Freeview audio cutout during TV3 news tonight?

Forums › Freeview (DVB-T/DVB-S) › Freeview audio cutout during TV3 news tonight?

casewindow

310 posts

Ultimate Geek

#66791 23-Aug-2010 18:31

We have just got a MagicTV box in the last few days and tonight watching TV3 news (outputting digital audio over optical to a Denon AVR589) the audio cut out for a split second twice. Once when talking to the Australian correspondent and then once when the newsreader was talking.

What can cause these cutouts?

I checked the signal strength (which was 73% strength and 100% quality) which was the same as when I checked it the other day.

1 | 2

14 posts

Geek

#373113 26-Aug-2010 13:41

check to see if your decoder gives a COFDM average reading if it does then it should be -250 or greater, if below -250 then you will have audio and picture issues.
water ingress in the aerial cabling or the aerial connection will cause these sorts of issues

casewindow

310 posts

Ultimate Geek

#373130 26-Aug-2010 14:17

Hi there,

I searched the magicTV manual for COFDM but didn't find anything.

I guess I could go into the roof and check for any problems where the aerial comes in (that would be the first point of water entry I would think?)

Also the old Zinwell box never did this.

Interestingly the Zinwell reports 100%/100% for strength and quality on the frequency that MagicTV reports 74%/100%. Though the Zinwell is now on a different port in a different room (closer to the aerial) but I would not have thought 10 meters or so would degrade signal strength by 26%.

This problem only happens on TV3 outputting Dolby Digital. Other channels are fine.

geoffp

14 posts

Geek

#373151 26-Aug-2010 15:21

The Zinwell box is by far the best there tuner is able to run at a very low signal level
It would sugest that the magic tv box has a software issue, all non approved freeview boxes struggled at the start with audio on TV3.
The first point for water to get in is at the belun on the aerial, i suspect this is not the issue and it is the magic tv box

casewindow

310 posts

Ultimate Geek

#373161 26-Aug-2010 15:34

Ah ok thanks for that. The house is pretty new so I wouldn't think there would be water issues. Plus the zinwell worked without a hitch right up until we swapped over.

The thing is - it has only happened 3 times and always during the TV3 news. I have emailed magictv support - hopefully they can shed some light. I just hope it isn't some hardware issue with my box.

The Zinwell was reliable, just lacked any features (the most infuriating of which was the lack of a simple timer).

As such when I saw the Zinwell 250gb PVR on sale for $300 I ignored it and got the MagicTV for $560. So far other than this audio glitch it has been really good and revolutionised how we record and watch TV.

Edit: I should probably get our aerial checked as it was only installed 2.5 years ago and we have a clear line of sight to the mount kaukau transmitter in wellington.

geoffp

14 posts

Geek

#373285 26-Aug-2010 18:41

Nice, word of advise, your aerial is installation is new in the big scheem of things, HD tuners will fail if FM and VHF sigals are there over 65db, get your local tech to install a UHF ? VHF diplexer to filter out any of these signals. TV tuners are very similar to launch amplifiers and can be overdriven by outside transmision signal levels, Kingray make a great filter that separates all 3 bands if used in reverse and only alows UHF through if confg correct, too much VHF will distort the data on UHF, and standing wave will cause these issues.
Good luck, hope this helps

casewindow

310 posts

Ultimate Geek

#373329 26-Aug-2010 20:01

Thanks for that. I am pretty sure we have a UHF only aerial as I got it specifically installed to only receive terrestrial freeview. It picks up analog channels but the quality is very low for all of them.

geoffp

14 posts

Geek

#373341 26-Aug-2010 20:39

ok, this tells me something, VHF will be low as the aerial is not matched to those signals, however a UHF aerial will attract FM, if the analog UHF appears low it may not be the case, the UHF analog signals may be very noisey from RT digital crossover, therefore install a 520 high pass filter, this will reduce all noise levels from that frequency down by 40db, this will clean up the UHF analog signals above 520 mhz and allso clean up the data in the DVB-T transponders
happy viewing
Keep in mind that UHF analog signals are on average 12 lower than DVB-T carrier measurement, so if Prime for example appears very poor quallity almost black and white then the DVB-T carriers will be on the lowest end of the stb threashhold

Sharesies

Trade NZ and US shares and funds with Sharesies (affiliate link).

casewindow

310 posts

Ultimate Geek

#373360 26-Aug-2010 20:56

Thanks for that - I'll look into getting that type of filter. First I want to check what is in the 'comms' junction area in the garage and make sure everything is screwed in tightly there. I looked on the hills site at their high pass filter & I vaguely recall a similar looking thing in there.

bfginger

1268 posts

Uber Geek

#373679 27-Aug-2010 17:20

Has Freeview comitted to not do broadcasts below 520MHz in future?

geoffp

14 posts

Geek

#373724 27-Aug-2010 19:40

Confirm, all FV TX will be above 520mhz C27 through to C45 666mhz, there is too much cross over from digital RT below 519mhz and they have sold off 750mhz up to Telecom

casewindow

310 posts

Ultimate Geek

#374476 30-Aug-2010 18:56

Regarding the 520 high pass filter. These are the junction points in our 'comms cabinet' in the garage:

https://i.imgur.com/KRtbO.jpg
Which seems to be this splitter:
http://www.pimfg.com/Product-Detail/VS22-08

https://i.imgur.com/W4099.jpg
Which seems to be a "5 way TV/Video combiner"

I take it that the 520 high pass filter would come after the cable has been through these devices?

geoffp

14 posts

Geek

#374659 31-Aug-2010 07:56

The 520 hp filter should be installed on the uhf aerial feed only,if you have vhf signals as well then the filter will knock those signals out as well, if all of you tv's are hd then this will not matter, it is recomended that all aerials should be cabled seperatly this is why a 5 way combiner is now common in home hub systems

casewindow

310 posts

Ultimate Geek

#374723 31-Aug-2010 09:48

So what is the purpose of the combiner again?

Currently the aerial (just one, a UHF one) goes into the splitter, and the splitter goes off to all the rooms in the house. We have only 2 TV's both are flatscreen HD LCD's.

Should I somehow be using the combiner instead?

geoffp

14 posts

Geek

#374852 31-Aug-2010 12:47

No if you only have uhf aerial and only 2 hd tv's then running the aerial cable into the splitter is fine, the combiner is for introducing other signals such as Sky tv or door camera's or vcr's so that they can be viewed in all rooms

casewindow

310 posts

Ultimate Geek

#374952 31-Aug-2010 15:46

MagicTV support replied to my email and suggested I reload the existing firmware (3.12) to rule out firmware corruption.

I know there is a beta firmware out there as well (3.13b2) which I may try.

I tried finding a 520mhz high pass filter but they seem to be as rare as hens teeth. I found a reference to one on the hills site but their bandwidth has been exceeded so no details!

1 | 2