Video: Tecsun PL-880 vs. PL-660, using the hidden DNR feature

Photo source: Tecsun PL-880 Yahoo Group

Photo source: Tecsun PL-880 Yahoo Group

In this video, I’ve tuned both the Tecsun PL-880 and PL-660 to All India Radio on 9,445 kHz (transmitted from Bengaluru, India, some 8,800 miles away).

Thanks to an image of a (prototype?) PL-880 keypad posted on the Tecsun PL-880 Yahoo Group–an excellent group you should join, by the way–I’ve discovered that if you press and hold the number 6 on the PL-880 keypad, it engages the hidden DNR function. I assume DNR is an acronym for “digital noise reduction.”

I engage the PL-880 DNR feature in this video and compare with the PL-660 audio.  Again, apologies for quality as this was made using my iPhone.

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24 thoughts on “Video: Tecsun PL-880 vs. PL-660, using the hidden DNR feature

  1. Dave

    Just tried this on my PL880: held button 6 and all I got was a 6 on the display rather than an on / off message.

  2. Ted Bouten

    My tecsun pl-880, has mods,upgraded,software,4-26-2019 mfg
    Dnl,fixed,am/lw,press am hold too change am,too lw modifications in softeware,
    Direct control over filtering ssb,am
    Tripalconvertion software 4-24-2019,
    They did not change upgrade version read out

  3. KB1IVQ

    In my experience DNR is most definitely automatic receive bandwidth adjustment. It seems to follow an algorithm involving signal stregenth i.e the stronger the signal the wider the filter is and vise versa.

  4. Mick Aitch

    Great information here and in the other sections of the ‘hidden’ features. The additional notations in the photograph are a very handy reference and I’ve printed the photo and added it to my user manual.

    Has anyone got to the bottom of what ‘DNR’ actually means and does on this radio?

    BTW, great music in the video above, from one of my favourite films.

  5. Rick Filcoff

    I forgot to mention, I actually verified using lab equipment that the sensitivity on the TS-830S that I compared to the PL-880 be better than 0.10uV for 10db S/N.

  6. Rick Filcoff

    I had a PL-660 and sold it on eBay. replaced it with the PL-880. It is well known and well documented that the BFO on the PL-660’s doesn’t work properly (or at the least it is very quirky). It would annoy me to no end when copying the mail listening to sideband or CW. I believe the 10 Hz and 50 Hz fine tuning increments on the PL-880 are incomparably better than the BFO on the PL-660. I have not noticed any problems with stability of the PL-880. I have two Kenwood TS-830’s (one gold edition). You may know that the TS-830S is one of the most sensitive (0.11 uV/10 dB S/N) with best noise figures ever made in amateur radio HF equipment. I can detect almost no difference between the sensitivity of the PL-880 and my TS-830S. Sensitivity was not a problem on the PL-660, however, selectivity was not the best. The variable bandwidth on the PL-880 provides a much better listening experience on crowded amateur bands than the PL-660. Also, the ability to turn on the display light and keep it on is very useful. Much better than the display light function on the PL-660. I rarely listen to anything other than amateur bands on the PL-880 so I can’t credibly comment on the other features comparison. I used the PL-660 synchronous detector a few times on weak shortwave broadcast stations. It seemed to me to make the signal easier to copy. By the time you add the cost of replacements for the poor quality rechargeable batteries included with the PL-660, the price difference between the two radio is less than $40. In my opinion, the PL-880 is easily worth the additional cost.
    Rick F.

  7. almir torquato de araujo

    informar qual o melhor entre o TECSUN PL 880 OU PL 660 qual dos dois tem mais recurso

    Desde já agradeço.

  8. Gerhard Hoehne

    From my point of view has this hidden feature nothing to with DNR, if you switch this feature “on”, you will observe, that it is an automatical bandwith-tool, switching automatically to a bandwitch, that is optimal for listening, often changing, while listening, when the signal-strength is changing. In this mode, you cannot switch the bandwith after your desire, but the machine will do this. For a stable bandwith, please swich this tool off by pressing the “6” some seconds.

  9. RadioFlynn

    Another possibility for the “DNR” feature: different settings of maximum gain for the AGC. This would only affect the output of the weakest signals.

    From the Si47xx Programming Guide:
    “The maximum AVC gain affects audio output level, especially under weak signal conditions. It amplifies the signal as well as noise. When a signal is very weak (needs a lot of gain) then the maximum gain will be applied, and may make the noise too harsh for the listener, even the soft
    mute functions. The user can reduce the noise further by adjusting the maximum AVC gain. The property allows the user to optimize the trade-off between maintaining output level and suppressing noise.”

  10. RadioFlynn

    The manual for the Silicon Labs Si473x series chipset has this to say about noise reduction:

    “Adaptive noise suppression is employed to gradually combine the stereo left and right audio channels to a mono (L+R) audio signal as the signal quality degrades to maintain optimum sound fidelity under varying reception conditions. Three metrics, received signal strength indicator (RSSI), signal-to-noise ratio (SNR), and multipath interference, are monitored simultaneously in forcing a blend from stereo to mono. The metric which reflects the minimum signal quality takes precedence and the signal is blended appropriately. All three metrics have programmable stereo/mono thresholds and attack/release rates.”

    Could the hidden DNR feature possibly be alternate stereo/mono thresholds and attack/release rates for FM signals? Maybe this is an FM DXing feature?

    1. Michael Black

      You can hear a mono FM signal fine, while switching to stereo will give you a noisy signal.
      You need a stronger signal for stereo. This is why most or all stereo decoders have some switching, at a certain signal level, it will automatically switch away from stereo.

      The alternative is to blend things, I forget the exact details. The stereo spacing is not as strong, but the signal isn’t noisy. Some receivers have a variable blending of the stereo signal, none at all if the signal is strong enough, then quite a bit if the signal is weak, right down to now stereo if the signal is even weaker.

      That’s what is being described, a place in between full stereo and mono.

      I suspect that may be what is being talked about by “DNR” here, the “Adaptive noise suppression” mntioned in the datasheet sounds too much like “DNR” for there likely to be more than one feature in the radio along those lines.

      If that’s the case, then the DNR will only work on FM, because it’s only about FM.

      I’m not sure it’s really a DXing issue, if you are DXing you might as well just have mono reception. But it is certainly useful with car radios, where the signal levels can vary quite a bit, and the noisy stereo coming and going would likely be distracting. Same with portable operation, though you aren’t likely to move as fast.


  11. Michael Black

    There used to be a commercial product for hifi labelled “DNR”. I can’t remember if it was specific to a company (or what company) or was licensed out. part of me thinks I had a car radio with DNR once.

    It stood for “Dynamic Noise Reduction” and the concept, as detailed in the hobby electronic magazines, was a voltage controlled low pass filter. When the volume was loud, the low pass filter was at some frequency out of range to affect things. As the audio level went down, the low pass filter would go lower in frequency. The idea was to wipe out the noise that’s there that would be blocked by higher levels of audio. And unlike some nose reduction schemes, it worked on any source, there didn’t need to be an encoder like for Dolby.

    I have no idea if this “DNR” is that sort of thing.

  12. millerliu

    I suggest you try DNR usabiligy on weak LW/MM/SW and strong LM/MW/SW signal. The same applies to SSB and CW signal. Thanks your effort!

    BTW, could you try the tone(bass/treble) usability for decoding marginal signal ? Last adjacent interference 10kHz away trial was just based on BW and SYC functions.

  13. millerliu

    It seems DNR unusable in AM mode, how about try SSB or CW signal ? And 50/75us should be FM deemphasis, the setting was shown on ATS-909X mod listing.

  14. Thomas Post author

    Hey, Tom,

    I’m still trying to figure out the number 5 feature. I assume it has to do with the AGC circuit, perhaps an attack figure? Not sure. I haven’t tinkered with it a lot. This PL-880 arrived at a rather busy time of my life, so I’m fitting in tinkering time with other tasks. 🙂

    I should know soon, though. Check back.

    (BTW: took 2 Captcha tries for me!)


    1. Tom Stiles

      I greatly appreciate all your postings. They are filled with valuable information. I should be getting my PL-880 tomorrow according to UPS.

      Thanks for your time,


    2. Jonesy999

      Has to do with dolby noise reduction on older amps, im guessing for the line out thingy, i have a switch for it on my old sta2100 realistic

  15. Tom Stiles

    Interesting, in the picture there are some extra notations above some of the keys such as the DNR and above the 5 key is 50/75 us. I wonder what that key (5) does? These don’t appear to be in your video and they are not in the manual (website pdf).



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