jks

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.

No time soon. I have to do something about mobile. It's intolerable. And Daniel has been rightfully taking me to task, viz:

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.