Some comments on
performance of the QROlle II
By: SM6DJH Olof Holmstrand - The constructor of the analogue part of the QROlle Classic and QROlle II - June 1, 2011
You can see the filtercurve given for SSB and CW (dotted). As you can see the filter gives great performance and selectivity for both SSB and CW. Remeber, you can select the narrow filter mode although in SSB. This can be good to use for digital modes like PSK31 or RTTY.
Regarding sensitivity, it is very difficult to answer. This is because many perceive noise as very disturbing and prefer a receiver with low noise level.
The problem is the following. If the noise is low, so it is probably due to be beneficial for low gain or a lack of AGC control. Of course, one could imagine a receiver with very low noise figure, but then you have to compromise with less intermodulation, which is very inappropriate on shortwave. Such an action may nevertheless have a substantial noise contribution when the antenna is connected, because of atmospheric noise on shortwave.
In reality a low noise factor is not so important.
Obviously you can imagine that a receiver destroys the signal to noise ratio with poor signal in the various stages and noisy oscillators. However, we are pretty sure that QROlle: n does not have such bad qualities.
As a guide to sensitivity, one can say that a CW signal shall be clearly audible, despite the input level is only -120 dBm. As an aside, may be mentioned that -121 dBm equivalent S1 with a calibrated S-meter. The speaker is also the weak signal is heard properly, without the need to increase the volume control in comparison with strong signals. This is a good indication that the AGC system works well. Of necessity therefore noise heard when the signal is lost and this is what many find disturbing. You will notice that the AGC-system is doing a great job in that you very seldom need to do AF-gain adjustments when using your QROlle II.