> From: awalls@radix.net
> To: ivtv-users@ivtvdriver.org
> Date: Mon, 15 Feb 2010 19:14:00 -0500
> Subject: Re: [ivtv-users] hvr-1600, frame CRC mismatch - incomplete frame
>
> On Mon, 2010-02-15 at 16:22 -0500, Kyle Lil wrote:
>
> > Previously I'd had the tuner connected at the end of additional
> > splitters and devices, but I shortened the chain in troubleshooting.
> > I'll try attenuating the signal again to see if that helps. I hadn't
> > consider the possibility that the cable signal might exceed the
> > devices input limits.
>
> Actually, I've just verified that my antenna and preamp is overdriving
> my HVR-1600 for two digital TV stations. I could verify independently
> with my Sony TV, which provides SNR, signal, and Error readouts of the
> same channels. For me, WJLA and WUSA over the air are *really* strong
> according to the TV, but my MythTV recordings show errors. Here's the
> output of femon while MythTV is showing WUSA:
>
> status 1f | signal 011d | snr 011d | ber 000001c9 | unc 000001c9 | FE_HAS_LOCK
> status 1f | signal 011d | snr 0118 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 0000006a | unc 0000006a | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 000007f3 | unc 000007f3 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0113 | snr 0118 | ber 00000836 | unc 00000836 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0122 | snr 0122 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0122 | snr 0122 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0122 | snr 0122 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0122 | snr 0122 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
>
> SNR is great, but I get errors every once in a while.
>
> The pattern looks really similar to what you reported from azap.
>
> My problem is subject to weather variations for me, so it doesn't happen
> all the time. However, clear, cold winter nights seem to lead to the
> most problems recording these station with my HVR-1600. (I could turn
> down my amp, but since WETA, a really good station, is a really weak
> signal for me, I probably won't.)
>
>
> I think you'll just need to attenuate your cable signal before it hits
> the HVR-1600.
>
> Regards,
> Andy
>
>
> _______________________________________________
> ivtv-users mailing list
> ivtv-users@ivtvdriver.org
> http://ivtvdriver.org/mailman/listinfo/ivtv-users
I built a -10dB attenuator as you described in your link (thanks for that) and still saw the glitches. In fact, I see them whether I connect the cable line straight from the wall into the HVR-1600 or through two splitters and the attenuator (and every other combination). In trying to get a better sense of what's happening to the signal, I went into the service menu of my cable box, a Motorola DCH-3200, which lists various signal statistics. One of the parameters it lists is "AGC", which I'm guessing is some sort of automatic gain control that puts the signal into the optimal range for the tuner. If the cable box is connected after the second splitter, AGC is 18%. If it's connected to the first splitter, it's a few percent lower. If I add the attenuator, the AGC goes up another 5%. It makes sense to me that the attenuator would cause the AGC value to go up, but I'm sure why it only went up 5% with a -10dB attenuator.
Does the HVR-1600 have similar AGC built in? If the cable box cuts the signal to less than 1/5th of its amplitude (even after two splitters), maybe this is an indication that I need to build an even stronger attenuator? Do you have any insight into what value attenuator I should be shooting for?
Kyle
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> To: ivtv-users@ivtvdriver.org
> Date: Mon, 15 Feb 2010 19:14:00 -0500
> Subject: Re: [ivtv-users] hvr-1600, frame CRC mismatch - incomplete frame
>
> On Mon, 2010-02-15 at 16:22 -0500, Kyle Lil wrote:
>
> > Previously I'd had the tuner connected at the end of additional
> > splitters and devices, but I shortened the chain in troubleshooting.
> > I'll try attenuating the signal again to see if that helps. I hadn't
> > consider the possibility that the cable signal might exceed the
> > devices input limits.
>
> Actually, I've just verified that my antenna and preamp is overdriving
> my HVR-1600 for two digital TV stations. I could verify independently
> with my Sony TV, which provides SNR, signal, and Error readouts of the
> same channels. For me, WJLA and WUSA over the air are *really* strong
> according to the TV, but my MythTV recordings show errors. Here's the
> output of femon while MythTV is showing WUSA:
>
> status 1f | signal 011d | snr 011d | ber 000001c9 | unc 000001c9 | FE_HAS_LOCK
> status 1f | signal 011d | snr 0118 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 0000006a | unc 0000006a | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 000007f3 | unc 000007f3 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0113 | snr 0118 | ber 00000836 | unc 00000836 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0122 | snr 0122 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0122 | snr 0122 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0122 | snr 0122 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0118 | snr 0118 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 011d | snr 011d | ber 00000000 | unc 00000000 | FE_HAS_LOCK
> status 1f | signal 0122 | snr 0122 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
>
> SNR is great, but I get errors every once in a while.
>
> The pattern looks really similar to what you reported from azap.
>
> My problem is subject to weather variations for me, so it doesn't happen
> all the time. However, clear, cold winter nights seem to lead to the
> most problems recording these station with my HVR-1600. (I could turn
> down my amp, but since WETA, a really good station, is a really weak
> signal for me, I probably won't.)
>
>
> I think you'll just need to attenuate your cable signal before it hits
> the HVR-1600.
>
> Regards,
> Andy
>
>
> _______________________________________________
> ivtv-users mailing list
> ivtv-users@ivtvdriver.org
> http://ivtvdriver.org/mailman/listinfo/ivtv-users
I built a -10dB attenuator as you described in your link (thanks for that) and still saw the glitches. In fact, I see them whether I connect the cable line straight from the wall into the HVR-1600 or through two splitters and the attenuator (and every other combination). In trying to get a better sense of what's happening to the signal, I went into the service menu of my cable box, a Motorola DCH-3200, which lists various signal statistics. One of the parameters it lists is "AGC", which I'm guessing is some sort of automatic gain control that puts the signal into the optimal range for the tuner. If the cable box is connected after the second splitter, AGC is 18%. If it's connected to the first splitter, it's a few percent lower. If I add the attenuator, the AGC goes up another 5%. It makes sense to me that the attenuator would cause the AGC value to go up, but I'm sure why it only went up 5% with a -10dB attenuator.
Does the HVR-1600 have similar AGC built in? If the cable box cuts the signal to less than 1/5th of its amplitude (even after two splitters), maybe this is an indication that I need to build an even stronger attenuator? Do you have any insight into what value attenuator I should be shooting for?
Kyle
_________________________________________________________________
Hotmail: Trusted email with powerful SPAM protection.
http://clk.atdmt.com/GBL/go/201469227/direct/01/