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How do I set noise reduction on the 160m band


Above please se the state of my radio on 160m in the evening. It is difficult for me to understand your manual instructions on noise mitigation. Please instruct me how to set the noise mitigation fror the case you see above.

Amos 4X4MF



  • VE7ATJ_Don
    VE7ATJ_Don Member ✭✭✭

    Hi Amos.. I note the Flex is in WIDE mode, which would imply that you have other panadapters operating on other bands? The WIDE setting (top right) means that the Flex is running without the built-in band filters. If you can, it will help with noise reduction to operate on only a small portion of the band visible on the panadapter.

    It also appears you are running in DIGU mode. Is this for FT-8 or something similar? If so, others can correct me, but I don't think you want any NR turned on during FT-8 operation.

    Specifically, for noise reduction, the best tool is the AGC-T, which you adjust from the 'speaker' icon on the flag. Make sure the NR is turned off (grey colour, such as you have above), then select the speaker icon. At the bottom of the small display that comes up, you'll see a selector (with either FAST, MED, or SLOW) and a slider. This is AGC-T control. Select FAST, and move the slider all the way to the right. Then slowly move the slider to the left until the noise JUST starts to decrease. This is known as the 'knee' or '****'. This works best when your on a clear spot on the band (no signals). Then change the selector to MED.

    If you need additional NR, then select DSP button, select the NR button (it will turn blue) and use the slider to select the amount of NR you like.

    Hope this helps.

  • Amos Sobel
    Amos Sobel Member ✭✭


    Your answer was very helpful but it does create another questions:

    I am using Flex 6600 with 2 Antennas and 4 Panadapters with 1 slice in each. Panadapter . Each slice is feeding one instance of WSJT-X and JJalert. When I connect more then 1 panadapters to 1 antenna, they become WIDE. How many band-filters are there: 1, 2 or 4? Can I connect a band-filter to each slice or there is a limit of 2 or 1?

    I am using a bandwidth of 3 KHz on each slice. Do I gain any performance by spreading the frequency range of the slice to almost 3 KHz?


    Amos 4X4MF

  • Amos Sobel
    Amos Sobel Member ✭✭


    Giving the matter additional thinking I have come to the conclusion:

    1. There are 2 Band-Filters which are just the 2 main processing channels fed by the 2 A/D converters connected to the 2 antennas.
    2. For best performance only 1 panadapter and 1 slice can be connected to each antenna.
    3. For best performance Flex 6600 can operate on only 2 bands and connected to 2 separate antennas. It is possible to bypass the 2 antenna limitation by switching 1 antenna to the 2 antenna connectors.
    4. I am using a bandwidth of 3 KHz on each slice. Do I gain any performance by spreading the frequency range of the slice to almost 3 KHz?I

    Amos 4X4MF

  • VE7ATJ_Don
    VE7ATJ_Don Member ✭✭✭

    Hi Amos.. glad I could help, but unfortunately, you are reaching the end of my technical expertise. I'll try my best, but others (or Flex!) with more in-depth knowledge, please chime in!

    1. I believe the ATU incorporates band filters for each of the ham bands. These are most effective when operating on one band at a time. Having widely separated bands operating on different panadapters will, I believe, bypass these filters by putting the radio in WIDE mode. I can't comment on the rest of your conclusions, although I would expect there to be separate filters for each of the A/D converters.
    2. I would agree with this.
    3. I only have a 6500, so I can't speak effectively to this. Based on what I've heard from 6600 and 6700 owners and my own experience with a single SCU (spectral capture unit, to use Flex's terminology) I think your initial statement is correct, but I'm not sure about the second.
    4. I would say no. Slice bandwidth is dependent upon the mode you are operating and generally, the tighter the better. CW, for instance, works best with very narrow bandwidths (500Hz or so), SSB for me is best @ 2.4Khz, FM is 16Khz. I've heard that 3Khz is good for digital modes (FT8 and the like), but I don't run digital very often so I can't really speak authoritatively about this. As with any SDR, the best performance is achieved by narrowing the 'amount' of signal you are expecting to process at any given instant. Hence, having the panadapter focussed on a specific part of a single band makes life easier for the SCU and the processing software. Having the slice bandwidth reduced to the minimum needed allows it to better see 'signal' vs 'noise' and make the appropriate adjustments.

    Again, I'm not a technical guru in this area and your mileage may vary, as they say. Please others, help me out!


  • K3SF
    K3SF Member ✭✭✭

    hi amos

    i have a 6600m...

    You are correct each scu has a set of band-filters...that operate on all the contest bands...not the warc bands

    so operating more than two bands/scu's will bypass these filter

    Band width of the slice makes little to know effect since the SCU is collecting RF across 15MHZ of RF

    your display shows it operating on 160m on ANT1

    first step to noise reduction on 160m .....Make sure you have turn down the RF gain on ANT1..

    set rf gain to -8db for starters.....

    There is no need a for any receiver ( RF) gain on 160m

    there is nothing to be achieved for noise reduction by having the display just cover 3khz

    as this appears to be some wideband noise, it may help to engade the WNB...Wideband Noise Blanker

    this WNB is extremely effective on wideband band noise

    in addition you can adjust agc-t to where you just start to hear the noise floor rise then turn back ever so slightly

    hope these tidbits help in your quest fro better noise reduction on 160m

    Paul K3SF

  • Tim - W4TME
    Tim - W4TME Administrator, FlexRadio Employee admin
    edited January 2021

    @Amos Sobel what wrote @K3SF is correct. My only comment is if you do not have wideband noise where WNB is visually and audibly reducing the noise, turn it off. Setting the AGC-T properly makes the biggest difference for noise mitigation after you have the RF preamps set correctly.

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