VRT and VITA 49 — a video and discussion about Radio Transport Protocol Objectives, Overview, and Ap

John WA7UAR

K1VL

Terry K8EET

Most of it is over my head but it looks like the future of communications is still evolving. CW Forever.

John WA7UAR

The reason I posted it is because our Flex ecosystem uses Vita 49 (.0?) and the video and PDF are now talking about .2. It was also interesting to hear him talking about how important it was for .2 to incorporate the .0 API. It had echoes to me of the recent Flex upgrades to its API. I’m imaging a long term project that allows Flex users anywhere to share receivers and transmitters among themselves globally. Want to work Europe the easy way? Use the Vita 49.2 protocols to find an available transmitter somewhere near the grid that you are looking for and give a call.

John WA7UAR

Here is a short 2019 update about VITA 49.2, again from Roger Hosking. I’m hoping to hear more from interested Flex users who see the potential in upgrading our equipment to incorporate this expanded protocol.
https://www.vita.com/VPX-News-Portal/...

John WA7UAR

I came across this "Software-Defined Radio Handbook: 12th Edition" from August 2016 by Rodger Hosking (who I have mentioned in this thread previously.) The opening Preface is provided below. The handbook contains well written (and largely comprehensible) information that (I strongly suspect) forms the engineering underpinnings of the 6xxx Radio Servers from Flex. And since this is from a public source I wanted to share it with all of you.

Quoting, "SDR (Software-Defined Radio) has revolutionized electronic systems for a variety of applications including communications, data acquisition and signal processing.

This handbook shows how DDCs (Digital Downconverters) and DUCs (Digital Upconverters), the fundamental building blocks of SDR, can replace legacy analog receiver and transmitter designs while offering significant benefits in performance, density and cost.

In order to fully appreciate the benefits of SDR, conventional analog receiver and transmitter systems will be compared to their digital counterparts, highlighting similarities and differences.

The inner workings of the SDR will be explored with an in-depth description of the internal structure and the devices used. Finally, some actual board- and system-level implementations and available off-the-shelf SDR products and applications based on such products will be presented."

And the link to the handbook is: https://cdn.everythingrf.com/live/software-defined-radio-v12.PDF

Your continued comments and insights are welcomed here in this thread. And... I'm tagging @Tim - W4TME ;-)

Lasse SM5GLC

Looking at an old Youtube video: https://www.youtube.com/watch?v=LuWaStl0GgI

N5AC presents VITA49.0-2009 when talking about the API. Not sure if this is what been implemented though.

John WA7UAR

@Lasse SM5GLC VITA 49.0 is what is implemented in the Flex architecture. I'm interested in seeing what it would take to get everyone to VITA 49.2.

Thanks for your Youtube video reference!

John WA7UAR

At the recent March 2021 QSO Today Virtual Ham Expo, Steve Hicks, N5AC and VP of Engineering at Flex, gave an excellent presentation about "SDR as a Platform" and gives additional insights into VITA 49 as part of the Flex ecosystem. This YouTube link starts at at 12:35: https://www.youtube.com/watch?v=BMc4hoVcJE8&t=755s

KD0RC

Thanks for the link John. That was a really informative video. I have almost no knowledge of VITA 49, but with the IW7DMH Arduino library (which parses VITA 49), I am able to control a Flex radio pretty easily.

John WA7UAR

Fantastic insight and information @KD0RC !

Here is a link to the Arduino library you referenced that parses VITA 49:

https://iw7dmh.jimdofree.com/flexradio-related-projects/arduino-flex-libraries/flex-library/

Nick RN3KK

@John WA7UAR many tnx!

John WA7UAR

Documenting more insights about VITA-49 from @Annaliese - NH6Z (starts at 22:05):

https://www.youtube.com/watch?v=sUhLGnixdaM&t=1325

K1FR

John:

Thanks! Most interesting.

Just wondering if you have looked at the I/Q values coming from the Flex via VITA-49? If so, please let me know what kind of levels you see for individual I and Q samples.

I have been playing around with some code to process that data and find the individual I and Q samples seem extremely large (posted details in a fairly long thread on this forum back in September time frame). To try to make sense of things and establish a reference for something that works, I backed off to just using the IQ streams via the Windows Sound System (WSS) and found the levels there are much more reasonable - when processed, they give Power Spectrum Density numbers that essentially overlay what the Flex is showing on the SSDR display. When using the UDP VITA-49 stream, the PSD does not come anywhere close.

Hoping to find out what is going on in the Flex VITA-49 stream. Its I/Q values are two to three orders of magnitude larger that the WSS IQ numbers. Am guessing it is something lacking in my understanding.

This project for me has been mainly a learning exercise. At this point, I am hoping someone more experienced could share data.

Thanks again.

73, Tom K1FR

Nick RN3KK

Hi Tom. Maybe you're not converting types of data correctly? For example, the number of bytes in a number can be different.

K1FR

Nick: Thanks for the reply. Well, certainly could be the issue. However, the values are supposed to be Float32, and that is what my results show. I did try looking at the 32 bits as INTs as well just in case.

The WSS I/Q values are indeed Float32s. They work fine in the Python code I wrote.

My UDP VITA-49 code is also in Python. Another Flexer sent me some C++ code he has used. That produced the same I/Q values as my Python stuff. Still lots of room for something going one I do not understand for sure. Learning curve is still pretty steep here. 😀

73, Tom K1FR