[linux-dvb] Afatech af9005 unstable reception [added: mt2060 gain control?]

Luca Olivetti luca at ventoso.org
Sat Apr 14 12:31:40 CEST 2007

En/na P. van Gaans ha escrit:
> My last question for a cheap USB DVB-T stick took a whole other turn. 
> Earlier I bought an Allnet all2006 USB DVB-T stick, just praying it 
> would run on Linux. It didn't. At least it didn't back then.
> On Windows I figured out it's an Afatech AF9005 clone. On Google I 
> figured out there is a driver and firmware here, recently written: 
> http://ventoso.org/luca/af9005/
> Happy was I! I installed everything and yes, the device is detected. But 
> it hardly ever locks correctly on a frequency. I see the "lock" thingie 
> in Kaffeine light up, as well as a blue led on the stick. But few times 
> do I read some channel information. Once I was able to read the radio 
> transponder, but the radio stutters. That doesn't really say much, radio 
> stutters with another DVB-T device on Windows as well at that frequency, 
> and I have no idea if my reception or buggy software is the problem here.
> The main problem is I can't read all channels. I'm missing almost all 
> the channels. The -/+167 trick didn't help.

Well, I found that reception with this stick isn't very good, but since 
it does the same under windows (actually under Linux I can catch more 
channels) I thought it was just a problem with the hardware. OTOH I have 
other users reporting that the stick works just fine for them. Maybe it 
depends on the tuner used (I have an mt2060, others have a qt1010) or on 
the overall quality of the stick (there are various no name ones using 
this chipset and the terratec cinergy xe).
If you have a stick with an mt2060, there's a commented out section of 
code that tries to reduce the gain of the mt2060 if the demodulator 
detects a strong signal. I tried it talking directly on the i2c bus with 
the mt2060, since the mt2060 code doesn't provide such an option (maybe 
one of the tuner ops should provide for gain adjustment?), but since I 
saw it didn't make a difference here (and I live pretty close to the 
transmitting tower) I just commented it out. You can however look in the 
logs (enabling at least debug=1) for messages "adjust for strong signal 
1". If you see them you can try to uncomment the code in af9005-fe.c 
(look for the comments "adjust mt2060 for strong signal (test)").


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