[mythtvnz] DVB-T signal strength

[Dr. David J. Knowles]

Try 2.

There appear to be a number of potential issues with the Nova T card. I
will list all the possible fixes but I believe that some are fixed in
the later kernel releases.

In case you don't know this dmesg is a very useful tool. It reports how
the kernel started and loaded its modules (and any subsequent errors).
Run this as root

sudo dmesg | more


These are changes to the/etc/modprobe.d/options file (in some versions
of Linux you can put this in a different file in the modprobe.d
directory and it will be taken up, I think ubuntu is one of these).

You know about the signal strength one:
#switch on onboard amplifier on Nova-T-500 card
options dvb-usb-dib0700 force_lna_activation=1

As the card is a hybrid one which promotes a USB interface it is
possible to have problems with the USB system disconnecting the Nova T
capture modules. The following option line stops this behaviour

# stops it from going to sleep thereby giving the disconnects
options usbcore autosuspend=-1

The inbuilt remote control module can also cause problems. The following
line turns this off.

# disable the on-board remote control. This is the bit that was giving
me errors in demsg relating to MT2060 and worryingly 'over current warnings
options dvb_usb disable_rc_polling=1


There are two versions of the firmware for the Nova T card. They are:

    * dvb-usb-dib0700-1.10.fw
    * dvb-usb-dib0700-1.20.fw

The second firmware is a later version but has been reported to be
somewhat flaky. I have seen late versions of Linux requiring the second
firmware. Both work and it is possible to change to the earlier version
of the firmware by simply using a link in the /lib/firmware directory.

cd /lib/firmware
mv dvb-usb-dib0700-1.20.fw /root
ln -s dvb-usb-dib0700-1.10.fw dvb-usb-dib0700-1.20.fw


These are the OS related things, now for the MythTV configuration.

run the mythtv-setup program

Select capture cards
Select the DVB device(s)
Select Recording Options

Make the DVB Tuning delay at least 75ms, both 75 and 100 have been
reported to help.

Check the Open DVB card on demand
Uncheck Use DVB card for active EIT scan.

The last two turn off the detection of the program guide. This means (I
think) that the program guide will not appear to MythTV direct from the
card. The real reason for the last two is to turn off the card when it
is not in use recording.

As a number of these changes reduce functionality of the card I suggest
you try them one at a time to see which works for you. The DVB Tuning
one is a popular fix.

I hope this helps.

David

------------------------------------------------------------------------
Dr. David J. Knowles  <dknowles at clearfield.com> Senior Systems Architect
Phone (+64 9)  358 2081                          Clearfield Software Ltd
Fax   (+64 9)  358 2083                    1st Floor 8-10 Whitaker Place
Mob   (+64 21) 75 9090                P O Box 3901 Auckland, New Zealand
------------------------------------------------------------------------



Graeme Woollett wrote:
> I'm having some issues with my Nova T 500 card.  I can scan and lock to 
> channels, but after a while they go jumbled and I get "error encountered 
> displaying video"
> I suspect that it is a interference or signal strength issue.
> I'm running the latest DVB source (it supports for my HVR4000 card).
>
> Is 58% signal strength (from OSD) enough?
>
> What are typical figures?
>
>   
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