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apf gain control needed. 0-10db adjustable would be great.



  • Walt - KZ1FWalt - KZ1F Member
    edited November 2016
    Steve, that sounded like a great explanation. I say that because I kinda sorta understood it. However, as I don't have much of a horse in this race, vis-a-vis, the EE of making a signal better, the issue has been mentioned a couple of times in this thread about how it worked better pre-SSDR 1.2. Could I maybe impose upon you to explain what changed and why? I could be wrong and I hate speaking for others but it sounded to me like some were saying it was better then.

  • Steve N4LQSteve N4LQ Member
    edited September 2015
    Now since we're on the subject. Could you explain why AGC-T has to be manual? To the outsider it would seem easy to have the software decide the optimum setting instead of the user fiddling around looking for "sweet spots" as if this were a Hammarlund HQ-129. The whole thing seems so archaic.  I know other rigs use hardware AGC loops. Is there an aversion to that for some reason?
    Steve N4LQ
  • W5UN_DaveW5UN_Dave Member ✭✭
    edited November 2016
    N5AC Steve, I can only speak from what I experience by comparison: my K3 APF severely out performs the 6700 APF. I believe the K3 APF is also done in software.

    I appreciate and commend what you guys at Flex are doing. Keep up the good work.
  • Steve N4LQSteve N4LQ Member
    edited September 2015
    As for the K3's APF. Having owned a K3 for 7 years I'll make the claim that its APF sounds better because without it the radio is noisier and APF has more to work with. It's just a matter of contrast.
     Face it....If there were no noise getting past the normal filters, APF would be redundant a fact proven by the Flex. The much used term "signals seem to pop out of the noise" really applies when there is noise to "pop out of". 

  • Al_NN4ZZAl_NN4ZZ Loganville GAMember ✭✭✭
    edited December 2016
    N5AC Steve,
    Does the FLEX  APF operate in the audio domain where I assume the RX equalizer operates?   My assumption is that APF is essentially a super narrow audio equalizer.  It would boost the audio signal at the sidetone audio frequency and within the bandwidth selected.  It would attenuate the audio frequencies outside the selected audio bandwidth.  And providing more control over the boosted bandwidth and gain would allow us to tailor the performance to our liking.   (essentially like the Autek QF-1A and other external audio filters).   Is this a correct assumption or does the APF operate at a different stage in the FLEX 6000?

    Do you know where in the signal chain the APF is located in the K3?

    I guess the big question is:  Can the APF be better or is the current performance the best we can expect to see on the FLEX? 

    Regards, Al / NN4ZZ  
    al (at) nn4zz (dot) com

  • W5UN_DaveW5UN_Dave Member ✭✭
    edited February 2019
    Steve, my experience with the K3 APF was over the last several years on 160 meter DXing where signals can be challenging. I would try with the 6700, and then always go back to the K3, where I could dig the signals out better. The two radios are side by side with antenna switching and separate keys. Maybe it's just me, but I know what works best here.

    Let me finish by saying I want my 6700 APF to work as well or better than the K3 APF. As far as noise, well yes, 160 has plenty of that.
  • Steve-N5ACSteve-N5AC Community Manager admin
    edited December 2016
    Would you be willing to do a video recording of both on the same program material and show us what the differences are?  We'd be happy to do an analysis and see if we can't make things better.
  • Steve N4LQSteve N4LQ Member
    edited September 2015
    That could end up like my video comparing the K3 to the 2B. https://www.youtube.com/watch?v=Z9mAzxkuk18
  • W9OYW9OY Alpha Team Member ✭✭
    edited June 2015
    I did a recording and I think the APF works fine.  If you want the post AGC effect simply turn off the AGC and set it to a level consistent with the volume you want.   OMG run without AGC!!!  Yea you get blasted once in a while... so what.  There are many ways to make this radio do what ever you want.


    73  W9OY
  • W5UN_DaveW5UN_Dave Member ✭✭
    edited February 2019
    Steve, I just again sat down to do a side by side comparison of APF's. and found by using W9OY's method, the Flex APF does a pretty decent job. I now see where my real issue is, ease of adjustment. Finding an extremely weak 40 meter signal (no waterfall detection) out of Europe in mid afternoon here I again did the comparison. It was really easy to peak the signal on the K3 with the APF engaged, by using the shift knob to find the sweet spot. What is happening on the K3 is that the knob changes the AUDIO pitch, not the frequency. This is what is lacking on the Flex: the ability to change the audio pitch. Am I wrong here?  I think the question was asked earlier by someone about whether the Flex APF is an audio filter or is it something else. If it is an audio filter, and if a button on the Flex Control were to be programmed to allow the Flex Knob to adjust that pitch in 5hz increments, I think that would be perfection for me!
  • Steve N4LQSteve N4LQ Member
    edited September 2015
    To aid in understanding Dave's post here is a snip from the K3 manual:

    APF and Dual-Passband CW Filtering In CW mode, DUAL PB is used to turn on either an Audio Peaking Filter (APF) or Dual-Passband Filtering. Both are described below. CONFIG: DUAL PB selects the desired function. APF can make a dramatic difference in copy of weak signals buried in noise. When APF is turned on, SHIFT fine-tunes the center pitch, and NOR M resets the pitch to that of your sidetone. The filter graphic will be similar to that shown below. Dual-Passband Filtering (Dual PB) sets up a 150- Hz-wide focus filter, set within a wider context bandwidth that is attenuated by about 20 dB. This lets you hear off-frequency CW signals, which may be useful if you’re calling CQ, running a net, etc. WIDT H varies the width of the context filter. The filter graphic appears as above.

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