I thought the MT352 is a demodulator... isn't the tuner a separate entity?? For example my cards both use a MT352 demod and they also both have a Thomson 7579 tuner.... so it may be that your devices both had the MT352 but different tuners... here's what I discovered on the wiki http://www.linuxtv.org/wiki/index.php/Demodulator incidentally, was the misbehaving USB stick one of the ones listed between 33-42 in the following list?? http://www.linuxtv.org/wiki/index.php/DVB_USB#Twinhan_DVB-T_USB2.0 Viktor
The reception quality on a card is based on two things, the receiver and the demodulator. After the demodulator, the signal is digital, so there is not much more to be done other than running trough error correction, which will allways be done the same way. On DVB-S, the tuner is the most important part as virtually all muxes run with the simple QPSK modulation. On DVB-T the modulation is quite complex. The fact that a single frequency can be transmittet from different places with the same data together with all the signals bouncing off mountains and such gives the demodulator a much harder job than with DVB-T. How the connection is made between frontend and demodulator can also affect the signal alot since some ways will introduce more noise on the way to the demod. How much that last thing affects performance I cannot tell, but it is very individual for each setup. The performance of these cheap frontends and demods will also vary quite a bit, so luck has something to do with the performance also. That being said, usually this type of equipment will have varying performance, and as much as 3dB signal sensitivity difference is not uncommon. Still, a bad version of one could be as good as a good version of the other. It is impossible to tell for certain. One could make a database where everyone with at least two tuners could enter which ones they have and what the performance difference is, but I am not sure how accurate that will be over time. An inline variable attenuator is good for signal sensitivity testing in many cases, but attenuating the signal also attenuates the noise, so the carrier to noise level stays the same. That must be taken into account when testing like that. If the difference between two card is that one gets a better signal quality from a given carrier to noise level, but the other has a higher gain preamp, the one with the better preamp will win this test, but is not nessesarily the best card anyway. Adding an external preamp will give the loser a higher signal to work with so you get better signal quality, but the same could do little for the test winner as it already has a strong enough signal but is unable to take advantage of it. A white noise generator is very expensive though, so that is in practise the only solution most people have. -Morgan- _______________________________________________ linux-dvb mailing list linux-dvb@xxxxxxxxxxx http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
