FreeDV is a new digital voice system for HF communications. It is discussed in this month’s Practical Wireless magazine. It does look quite impressive. I wonder who will make the first FreeDV SOTA contacts?
Demo at low signal strength:
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Each to their own but I prefer the ssb analogue noise than the modulated digital noise.
Impressive they can get digital voice over that path and I can see the use cases and advantages it can bring. Might have a dabble in it but I prefered the sound analogue ssb makes.
73
Anthony
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It is hardly new. FreeDV has been around since 2015 and the RSGB have been running GB2RS News broadcasts on FreeDV for a couple of years. I tried it for a couple of weeks last year, but soon became bored with it. I concluded that it offered no advantage over standard SSB on the HF and LF bands.
73,
Walt (G3NYY)
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Thanks for the links, Richard. I was vaguely aware of FreeDV, but haven’t investigated further.
Reduced bandwidth, better overall SNR performance. Can sound a bit funny at first. Reminiscent of “Donald Duck” mode which was so disparaged in the early days. Whatever happened to that - I guess it never caught on? 
Open source is good too 
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It’s actually older than that Walt. As I used it twice to transmit the Wireless Institute of Australia (WIA)'s weekly broadcast when I still lived in Australia and I left Australia in February 2014. I’m sure the actual date is shown at freedv.org but my guess is that the first alpha versions came out at the start of 2013.
The latest version with 700D mode (700bits/sec 1.25kHz wide signal) is a major advance over the earlier versions.
Think of this on busy bands - 2 stations in the space of one SSB station and then with the advantage of a narrower bandwidth and hence better signal to noise ratio. Audio quality is still not brilliant but if you’re used to digital voice on VHF/UHF then it isn’t a lot worse than that. A good quality semi-pro microphone helps A LOT on freeDV as does setting the audio processing settings.
I believe it has already been used from a SOTA summit in Australia.
The Chinese RS-918 HF transciever and the Flex 6000 range both come with FreeDV as one of their voice modes and there is also an SM1000 speaker microphone from the inventor of CODEC2 that FreeDV uses if you want to avoid having to have a PC connected to the rig to run FreeDV. At the moment however none of these three options support the latest 700D mode - for that you need a PC beit Windows, MAC, Linux or Raspberry Pi.
73 Ed.
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I had my first freeDV in spring '17 on dm/ns-121. Coincidentally, my qso partner has the same trx as me, a mcHF from M0NKA. Unfortunately, the QRG had a lot QRN.
Here is the video: DL1CR DG5FBO SDR mcHF freeDV - YouTube
After that I had a few QSOs with Wolf, DK1HW.
73 Chris
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FreeDV has now a new mode called RADEV1.
I just had my first FreeDV RADEV1 QSO on 40 meters, and I have to share that it is really impressive compared to the other DV modes: high quality audio on HF without any background noise or QRM, using a lower bandwidth than SSB.
Most stations that can use FT8 should be able to use FreeDV. No special hardware nor registration of any kind needed.
I am available for skeds if needed.
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Should the ITU be encouraged to rework bandplans with a Free DV section in between digi modes and SSB? There’s continual pressure for more bandwidth for digi modes and yet it seems to me, the solution is staring us in the face. Free DV could free up many KHz on our crowded bands.
73 de OE6FEG
Matt
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Hi Matt,
I think it’s the IARU who defines the band plans within the allocated amateur bands, rather than the ITU who gives the first and secondary user of a range of frequencies. In any case, FreeDV has been around for some time and being a voice mode over a digital data channel, it does indeed present some interesting bandwidth reduction capabilities compared to SSB.
The question also comes up whether, being a digital mode, in IARU regions 1 & 2, it may be able to be used on the 30 metre band (some countries in region 3 allow SSB on 30m already).
FreeDV, of course, is larger than a single digital data channel but not as large as the bandwidth used by multiple concurrent FT8 stations, as an example. So while FreeDV may only need around half of the bandwidth of SSB, it does use quite a bit more than most digital data modes.
Using open source code, it may be possible to add the upcoming FreeDV RADE V2 implementation inside the Linux based transceivers which we are starting to see these days as an alternative of needing an attached PC/headset etc.
It’ll be interesting to see how this develops.
73 Ed.
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Of course! IARU, not ITU: bad case of posting before thinking. I think the main point is, that whilst it is technically a digital mode, it replaces SSB, which uses a huge amount of bandwidth per channel. One SSB channel can be replaced with 1 free DV channel, and several WSJTX channels, which represents a considerable easement in terms of bandwith. SSB users would have no cause to complain, as telephony would end up with MORE channels overall, it’s just some would technically be digi. Given the huge rush to FT8, it’s hard to imagine a reasonable argument that Free DV is not possible to implement for the average SSB op. I emailed Elecraft asking if it would be possible to make Free DV native on the K4, they said no problem in principle, but I don’t know if they actually took the idea forward.
73 de OE6FEG
Matt
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Ed,
The commercial hf CODECs used by CODAN apparently work very well but they are guarded with vigour. The amateur ones have been but a shadow of them except on VHF.
I tried for weeks with Waldis VK1WJ (SK) to compete a QSO on 40 and 20 m and failed every time.
Examining the spectrum I could see the effect of ( frequency) selective fading or multi pathing across the signal, swallowing critical bits of code like a hungry black serpent wriggling across the signal spectrum. It was the bane of AM hf transmissions in days of olde. (See edit)
Reducing the bandwidth may not help.
Redundant multiple carriers as per digital TV should work. But it may require 2 5 kHz of BW.
I will wait the outcome of further testing on hf.
73
Ron
VK3AFW
Edit. We called it “phase distortion” back in the middle of last century.
Hi Matt,
Well, Flex have supported FreeDV for several years and one of the Chinese radios “RS-918”? came with it as well, I think.
There is even a plug-in microphone to update standard SSB transceivers (although that is at an old version of FreeDV I think).
For the newer SDR, Linux based radios, technically it should not be a difficult implementation, however those of us who have been testing it for the last 14 years are finding “take-up” rather slow.
73 Ed.
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The mode being digital is irrelevant as band plans are on the basis of bandwidth. So the current IARU region 1 band plan for 30m is divided into two sections for bandwidth of maximum 200Hz and maximum 500Hz.
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I believe many there would also have called Fosters “beer” back in the day.
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Hi Matt, right now they’re quite behind schedule with the software side of things, at a Q&A event at Hamvention they said they didn’t even start working on DPD yet.
I wouldn’t sit tight for FreeDV native support on the K4 (I’m still waiting for CESSB on the KX3).
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Rob,
I wouldn’t get too far into a discussion about beer mate. Fosters was not just one beer and lost its local appeal after a couple of years. Besides, we drink all the good stuff here. 
We have to thank the Dutch for teaching us brewing.
What we were served at Munich Oktoberfest many years ago was cold stuff with aeration. It didn’t compare with other beer else where in Germany and that was a low bar. 
Cheers,
Ron
VK3AFW
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