jks

One of my tests of the new 20 kHz bandwidth mode was to run my Kiwi with 3 simultaneous connections, each using the WSPR extension, to put some load on the system. My active antenna coupler has been broken for months now as evidenced by the "flatline" waterfall/spectrum I have (save the Ethernet spurs). I think there is a broken wire, component etc. someplace such that I essentially have an air gap in the connection (AM BCB signals are 45 dB down from where they should be). So I didn't expect the WSPR decoder itself to be running for long after the two minute capture window.

Well, you can guess what comes next. I take a look 30 minutes later and all 3 bands (40m/30m/20m) are filled with WSPR decodes. Including a guy 400 km away running 10 mW on 30m. This was in the middle of the day. SMH. From the upload to wsprnet.org:

26 spots:
 Timestamp           Call        MHz         SNR Drift   Grid        Pwr     Reporter    RGrid       km      az
 2018-12-31 01:34    ZL1TIU      7.040105    -26     0   RF73je      0.2     ZL/KF6VO    RF82ci      156     127 
 2018-12-31 01:32    ZL2MWS      10.140160   -22     2   RE78mv      0.01    ZL/KF6VO    RF82ci      397     15 
 2018-12-31 01:28    ZL2MWS      10.140246   -21     2   RE78mv      0.01    ZL/KF6VO    RF82ci      397     15 
 2018-12-31 01:25    ZL1TIU      10.140203   -15     0   RF73je      0.2     ZL/KF6VO    RF82ci      156     127 
 2018-12-31 01:25    ZL2IK       10.140241   -6      0   RF74ci      1       ZL/KF6VO    RF82ci      285     142 
 2018-12-31 01:25    ZL1VCC      14.097009   -6      0   RF81cu      5       ZL/KF6VO    RF82ci      56      0 
 2018-12-31 01:20    ZL1ER       14.097151   -15     0   RF81du      0.05    ZL/KF6VO    RF82ci      56      352 
 2018-12-31 01:20    ZL2MWS      10.140130   -17     1   RE78mv      0.01    ZL/KF6VO    RF82ci      397     15 
 2018-12-31 01:18    ZL1TIU      14.097104   -25     0   RF73je      0.2     ZL/KF6VO    RF82ci      156     127 
 2018-12-31 01:16    ZL2IK       10.140243   -5      0   RF74ci      1       ZL/KF6VO    RF82ci      285     142 
 2018-12-31 01:16    ZL1TIU      10.140203   -16     0   RF73je      0.2     ZL/KF6VO    RF82ci      156     127 
 2018-12-31 01:14    ZL1VCC      14.097008   -9      -1  RF81cu      5       ZL/KF6VO    RF82ci      56      0 
 2018-12-31 01:14    ZL1TIU      7.040105    -22     0   RF73je      0.2     ZL/KF6VO    RF82ci      156     127 
 2018-12-31 01:12    ZL2MWS      10.140145   -20     0   RE78mv      0.01    ZL/KF6VO    RF82ci      397     15 
 2018-12-31 01:08    ZL1ER       14.097151   -21     0   RF81du      0.05    ZL/KF6VO    RF82ci      56      352 
 2018-12-31 01:08    ZL2MWS      10.140150   -21     0   RE78mv      0.01    ZL/KF6VO    RF82ci      397     15 
 2018-12-31 01:06    ZL2IK       10.140243   -5      0   RF74ci      1       ZL/KF6VO    RF82ci      285     142 
 2018-12-31 01:06    ZL1TIU      10.140203   -15     0   RF73je      0.2     ZL/KF6VO    RF82ci      156     127 
 2018-12-31 01:04    ZL2MWS      10.140137   -21     1   RE78mv      0.01    ZL/KF6VO    RF82ci      397     15 
 2018-12-31 01:04    ZL1TIU      7.040105    -24     -1  RF73je      0.2     ZL/KF6VO    RF82ci      156     127 
 2018-12-31 01:02    ZL1VCC      14.097009   -25     -1  RF81cu      5       ZL/KF6VO    RF82ci      56      0 
 2018-12-31 00:56    ZL2MWS      10.140183   -25     2   RE78mv      0.01    ZL/KF6VO    RF82ci      397     15 
 2018-12-31 00:56    ZL2IK       10.140242   -8      0   RF74ci      1       ZL/KF6VO    RF82ci      285     142 
 2018-12-31 00:56    ZL1TIU      10.140203   -7      0   RF73je      0.2     ZL/KF6VO    RF82ci      156     127 
 2018-12-31 00:54    ZL1TIU      7.040105    -21     0   RF73je      0.2     ZL/KF6VO    RF82ci      156     127 
 2018-12-31 00:52    ZL2MWS      10.140144   -22     0   RE78mv      0.01    ZL/KF6VO    RF82ci      397     15 

Three channels at 20 kHz is subject to being reduced to only two depending on experiences with stability. I would have set it at two but I couldn't get the FPGA code to compile using only two channels for reasons I still don't understand. From the CHANGE_LOG file:

v1.250  December 31, 2018
    Add 20 kHz wide audio bandwidth mode.
        A third entry to the list of FPGA configurations. See admin "mode" tab for details.
    
    Add Ethernet 10/100 speed select to admin network tab.
        The speed changes after a few seconds of delay (no Kiwi restart required).
        This allows you to be looking at a waterfall in another window and see if
        the Ethernet spurs (if present at your installation) improve or not.
        Be sure the device (router, switch) your Kiwi connects to supports 10 Mbps Ethernet.
    
    Accept 'k' & 'M' scaling suffixes in frequency and passband parameters.
        Examples: Type "/15k" in frequency box to get a 15 kHz wide passband. Or "/2.7k", "-5k,10k" etc.
        Use a URL of "...?f=7.4M/16.5k" to set a frequency of 7.4 MHz and passband of 16.5 kHz.
        Note uppercase 'M' since 'm' is already keyboard shortcut for mute.
        You can remember this because the 'M' in MHz is always capitalized whereas 'k' in kHz is not.
        Note also 'k' used to be paired with 'j' as the frequency up/down jog shortcut.
        Now use the 'j' and 'i' keys are used (also 'J' and 'I' to jog faster).
        Using the 'i' key is actually more natural because it fits the placement of your
        index and middle fingers better than 'j' and 'k'.
        Finally, 'i' was previously used to select IQ mode. Now use 'q' instead.
        Type 'h' or '?' to see the complete keyboard shortcut help panel.

Chris,

Since the very beginning people have asked for a mode where the Kiwi could act like a traditional SDR, providing a single IQ channel with as wide a bandwidth as possible (so external SDR software could be used etc.) I have resisted doing this because its not really in keeping with goals of the project. You can buy cheaper/better SDRs if this is what you want to do.

But it seems like we're slowly going in that direction. We didn't used to have IQ output, or an external connection API, or even the selectable channel configuration modes that we do now (4snd + 4wf or 8snd + 2wf). So maybe someday we'll end up with a third option of a single channel at whatever bandwidth turns out to be possible.

As to what the single channel bandwidth might be, well, that's a difficult question. There are some bottlenecks due to the simple low-cost design of the Kiwi. It would just have to be tried with increasing bandwidth until there started to be buffering/realtime-response problems. Since you can get 8 channels at 10 kHz each now you would expect a single channel at 80 kHz (minimum) shouldn't be a problem. That's probably correct.

Press 'x' to quickly toggle the visibility of all control panels.

Press 'y' to toggle the top bar and band/tag bars as follows: both visible, one visible, the other visible, none visible. The frequency scale remains always visible.

Mobile-device equivalents of this, and mobile improvements in general, are being thought about.

It's also worth noting that the SEEED metal case does not have a direct connection between the antenna ground, or any ground, that may or may not, be provided by the DC input cable. So the metal case is effectively 'floating' at whatever potential it likes, relative to the other ground connections.

I first read this as implying there was no connection between the antenna ground (SMA outer threads or green header block GND terminal) and the Kiwi, Beagle or enclosure grounds. Just to be clear, that notion is false. They are all grounded together. It is true that the ground of the DC input passes through the CMC which has a significant resistance from a grounding/ESD perspective.

What the Kiwi doesn't have is a ground loop that would occur if the outer RF SMA threads were attached to the metal enclosure. That's why there is that oversized cutout surrounding the SMAs. I actually measured a small increase in the noise floor during enclosure design with the RF SMA connected to the enclosure.

The question of establishing a proper system/ESD ground is very valid. Most of this has to be solved external to the Kiwi. Probably a stiff earth ground wire should be attached to one of the screws of the enclosure and a power supply and antenna connection used that does not provide a DC path to earth ground. It important to note the Ethernet RJ45 is transformer coupled for ground loop / safety considerations. But voltage spikes/pulses can still get through hence the ESD precautions.

The BBG schematic and RJ45 schematic are attached. The scrubbed values on the RJ45 are 75 ohms and 1000 pF.