AncientBrit wrote:Is this a first??
Harry Dalek wrote:Very interesting Steve i have only tried this with nbtv where as i just used a solar cell as the reciever as posted a while back ..has me wondering if a solar cell if given enough transmitting light would also do away with any recieving electronics at these higher bandwidths also ? as in i mean no head amp electronics and well apart from my case the laptops mic amp and your case the tv monitor ...it is sort of the same idea but up scaled ...
Harry Dalek wrote:I am not sure a IR transmitting led would be any good but a white led might give the same results as my little try ...
Harry Dalek wrote:I don''t know if english people have solar cell panels on their roof as much as here in Australia but crazy as it sounds at night i wonder if they could be picking up tv signal if you used a light tv transmitter and pointed it at it ...as in an antenna to a crystal radio electric reception?
Harry Dalek wrote:and BTW do you still have to pay for a tv licence fee in the uk ? outrageous ! i just came across 2 vintage aussie tv licence fee cards from the 60s but i think that ended in the 60s i can never recall it later than that .
Harry Dalek wrote:BTW have you tried a night test by reflection off different surfaces ?
Harry Dalek wrote:i suppose it would have to be close depending how much IR your led or leds can do ,i like the idea of light skip like Radio propagation .
Harry Dalek wrote:As i remember head amps or LNBs on satellite dishes work better if you can cool them to stop thermal noise....I wonder if you did the misty light transmitting test and got some cold spray and cooled your detector would the noise decrease
Harry Dalek wrote:IS IR light or heat ? or the same
Steve Anderson wrote:I wonder, over longer distances of several km would atmospheric disturbances affect the signal?
Harry Dalek wrote:Chris had the advantage of a hilltop-to-hilltop path away and above the rubbish in the air that a large city creates. I also think these voice links were conducted at night when maybe the atmosphere is more settled.
Klaas Robers wrote:Steve, I can't find your circuit diagrams back, but you will know that the cumbersome capacity of a photo diode (of ALL diodes) decreases if you apply a voltage in the non conducting direction. This is the effect that is used in varicaps. In reality all diodes are rectifiers, varicaps, zeners and photocells, but the effect is only specified (measured) for diodes that are named in that way. A semiconductor diode is just a semiconductor diode.
Klaas Robers wrote:Secondly try to find a coloured filter that is transparent only for the colour of light that you use. This will remove the noise introduced by all other colours of light that might hit the detector diode. For near infra red these filters exist in remote controls.
Panrock wrote:Yes I tried this, for the reason you mentioned. However in this case, and with this diode, it seemed to give no advantage over photo-voltaic mode, which - as I understand it - also offers the advantage of the best linearity. Since I'm amplitude modulating with an analogue signal, itself amplitude modulated, linearity is an important factor.
Steve O
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