n6gn

I've not examined recent products from the Ukraine but I can not recommend the earlier transverters. Perhaps the receive converters are different/better.

How much interest would there be in the creation of a fast-switching block down-converter for the Kiwi? This would be something with a high side, say 3 GHz IF preceded by a [20 MHz] stepping LO that went from, 3-6 GHz, mixer and LPF?

The result would be an "all band" down-converter one [20 MHz] swath at a time such that the Kiwi could use any of it's capabilities over 0-3 GHz? NF and IMD could be good and no additional filtering would be necessary as long as out-of-band signals were kept tolerably low compared to a mixer's spec. +20 dBm TOI should be fairly easy. Of course, filtering could be added at the input, as for a band-limited converter of the type most often used.

It would seem to me that a Kiwi extension to use I2C to control the LO/receive_frequency should not be difficult. The goal would be fast switching so that multiple 20MHz chunks might be stitched together to create a wider spectrogram.

Glenn n6gn

I'm attaching a write-up of what has worked well for me to improve Kiwi noise performance by reducing common-mode current paths through the Kiwi.

For a stock, wired-LAN Kiwi it is very common for noise and coherent signal current on the LAN cable to find a path through the Kiwi PCB ground and out either the Power Supply return or, more often, via common mode current on the antenna feed attached to the SMA input. This kind of QRM/QRN is insidious because it may mostly show up when an antenna is attached causing the user to believe the problem is elsewhere.

By operating the Kiwi with an inexpensive WiFi router, powered from the Kiwi and connected by only a single micro_USB <==> USB-A cable, the common mode current paths which can cause this degradation can be eliminated.

Because of the success of this scheme in both improving performance of previously wired-LAN installations and also the possibility of building a completely isolated, portable Kiwi system to use as adiagnostic tool for improving Kiwi and general site performance, I'm offering this description.

Write me for more information or for the 3D printable file for the USB clamp described.

Glenn n6gn

The family of lines in 6.5-7 MHz you suggest seem to me to be power line related, though this is true of many SMPS noise sources. When I detect in 10 kHz AM and analyze with Audacity I see astrong 50 Hz family/component

This is as expected from an imperfectly filtered SMPS input. Furthermore, the spectral width of the lines is consistent with jitter/phase noise of a switcher's rate and it appears to have stronger even harmonic components, as is common from full-wave rectification.

But as to the actual source and coupling mechanism - that's harder to say. There are so many uses for SMPS supplies these days, some of them for lighting related power that an after-dark correlation is not unlikely.

To put things in perspective, while your noise floor is no doubt raised considerably by this, you are in pretty good company and a lot kiwiSDRs reveal similar and worse results. If you are using a well matched antenna, your noise is about 30 dB above kTB which isn't so dreadful at that frequency. OTOH, it may be higher than that if your system is not well matched to the radiation resistance. You could be seeing CM currents, current in the earth below or other coupling mechanisms. I suggest not first considering it to be inverse-square radiation. That is actually much rarer, in my experience.

Glenn n6gn

I just run multiple tabs in a single browser, one tab/kiwi-receiver. That allows separate audio, squelch ... for each of the receivers.

It's sometimes useful to do this on kiwis that differently located and experience varying and different propagation. One can pick the best, even run squelch and let the best one win. There can be a differential delay problem but that can be dealt with.