buus at hbuus
Dec 5, 2009, 1:50 PM
Post #1 of 4
Re: Can't find clear QAM channels on frequencies 543000000 and 549000000
Devin Heitmueller wrote:
> On Sat, Dec 5, 2009 at 1:44 PM, faginbagin <mythtv [at] hbuus> wrote:
>> I have an HVR-1600 that can't find three clear QAM channels. Using
>> information from silicondust.com, I think these channels are on frequencies
>> 543000000 and 549000000 (analog cable 77 & 78). I can see these channels on
>> HDTVs in other rooms of my home. And the HVR-1600 can tune 8 clear QAM
>> channels on 5 different frequencies:
>> three on 93, 639000000
>> one on 94, 645000000
>> two on 102, 663000000
>> one on 106, 687000000
>> one on 118, 759000000 (although this one is video on demand and is noisy)
>> So I guess I'm wondering if you can offer any insight as to why I'm having
>> trouble with frequencies 543000000 and 549000000. Could it be a clue as to
>> whether the problem is the coax cabling leading to the HVR-1600, an issue
>> with the PCI bus, or just the fact that a PCI card doesn't have the
>> shielding an HDTV has?
>> FWIW, I have yet to try connecting one of my HDTVs to the same coax input.
>> However, I did try connecting the HVR-1600 to the same input used by my
>> cable modem back in March/April (should be cleanest coax connection in my
>> house) and MythTV's scanner couldn't find these three channels there. It's
>> been so long, I don't remember if I tried the scan utility with that
>> connection. My focus at the time was an issue with audio noise on some
>> analog channels (which Andy was able to fix, Many Thanks).
>> P.S. Thought Devin would like to know his recent cx18 fixes have improved
>> signal quality on the clear QAM channels I can tune. Tuning 7 channels for
>> about 23 seconds each and playing with mplayer 3 seconds after tuning
>> (excluding video on demand), I found that:
>> - Signal strength reported by azap increased from an average of 12c to 13F
>> - Reports of non-zero BERs and/or UNCs dropped from 6 in 147 samples to 1 in
>> 147 samples
>> - mplayer reports of 'a52: CRC check failed!' dropped from 24 to 2
>> Subjectively, the audio and video quality is better. And MythTV seems much
>> happier as it's less likely to dump core playing back recordings from two of
>> these channels.
> Hello Helen,
> Thanks for taking the time to try out my patches before writing the
> mailing list - since that would have been the first thing I suggested.
> I would suggest trying the following:
> See if the results differ with /usr/bin/scan. This could be some
> issue with mythtv's channel scanner.
My most recent tests were with scan, using both w_scan output and various scan files provided with dvb-apps. Guess I didn't make that clear.
> Try an actual TV and see if it can receive the channel.
That is my next step. Either that or live without the channels.
> Try the HVR-1600 under Windows, if possible. As far as I know, the
> Linux driver is at the point where it should behave identically to the
> Windows driver, so if there is some inconsistency, I would definitely
> be interested in hearing about it.
I did try that back in March/April and the Hauppauge s/w couldn't find the channels either. In order to do that test, I had to move the cards into another machine with XP installed, and I don't have that computer anymore. The current machine only has Win2000 (new computer, old win2k CD) and the Hauppauge s/w wasn't happy with that OS.
I guess I was hoping mostly for some insight into where these frequencies are on the VHF band, if they're somehow more vulnerable to signal quality, noise, etc. Something that might explain why they're giving me trouble.
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