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For an introduction, read User_Manual:DVB.


Adjusting Antenna

Picking up DVB-T can be very challenging. Using MythTVSetup, you may notice channels being detected, but too weak for MythTV to identify and record in its database. This does not mean that it is impossible to pick-up the channel, you may just need to change the direction your antenna faces. Doing this with repeated MythTV scans is not a pleasant option as it takes so long to scan for channels.

There are 2 options to ease this process:

  • Add the channels manually to the MythTV database. There are 2 tables to update with this method, dtv_multiplex and channel. Even if you are comfortable with the SQL to do this, and you will likely have to guess at some of the values. Furthermore, you are entering possibly dirty values (that you guessed at) into your database, and it might be wise to remove these rows in the future once you have your antenna in the ideal position, so that you can get the values that mythtv thinks you should use.
  • Use Kaffeine. This involves hacking up the ~/.kde/share/apps/kaffeine/channels.dvb:
    • Start by running something like
      scan -A 1 -d 0 -t 1 /usr/share/dvb/atsc/us-ATSC-center-frequencies-8VSB
      (for ATSC DVB-T). It will report the channels found now.
    • Hopefully you have some resource that will inform you of what channels are a possibility (for me here in Ottawa, I was lucky enough to find this site. Once you've identified the channels, use wikipedia to determine the frequencies.
    • Do a DVB scan in Kaffeine... press 'c' to go to the channel editor, then Start Scan. Add any channels found, and quit Kaffeine. This will create a ~/.kde/share/apps/kaffeine/channels.dvb such as:
 TV|4-1 CBOT-DT|49(2)|52(eng)(ac3),53(spa)(ac3),|0|10|17193|Atsc|539028|0|v|-1|-1|108|-1|-1|-1|-1|-1|4097|||0|
 TV|20-1 CKXTDT3|65(2)|67(eng)(ac3),68(eng)(ac3),|0|2|23297|Atsc|509028|0|v|-1|-1|108|-1|-1|-1|-1|-1|20481|||0|
 TV|20-2 CKXT|81(2)|83(eng)(ac3),|0|3|23297|Atsc|509028|0|v|-1|-1|108|-1|-1|-1|-1|-1|20482|||0|
 TV|9-1 CBOFT-D|49(2)|52(eng)(ac3),|0|1|23297|Atsc|521028|0|v|-1|-1|108|-1|-1|-1|-1|-1|4|||0|
    • Now with the knowledge of what other channels should be possible to pick-up, duplicate a line for each possible missing channel. Now modify the new rows, change the channel name, and frequency. Determine the frequency by comparing the frequency on the wiki site to the frequencies in /usr/share/dvb/atsc/us-ATSC-center-frequencies-8VSB, then remove the '615' suffix from the frequency in the file. In this example, the rows added were:
 TV|7-1 CBS, WWNY|49(2)|52(eng)(ac3),|0|1|23297|Atsc|177028|0|v|-1|-1|108|-1|-1|-1|-1|-1|4|||0|
 TV|50-1 ABC, WWTI|49(2)|52(eng)(ac3),|0|1|23297|Atsc|515028|0|v|-1|-1|108|-1|-1|-1|-1|-1|4|||0|
 TV|18-1 PBS, WNPI|49(2)|52(eng)(ac3),|0|1|23297|Atsc|527028|0|v|-1|-1|108|-1|-1|-1|-1|-1|4|||0|
 TV|27-1 OMNI 1|49(2)|52(eng)(ac3),|0|1|23297|Atsc|551028|0|v|-1|-1|108|-1|-1|-1|-1|-1|4|||0|
 TV|57-1 PBS, WCFE 57|49(2)|52(eng)(ac3),|0|1|23297|Atsc|617028|0|v|-1|-1|108|-1|-1|-1|-1|-1|4|||0|
 TV|16-1 PBS, WPBS 16|49(2)|52(eng)(ac3),|0|2|23297|Atsc|635028|0|v|-1|-1|108|-1|-1|-1|-1|-1|4|||0|
 TV|66-1 OMNI 2|49(2)|52(eng)(ac3),|0|1|23297|Atsc|785028|0|v|-1|-1|108|-1|-1|-1|-1|-1|4|||0|

No doubt about it, these are hacked values, and kaffeine would likely have set some other values, but they seem sufficient to show you the strength of the signal in real time in the next step. Don't worry if you get into trouble, just delete the file and run kaffeine again, doing another DVB scan.

    • Start kaffeine, click on TV, and select a channel. Once selected, press 'c' to view the signal strength. Now the person helping out can adjust the antenna, and you can tell them if they are getting a stronger or weaker signal. The only way to change the channel you are viewing the strength of is to leave this dialog, select the new channel, and press 'c' again.

No matter what option you choose, I recommend you read

See Also

The following site has a great deal of useful information about antennas, such as safety tips: