NBTV on 2.4GHz.

Forum for discussion of electronic television. Generally, stuff to do with CRTs and not using mechanical displays.

NBTV on 2.4GHz.

Postby Steve Anderson » Thu Jun 23, 2022 11:52 am

Some years ago a item of mine appeared in the newsletter which used a red laser-diode to transmit NBTV over a distance of about 100m. The item was called, "NBTV on 261THz" or something similar. A photo of the assembly follows...

Photo 1.jpg
Photo 1.jpg (275.08 KiB) Viewed 2340 times


This time it's the same idea but at a much lower frequency of 2.4GHz, within the 'no-license-required' ISM band (Industrial, Scientific and Medical). The band is shared also with other services like Wi-Fi, Bluetooth and so on. More data here...

https://en.wikipedia.org/wiki/ISM_radio_band

nRF24L01 2.jpg
nRF24L01 2.jpg (20.52 KiB) Viewed 2340 times


Making the whole process simpler are small modules, they're available as shown above with a PCB antenna, a 'Rubber Duck' version (extended range), or a multi-element Yagi antenna (up to 20Km, but very directional). A generic term for these modules is nRF24L01, search that and you'll end up with hundreds of hits, the basic PCB antenna version is usually less than US$3.00 each. The vast majority of users couple this with an Arduino of some version, but I've decided to interface it with a PIC micro - not as easy and very few examples 'out there'.

I've ordered a few of the PCB antenna version, now it's a case of getting them to talk to each other. At 1Mb/s it should be possible to get two bi-directional channels for NBTV video and audio. The I/O is a UART and/or USB, analogue signals will need conversion to/from binary/digital. These modules have three data rates, 2Mb/s, 1Mb/s, or 250kb/s, a trade-off between range/noise immunity and bandwidth.

An initial fag-packet sketch follows which will be my starting point...updates as and when...the non-programming version will be somewhat simpler...(omit most of the blue stuff, red items are just notes to myself)...

NRF24L01 A.gif


NOTE:- The nRF24L01 is a 3.3V device, though the inputs are 5V tolerant. If you apply a 5V supply you'll soon be saying "Goodbye" to it. The PIC is OK from 1.8 to 5.5V.

This isn't my only planned use for this, depending on how these perform I'd like to replace and expand my home intercom system for example, other applications will surely surface too...

I chose this PIC for two reasons, 1) For some reason I have a whole load of them sitting around, though I may choose a different one later...
2) It has an in-built USB engine so it's possible to bypass the UART-to-USB external FTDI converter. But if you've ever even glanced at the USB 'how-to' guides you'll understand why I've not used USB so far. I guess it would take at least a weeks full-time study and experimentation to comprehend and maybe get results!...someone please prove me wrong!

Steve A.
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Steve Anderson
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