jks

About

Username
jks
Joined
Visits
22,705
Last Active
Roles
Member, Administrator, Moderator
Points
203
  • QRSS and the Kiwi

    A simplistic but useful way of thinking about this issue is this: Suppose the waterfall is slowed to draw one line every ten minutes. During those ten minutes it could be sampling at ~21 Hz (full rate) and integrating those samples so the coherent QRSS signal is gaining a huge SNR advantage over the random noise. But the waterfall doesn't do that currently. It would just sit idle for ten minutes then take one sample.

    The integrate extension does a little better. It does integrate every time its waterfall output wraps around top-to-bottom. If the integration period (time to draw everything top-to-bottom) is short (e.g. 1 sec for time stations) then this is useful. But it isn't designed to work any better with long periods. So it's no good for QRSS signals.

    On the wish-list for a long time is a high-resolution FFT extension. One that could for example be used to resolve the millihertz differences of AM BCB stations (a technique already used very effectively by AM BCB DX'ers). Such an extension would naturally do long-period averaging in addition to high frequency resolution.
    k5mo
  • Whistle or tone when not tuned exactly - version v1.397 [fixed in v1.398]

    Your IQ balance is almost certainly off as a result of pushing the "IQ bal" button in the IQ display extension when not tuned to a quiet part of the spectrum (or having the antenna disconnected). There is a topic explaining all this: http://forum.kiwisdr.com/discussion/699/why-a-beat-in-am-incorrect-iq-offset/p1

    Easiest way to confirm this is to check the beginning messages in the log tab on the admin page. You should see numbers for the I and Q balance that are either the default (-0.02) or roughly the same. Example:
    Thu Jun 18 15:46:49 00:00:32.361 ....      using DC_offsets: I -0.020000 Q -0.020000
    
    Powernumpty
  • 30 min disconnection!?!?

    Time remaining (if any) appears in orange in the "users" tab of the main control panel as "h:mm:ss" counting down towards zero. The suffix is "act" if the limit is on activity per connection and "24h" if the limit is per 24-hour period. The time in white preceding is how long you've been connected and counts up.

    image
    mdfrc99WA2ZKD
  • 30 min disconnection!?!?

    Time remaining (if any) appears in orange in the "users" tab of the main control panel as "h:mm:ss" counting down towards zero. The suffix is "act" if the limit is on activity per connection and "24h" if the limit is per 24-hour period. The time in white preceding is how long you've been connected and counts up.

    image
    mdfrc99WA2ZKD
  • RSSI value doesn't match Spec plot

    The S-meter code is literally:
    s_meter_power = I*I + Q*Q
    s_meter_dBm = 10.0 * log10(s_meter_power / SND_MAX_VAL)
    s_meter_value = an_averaging_function(s_meter_dBm)
    
    Where I and Q are the two quadrature components (complex number) of the audio signal after passband filtering. So it contains all the data you see (and hear) within the yellow passband area on the waterfall, except that the actual data is coming from the audio path not the waterfall path. So it doesn't have anything to do with the spec plot. The spec plot is just the waterfall data plotted in a non-scrolling way (as a 2D graph).

    It's easy to forget because they both typically tune together. But the audio and waterfall are two entirely independent DDC (digital down conversion) receivers. You can re-tune the waterfall to go look at a completely different part of the spectrum without effecting the currently received audio. So a "4-channel" Kiwi is actually an 8-channel DDC SDR. This is why the unbalanced FPGA configurations are possible, i.e. rx8_wf2. The lack of waterfall on the other 6 audio channels is made up for by the audio FFT computed on the browser basically for free.
    bensondjacobs