n6gn

Getting rid of differential noise is fine, though the power management IC regulators in the Kiwi's BB is so good that this is seldom to never a problem, in my experience. (Try deliberately introducing differential noise and check the Kiwi's response. I haven't done this for a while but I think even 100 mV tends to be pretty invisible)

But just looking the schematic of this typical linear regulator and wondering ...

What would happen if we built a PS, either linear or SMPS and then added another series pass device in the 'GND' leg of the output to raise the impedance and reduce CM current? Against typical CM source/load impedances, would it significantly improve the situation in real circumstances?

It likely might not since typical total CM impedance may be in the 100's of ohms territory and well above the effective resistance of the series pass devices, but it wouldn't be difficult to try.

I think the question was reasonable since it was "using down converters". For this reason using a frequency converter/extender such as the 0-2 GHz transverter I use here suggests the value of having many additional bands listed as options.

Amateurs have already made a great deal of use of narrow band modes above HF, particularly WSPR on 2m and shorter wavelengths.

6m FT8 is very active now in the Northern Hemisphere as we are in the midst of the sporadic E season. With the LO offset JKS has added, the KiwiSDR already natively supports all-modes on all-bands. Adding FT8 support and even all-extension support makes a lot of sense to me.

Why not support it all in a Kiwi?

I worked in an HP microwave lab and as I remember the production line spec for torque was surprisingly low, only 7 inch-pounds. That was with quality connectors on the highest quality vector network analyzers as well as on swept signal sources. As time went on other connector types good to above 18 GHz came to the fore but I don't think they were tightened more.

As Martin suggests, it's very easy to over-tighten these beyond that specification thinking it will make things better. It probably will only make things worse.

Glenn n6gn

Just 1:1 on small PCB, SMA male to Kiwi Completely isolated from SMA female to antenna feed line. This leaves only about 1 pF of common mode coupling between Kiwi and antenna line.

top side of board shown above, Center tap, if present T1-1T, is unused.

T1-1 from Mini-Circuits,

SMA edge connectors from eBay,

unzip & drop .brd file onto OSHPark.com. 3 boards postpaid in US in about 10 days, probably < US$5.

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