[Laser] Re: to F1AVY{ CONCLUSION TO >>> focal length question}

[George Vastianos]

From: <F1AVYopto at aol.com>
> The  BPW34 is a good choice for medium and low speed  modulation.
> Its  7,5 mm² sensitive area is well matched to the Fresnel lens focusing
area
> always bigger than the one provided by a good glass lens.
> The  focal point quality and size depends on the engrave lines number per
> inch. You  will notice the signal level does not depend critically of the
focal
> point  adjustment.

So If I understood correctly i'll just put the sensor behing the lens at the
theoretical focal point without wasting time on further experiments????

> Until  the lighted area does not overlap over the sensitive area limits,
the
> signal  intensity will stay the same.

Yea i agree, this was the idea i got after the first replies to my
questions....

>With  a laser this is not true for a very short path but, above one km, the
> light  coherence is lost in the received beam and the effect in the
detector is
> the  same the one from a LED light. The  enormous gain with the laser use
> is only from the TX lens that can give a very  narrow beam.

Well Iam not planning to experiment with lasers, I have in stock about 50 IR
Leds
and I want to stack them in order to transmit... I prefer to have a wider TX
angle
and not to have so much hard time in order to find where the tiny spot of my
laser looks
especialy if my target station is many KM away......

Yves Tnx Agn for your responce

73 George