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).

From the CHANGE_LOG file:

From the CHANGE_LOG file:

@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.

And now SDR++Brown has Kiwi support. Audio bandwidth only of course (for now). Nice Kiwi map integration.

I'm still working on "advanced tech" that will make the bandwidth increases mentioned in the posts above more easily obtained. Which would directly translate to increased bandwidth with SDR++Brown.

https://sdrpp-brown.san.systems/#kiwisdr-support

In the next release I'll add a "custom" entry in the SNR measurement interval menu with a corresponding time field where you can enter the number of minutes you want.

I think I can also add a checkbox that asks for each ham band to get a separate measurement in addition to the 0-30 and 1.8-30 MHz measurements.

The most common three Alpha stations are currently active. ID'd by their relative timing using the Kiwi FFT extension with Alpha integration preset. Heard on Kiwi in Finland, Tambov and Khabarovsk.

Questions from the Tech Minds YouTube review:

Yes, it was designed as "shortwave" receiver covering 10 kHz (VLF) to 30 MHz (32 MHz with reduced specs). It is possible to use a downconverter ahead of the Kiwi to cover VHF/UHF and a number of public Kiwi owners have done just that. See here: non-HF Kiwis

The my.kiwisdr.com page will only show information about your Kiwi if the network your Kiwi is attached to has a connection to the Internet at the time it starts up. Also, that network must have a DHCP server to assign a local IP address to the Kiwi. Try restarting the Kiwi. Our documentation describes other methods for determining the local IP address including decoding the pattern blinked out by the 4 blue LEDs.

The BeagleBone Green we used back in 2016 did not include WiFi. There is something called the BeagleBone Green Wireless, but it is not physically compatible with the Kiwi board. Instead, we recommend using a TP-Link TL-WR802N WiFi nano router which can plug directly into the Kiwi's Ethernet connector and your WiFi network. It requires minimal configuration and none on the Kiwi side if you use DHCP to assign the Kiwi its local IP address. Future products will definitely include WiFi.

From the CHANGE_LOG file:

Okay, I think the new admin password reset scheme is working well. See image below.

The option will appear only if you connect from your local network. Not from an Internet connection (e.g. not from a Kiwi-2 serial number based proxy connection: 2xxxx.proxy.kiwisdr.com/admin). Use my.kiwisdr.com to find the local IP address link to your Kiwi's admin page (e.g. 192.168.1.101:8073/admin).

You must also provide the Kiwi's serial number. This should be easy since it's written on the physical hardware (Kiwi-1: written in the white box on the Kiwi PCB, Kiwi-2: written on a label on bottom of case).

As a further security measure the option will only appear for the first 5 minutes after the Kiwi software starts (power-up or software restart).

So the restrictions should guarantee the Kiwi is in your immediate physical control. So no good for your remote Kiwi located 300 km away on a mountain top.

If anyone can think of a flaw in this reasoning please let me know ASAP.

Everything is carefully validated on the server-side. So anyone hacking Javascript on the browser shouldn't be able to exploit the scheme.