Dear group,
In the picture in this mail i show the circuit of the simpelst way to transform
the optic signal back to an alternating voltage that can be connected to the RX
imput. It is the version with a phototransistor. This way is working and a good
start point for further (individual) experiments, e.g. if noise really
decreases significantly...
The potentiometer should be adjusted to a miximum signal on the s-meter,
depending to the input impedance of the cable (cable + RX). It can be replaced
later by a fixed resistor. The 100k resistor can be replaced by an inductance
and adjusted to maximum strenght and so on. First, the circuit should be
supplied by a battery and later by the power supply of the RX. So it can be
seen if there comes an additional noise by the supply. I have integrated this
little circuit in my K2, to minimise the effort of cables and housings. A
simple switch can be used to change the input (optic / coax). So one can
compare both transmission paths...
Due to the snow the post has problems to reach my house and so i still do not
have the SFH250V (photodiode). But soon i will try it this way and will see if
noise even can be even decreased...
73 es gl ;-)
Stefan/DK7FC
<<winmail.dat>>
|
