Narrow-Bandwidth Television Association

The last link is interesting. (no audio), any further information?

Steve A.

Steve Anderson wrote:The last link is interesting. (no audio), any further information?

Steve A.

More here Steve as i recall he explains the system in one of the earlier videos you might understand how he has done this

https://www.youtube.com/@kargaroc386/se ... %20line%20

Hi All,

I have setup a Get-hub account, both the NBTV_TX and the NBTV_RX files are there for version 2.9. Here is the Link: https://github.com/GrantXTV/NBTV-Project

There are bugs in the software, let me know if there is any issues getting the files and installing them?

In the last few day I have experimented with different ideas for the configurations for the modulator and the demodulator, I tested out the new design with sending to file and receiving back from file. As I still running my CPU full out at 100%, giving me a frame rate of about two video frames per second. Once I get some feedback from the encoder / decoder software that up on on GitHub, I will make the GNU Radio files available to limited number users to tryout. As it is not that easy do a full testing with my current hardware, until I can get a newer computer to work with.

Here are a few images showing the upper level of the GNU Radio modulator and the demodulator, with the other one showing testcard F, of the video coming back to the decoder. I was testing with mode 4 the uncompressed video mode at 120 x 96 x 8, 1/3, as I get a number of errors with modes 1 to 3, which is still been worked on. This new type of NBTV system designed for HF radio sky wave propagation, still very much a work in progress. Software was tested with Ubuntu Linux, using Gambas3 modules as the base layer, that will need to be install as well as the NBTV application.

Grant

Hi All,

There has been a few improvements to the OFDM software using GNU Radio and now I am working on the Code Division Multiple Access (CDMA) modulation system, as there are a few advantages over the OFDM approach.

The CDMA modulator and demodulator that will most likely take up the same bandwidth as the OFDM using PN codes. By doing this I will be using a spread spectrum approach where the 192 data streams will be multiplexed across the full bandwidth. Since I going with code spreading this should get me around the issues with the time domain that I was getting TDM experiments, as there is so many unknown to test and work through at this stage. The unknowns are the impact of selective fading and channel interference and noise, far as I can tell CDMA will reject any unwanted signals, if there is no correlation with PN codes. From the research I have done on this topic, CDMA is very good at combating multipathing, which is very useful in this application. Another idea is look at adding in noise reduction, within CDMA modulation, as the amount of data streams within a fixed bandwidth will have an impact on the signal to noise performance and this where the noise reduction could be useful.

To do anything with CDMA, I first need a faster computer as there a lot more going on with processing steps than what was required with OFDM. From the basic GNU Radio testing done this looks like a good way to send television, this is one of the ideas I plan to play around with in the new year. This way you will have two types modulation to use on HF, where there is OFDM and the other is CDMA. As with OFDM software I plan make avalible when I get it all working, as there as still a number issues to work through with this approach, for now version 3.4 is out for the NBTV encoder and decoder software.