Testing reception quality

DVB specific tests

Testing all channels and get an average

Why? When?
Can be good when doing major changes to the installation, like replacing cables or installing a masthead amplifier. Create a baseline, then compare.

Script

This following script gets you all channels and averages everything

#!/usr/bin/perl -w

# Original script from José Oliver Segura
# From Hex to % for signal strength by Nicolas Will, with help from GT, Feb. 1, 2008
# License unknown....
# Make sure that the tzap and channels.conf locations are correct
#
# Changes 2009-04-21
#   * moved channel.conf variable to beginning of script
#   * applied channel.conf to tzap arguments
#   * removed unused variables channelsFEC1 and channelsFEC2
#   * added ignoring of first X output lines to let tuner/decoder settle
#   * sorting output by frequency
#   * changed formating of output to be more readable
#   * added samplesPerChannel variable (used to be hard coded 10)

use strict;
use warnings;

my $tzap = "/usr/bin/tzap";
my $channelsConf = "$ENV{HOME}/.tzap/channels.conf";
my $ignoreFirstLines = 2 ; # sometimes ber/unc can be be extremely high after switching to a new channel
my $samplesPerChannel = 10 ;

my $tzapArgs = "-r -c $channelsConf";
my @channels;
my %channelsHz;
my %signalFreqAcum;
my %signalFreqCount;
my %berFreqAcum;
my %berFreqCount;
my %uncFreqAcum;
my %uncFreqCount;

sub loadChannels() {
        my $file = $channelsConf;
        open (CHANNELS,'<',$file) or die $!;
        while (<CHANNELS>) {
                chomp;
                my ($channelName,$value) = split (/:/);
		 $channelsHz{$channelName} = $value;
                push(@channels,$channelName);
        }
        close CHANNELS;
}

loadChannels();
print "Starting...\n";
foreach my $channel (@channels) {
	my $count = 0;
	my $ignore = $ignoreFirstLines;
	my $freq = $channelsHz{$channel};

	print "================================================================================";
	print "\n";
	print "Tunning channel $channel ($freq)\n";
        my $zapPid = open ZAP, "$tzap $tzapArgs \"$channel\" 2>&1 |" or die $! . ": $tzap $tzapArgs \"$channel\"";
	while ( $count < $samplesPerChannel && defined( my $line = <ZAP> )  ) {
     		chomp($line);
		if ($line =~ /FE_HAS_LOCK/) {
			if ($ignore > 0 ) {
				print "$line (Ignoring to let tuner/decoder settle.($ignore)\n";
				$ignore--;
				next;
			}
     			#print "$line\n";
			$count++;
			##
			## status 1f | signal a1ae | snr 0000 | ber 00000000 | unc 00000012 | FE_HAS_LOCK
			##
			$line =~ /.+signal (....).+ber (........).+unc (........).+/;
			my $signal = hex $1;
			my $ber = hex $2;
			my $unc = hex $3;
			$signalFreqAcum{$freq} += $signal;
			$signalFreqCount{$freq}++;
			$berFreqAcum{$freq} += $ber;
			$berFreqCount{$freq}++;
			$uncFreqAcum{$freq} += $unc;
			$uncFreqCount{$freq}++;
			print join("\t","Signal: ".int($signal/65536*100)."%","BER ".$ber,"UNC ".$unc),"\n";
		} else {
			print "$line\n";
		}
   	}
	close ZAP;
	print "\n";
}

print "Summary statistics:\n";
print "Frequency\tSignal  \tBer     \tUnc\n";
print "=========\t========\t========\t========\n";
foreach my $freq (sort(keys(%signalFreqAcum))) {
	print "$freq\t";
	printf "%6.1f %%",$signalFreqAcum{$freq}/$signalFreqCount{$freq}/65536*100;
	print "\t";
	printf "%8.1f",$berFreqAcum{$freq}/$berFreqCount{$freq};
	print "\t";
	printf "%8.1f",$uncFreqAcum{$freq}/$uncFreqCount{$freq};
	print "\n";
}

Original author: José Oliver Segura

It requires a channels.conf file, tzap. Also veryfy the locations of programs and files in the above code.

Its usage is as such:

perl signaltest.pl

Which produces output similar to the following sample:

================================================================================
Tunning channel DSF (754000000)
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
tuning to 754000000 Hz
video pid 0x0081, audio pid 0x0082
status 07 | signal 5cbf | snr 0000 | ber 001fffff | unc 00000000 |
status 1f | signal 5c99 | snr 0000 | ber 000002f0 | unc 00000000 | FE_HAS_LOCK (Ignoring to let tuner/decoder settle.(2)
status 1f | signal 5db6 | snr 0000 | ber 00000160 | unc 00000000 | FE_HAS_LOCK (Ignoring to let tuner/decoder settle.(1)
Signal: 36%     BER 1664        UNC 0
Signal: 36%     BER 84272       UNC 254
Signal: 37%     BER 30176       UNC 493
Signal: 36%     BER 27808       UNC 334
Signal: 36%     BER 4528        UNC 185
Signal: 37%     BER 400 UNC 20
Signal: 38%     BER 464 UNC 2
Signal: 38%     BER 816 UNC 0
Signal: 37%     BER 1808        UNC 18
Signal: 36%     BER 7952        UNC 18

================================================================================
Tunning channel n-tv (778000000)
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
tuning to 778000000 Hz
video pid 0x0101, audio pid 0x0102
status 07 | signal 3e01 | snr 0000 | ber 001fffff | unc 00000188 |
status 1f | signal 3e4f | snr 0000 | ber 00000000 | unc 0000000a | FE_HAS_LOCK (Ignoring to let tuner/decoder settle.(2)
status 1f | signal 3efa | snr 0000 | ber 00000000 | unc 0000000a | FE_HAS_LOCK (Ignoring to let tuner/decoder settle.(1)
Signal: 24%     BER 0   UNC 0
Signal: 24%     BER 0   UNC 0
Signal: 24%     BER 0   UNC 0
Signal: 24%     BER 0   UNC 0
Signal: 23%     BER 0   UNC 0
Signal: 24%     BER 0   UNC 0
Signal: 24%     BER 0   UNC 0
Signal: 23%     BER 0   UNC 0
Signal: 24%     BER 0   UNC 0
Signal: 24%     BER 0   UNC 0

Summary statistics:
Frequency       Signal          Ber             Unc
=========       ========        ========        ========
177500000         68.4 %          9121.6             0.0
191500000         88.4 %             0.0             0.0
506000000         58.9 %             0.0             0.0
522000000         80.5 %             0.0             0.0
570000000         47.3 %            30.4             0.0
658000000         45.1 %         15747.2             0.0
754000000         37.0 %         15988.8           132.4
778000000         24.3 %             0.0             0.0

While it's desirable to not have any errors, what really matters is how UNC changes over the measurement interval. Nonzero, but not increasing, UNC values are ok.

Test a channel continuously

Why? When?
Having the ability to monitor signal strength is highly useful when pointing/positioning an antenna. Here are two methods:

Using femon

Recent versions of femon, a command line utility included in the LinuxTV_dvb-apps package, have this functionality built-in, and simply require the user to run:

femon -H

which provides "human readable" output, as opposed to the default Hexadecimal representation of the varying attributes of the signal.

Script

This following script tunes a channel and simply converts the Signal strength into a percentage in the tzap output.

#!/usr/bin/env python

import sys

f = sys.stdin
while True:
       l = f.readline().strip()
       fields = l.split(" | ") 
       if len(fields) < 2:
               print l
       else:
               # Sig Strength
               sigStr = fields[1].split(" ")[1]
               sig = int(sigStr, 16) / float(0xffff)
               fields[1] = "signal %.1f%%" % (sig * 100.0)

               # BER 
               berStr = fields[3].split(" ")[1]
               ber = int(berStr, 16) 
               fields[3] = "ber %08d" % (ber)
               print " | ".join(fields)

Original author is : Matt Doran

It requires a channels.conf file, and tzap. It would be used by running:

tzap channel 2>&1 | tzapfilter.py

which would produce output like the sample shown below:

using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
tuning to 578000000 Hz
video pid 0x0000, audio pid 0x0000
status 1f | signal 51.0% | snr 0000 | ber 02097151 | unc 00000000 | FE_HAS_LOCK
status 1f | signal 51.1% | snr 0000 | ber 00000000 | unc 0000000f | FE_HAS_LOCK
status 1f | signal 51.1% | snr 0000 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
status 1f | signal 51.1% | snr 0000 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
status 1f | signal 51.0% | snr 0000 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
status 1f | signal 51.0% | snr 0000 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
status 1f | signal 51.0% | snr 0000 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
status 1f | signal 51.1% | snr 0000 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
status 1f | signal 51.1% | snr 0000 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
status 1f | signal 51.1% | snr 0000 | ber 00000000 | unc 00000000 | FE_HAS_LOCK

Also See

• Improving signal quality