UV-K5 All-Band Mod, Part 2: Easier Install, Better Audio, And Two Antennas

OK, it’s official: the Quansheng UV-K5 is the king of hackable ham radios — especially now that a second version of the all-band hardware and firmware mod has been released, not to mention a new version of the radio.

If you need to get up to speed, check out our previous coverage of the all-band hack for the UV-K5, in which [Paul (OM0ET)] installs a tiny PCB to upgrade the radio’s receiver chip to an Si4732. Along with a few jumpers and some component replacements on the main board, these hardware mods made it possible for the transceiver, normally restricted to the VHF and UHF amateur radio bands, to receive everything down to the 20-meter band, in both AM and single-sideband modulations.

The new mod featured in the video below does all that and more, all while making the installation process slightly easier. The new PCB is on a flexible substrate and is considerably slimmer, and also sports an audio amplifier chip, to make up for the low audio output on SSB signals of the first version. Installation, which occupies the first third of the video below, is as simple as removing one SMD chip from the radio’s main board and tacking the PCB down in its footprint, followed by making a couple of connections with very fine enameled wire.

You could load the new firmware and call it a day at that point, but [Paul] decided to take things a step further and install a separate jack for a dedicated HF antenna. This means sacrificing the white LED on the top panel, which isn’t much of a sacrifice for most hams, to make room for the jack. Most of us would put a small SMA jack in, but [Paul] went for a BNC, which required some deft Dremel and knife work to fit in. He also used plain hookup wire to connect the jack, which sounds like a terrible idea; we’d probably use RG-316, but his mod didn’t sound that bad at all.

Keen to know more about the Quansheng UV-K5? Dive into the reverse-engineered schematics.

Thanks to [Sam] for the heads up on this one.

46 thoughts on “UV-K5 All-Band Mod, Part 2: Easier Install, Better Audio, And Two Antennas

  1. Something tells me “Don’t do it!”. Could it be the transmit section spurs would be inadequacy of filters left over. ie: uhf, vhf high frequencies. Or big fines to the HAM’s for unknowingly transmitting spurs. Because they did not redesign the transmit section. HF radios have whole sections of filters switched in and out for the different bands. UV-K5 does not. Let’s not even go near all the other frequencies not HAM authorized.

    1. “Or big fines to the HAM’s for unknowingly transmitting spurs. ”

      Yea…..No,,,, Not in the USA. FCC could care less these days.
      There has been almost NO enforcement of Part 97 in over
      20 years and I don’t see that changing.
      Now—Put on a low power FM broadcast and you will see them!!

      1. Want to kill a hobby and hinder communications? If dirty Chinese radios proliferate FCC (spurred by the ARRL) inaction now won’t stop them from enforcing their regulations. Besides, it is the law.

      1. Correct, this is just another idiot jumping up and down spreading FUD because the UV-K5 was mentioned without actually understanding what’s going on.

        This doesn’t transmit. Si4732 is a RECEIVER chip.

        And the stock UV-K5 is perfectly compliant within the FCC HAM bands.
        I’m so tired of this bullshit that’s designed to scare new amateurs away from these amazing radios.

        Get on the air, people. You can get a better radio later if you find you do need one. But right now, you can get your license and a $30 radio and *get on the air*.

        1. “the stock UV-K5 is perfectly compliant within the FCC HAM bands.”

          SA plots ???
          Seeing is (maybe) believing.
          I have tested at least a dozen of the cheap(sorry..low cost)
          HT’s from China and NONE were legal. (2nd harmonic too high)
          Fine as a RX but crap on TX.

  2. My advice, go ahead and do the mod. Any “spurs” shall be in the order of microwatts, and not noticeable to anyone. Presumably the original five watt power has remained the same.

  3. Good reminder. I should look into a decent but lightweight, portable, AA powered ham radio for my emergency kit. Still don’t understand why I can’t take a private version of a technician license. At the current state of things, there’s a zero chance I’m going to do the exam. I don’t like my private information to be spread on the internet for no reason.

    1. Are you kidding Bob? You got doxed years ago. Nothing comes of it because no one cares.

      Just don’t get the ham license plate if they have that where you are. Everyone makes mistakes. You never know when you might accidentally cut someone off or something and they lose their minds over it.

      1. I haven’t been doxxed. If you type my information into search engines, you won’t find me. I don’t want to make it easy to find me. If you go to the exam you get registered and your address is being public information. No thanks. I’ve helped to get rid of the phone books in my country because it’s a violation of my privacy.

        1. Search engines! Oh man… you really don’t know do you? Search engines are for kids! No, they are for Babies. Little ones. Or worse, normies!

          The real doxing lists are on the dark web, section 1337. And believe me.. we have EVERYTHING about you in there!

        2. According to google:
          The character Bob the Builder’s address depends on the series he appears in:
          Bobsville: The main location in the original series (series 1–9) and a major location in series 10 of Project: Build It. Bobsville is also a minor or recurring location in series 11–16 of Project: Build It.
          Sunflower Valley: The main setting for the series in Ready, Steady, Build! and beyond. Bob moves to Sunflower Valley with Wendy and the machines to build a new community after winning a contest to design the town.
          Fixham Harbour: The location for Ready, Steady, Build!.
          Spring City: The location for the 2015 reboot of the series.

          1. Yah. He moves around a lot to maintain his privacy. All it takes is a little social engineering though. Buy Wendy a few drinks and she sings like a canary!

    2. Hey Bob,

      Just a heads up, you can’t possibly usefully transmit (i.e. produce several watts of RF) from AA batteries. They simply don’t have enough juice in them. Maybe you could store enough for QRP morse in a capacitor, or stuff like WSPR, but, generally speaking, the internal resistance is just too high. The voltage drop when you pull current from them will throw your circuit below your regulator’s dropout before you know it.

      Sorry Bob, it’s all about the lithiums. Grab a UV-K5 for your kit.

      1. What?

        My wife’s HTX400 does just fine on the local repeater with 2 AA batteries! It’s rated for 1Watt out which is probably at least twice what is needed for that job!

        I saw your earlier comment complaining about people complaining about cheap radios.

        That was kind of sketchy b/c with the cheap ones you can buy two of the same model, test them, one is in spec and one isn’t.

        I agree with you that unnecessary gatekeeping is bad. But… so is a dirty signal.

        Take them to the next hamfest with an ARRL booth and get it tested.. replace it or buy a low pass filter to go between the antenna and ht if it is bad. That’s better advice.

        I didn’t reply b/c… yah, gatekeeping and all.. But after seeing this… Now I know you just don’t know what you are talking about.

        1. I don’t know what I’m talking about? You’re claiming 1W out. Generously assume the whole thing has 50% efficiency. Therefore, it’s consuming 2W. What is the minimum voltage it requires to do so? You have 2 AA batteries. Let’s again generously assume they’re 1.5V alkalines so you have a nominal voltage of 3V, with a capacity of 1700mAh. You have 3V * 1.7Ah = 5.1Wh. Best case. If you could actually use all that capacity, great, you can transmit for nearly 2 and a half hours before you have to dispose of those cells forever. In reality, the combination of lowered battery voltage and voltage droop from high internal resistance will be fucking with your radio after like 10 minutes. You could use a boost circuit, but that will eat away your efficiency and probably produce more EMI than is worth dealing with. I simply don’t buy that this thing doesn’t eat just cells.

          Does it even work on NiMH?

          1. It’s an FM radio, therefore the PA will be Class C and that could easily be 75% efficient and its maximum output when powered by AA cells is 300mW so it’s not consuming anything like 2W on TX and considerably less on RX.

            Decent quality alkaline cells can be 2.8AH, a Lithium AA cell can be 3.3AH.

            Do the math.

        2. It’s amazing, truly amazing, that you’re complaining to me about dirty signals while defending something running off AAs. Did you test that? What is wrong with you people who gatekeep when you don’t even have the knowledge to back it up?
          I have tested ALL of my Quansheng radios and they have ALL complied, with headroom. Truth be told, performance on the second harmonic on the 2m band could be better, but it’s compliant. I do encourage people to test their radios, but testing equipment is expensive and coordinating access to club members’ equipment takes time. Did you actually find one that isn’t in spec, or is that a rumor you’ve heard, or are you just straight up lying?

  4. As a licensed ham I can only second this.
    I’ve never seen anyone doing some measurements of spurious emissions an pimped rigs like this.
    And receiving signals far from the intended frequencies makes me believe there’s almost no pre filtering. That leads us directly to the question of large signal strength….
    It’s great to see what can be done, but imho you should use a modified rig like this as a daily driver.

    1. Amature Radio. one of the few times where the liuttle guy actually got declared the right to exist.

      Granted at the time it was at ‘useless’ frequencies that hams of the day made work anyway because as it turns out… MOST THINGS WILL ANTENNA.

      I wish i could convince myself to get my license back but given my life and financial situation. ‘Why bother?’


        This was the most valuable thing I learned my elmer. Basically anything that is metal can in some means become an antenna. We used a copper ground strap on an aluminum light pole in a parking lot to make some CW contacts 900 miles away on 5 watts. “If it’s under ten to one, call CQ.”

  5. Seems to me that this has highlighted a reason d’etre. A diy radio mod has the community up in arms and essentially saying you should be using radios you bought not built. If that’s the case why not get a CB license or FRS GMRS?

    Somebody really should test emissions though.

  6. Excuse me for bringing this up again, but the line about how the hardware mod makes it “receive signals down to the 20-meter band” still doesn’t make sense. Even if you don’t trust me about it, the description of the video linked by the original article says “After this mod. you can receieve AM/SSB signals from Long Waves up to 30MHz(CB included)”. Longwave, at a few hundred kilohertz, is a lot lower than 20m which is 14 megahertz. The original uv-k5 could only go down to 18MHz with a software mod, so 14MHz is instead the highest band that couldn’t be done without hardware, not the lowest.

    As for emissions, these 4732 chips are *just receivers*, and the transmitter in the uv-k5 is only properly filtered for VHF and UHF. If you try transmitting in a vastly different band it will emit a few milliwatts in that band and a couple watts in various other bands, which is absolutely not what you want to do. But that’s not the point of the hack anyway. Wide receiver coverage is great, and entirely responsible and legal to desire.

  7. Although the mod PCB doesn’t cost much, it is now (with a 39% discount on Aliexpress) still more expensive than what I’ve paid for the entire UV K5 radio. It still amazes me how cheap are these transceivers from China.

  8. It’s a lot of radio for the money. I got one and I plan on trying some of the alternate firmware, but the impression I got from a little research is that the added HF capabilities you get from the hardware mod is not very impressive – ie you don’t suddenly have a HF DX rig in your pocket – so I’m not yet tempted to do the mod.

    Has anyone here done the hardware mod, and if so, how did it change your life?

      1. Agreed… but do you end up with a fairly useful HF receiver, or is it mediocre? For the price of the UV-K5 plus the mod board, you could instead buy a 4732-equipped HF receiver with a better front end.

  9. Does the software mod enable the PTT for bands it shouldn’t?

    I assumed this would turn out like many commercial HTs where they have receive capability all over the place but only transmit where there are filters.

    Reading through the comments however…

    1. It’s not related to the receiver chips this mod uses, but I believe various of the alternative firmwares for this radio say that you can choose to change the transmit frequency ranges if you want, but that you shouldn’t because of laws. I didn’t confirm this, but I think this guy basically said he didn’t change anything transmit related from the defaults, just made it receive more.

      1. That makes a lot more sense.

        If I were doing this.. I might wait or one of those hamfests where the ARRL has a booth and will test your ht for you. Then I might try opening up the 1.25M band for transmit, get it tested, and if it is clean enough keep it open or if not then close it again. But to try to transmit all the way down to 20M? No way. Besides, isn’t it FM only?

        1. If I remember right, it’s got a couple of bandpass filters, and 1.25m wouldn’t go well enough. I could be wrong, though. And yeah, natively FM like many others- maybe somebody could play with things programmatically on this one, but I’m not sure to what extent.

      2. The transmit signal is unlikely to be clean when you transmit far out of band. In fact, the spurious signals and harmonics that fall inside the PA/filter passband will most likely be stronger than the carrier 😑

  10. I agree some testing should be done but building and modifying radios is one of the major benefits of Ham radio. We could even call it the origin of Ham radio. If we give that up we might as well use cell phones and bubble pack radios.

    1. Well said. I’m optimistic here. There are still new fields that can be experimented with.
      Let’s take the geostationary Oscar 100 satellite, for example. It still involves DIY, gratefully.
      And once there’s a colony on moon, mars, titan or an asteroid, ham radio will be there.
      Despite all odds, ham radio remains the embodiment of freedom, curiosity/science, independence and international friendship.

  11. First it was radio, then television, then computers and programming, then software defined radio.
    Hams have always been the bunch to experiment with new technology.
    If you showed a ham operator from the 1920’s the technology of today, it would seem incredible
    to them. Like in the 80’s when cellphones were first starting to catch on. Nowadadys, we have
    mutiple generations who have never lived without a cellphone or computer or internet.
    Take that stuff away and the modern generations would be lost.
    The older hams, those who know how to build antennas, radios etc., those are the hams who
    will be able to communicate should everything else go kaput.
    Key difference? Hams don’t necessarily have to rely on infrastucture.
    That abandoned copper twisted pair known to the general masses as a telephone line?
    There’s your HF antenna. That old motor? Hook it to a bicycle and you have a generator to charge
    a battery. Hams will always find a way. They like a challenge and figuring things out.
    For instance, I was watching Gilligan’s Island the other day. It was the episode where they
    were recreating the shipwreck because the Skipper was blamed for it.
    There is one scene where I think it was Ginger was creating a little version of lightning with
    a motor or something and a wand. My first ham thought? Spark gap transmitter. :) :) :)
    Yeah, I’m a ham and am happy to be one. Old, curmudgeonly gray haired and grouchy. :)
    Now get off my lawn you rotten kids! :)

  12. Most handheld tranceivers use the same filters for both transmit and receive. I don’t know anything about this mod, but I’m guessing that the filters have to be modified in order to extend the receive range downward to 14 MHz. Some inexpensive tranceivers don’t switch filters between VHF and UHF, so they may produce spurious emissions throughout the UHF spectrum when operated on VHF. That is because FM amplifiers are usually nearly class C for efficiency reasons. Class C amplifiers make lots of harmonics, so they need good low pass filters to be legal. There are well know examples of remarkably low priced radios that have this problem being sold on the internet. You can transmit on 2m and be heard at quite a distance on 73cm with these units.
    If there is up-conversion or frequency multiplication (or d-to-a converters) in the transmitter signal chain, they might need good low-pass filter characteristics too, because of intermodulation distortion in the amplifier. That’s where this mod could make spurs worse. I’m guessing that this radio isn’t fully compliant even without the mod anyway.
    Another problem with wide-band filters is receiver overload and desensitization from out of band signals. The receiver is probably sub-par.
    As a licensed ham [Extra] with an engineering degree-Master of EE– , I wouldn’t even buy this radio, let alone install the mod. At least , without going through the design. I know how to do the tests. Hams are granted great latitude in designing and modifying their stuff based on the belief that they understand the rules, know their limitations, and will act accordingly. These privedges don’t extend to any other radio services.
    By the way, do something that regularly interferes with military, navigation, emergency services, or broadcast services and see what happens.

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