[linux-dvb] TT budget DVB-C 1.0 tuning issues

[Esa Loukkola <esa@nic.fi>]

Hello,

I recently bought a Technotrend 1.0 budget DVB-C card with a VES1820
frontend (along with a Siemens DVB-C card, but that's another story),
as featured on http://www.usa-x.org/1shop/product_info.php?products_id=44.
I have a slight problem with tuning to certain transponder frequencies in
the Turku, Finland cable network:

146MHz, symbol rate 6900 and QAM128 and 154/6900/128 do not tune at all;

./czap -r -n 8
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
 8 SubTV (TV):154000000:INVERSION_OFF:6900000:FEC_NONE:QAM_128:353:609
 8 SubTV (TV): f 154000000, s 6900000, i 0, fec 0, qam 4, v 0x161, a 0x261
status 00 | signal b4b4 | snr c2c2 | ber 00000a0a | unc ffffffff |
status 00 | signal ffff | snr c6c6 | ber 00000a0a | unc ffffffff |
status 00 | signal ffff | snr c4c4 | ber 009ffff6 | unc ffffffff |
status 00 | signal ffff | snr c4c4 | ber 009ffff6 | unc ffffffff |
status 00 | signal ffff | snr c4c4 | ber 009ffff6 | unc ffffffff |

getfrontend says at the same time:
./getfrontend.c /dev/dvb/adapter0/frontend0
Signal=65535, Verror=10485750, SNR=50629dB, QAM_128, FREQ=154.000000MHz,
SR=6.900000Msym, INV=OFF, BlockErrors=?, ()

i.e. it seems it has not finetuned the frequency as it does with the other
transponders:
./getfrontend.c /dev/dvb/adapter0/frontend0
Signal=65535, Verror=4430, SNR=60395dB, QAM_64, FREQ=161.979786MHz,
SR=6.900000Msym, INV=OFF, BlockErrors=0, (S|L|C|V|SY|)

On the other hand, other frequencies, both QAM64 and QAM128 tune well.

The common denominator for the two frequencies that don't tune are that they
are the lowest in my network. 162MHz and all above it tune well -- even
without changing anything in the source.

Upon browsing this mailing list, I came upon several alternative magic
numbers for inittab values and PWM values in ves1820.c. I have gone through
all the variations I could think of, including changing the zigzag code in
dvb_frontend.c to enable zigzagging for DVB-C (I hope) and going through
0x00 to 0xff in 0x0a steps for the PWM - no help.

I have tried both the latest DVB CVS version, the dvb-kernel latest CVS
version and a DVB CVS version from 13.1.2003 with Jaakko Hyvätti's
diff6-patches -- same problems.

Does anyone have any good suggestions as to what might be good to try? I
haven't tried the card in Windows yet but I will should someone think it's a
hardware problem and not a driver issue.

Other pertinent info:

uname -a
Linux localhost 2.4.22 #1 Sun Sep 21 15:46:01 EEST 2003 i686 GNU/Linux

Should you need any other info, I will naturally provide it.

Greetings, Esa

--
Esa Loukkola
esa@nic.fi



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