Nov 26 2012

Baofeng BF-666/777/888 audio mod + frequency adjustment

While I regarded the short review of the Baofeng BF-666/777/888 series as a side note, my readers apparently did not. Comments and questions rolled in, and it’s still one of the most read articles to date.  Personally I think they are quite fun to own; $25 isn’t much, and my dogs can’t destroy them while we’re playing in the park. After the first batch I bought another lot of them, branded Baofeng BF-666S, and distributed them amongst other hams.

Audio distortion
I immediately noticed that the RX audio was a bit raw and mentioned that in the review. It didn’t bother me much. A few days ago Tom PA2TSL bought two of my remaining BF-666S radios. He knew of the flaws, but couldn’t stand the audio distortion in the end. He started to experiment (strange folks, hams, trying to perfect a $25 hand held… it must be in our genes). We both looked at a few waveforms on our oscilloscopes and saw small, yet distinct ragged edges.

Finding the fix
The first thing Tom noticed is that the audio was fine on an external speaker. This could imply that the internal speakers are low quality, but when he connected an audio source to the internal speaker, it was fine too. Puzzling. Impedance problem? Something else? We discussed these findings on 2 meters, but all we could do was guess.

Tom checked the circuit board again and noticed something strange. The internal speaker wasn’t connected to PCB ground, while the external speaker was. After soldering the speaker wire to PCB ground, the problem was gone. This is what you have to do.

Remove belt clip and the 2 screws at the bottom.

Remove knobs and nuts

Carefully lift and pull the PCB out. Take it easy, the speaker wires are short.

Remove wire from position 1 and solder it onto position 2 (PCB ground)

Before – After

Tom also noted that one of the Baofengs was off frequency by a generous margin. Also easy to fix, see below. Don’t adjust this trimmer unless you own an accurate frequency counter.

While you’re at it, you might want to check the frequency accuracy.

Various notes

  • Don’t expect the Chinese voice to get much better – the sample is low quality by nature. Listen to other stations instead.
  • All PCBs we looked at needed some serious cleaning with alcohol. Strange white stuff there.
  • After the mod we both checked if there wasn’t a catch with programming or anything similar. We couldn’t find any. Have fun with the mod!

Hans PD0AC, Tom PA2TSL

36 comments on “Baofeng BF-666/777/888 audio mod + frequency adjustment”

  1. Pingback: Baofeng 888 | vlatic

  2. Hi,

    Have you ever had a chance to check the power output, the case say almost 5 watts. But I did an actual check it only transmits inside a city for around 600 meters. So that translates to just around 2 watts.

  3. What did I see…. ? This BF888 have a CD-Approval ? From friends I hear, German Custom-Guys handle it restrict if you try to import a non-CE Item. I order as “privat” in small lots, 50 BF888.
    If they have now CE , i can import this toy without a custom-risk

  4. Tom again

    actual Reseller-factory Price is 12,90Us-$ ( That`s below 10€ )
    All other Toy-PMR-Radios are more expensive.
    (End-user / customers, this is by far not the street-price in Europe)

    the fail-Items rate is to high. From 50 radios are 5 not working well. 2 of the I can fix. Kenwood / Maas / Wouxun have a Zero-faulty rate.

    Output-Power . Of course not a 20€ CB-Tester…. All radios have round 3 Watts and a clear Modulation

    The squelch did open some times / from time to time for a half second
    Other radios at the same place did not do this

    The power is not adjustable with the software. i do not use the trash-Software from Baofeng. Zastone have a better once. ( ZT-V68 ) The Software offers a “Power-Selector” but there are no effects on the radio.

    Conclusion: w
    It is a Toy . Low price , working well ( when its work !! )
    For hams as a toy , for PMR-User a better Toy ( not not legal ) as this Mickey Mouse Radios / Discounter-marked offers.

    My recommendation if you are not watching out for a “security-professional-radio”

    • On professional (HP) measuring equipment I never saw power output rise above 2 Watts. I ordered 20 in total, all fine except one (speaker wires had to be re-soldered). I’m surprised about the factory price! Unbelievable, when you realize it’s delivered with battery, charger etc.

  5. ive downloaded several versions of software that is said to let you read and program the BF-888s….installs fine, but the software keeps telling me it cant read and that i need to check my connections and my comport settings….im using my TYT UVF-1 cable…would that make a difference why it wont read? Im looking for help and im about aggrivated with it but i refuse to give up LOL…so im open to suggestions.

  6. for the price BF666S radios are brill and at a throw away price
    did buy 4 to sell.
    one charger blow up so made zero out of that !!!!! found radio software very hard to get working on my computer as well took 2 days to get going please dont tell anyone i am putting 2 watts out in the uk on PMR lol

  7. The reason the internal speaker was not connected to ground, may be that its a BTL (Bridge Tied Load) rather than a SE (single ended) amplifier circuit. If it is a BTL circuit then an electrolytic capacitor of around 470uf should be connected to the BTL – output (+ side of cap to BTL output) into the + side of the speaker and then the – side of the speaker goes to ground. Failure to use a capacitor may damage the amp or speaker. I have not been able to find a schematic of these radios yet, so am unable to confirm which type of amp circuit is used. if it is a SE amp circuit then no problems connecting the speaker to ground.

    • Tom PA2TSL did probably considered this. The fact that the external speaker is connected to PCB ground supports his assumption that rewiring would do no harm. Why the rewiring results in less distortion is still a bit of a mystery.

  8. Hey. I also got the BF-888s. My Channel knob is a little bit wrong and the line always stands exactly between two. So I don’t know which channel I selected. I also don’t like the voice talking 😉
    I thought I could adjust the knob a bit and put him correctly. Sadly I cannot get off the knob. I pulled like crazy but he don’t get loose. I also don’t wanna break anything. Can you maybe tell me how to take it off?
    Much greetings.

      • Thanks very much for your fast answer. I see, maybe then I try to lift the knob carefully with a screwdriver. Sadly I also didn’t find any help in Internet. Maybe I have any newer Version. At least when I take the battery off there’s a small sticker with “UPDATE” written on it.
        Maybe you can answer me another question about the devices 🙂 I searched also very long for the channel spacing setting till I realised that the device is doing it apparently automatically by the “distance” of two channels.
        If I program 8 channels (from 1-8) with PMR frequencies and then at Ch9 any other random frequency (e.g. 434.100MHz). Do you know if I have then the maximum spacing (25kHz) on Ch8 or also 12,5kHz?
        Many thanks!

      • This radio doesn’t know fixed ‘channel spacing’ as in other radios. You can program about any frequency in any order with any spacing you like.

      • I’m so sorry to take more of your time. I wrote channel spacing but I actually ment bandwidth. I can do batch programming for all 16 channels and there I can choose different channel spacing (5kHz – 25kHz). But the used bandwith is not mentioned anywhere. I found in internet anywhere something like WIDE is 25kHz and NARROW is 12.5kHz bandwith. But I don’t know if that’s correct. Do you have any information about this? I experienced problems in quality and volume with connecting to common PMR-radios. I researched in internet about PMR bandwidth but I almost didn’t find anything except that it’s apparently very low bandwidth (like 6,25kHz).
        Very much thanks in advance.

      • What you found is correct. Most times I program PMR frequencies into this radio, I set the bandwidth ar ‘Narrow’. If you only communicate with other Baofeng radios, ‘Wide’ will give you louder and better audio.

  9. hi,

    awesome mod u have there. have you tested whether external speakers works after this mod?

    regards,
    jim

  11. I have done a few tests on the BF-888s and would like to report that, VOX can be activated without the need of earpiece/headset.

    Also, contrary to what is stated on the manual, these radios could be set at 477 MHZ frequencies… Good for those in Malaysia/Australia/NZ.

    regards,
    Jim

  13. Just want to confirm on the power output thing. As I’m a poor excuse for a ham and don’t have a power meter (it’s on my wish list), I can’t verify this myself. You say the software Hi/Low power option does nothing. Is this also true when the monitor button is reassigned to be a power hi/low button? I gave up monitor to gain high/low, and wonder if this was a mistake.

  14. I see the Hi/Lo option in the software, but with hi power being 2-3 watts, I’ve never given low power a thought.

    I do know that the option for the side button on mine doesn’t work as a power setting. On both of my 888S radios, setting the switch via software to power puts the radio in the alarm mode.

    John K3NXU
    http://www.miklor.com/BF888

  15. I’d like to think low power means less battery consumption, and when I’m just using them around the house, a half watt would be fine. I guess I’ll have to break down and get a power meter at some point.

  16. Do anyone know whether the frequencies could be moved to 476-477 range, so this could be used in Australia? (Yeah, I know nothing about radios! Sorry!)

    • Yes you can. I’ve programmed 477-478Mhz on Baofeng bf-888s/777s.

      The box stated up to 470Mhz which is not true. It can go beyond.

      I know because I’m fr Malaysia and here we use 477 as our CB UHF.

      Cheers!!

  17. It’s a hidden secret not many know. The ones with the K sticker (without scrambler) are programmable at 477 Mhz.. I tried informing those at Miklor to update that but they didn’t.

  18. Jim,
    I have no record of the frequency expansion capability beyond 470 MHz
    Send the information that you have regarding the software, settings, frequency limits, etc. I would be interested in reviewing this.
    Send to . . misc (at) Miklor (dot) com

    John
    http://www.miklor.com

  19. I noticed a similar result with the UV-B5, but stranger. The inbuilt speaker does sound harsh, but when I connected a pair of headphones (Pioneer SE-305 – 8 ohms) I pretty much had to back the volume to the point where it was about to switch off. The sound quality (on FM and voice) seemed much improved. My /guess/ is that baofeng are using some kind of BTL for the speaker – perhaps for extra punch.

    Being a DSP o/p, if you don’t get everything just right, you get distortion. Perhaps single-ended doesn’t suffer in this case…

    My two cents..

  21. I have a GT-3 Baofeng Radio with a defective internal speaker. It is a 16 ohm, 1watt,
    3.2 CM diameter speaker. Does anyone know where I can purchase one?

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