[mythtv-users] HDHomerun signal strength required
backuppc at sundquist.imapmail.org
backuppc at sundquist.imapmail.org
Sun Feb 24 23:05:23 UTC 2008
On Sat, 23 Feb 2008 09:16:56 -0500, backuppc at sundquist.imapmail.org
said:
> I will try each antenna individually and
> tweak the aim to get the best reception and then compare it to when both
> are hooked up. If the signal is much weaker when combined, I will try
> small adjustments to see of steer out of a null for the channels I need.
> Maybe even set up a second attic mast and separate then laterally.
>
> After I get the best aim on the north/norhwest one, I'll see if I can
> get the big ABC/CBS/NBC towers located not too far to the south out
> the back of that same antenna.
Findings:
Disconnected the south facing antenna, connecting the 50-foot RG-6
directly to the other antenna's balun. That antenna (the one aimed
towards Grand Island/CN Tower) seemed to be aimed well, changing
direction just made it worse.
Most interestingly, I got the ABC/CBS/NBC signals "out the back" just
fine with only one antenna, pointed the other way.
This is all with the pcHDTV 5500 Here are the results from before (two
antennas):
> The pcHDTV came with two great utilties that I'll probably use. First
> is dtvsignal. Here's the current output using my pcHDTV 5500:
>
> user at mythtv:~/dvb-atsc-tools-1.0.7$ ./dtvsignal 34
> using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
> tuning to 593000000 Hz
> video pid 0x0021, audio pid 0x0024
> dtvsignal ver 1.0.7 - by Jack Kelliher (c) 2002-2007
> channel = 34 freq = 593000000Hz
> 30db 0% 25% 50% 75% 100%
> Signal: | . : . | ._____:_____._____|
> Signal: 048 ------------------------
>
> (the signal bar on the last line is "live". Not doing too well on
> channel 34 [Grand Island] today)
>
> For comparison, here's CBC from the CN tower:
>
> channel = 20 freq = 509000000Hz
> 30db 0% 25% 50% 75% 100%
> Signal: | . : . | ._____:_____._____|
> Signal: 011 -----
>
> The other tool is dtvsnr:
>
> Grand Island:
>
> channel = 34 freq = 593000000Hz
> dB -10 0 10 20 30 40
> SNR: | | | | | |
> SNR: 017 ============================
>
> CN Tower:
>
> channel = 20 freq = 509000000Hz
> dB -10 0 10 20 30 40
> SNR: | | | | | |
> SNR: 003 --------------
>
> The hills south of me:
>
> channel = 38 freq = 617000000Hz
> dB -10 0 10 20 30 40
> SNR: | | | | | |
> SNR: 026 $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
And here's the results with one antenna (with the pcHDTV 5500):
signal stength:
channel = 34 freq = 593000000Hz
30db 0% 25% 50% 75% 100%
Signal: | . : . | ._____:_____._____|
Signal: 051 -------------------------
channel = 20 freq = 509000000Hz
30db 0% 25% 50% 75% 100%
Signal: | . : . | ._____:_____._____|
Signal: 014 -------
channel = 38 freq = 617000000Hz
30db 0% 25% 50% 75% 100%
Signal: | . : . | ._____:_____._____|
Signal: 077 $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
S/N:
channel = 34 freq = 593000000Hz
dB -10 0 10 20 30 40
SNR: | | | | | |
SNR: 017 ============================
channel = 20 freq = 509000000Hz
dB -10 0 10 20 30 40
SNR: | | | | | |
SNR: 003 --------------
channel = 38 freq = 617000000Hz
dB -10 0 10 20 30 40
SNR: | | | | | |
SNR: 026 $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
So about the same. I took the second antenna out of the attic.
But the HDHR is disappointing me so far. Following the Craig's advice:
> > SiliconDust provides a utility to work with the HDHomeRun that can
> > help for testing reception. Do a full channel scan on one of the
> > tuners, which will take several minutes, with:
> >
> > hdhomerun_config FFFFFFFF scan /tuner0 scan0.txt
> >
> > Focus on the bits of interest with:
> >
> > grep -B1 -A1 '8vsb' scan0.txt
I get:
SCANNING: 473000000 (us-bcast:14)
LOCK: 8vsb (ss=59 snq=72 seq=100)
PROGRAM: 3: 29.1 WUTV-HD
--
SCANNING: 581000000 (us-bcast:32)
LOCK: 8vsb (ss=67 snq=73 seq=100)
PROGRAM: 3: 23.1 WNLO-HD
--
SCANNING: 587000000 (us-bcast:33)
LOCK: 8vsb (ss=98 snq=89 seq=100)
PROGRAM: 1: 2.1 WGRZ-HD
--
SCANNING: 593000000 (us-bcast:34)
LOCK: 8vsb (ss=48 snq=48 seq=100)
PROGRAM: 3: 49.1 WNYO-HD
--
SCANNING: 617000000 (us-bcast:38)
LOCK: 8vsb (ss=70 snq=69 seq=100)
PROGRAM: 3: 7.1 WKBW-HD
--
SCANNING: 623000000 (us-bcast:39)
LOCK: 8vsb (ss=91 snq=93 seq=100)
PROGRAM: 5: 4.1 WIVB-HD
--
SCANNING: 647000000 (us-bcast:43)
LOCK: 8vsb (ss=44 snq=43 seq=100)
PROGRAM: 2: 43.1 WNED-HD
...which are somewhat lower. Perhaps that is understandable because I
have the splitter in place with the HDHR. And in fact, I suppose the
numbers are not all that different for the three I highlight. But for
1,000 KW Fox (channel 14), the discrepancy is greater:
channel = 14 freq = 473000000Hz
30db 0% 25% 50% 75% 100%
Signal: | . : . | ._____:_____._____|
Signal: 076 $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
vs:
SCANNING: 473000000 (us-bcast:14)
LOCK: 8vsb (ss=59 snq=72 seq=100)
PROGRAM: 3: 29.1 WUTV-HD
But maybe the numbers aren't comparable between the two utilties.
So anyway, the antenna question is solved for now. Maybe this summer I
will install the now-decommissioned antenna on the roof and see what I
get.
In the meantime, I can't judge the HDHR image quality since it won't
play anything yet. Obviously must be a backend configuration issue, but
I can't figure out what is wrong. I didn't remove the pcHDTV card from
the set up (even though no antenna is plugged into it). I thought
mythTV would just switch over to the tuner with a signal.
I probably screwed upsomething simple, but I'll keep checking...
Jon S.
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