Easy Modifications For Inexpensive Radios

Over the past decade or so, amateur radio operators have benefited from an influx of inexpensive radios based around a much simpler design than what was typically commercially available, bringing the price of handheld dual-band or GMRS radios to around $20. This makes the hobby much more accessible, but they have generated some controversy as they tend to not perform as well and can generate spurious emissions and other RF interference that a higher quality radio might not create. But one major benefit besides cost is that they’re great for tinkering around, as their simplified design is excellent for modifying. This experimental firmware upgrade changes a lot about this Quansheng model.

With the obligatory warning out of the way that modifying a radio may violate various laws or regulations of some localities, it looks like this modified firmware really expands the capabilities of the radio. The chip that is the basis of the radio, the BK4819, has a frequency range of 18-660 MHz and 840-1300 MHz but not all of these frequencies will be allowed with a standard firmware in order to comply with various regulations. However, there’s typically no technical reason that a radio can’t operate on any arbitrary frequency within this range, so opening up the firmware can add a lot of functionality to a radio that might not otherwise be capable.

Some of the other capabilities this modified firmware opens up is the ability to receive in various other modes, such as FM and AM within the range of allowable frequencies. To take a more deep dive on what this firmware allows be sure to check out the original GitHub project page as well, and if you’re curious as to why these inexpensive radios often run afoul of radio purists and regulators alike, take a look at some of the problems others have had in Europe.

65 thoughts on “Easy Modifications For Inexpensive Radios

  1. I just received one of these radios as the price of 14.24€ (regular 19.45€) including shipping (1w from CN to DE) was too good to resist.

    Firmware update using `k5prog` went flawlessly after some problems: First was that my Baofeng programming adapter had to be pushed in quite hard (which I first did not realise). Second was the fact, that I initially did not know the difference between encoded and raw firmwares.

    python ../qs-uvk5-firmware-modder/fw.py dec ../UV-K5-Modded-Firmwares/k5_26_encrypted_18to1300MHz.bin > fw_modded_raw.bin
    /k5prog -F -Y -Y -Y -b fw_modded_raw.bin

      1. Take a look at your laws again. There usually requirements for both operator AND radio licensing. Many services require radios to be type accepted. Why? Because of a history of radios inadvertently interfering with other radios because of the spurious emissions.

          1. No, they are not. They legality friends on a number of factors, especially transmit power and frequency, but not having type certification means you have to be *more* careful, not less.

          2. Only licensed Amateur Radio Operators can create home brewed equipment. They passed a license exam knowing the basics how to test and troubleshoot equipment. Other radio services like CB, GMRS, and Marine Band must be type accepted.

    1. If you can’t deal with noise in the ether then perhaps it’s your equipment that’s faulty. People should be able to use radios as they wish. For my final engineering thesis project I’ve used inexpensive FPGA and made a two-way, crypted FHSS radio which was hopping over 70-130 MHz range. I was able to converse with a friend on distance of about 30 km using bugger all power compared to traditional pirate FM transmitter. Was it borderline illegal to operate? Probably, but neither me nor my prof gave a damn because the project was much more ambitious than yet another H-bridge, PID boiler temperature controller or line following robot. Officially I’ve always tested it with dummy load… yeah. I was never caught by the UKE (our regulatory authority) either, even though they operate 24/7 automatic spectrum monitoring station in my town.

      1. Spot on! Assuming of course that you are referring to liberal and conservative in a USA context. Other countries use the same terms, but much different ideals behind them.

      2. Protecting small children from Marxian (as the academics now call themselves) zealots in the schools is not a ban. It only takes a few years to raise a new generation of brutal children not recognizable by their parents, as a German Reich Chancellor once said. You can see this in how quickly the liberals in the US have turned the universities away from reason and logic and all things related to Western civilization. Basically a decade that will take half a century or longer to fix. It is a real Chesterton’s Fence.

      3. its funny you see it that way…. Outside of America most people seem to think both sides of your political system is just a clusterfuck of trying to cause as much damage to the other sides fundamental beliefs and values… I am truly saddened by how your entire political system seems to be degrading into completely polarized islands where any attempt of compromise is seen as weakness and loss by both sides.

      4. Not hard to see where your world point of view has been installed from.

        No, liberals could give a crap what you have access to. You know, like women’s health and stuff.

        The right just wants you to do whatever they feel is right. This week. Because some mythical diety might hear them murmur tonight…. Along with tens of millions of others, and then give them a new thing to be apeah1t over. A sign.

        We have words for people like that. Lunatics.

      5. Yep, that seems to be a common view among US “conservatives”.
        At least until they get caught not being “responsible about it”.
        They rarely (My Opinion) actually mean that lip-service to personal responsibility though.
        It’s just something they say to try to feel morally superior even as they are acting the opposite.

        Meanwhile, no one is coming for your radio, your gas stove, your sexy m&m or whatever today’s rant is.

    2. I disagree. My point of view is to encourage understanding, encourage testing and experimentation, and to follow the very basic rules, which are

      Don’t transmit where you’re not allowed
      Don’t transmit at more power than you need
      Don’t cause harmful interference

      If you can’t be reasonably sure, then don’t press the side button.

      On the other hand, if you’re at 0.5 watts on an FRS channel in the middle of the desert and there’s no issues on adjacent channels, then what’s the problem, aside from a technical violation of rules? And plenty of people here have the capacity to analyze the RF output spectrum of their radios besides.

      This is coming from a licensed HAM. You can’t be a hardcore gatekeeper and complain that the hobby is dying at the same time. I’m not advocating rule breaking so much as common sense. I agree that sometimes that’s asking a lot. And there will be those fools that transmit on Air Band, but what’s to stop them from just buying an aircraft radio on Amazon anyways?

      1. +1

        The radio spectrum is a bit akin to world heritage.

        We people on this world require to share it in a respectful and responsible manner.

        Causing interfence is like pollution of the land and sea.
        In a philosophical way, I mean.

        1. Land/sea pollution is a bad analogy, and light pollution is a better analogy. It doesn’t linger after you turn off the source, and it only matters if it effects someone else. Given that you are only getting half a watt out of this thing in the newly opened bands, I find the likelihood of inference — intentional or spurious — to be pretty unlikely. In the light pollution analogy, it’s like complaining about someone being able to put out a faint blue glow from their bright white LED.

          1. I’m not sure about that. While propagation is a special field of its own, it’s possible to ‘jam’ (or let’s say annoy) worldwide shortwave communication with just a battery, a simple 5v TTL oscillator and an antenna that’s just effective enough. The square waves emitted cause harmonics across all bands. That’s especially bad for people who’re into weak CW signals and QRP. Let’s never, ever underestimate radio interfence.

          2. “it’s like complaining about someone being able to put out a faint blue glow from their bright white LED.”

            It depends, I think. A laser pointer with a few mW power can distract a pilot flying an aeroplane or a helicopter. So it’s always good to be becareful and try to act responsible.

        2. And then, there’s something else to consider. FM, as a modulation, is destructive. FM signals cannot “become one” like AM or SSB signals can. If someone causes interference with an FM two-way radio, it’s twice as bad.

      2. Now that almost every PMR organisation (and many Hams) are moving over to digital transmissions, it hardly matters what occurs on analogue radio frequencies. That comment is from the horses mouth too…OFCOM themselves!

    3. Rather that outright discouraging this, I would say: use as appropriate.
      If you choose to change the FM bandwidth, for example, you could improve the NOAA signals around 135-140MHz without impacting anyone.

    4. Rather than discourage radio modding I would rather see people encouraging responsible radio modding.

      • Do what you want on receive.
      • Measure your spurs and correct them if needed before transmitting into an antenna.
      • Obviously knowing the band limits and which services you should/should not be on and all other rules is also important although not necessarily unique to operating a modded radio.

  2. Is there a UI-less radio using some of these chips?
    I find the radio UI (apart from transmit button and other obvious stuff) to be totally unusable – but if you could control it from an iphone or computer that would make a huge difference.

      1. Thanks.
        That does look like a different module though – if I search for BK2819 I get basically this article and nothing else. Is the beken chip just a rebrand of something else, or is it just mysteriously unavailable on it’s own – Can’t even find a datasheet for it.

  3. Unfortunately, as some YT’ers have already pointed out with this radio they fail to meet FCC requirements for the frequencies you’d be opening up with the firmware hack. They have bad harmonics in those channels, outside what is allowed, and also only will transmit with very low wattage, under 1 watt. So regardless of your license level, they are not approved by the FCC to use on the expanded bands the hack provides. Of course YMMV, but don’t pick one up thinking you’ll have a legitimate HF HT for under $20.

    1. Hi, the author of the repo here.
      – Please, if possible, link to amnemonic’s brilliant documentation repo (https://github.com/amnemonic/Quansheng_UV-K5_Firmware) rather than to a random Blogspot blog.
      – I moved the warnings about this being a RESEARCH firmware rather than some kind of full-blown no-caveats hack, as well as the unsuitability of the output stage for the frequencies that are unlocked, to the top of the page, to hopefully help people realize what this is and what it *isn’t.*
      – If you want more control and customizability, check out amnemonic’s uvmod-kitchen (https://github.com/amnemonic/Quansheng_UV-K5_Firmware) which allows you to “bake” your own firmwares with the modifications you want.

      All the best! Thanks for posting about our work!
      73 de K8TUN Andrej

    2. Why link to some random blog instead of the GitHub repos with all the goodies by the folks who have put in the work?

      Amnemonic has the very cool and hacker compatible tool for creating your own modded firmware with just the mods you care about:

      Tunas1337 has a nice pile of modified firmwares and the tools for decrypting and reencrypting firmwares:

      Or amnemonics firmware collection

    1. The air band receiver functionality does not require a hacked firmware. However, the AM demodulation is done by some magical hacking of the DSP on an otherwise FM-only radio chip, so the output audio is atrocious. People are still trying to figure out how to make it not so.

      1. Ideally, Synchronous AM detection should be used nowadays for AM reception.
        It gets near-FM quality under difficult conditions, without all the disadvantages of FM.

      2. I bought one thinking it would make a useful, cheap airband hand held but, as you say, the audio is terrible! I’m pretty sure I’d not be the only person who’d be interested if someone did manage to improve this.

  4. Great article. I have a cheap older Baofeng and use it mostly as a scanner connected to a PC. It came unlocked and can already use what are commercial bands in my area.

    That said, since swearing is illegal on the radio, some of us are using “Baofeng” in place of a variety of 4 letter words.


  5. I have a questions to the people who did (and are still doing) the reverse engineering on this BK4819 platform – Andrej, K8TUN and others:

    How realistic is it, if we somehow master the DSP operations, that we can put new modulations in firmware (like NXDN, Pulse Position Modulation (PPM) that is used by ADS-B, MSK – used by ACARS, standard FSK, etc) and corresponding interfaces for it on the display?
    I mean, how much space is there on the flash?

    1. Здравей! There is 64KB flash, and either 4 or 16KB flash. The marking on the MCU is dremeled out, so no one knows what it is, other than that it’s a Cortex-M0 core. The BK4819 handles the FSK capabilities, and I don’t think it can do anything other than FSK as a result. Look at amnemonic’s repo called UV-K5-Firmware, I cannot link it because of the antispam measures. Or, write in the GitHub Discussions area on my repo. 73!

  6. I’m not sure I see the point of this. If you’re going to modify it is such a way that it is strictly speaking illegal, why not use it as is … it’s not like any regulating entity is likely to bother trying to catch you.

    1. Pretty sure illegal activity is carried out on cell phones. Scan the bands its not exactly teeming with nefarious plots and wild harmonics.

      TXing on airband has always been illegal but its possible to purchase a purpose built AM transceiver on Amazon right now with no evidence of legal use required. Good luck becoming an ATC operator on a K5 lol it can only TX in FM for starters and outputs power slightly higher than a PMR446 radio.

      Give it a rest fun sponges, this is an amateur radio research project. Personally I’ve disabled TX 18MHz-1.3GHz.

      Congrats to all the modders your work is much appreciated.

    2. David, I take it you’ve never read the FCC’s disciplinary findings and rulings page! With rulings from lifetime bans, to extremely punitive fines, and in some cases prison, it’s really hard to claim that no regulatory agency is “likely to bother trying to catch you”!

        1. Yeah. Because thr UK has always been a bastion of free radio.

          Thinking back to pirate ships, radio Caroline, vans in the 70s and 80s driver ng around and busting people for unlicensed receivers.

          Yeah, great analogy there.

  7. I own several baofeng radios, yes I am licensed as a n Extra. How do I know which radio’s can use this firmware patch? Only as an experiment. I’ve enjoyed this hobby for years. Receiving is all I would use it for. As I understand the laws I’ve done nothing wrong as long as I do not transmit.

  8. I am friends with an very elderly couple who wouldn’t break any laws and find it difficult to deal with modern tech. However, because his wife is bedbound and her husband has to look after, they use 49Mhz radios to chat to each other around the house or when he’s in the garden. They’ve proved ideal and it helps to keep them physiologically active. The problem is reliability and availability of 49Mhz units. The PTT buttons don’t last long and neither do batteries. If these UV-5K’s can receive 49Mhz , perhaps they could be made to transmit in that totally legal band. If so, they would be ideal for the couple. One thing is certain, they would never use them to TX on any other frequency. Does anyone know if these radios can be modified for 49Mhz?

  9. I work as a security officer in a town centre and we have walkie talkies. They us a DCS tone to access. I like to listen to what’s going on while I’m off duty so I bought radios capable of accessing the frequencies but even though I’ve entered the correct DCS tones, my radio TYT and a wouxun won’t access our repeater. Yet, my Puxing will . It;s truly puzzling. Any ideas?

  10. As a licensed Amateur Radio operator in the USA myself, I say – ROCK ON!

    I can create my own RF filters to clean up any emission that a “hacked” radio can emit. In fact – the FCC *explicitly* *encourages* USA hams to experiment with/modify/repurpose/etc. equipment as part of its stated mission in support of Amateur Radio licensees. We have the technical know-how; and, if we don’t, we are admonished to DEVELOP that know-how as part of our justification for being a licensee.

    Additionally, all USA licensed radio operators are REQUIRED – by law – to adhere to the limitations of our licenses, which includes frequency, bandwidth, spurious-emission and other technical limitations on any transmissions we may chose to undertake.

    So, I encourage readers to stop over-analyzing this issue. There’s nothing “wrong” with playing around with a device that you legally own, including modifying its firmware for your own fun and/or learning. There’s nothing ‘wrong’ with supporting inquisitive, industrious individuals playing around with something – no matter “why” (you think) they’re doing it. Relax; you’ll live longer. Some of us are actually ADULTS, and even (gasp) responsible adults. We’re having fun, and there’s nothing you can do to stop us, or crush our enthusiasm.

    If you want to be a killjoy, just go become a political activist. They spend their entire day stopping people from having any fun. Leave the rest of us adults alone. We DIG RADIO, and you can’t stop us!! =)

  11. In Canada, you can update software in a radio as long as the radio itself is not physically modified. However, if you have your advanced licence, you can physically modify hardware, create and maintain repeater sites and create your own radios. I hope this enhances your research.

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