if that’s what you’re after.

  7. China = CRAP, NOT-China = Unaffordable. This spells out a HUGE business opportunity. Why isn’t this vacuum being filled? Gee… Maybe NOT-China means OVER REGULATION and BIG GOVERNMENT SOCIALISM (especially YOU in the EU)? It is amazing. Communist China gets away with this crap, yet Socialist Governments in the “West” prevent any form of reasonable competition.

  8. “5 MICROwatts. Who’s even going to be able to pick that up?” Well let’s see, that’s -23 dBm. Even a POS receiver is sensitive to -100 dBm unless of course your radio is a crystal set!

  9. Drone, did you ever stop to consider or do any research into the reasons why such tight RF standards exist? Some standards are actually based on science and public safety and not politics. Before overreacting over ONE stranger’s unqualified opinion, you might want to do some studying of RF theory or take some engineering classes rather then go off on a political rant. Every time I fly on a plane I’m very grateful for the “OVER REGULATION” you are shouting about! I am however very dismayed that so many licensed hams would even buy a radio as if it were a bargain toaster without knowing or caring about a critical issue such as spurious emissions. Go listen to the CB frequencies if you need a reminder of what life would be like without regulation or enforcement. Buying a cheap radio based on price alone just demonstrates a complete lack of understanding of what it takes to actually make a good radio in the first place. Or a complete disregard for anyone else’s right to communicate on an interference free portion of the radio spectrum.

  10. For better or worse, these radios are available and people are buying them.

    Is there any initiative within the ham community to come up with ways to bring the offending models into compliance – like a mod or inline antenna filter?

    While they may fail a bench test, I haven’t seen much to indicate that a plague of these cheap receivers is actually causing noticeable real interference. Of course it’s probably impossible to hear such interference over the racket produced by dimmers and switching wall-warts. :-(

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