[mythtv-users] Thinking of moving on from MythTV :-( Any suggestions? (for the UK)

[Mike Perkins]

On 02/01/17 00:25, Damian wrote:
> On 01/01/2017 21:16, Simon Hobson wrote:
>> Damian <myth at surr.co.uk> wrote:
>>
>>> I meant the Live TV from within MythTV.
>>> I don't have a real TV to check signals with, but did have TV guys come out and check the signal
>>> a couple of years ago. The signal runs through 2 boosters now.
>>  From those last 7 words tell me that you have an aerial problem.
> I understand why you have come to that conclusion, but I'm sure that's not the whole story. If it
> was, why would the chanels almost always be available after a reboot?
> I have has all of the channels working fine since all of the major transmitter changes. This problem
> has been going one for about 4 months.
> Earlier today, I only had a few channels working.
> Just now, I logged into the sever (via vnc) and checked the transports. They are all correct
> compared to https://ukfree.tv/transmitters/tv/Mendip
> After closing mythtv-setup, which then restarted the backend, all of the channels are working fine
> again. I didn't even reboot this time, just restarted the backend.
> What will happen now is that the BBC channels will probably stop working by tomorrow. Then the rest
> may or may not follow.
> So, although my aerial setup is less than ideal, it doesn't seem to explain this 'working for a bit'
> pattern.
>
>> It would be a good idea to have at least one TV connected up as a TV - it gives you a most basic
>> bit of kit to check your signal with, without all the complication of having various layers of
>> hardware and software which may or may not be giving an issue.
> Agreed.
> I haven't owned a TV for years unfortunately. Don't want to buy one just for testing, and borrowing
> one seems a bit nuts too. Definately agree that it would be useful though.
>> But, you shouldn't have 2 boosters. It's a common misconception that chaining boosters will help -
>> in general it won't, because if you have that weak a signal, your boosters will amplify the noise
>> and you'll end up with plenty of signal but with a crap signal/noise ratio (snr). snr is probably
>> more important than signal strength !
> When the so called 'experts' came around a couple of years ago, they showed me how much better the
> signal strength was and that was the end of my problems for a long time.
> Although I don't question that your way of setting things up would be better, I just don't think
> it's the actual problem that I'm having due the the reason I mentioned above.
>> Ideally you want an aerial with enough gain that you don't need a booster at all - at least for
>> one tuner. A booster should only be needed to compensate for the loss of signal when it's split
>> amongst several tuners, or for very long cable runs.
>> Normally I would recommend getting the highest gain grouped aerial you can - avoid wideband
>> aerials. My normal supplier is http://aerialsandtv.com where there's a good choice, and "proper"
>> information. By proper information, I mean there are graphs of gain because there is no single
>> gain figure for an aerial.
>>
>> If you look at http://aerialsandtv.com/atvstockaerialtests.html you'll see that they provide
>> graphs for each aerial they sell showing how the gain varies with frequency (RF channel). You need
>> to look up the RF channels used by your local transmitter and select an aerial that provides good
>> gain for those channels.
>> The Log36 has a fairly flat gain across the whole band - but it's gain isn't very high, Except for
>> the lower end of group E, you'll see that the Yagi 18 has significantly higher gain within it's
>> band. For the frequencies used by my local main transmitter (Winter Hill), the Yagi 18CD provides
>> something like 6dB higher gain that the Log36. it doesn't sound much, but on a logarithmic scale,
>> 3dB is double the power, and 6dB is 4 times the power !
>>
>> Many aerial fitters are charlatans and will fit whatever is cheap - often "contract bacofoil"
>> types, of which the least said the better.
>>
>> And don't forget that the cable degrades as well, especially if it's poor cable or badly
>> installed. If having a new aerial fitted, have new WF100 (check that what they install is real
>> WF100 - many will tell you it is but fit crap) cable fitted, and make sure all the joints are
>> given a good dose of silicone grease (you'll need to provide it) to minimise degradation due to
>> corrosion. Applying it to all the fittings, bolts etc will also mean that they can be undone in a
>> few years time !
> Thanks Simon. This all sounds like great advice. However, due to the pattern I'm experiencing, I
> think I could go through all of that time and effort and not experience any difference.
>
A couple of points gleaned from your responses. First "signal strength" isn't the whole picture. If 
you have amplifier(s), then they are amplifying the noise as well as the wanted signal.

The important metric is "signal to noise ratio" and only after that is signal strength important. 
Even then, a signal which is too strong can be as bad as one which is not strong enough.

Second, you say that after a reboot everything is fine and then begins to go off after a while. That 
suggests to me a cooling problem. The chips in the tuners are fine when fresh but degrade once they 
have been used for a while. Is the ventilation around your box adequeate?

Another related problem may be the gradual failure of components in your tuner chain. Things like 
the chips, yes, but also caps and even power dongles if your tuners use them. Replacing a tuner may 
be one solution, though this involves spending money, of course. It would be preferable to locate 
the source of the problem before spending but sometimes that isn't possible.

If you have a spare box I would suggest making up a basic standalone system using one of the tuners 
and using that to test. That way you can see if the tuner is at fault or some other part of the 
chain. Swap tuners until you see something that gives you an answer.

-- 

Mike Perkins