[mythtvnz] MultiRec Turned Off?

[Stephen Worthington]

On Mon, 22 Feb 2010 08:21:47 +1300, you wrote:

>----- Original Message ----- 
>From: "Stephen Worthington" <stephen_agent at jsw.gen.nz>
>To: "MythTV in NZ" <mythtvnz at lists.linuxnut.co.nz>
>Sent: Monday, February 22, 2010 1:46 AM
>Subject: Re: [mythtvnz] MultiRec Turned Off?
>
>
>>>Looks to me that the table is the same for Warite and KauKau.
>>
>> I would think it would be sensible for the transmitters to all use the
>> same mplexid/serviceid values throughout the country.  So you would
>> expect to only have different freqid values from one transmitter to
>> the next.  But not having seen anyone else's channel table values
>> until now, I was not sure if they had been that sensible.  When the
>> transmitters are far enough away from each other, they can also reuse
>> the same frequencies for transmitting multiplexes, so it is entirely
>> possible that several transmitters in NZ share the same freqid values
>> too.  I would have thought though, that KauKau and Wharite were a bit
>> too close to each other for that.
>
>What is the issue that might make it "too close".  Are you referring to possible ghosting that would happen with single channel 
>analogue signals?  Seems that is not so much an issue with digital.  (Perhaps it is something to do with signal locks?)  Or are 
>there other issues?  Maybe historical channel selections / commitments?
>
>Looking at http://lincrad.co.nz/transmittersites.html the Sky Tower Digital channels are different.  (28,32 40)

In theory, UHF signals at those frequencies are line-of-sight only. In
practice, there are various ways that the signal can, on occasion,
under the right conditions, bounce and get to places where it should
not get to.  When it does, anyone getting both signals on the same
frequency is not going to get good reception, even with a digital
signal.  So best practice in assigning frequencies should take that
into account and try to maximise the distance between use of the same
frequencies.  Wharite and KauKau are normally high power transmitter
sites, so I am surprised that they were assigned the same frequencies
for the digital multiplexes.  I would have thought it better to assign
frequencies used by low power transmitters in each other's area.