jks

Here is a very early demonstration of using the Kiwi's synchronous AM detector (SAM) to subtract one sideband from the other. So a strong on-channel signal that is covering up a weaker one (either on-channel or close by) can be attenuated. This is something I'm tentatively calling "channel nulling". There is much work to be done, but this is at least an existence proof.

In the first image there is a local powerhouse on 882 kHz and a much weaker carrier on 880 kHz can just be seen in the RF waterfall (green arrow).

In the second image "null LSB" has been selected from the new menu on the SAM line of the audio tab (bottom right). This puts the SAM detector in "SAL" (synchronous AM LSB) mode such that the USB component is not passed through to the audio. However, just prior to that the USB component is subtracted from the LSB, and, given the sideband symmetry of AM signals, the LSB is effectively nulled (to a varying degree). In the spectrum display above the waterfall you'll note the weak station carrier 2 kHz away now appears above the noise and, sure enough, a Spanish language station can be heard which was impossible previously.

The "spectrum display" in this case is not the usual spectrum data from the RF waterfall but rather a single-sided spectrum of the audio channel (hence symmetry either side of center). Note that an extension called "FFT" has been selected. This is going to be an expansion of the existing "integrate" extension to include more general audio FFT and spectrum capabilities.

The RF waterfall doesn't change between these two images because it is from the RF/IF path and not the demodulated/nulled audio.

This technique is not perfect. Due to the subtraction involved It depends on excellent USB/LSB signal symmetry which can be easily upset by frequency selective fading. A very common problem on shortwave and medium wave at night (at a time when you're most likely to want to use such a feature). But in the presence of fading the nulling effectiveness will vary and it just might give you the chance to "bag a new one" on MW if conditions are right.

As usual, many thanks to Youssef of AirSpy who recently pioneered this idea. A superior implementation is found in SDR# (the "Co-Channel Canceller" https://swling.com/blog/?s=co-channel). Maybe someday I'll understand how he does it (but probably not, lol).

Bump. You know, for the incoming shit-storm.

v1.689 (and later) has countermeasures against the "botnet".

v1.690 (and later) is necessary for your Kiwi to resume using the proxy service.

These updates will happen automatically overnight (local time) unless you've disabled automatic updates. You can manually update by going to the admin page "update" tab and clicking "build now" and waiting 30 minutes or so for the build to complete. Your Kiwi will restart when the build is complete.

Don't start multiple threads about the botnet topic. They will be deleted.

The proxy service has been disabled because the money (for which I am not compensated) is now flying out of my back pocket:

I will try and develop a fix in the code to better identify and remove these connections.

Update: The proxy service has been re-enabled if you're running v1.690 or later.

The new git "rebase" I'm working on reduces the size of the Kiwi repo by about 90% to 55 MB. So that should fix this problem.

@ok1iak Well, here we are. Over two years later. I had not forgotten about this. For various reasons I decided now was the time to give it a try.

This is an extremely early result. There are all kinds of problems. Currently, all I can get semi-reliably without too many glitches is a wideband output of 240 kHz. I'm pretty sure more can be done with some optimization. There is no CIC filtering in the FPGA yet, so there is aliasing.

To get SDR++ working as quickly as possible on my Mac the easiest thing to do was write a very quick and dirty SpyServer implementation (partial) from the public spec. That's why below it says "SpyServer", "Int16" and "RTL-SDR". But it really is connected to a Kiwi-2 on the special SpyServer port 5555. I have not tried SDR# yet. This Kiwi is on the other side of the world from me. So it is streaming at 240 kHz over the Internet successfully.

You can't make any Kiwi user connections when the Kiwi is configured for wideband mode. But you can make an admin connection. Lots and lots of work to do before this is ready for any sort of release.

The cases have arrived and David, ZL2BA, has been busy assembling the units.

The store should open in less than a week. Everyone that emailed sales@kiwisdr.nz will receive an email reply when the store opens. It will also be announced here, on Twitter and the various web pages.

Many units will be shipped to ML&S (UK) and WiMo (DE) as well.

Thanks everyone for your ongoing support and patience.

Just waiting on the container with the cases now. Units otherwise assembled, programmed and ready to go. Should be in a week or two (early July).

Another build for August/September already underway.

Okay, I added a plugin that allows some content to be added to profiles. For now just Location, Callsign and "Additional information". Let me know if you think we should have others. Look at my profile as an example (click "jks" at the top of this post).

The content isn't presented very optimally. It just appears at the top of the user's profile page.

I also re-enabled the "reactions" feature (i.e. adding "helpful", "awesome" to posts like we used to have).