[mythtv-users] DVB-T Hell in Sydney

Mark Perkins perkins1724 at hotmail.com
Wed Jun 22 08:29:06 UTC 2016

> 	1. How do I identify the transmitter, is there some way to determine
> it from the network id or other data in the stream?

Personally I would go by matching the frequency in your database against the
frequency listed online against the various transmitters.

> 	2. Why are all my scanned channels shown as having vertical
> polarisation when the suspected channels from Newcastle (Australia)
> transmitters should have horizontal polarisation? I fear my antenna is
> horizontal 

I'm not 100% sure, but I don't think **from a mythtv perspective** that
polarisation would be relevant to tuning an individual dvb-t channel
(clearly it is important for your antenna etc). The details for the
dtv_multiplex table suggest that the polarity field has no default value but
the notes imply that it's usage is for dvb-s (satellite). My guess is that
the channel scan process is just chucking a 'v' value in there (rightly or
wrongly) for dvb-t. I have just checked my database and I have a
horizontally polarised antenna and transmitter but I also have the 'v' value
in my polarity field. I would ignore the polarity field for now.

My very very rough calcs based on a very very rough memory of how radio
attenuation works says that over linear unobstructed terrain the Newcastle
transmitter would be approximately 10times more powerful at your location
compared to the Bouddi transmitter. Once you include that your antenna is
polarised to match the Newcastle transmitter and that the frequencies in
your table match the details published online for the Newcastle transmitter
I would say with extremely high confidence that you are receiving the
Newcastle transmitter channels. Whether you would be better off changing
your antenna polarisation to match Bouddi would be subject to an analysis of
the obstructions over the two paths (or some experimentation with something
that can report signal strength and bit errors, maybe tzap or dvbscan or
equivalent) but my thoughts are that you would be better off sticking with
Newcastle for now.

More information about the mythtv-users mailing list