Hi Andy and Dmitry, Am Mittwoch, den 22.04.2009, 22:08 -0400 schrieb Andy Walls: > Dmitri, > > > On Wed, 2009-04-22 at 17:48 +1000, Dmitri Belimov wrote: > > Hi All > > > > 1. Change middle band. In the end of the middle band the sensitivity of receiver not good. > > If we switch to higher band, sensitivity more better. Hardware trick. first of all, Dmitry, you need to send all your patches, also the prior ones, to linux-media@xxxxxxxxxxxxxxxx Only there "patchwork" will parse for them and you might eventually find them here. http://patchwork.kernel.org/project/linux-media/list http://patchwork.kernel.org/project/linux-media/list/?state=* You seem to have missed that completely and thanks to Andy to start to comment on this one, even only on video4linux previously. > This concerns me slightly as it does not match the datasheet (hence the > design objectives) of the FM1236ME_MK3. > > How are you measuring sensitivity? Do you know if it really is the > middle-band preselector filter (and PLL and Mixer) or is it a problem > with the input signal? How do you know it is not manufacturing > variations in the preselector filters with the particular tuner assembly > you are testing? I did not look into the datasheet again, we did not have it at all for a very long time, but we had a similar case already and that time we made the decision like it can be found in this thread. No complaints ever until today. http://marc.info/?l=linux-video&m=112639247330257&w=2 Did not look up all frequency tables again, but if it is the same again, I would say the risk of doing something wrong is close to zero. For the rest I never noticed any difference and we have it on lots of other tuners like that. And, that one still means a lot of _different_ tuners and different manufacturers, filters definitely differ! ... > Also, as an alternative to using a different frequency for the > bandswitch, have you considered setting the Auxillary Byte in the tuner > chip (Infineon TUA6030?) to use external AGC and experimented with > changing the tuner AGC take-over point (TOP) in the TDA9887? > > By maximizing the gain in the tuner chip, but avoiding clipping, with > the proper TOP setting, you minimize the contributions by the rest of > the receive chain to the overall receiver Noise Figure: > > http://en.wikipedia.org/wiki/Friis_formulas_for_noise > > This may be a way to improve receiver sensitivity that does not conflict > with the data sheet specification. > > > > > > 2. Set correct highest freq of the higher band. > > :) > > This bothers me too; all the tuners in tuner-types.c have it set too > high (999.0 MHz). I think I rememeber at time when all the tuner_range > definitions had a real value there. > > It would be nice to have a real value there for all the tuners. The > function tuner-simple.c:simple_config_lookup() would then prevent > attempts to tune to an unsupported frequnecy. > > > > > 3. Set charge pump bit > > This will improve the time to initially tune to a frequency, but will > likely add some noise as the PLL continues to maintain lock on the > signal. If there is no way to turn off the CP after the lock bit is set > in the tuner, it's probably better to leave it off for lower noise and > just live with slower tuning. > > Leaving the CP bit set should be especially noticable ad FM noise when > set to tune to FM radio stations. From the FM1236ME_MK3 datasheet: > "It is recommended to set CP=0 in the FM mode at all times." > But the VHF low band control byte is also used when setting FM radio > (AFAICT with a quick look at the code.) > > Regards, > Andy > > > diff -r 43dbc8ebb5a2 linux/drivers/media/common/tuners/tuner-types.c > > --- a/linux/drivers/media/common/tuners/tuner-types.c Tue Jan 27 23:47:50 2009 -0200 > > +++ b/linux/drivers/media/common/tuners/tuner-types.c Tue Apr 21 09:44:38 2009 +1000 > > @@ -557,9 +557,9 @@ > > /* ------------ TUNER_PHILIPS_FM1216ME_MK3 - Philips PAL ------------ */ > > > > static struct tuner_range tuner_fm1216me_mk3_pal_ranges[] = { > > - { 16 * 158.00 /*MHz*/, 0x8e, 0x01, }, > > - { 16 * 442.00 /*MHz*/, 0x8e, 0x02, }, > > - { 16 * 999.99 , 0x8e, 0x04, }, > > + { 16 * 158.00 /*MHz*/, 0xc6, 0x01, }, > > + { 16 * 441.00 /*MHz*/, 0xc6, 0x02, }, > > + { 16 * 864.00 , 0xc6, 0x04, }, > > }; > > > > > > > > Signed-off-by: Beholder Intl. Ltd. Dmitry Belimov <d.belimov@xxxxxxxxx> > > > > With my best regards, Dmitry. Cheers, Hermann -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
