I’ve been tinkering with radios for over three decades now, and if there’s one topic that consistently causes confusion among newcomers, it’s spurious emissions. When I recently saw a question from someone who purchased a Baofeng AR-RM5 and was puzzled by YouTube reviewers criticizing its “spurious emissions” without explaining what they are, I realized this is a perfect opportunity to clear things up.
Let me break this down in plain language that won’t require an engineering degree to understand. I’ll share what I’ve learned through years of experience, testing various radios, and yes, occasionally making mistakes along the way. I do however, want to be very clear, this is my experience and what I think to be true, I am not an radio frequency engineer, and am more than imperfect (ask the wife). I put this information out here to help guide you but I urge you to do your own research and come to your own conclusions.
What Are Spurious Emissions?
Spurious emissions are essentially unwanted radio frequency signals that your transmitter produces outside of the intended frequency. Think of it like this: when you key up your radio to transmit on 146.52 MHz, that’s your intended frequency. But if your radio is also simultaneously transmitting weaker signals on other frequencies—like around 293 MHz (which is 146.52 × 2) or 439.56 MHz (146.52 × 3)—those are spurious emissions.
I’ve tested dozens of radios over the years, and I can tell you that every radio produces some level of spurious emissions. The difference is in how much. Higher quality radios typically produce far fewer unwanted emissions than cheaper models.
These unwanted signals are sometimes called “birdies” or “spurs” by ham radio operators. They’re not a feature—they’re a flaw in the radio’s design or construction that causes it to transmit where it shouldn’t.
Why Should You Care About Spurious Emissions?
When I first got into ham radio, I didn’t understand why people made such a fuss about spurious emissions. After all, if my friends could hear me and I could hear them, what’s the problem?
Well, there are several reasons why spurious emissions matter:
- Interference with other electronics: Your radio’s unwanted emissions could, in theory, land on frequencies used by emergency services, air traffic control, or other critical communications. Although widely circulated as a real threat, the reality is that unless you are standing in the Police dispatch center when you key up your Baofeng, you are highly unlikely to do this. You could, however, interfere with electronic devices in your local area. Think 20-50 meters from your transmit location at most.
- Easier direction finding: If you’re transmitting on multiple frequencies simultaneously, it becomes much easier for someone to locate you using direction-finding techniques. This is particularly relevant if you’re using radio for emergency preparedness or situations where you’d prefer not to be easily tracked.
- Reduced efficiency: When your radio is wasting energy transmitting on frequencies you don’t intend to use, it’s less efficient. This can affect battery life and overall performance.
- Legal compliance: The FCC has specific regulations about spurious emissions. According to 47 CFR § 97.307, “All spurious emissions from a station transmitter must be reduced to the greatest extent practicable.” There are specific technical requirements that vary based on frequency and when the transmitter was manufactured.
I once had a cheap radio that caused interference with my neighbor’s television whenever I transmitted. Not exactly the way to maintain neighborly relations! A cleaner radio solved the problem immediately.
How Bad Emissions Affect Radio Performance
In my experience testing various radios, those with excessive spurious emissions often exhibit other performance issues as well. Here’s what I’ve observed:
Reduced Range and Clarity
Radios with high spurious emissions typically don’t perform as well in terms of range and clarity. When your radio is wasting power transmitting on unwanted frequencies, that’s energy not going into your intended transmission.
I’ve done side-by-side tests with a high-quality Yaesu and a budget Baofeng, and the difference in range was noticeable even though both claimed the same output power. The cleaner radio consistently outperformed the “dirty” one.
Think of it this way; you have a garden hose with a spray head on it. When you pull the handle, it sprays a stream of water out the head, that is you transmitting on 146.520. Someone comes along and stabs the water hose the spray head is connected to with a nail, what happens to the signal (the stream coming out of the head)? The more nails, and the larger the nails, the weaker the stream coming out of the head.
Where I see people really ignoring, or not considering the implications of this, are with preppers, or people who just want a radio for “emergency” use. In my view, if the radio is a piece of “emergency” gear, it needs to work well. Would you go to Walmart and get the cheapest tires that fit your Jeep? Is your bug out bag a plastic Dollar General bag? Is your survival knife something you picked up off Temu?
I don’t know about you, but if I need to communicate in an emergency, I want as close to 100% of the power I am transmitting to be on the frequency that people might hear me and help me.
Battery Life Implications
Your radio’s battery has to power all transmissions—both the ones you want and the spurious ones you don’t. More spurious emissions mean more wasted power, which translates to reduced battery life.
This became crystal clear to me during a weekend camping trip where my friend’s cleaner radio lasted nearly twice as long as my cheaper unit, despite similar usage patterns.
Potential for Equipment Damage
Excessive spurious emissions can potentially lead to premature failure of components in your radio. When a radio is working harder than it should be (by generating unwanted emissions), it can generate more heat and stress internal components. In addition, a dirty signal is like a fever in humans, it is indicitive of cheap (not just inexpensive) electronics and it is highly unlikely that the part of the unit responsible for generating that signal (or not filtering it) is the only sub-standard component in a radio.
These same cheap internal components are unlikely to be resistant to spurious signals, which makes them more likely to feed back on themselves, induce electrical charges where their should not be any (or over and above what should be there), etc. Overall, it is just really bad for everything your radio does.
I’ve had two budget radios fail after about a year of regular use, while some of my higher-quality units have been going strong for over a decade.
This doesn’t mean all radios that generate spurious emissions will fail quickly, it just means they are much more likely to.
How to Identify a “Dirty” Radio
Without specialized test equipment, it can be challenging to measure spurious emissions precisely. However, there are some indicators that might suggest your radio has excessive unwanted emissions:
- Interference with nearby electronics: If keying up your radio causes static on nearby speakers, interference with TV reception, or strange behavior from other electronic devices, that’s a red flag.
- Heating issues: While all radios generate some heat during transmission, excessive or unusual heating patterns might indicate inefficiency related to spurious emissions.
- Poor battery life: If your radio’s battery drains unusually quickly during transmit operations compared to similar models, spurious emissions could be a contributing factor.
- Research and reviews: Before purchasing a radio, check reviews from reputable sources that actually test for spurious emissions. Many budget radios have been thoroughly tested by ham radio enthusiasts with proper equipment.
- Test it yourself: An inexpensive tool such as the $60 TinySA spectrum analyzer, can test all your handheld radios and show you first hand how they perform. Don’t forget to get an attenuator to lower the sigal strength before hooking it up to your radio or you will probably blow the TinySA up.
I’ve learned to trust certain reviewers who take the time to actually measure a radio’s performance rather than just unboxing it and giving subjective opinions. Or worse yet, websites that post “reviews” in which you can tell they never actually owned or used that radio at all.
Looking at the image above, you can see the tallest peak on the left, that is the frequency set on the radio when you transmit and in this case 146.520Mhz. The horizontal red line at -60 is the point at which all spurious emissions should be below. Note in this test, there are three obvious emissions that are too high, and actually there is a fourth that just barely tops the line. Which radio is this? A Baofeng K68.
You might be wondering what a good radio’s test looks like, and that is shown here. Note there is only one emission touching the -60 line which indicates this is an excellent radio. Which radio? A Yaesu FT3DR.
Legal Implications of Using “Dirty” Radios
Using a radio with excessive spurious emissions isn’t just a technical issue—it has legal implications as well. The FCC takes interference seriously, especially when it affects critical services.
FCC Regulations on Spurious Emissions
The FCC has specific requirements regarding spurious emissions for amateur radio equipment. According to 47 CFR § 97.307:
- For transmitters operating below 30 MHz installed after January 1, 2003, spurious emissions must be at least 43 dB below the fundamental emission.
- For transmitters operating between 30-225 MHz, spurious emissions must be at least 60 dB below the fundamental emission.
- For lower power transmitters (25W or less), different standards apply, but emissions still need to be controlled.
These aren’t just suggestions—they’re legal requirements for operating in the amateur radio service.
Potential Consequences
If your radio’s spurious emissions cause harmful interference to other services, you could face:
- Warnings and notices: The FCC might issue a warning or notice of violation.
- Fines: In more serious cases, monetary penalties could be imposed.
- License issues: Repeated violations could potentially affect your amateur radio license.
I know a ham operator who received a notice from the FCC after his poorly adjusted amplifier caused interference with a neighbor’s electronic equipment. It wasn’t a pleasant experience, and it could have been avoided with better equipment and practices.
Realities with a handheld radio
While using a radio with too much spurious emissions may indeed be illegal, the odds of you actually having someone find out and do something about it are extremely slim. In my opinion however, it isn’t really worth the risk, and I am not personally going to break the law just because I won’t get caught. That isn’t how I was raised.
Are All Budget Radios “Dirty”?
This is where I want to clear up a common misconception. Not all inexpensive radios produce excessive spurious emissions, and not all expensive radios are perfectly clean.
I’ve tested several budget-friendly radios that performed surprisingly well in terms of spectral purity. Conversely, I’ve seen some pricier models that didn’t live up to expectations.
That said, there is generally a correlation between price and quality. Higher-end radios from reputable manufacturers typically invest more in filtering and circuit design to minimize unwanted emissions. Well extablished brands such as Kenwood, Yaesu, and Alinco will almost always be consistantly better than cheaper alternatives.
The key is to research specific models rather than making assumptions based solely on price or brand. Some newer Baofeng models, for instance, have improved significantly compared to their earlier counterparts.
Improving Your Radio’s Emissions
If you already own a radio with less-than-ideal spurious emissions, there are some steps you can take to mitigate the issues:
- Use lower power settings: Operating at lower power levels often reduces the intensity of spurious emissions.
- Add external filtering: In some cases, external bandpass filters can help clean up your signal.
- Proper grounding: When using a mobile or base setup, ensure your station is properly grounded.
- Antenna considerations: A well-matched antenna system can sometimes help reduce certain types of unwanted emissions.
I’ve had good results using a simple bandpass filter with some of my budget radios, significantly cleaning up their output at the cost of a slight reduction in power. Keep in mind that this will reduce intereference and the emissions from being received by other equipment, but it does not solve the performance issues that a radio generating spurious emissions will have.
Making Informed Choices
When selecting a radio, consider how you’ll be using it and what level of performance you need:
- For casual use where absolute performance isn’t critical, a budget radio might be perfectly adequate.
- For emergency communications or situations where reliability is paramount, investing in a cleaner radio is worthwhile.
- If you’re operating near sensitive equipment or in densely populated areas, cleaner emissions become more important.
I keep both types in my collection—high-quality radios for serious use and a few budget options for situations where loss or damage is more likely.
Conclusion
Spurious emissions are a reality in all radio equipment, but excessive levels can cause problems ranging from reduced performance to legal issues. Understanding what they are and why they matter helps you make informed decisions about your radio equipment.
My personal opinion is that spectral purity matters more in some situations, such as emergency communications or network operations, and less when rag chewing with your buddies on the repeater. Whatever your budget or use case, being aware of spurious emissions and their implications will make you a more responsible and most importantly, more effective radio operator.
Have you experienced issues with spurious emissions from your radio? Or have you found a particularly clean budget radio? I’d love to hear about your experiences in the comments below!
