[Ronja] Vacuum tube in Ronja preamplifier

[Gullik Webjorn]

>Sun dominates during day. Receiver noise dominates during night or low
light
>conditions.

Then daytime performance is the limit, isn?t it? If the light could be
filtered,
maybee we could get rid of excess sun energy, and get receiver to be
limiting factor.


>No I didn't measure input sensitivity. In what units is it supposed to be
>measured?

The convention seems to be dBm @ SNR, or dBm @ BER, I have always tried to
work
in these measurements, because then it is possible to compare what I can do
in the lab
with what other people / products achieve.

I usually do SNR "estimates", you can do that by looking at a scope, and
just compare
no-signal to signal conditions visually, it does not work so good for SNR <
8, because
it is hard to evaluate "noise" vs. scope tracewidth.

I guess for Ronja the RSSI could be calibrated.

I have used a "large" photo diode ( small solar cell ). With that, a
resistor and a multimeter,
good optical power measurements can be made. It has to be calibrated for
wavelength, but after
that it is perfectly good. Even better, a Hamamatsu S1337-66BR is a 5.6 x
5.6 mm photodiode ( $50 )
that can be used to measure light sources by masuring short circuit current.
Then the datasheet
can be used to calibrate against wavelength conversion efficiency ( A/W)

For the Ronja RX, I think a measure of sensitivity would be good for people
troubleshooting,
or trying to optimise performance / distance.

One experiment you have done which tells a lot, but maybee could be improved
is the "floor test".

It should be possible to estimate the power that reaches the RX without
optics. It should also be
possible to take the test transmitter (starquake) and test it with a
commercial powermeter at a certain
distance.

Just some thoughts...

Gullik