Comparing the Airspy HF+ And KiwiSDR on Shortwave Radio

The Airspy HF+ and the KiwiSDR are two HF specialty SDR radios. The HF+ advertises excellent dynamic range and sensitivity, whilst the KiwiSDR has it's strength in it's internet connectivity and 30 MHz wide live bandwidth.

Over on YouTube icholakov has uploaded a video comparing the two SDRs on daytime medium wave and shortwave reception with a W6LVP amplified magnetic loop antenna. It is expected that the two SDRs should be quite similar in easy receiving conditions, but the Airspy HF+ should shine in challenging conditions with strong blocking signals and weak signals being received at the same time. The Airspy HF+ should also be a bit more sensitive in all conditions. It's not clear if there were any strong blocking signals in the tests, but the results appear to confirm the sensitivity expectations.

KiwiSDR and Airspy HF+ comparison

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Joao Fonseca

Hi Martin,

Many thanks for your reply.
I have an antenna switching as I have three different HF antennas: one loop, one LOG, and one skywire loop antenna. They are not close to my house.
So according to what you said, probably the best would be to forget the purchase of a kiwiSDR and just stick with the Airspy, correct?
I’m really happy with the Discovery but lacking android support and needing a software to be running (instead of a website) is a shame.

Martin - G8JNJ

Hi Joao,

If you have a low noise floor you may be able to take advantage of the Airspy, so in that case it would probably be the best option.

Joao Fonseca

Which one has the best SWL reception?
Airspy with the latest fw or the kiwiSDR? Shame that the Airspy can’t be acccessed via mobile, only with a computer and kiwiSDR in that regard is much more flexible.

Martin - G8JNJ

Hi Joao,

They serve two different purposes, so it’s like comparing apples with oranges.

The Airspy has better sensitivity and dynamic range but you can only see a small section of the spectrum.

The KiWi is less sensitive and has a reduced dynamic range, but you can see the whole of the spectrum from 1KHz to 32MHz, it has built in decoders and you can use it on any device that has a browser with a network connection.

However, unless you have the space for a large antenna farm somewhere well away from interference sources you can’t really take full advantage of the Airspy’s specification.

You can always use other peoples KiWi SDR’s anyway, so in most cases if you can only have a simple wire antenna strung near property, then a SDR Play RSP1A is probably adequate and costs less than either of the other two.


Thank you for your replies, i did not spend a lot of time listening with KiwiSDR and i did not mean that the browser’s software does not receive well once tuned properly but i find the operations a bit slow and when you explore signals you need to move fast. Working on the browser is also slower than working on a desktop software, at least for me. Maybe i should switch from Firefox to a lighter browser..
However i did not think to the possibility to pipe the I/Q audio to a SDR software; this is one more option to explore.
Thank you for the precious informations!


i posted in the wrong place sorry; this follows up my post and the replies from Timmy and Martin

Martin Ehrenfried

Hi Max,

The KiWi can be slow if you are using it remotely via an internet connection. The problem is not really with the KiWi but is due to network latency. If you own KiWi and connect over a local network the speed is pretty good.

Maybe this conversation is moving away from the intended pupose and use of the KiWi, as the HF+ is really designed for a different type of use.

Martin Ehrenfried

There is a flaw in this test – it’s the antenna.

Most active antennas do not provide sufficient dynamic range (the maximum signal level that can be received without unwanted distortion products relative to the antenna noise floor and the amplifier noise floor itself).

It is likely that both receivers have better performance than the antenna is capable of providing, so it would be hard to spot any differences between the two SDRs.

Differences between the two SDR’s AGC and receive bandwidth settings would also modify the results.


KiwiSDR is a great receiver with its 30mHz bandwidth but the software is at the same time the reason of its success and its limit. It’s a big advantage being able to access many receivers with the browser and that’s what made KiwiSDR’s success but the software is not at the same level of others like SDR Console. I would like to know if technically these SDR softwares installed in the pc could be developed to support KiwiSDR for the owner’s use or what prevents from doing it.


It would mean that the current software would need to be modified to accept a pre-calculated waterfalls (1024 pixels with 12 fixed levels of zooming) and up to four 24-bits 8.25 kHz IQ channel. It would probably also require some kind of custom stub code to execute on the beaglebone black to start and stop streaming raw IQ channels, retune channels, change zoom level, and ….

Martin Ehrenfried

Hi Max,

Although SDR console is very nice to use, it doesn’t really do much more than is possible via the KiWi interface.

You can set the KiWi up into an 8 channel mode where only the first two receivers have a full waterfall and the other 6 only have a narrow waterfall around the RX frequency. So if you own a KiWi you can actually receive 8 channels at once anywhere in the 0-32MHz spectrum. Many casual KiWi users don’t realise that it also has adjustable receive bandwidth and AGC plus a selection of built in data decoders including FSK, SSTV, CW and WSPR. Take a look at some of the options in the drop down control panels.

If you wan to use an external decoder / demodulator you can record I/Q audio from the KiWi and download it, or you can synchronise KiWI SDR with HDSDR or an actual radio by using

Use Virtual audio cables to pipe I/Q audio (12KHz Bandwidth) from you web browser to the I/Q input of HDSDR. You can then tune the KiWi using HDSDR and use the functions on HDSDR to demodulate the I/Q stream. By doing this you have the KiWi available as a wide spectrum display but can use the extra controls on HDSDR.

Cat Sync may eventually incorporate a rig emulation so that you can control a KiWi from other software such as SDR Console or decoder programs such as Multipsk etc.

If you want to perform really sophisticated demodulation you also can pipe I/Q data from the KiWi to Gnu Radio.


Martin – G8JNJ