Thanks for the kind comments and interesting references.
Monochrome wrote:I should like to ask a couple of questions if I may. My first question, are you still experimenting with the optical link?
Yes, but it's been put on the back burner for the moment while I attend to more pressing projects. However, I have now obtained some high power deep red "horticultural" LEDs. The next step is to try these in order to raise the transmitted power by a factor of 250. In the meantime, I shall be bringing the standard-power rig along to the NBTVA Convention, but will probably demonstrate it at 120-lines rather than 405, since this is more in the spirit of "NBTV".
Monochrome wrote:Also, in your most recent long distance tests could you clarify what sort of optics you used at the transmitting end of the link please.
This was a standard "club" condenser lens, mounted in a tapered paper section cut from a soft drinks dispenser cup! Once painted it didn't look too bad. Obviously the positioning of everything is critical in order to get a good beam. A photo is attached. The pot shaft adjusts the DC bias to the LED.
Monochrome wrote:And finally, did you send sound as an intercarrier or are your experiments confined to video only at present. Very interesting stuff and I hope you are still experimenting with the optical video link.
Vision and sound are first amplitude modulated onto two separate RF carriers: 45.0 and 41.5MHz, which then I suppose attain the status of "subcarriers" once the resulting complete System A television channel is in turn amplitude modulated onto a beam of light.
One reason for this experiment was to see if I could provide the BHTG with an alternative way to broadcast vintage television, should licensing of the original Band I spectrum prove impossible. Using this optical method, out of the pick-up emerges a complete Channel B1, ready for plugging in to the aerial socket of a vintage receiver.
Steve O