TVWORKS / TV3 / C4 Gone!

[rjbathgate]

Hi,

I live in Tauranga and pick up the Kopukairua transmitter, and have a Dvico TVix HD Freeview Tuner.

A week or so ago, I installed it, and got pretty poor reception, but I could get all the normal channels, 1,2,3,c4 etc etc...

I didn't use it for a week because the reception was poor, but today I've installed a decent mast head amp etc, and reception on TV1, TV2, and other channels is excellent.

However TV3 and C4 are not picked up at all. Channel Scan just skips past where they should be (which is C51 on this transmitter).

This seems very srange as a few weeks ago I could pick up TV3 and C4.

I therefore figured the new amp might be causing problems, however I've tested it with my old setup, and I also can't get these two channels anymore (when I could before!).

Any ideas/sugegstions would be most appreciated!

Thanks in advance,
Rob

[kiwisteve]

Have you checked with neighbours or a retailer to confirm the DTT is running ??

[rjbathgate]

Local retailer says no problems known about... don't have any neighbours to ask though...!

[rjbathgate]

Just an update on this...!

I've been in touch with a very helpful guy at TV3... he's looking at a few possibilties, doing signal tests etc but is equally confused!

He suggest a few ideas for me to try out, including the possibility that i've fluked a critical cable length for the frequency in question (i.e. the exact length results in a flattening of the wavelength), and he also mentioned a colleague once came across a similar problem which was caused by a splitter which was causing issues with a certain signal and dropping out a specific signal as a result. But we don't have a splitter anywhere.

I'm going to go back to basics with all the connections, and put things back one at a time, to see if there is any one thing that causes the drop out. Or if I can indeed get it back at all.

There is also a joiner up on the aerial on the roof which joins the two aerials (VHF and UHF) - TV3 guy suggested I remove the VHF connection to again try and isolate any specific problem area.

The channel missing (51) is 711.25Mhz, with ch49 at 695.25Mhz - and on ch49 I get excellent/perfect reception - strange since 51 is very close. With this in mind, am I safe presuming it's not a problem with it being out of range for the aearial? (We have a pretty big aerial collection on the roof).

Any thoughts / suggestions on the above would be most apprecaited,

Cheers

[kiwisteve]

Try adding the channel manually in the case of a Zinwell its Manual Channel Scan
also what is the Strength and Quality readings from the two other UHF Channels ??

[rjbathgate]

Have tried to go manually to C51, and there is no signal whatsoever.

On the other two UHF channels, readings at in excess of 25dB (in relation to where 14dB is considered too poor), and percentage reading lies between 98% and 100% - so pretty good.

Cheers

[kiwisteve]

Try entering 714.00 Mhz
also are you line of site to the transmitter ?

[rjbathgate]

Yeah I can see the transmitter from my window, and the other channels all come from the same transmitter.

I don't think I can manually enter a Mhz value into my STB.

I have just tried removing the VHF aerial as I was suggested to that that might be interfeering - Unfortuantly disconnecting the VHF aerial didn't make any difference... I removed the VHF aerial connection from the joiner box, leaving the UHF coming in and the output going out.

When I was on the roof however I didn't think to try avoiding the joiner box/diplexer altogether (connecting aerial to cable that goes into loft). The diplexer is in pretty bad condition, rusty and was full of spider webs and obivously not very weather proof anymore! Think it be worth going up again and connecting the UHF directly to the loft cable? I.e. is this joiner box possibly the problem? When disconnecting the VHF aerial I was just thinking the VHF signal might be causing the problem - didn't think maybe it's the actual box up there.

When staring at the tv is dismay before I went onto the roof, I did however get small bits of low signal on TV3 on channel 51 - very poor, and not for very long, but definately something there, which suggests the signal is there, just very weak indeed. I'm not sure what this indicates though, or where to go from here!

Cheers

[kiwisteve]

If you are line of site to the transmitter you should not need a mast head amplifier. A decent UHF antenna and Good Quality RG6 coax should be sufficient . I think I would try without the amp.
you could also try UHF antenna direct to DTV receiver no diplexers / splitters etc

[rjbathgate]

Yeah, tried without the amp (didnt have the amp when first got the STB), but reception was really poor (as is analg reception). Since having the amp, reception is great on all others.

Without amp, reception is poor on all others, and c51 still doesn't pick up anything.

I'll try it tomorrow without the diplexer on the roof either.

Cheers kiwisteve

[herbie_g]

There are a coupla other things to check as well...

1/ the orientation of the uhf aerial is correct for your area. Have a look around neighbours who have uhf aerials and orientate accordingly. IE: Horizontal vs, vertical polarity.

2/ make sure the aerial is pointing directly at the transmitter.

3/ remove all amps, diplexers, splitters etc... from the system (if pos) so the lead from the aerial to the STB is a straight run.

If that hasn't sorted the prob, them run a new length of RG6 cable as a temp feed from the aerial directly to the STB. You could try this first, but if you did you wouldn't know where exactly the fault is.

It's also a good idea to check your connections both at the aerial and STB to make absolutely sure there are no shorts between the inner cable and the outer braid.

Hope this helps.

Herb.

[Apsattv]

You should not need the amp, you must have a lot of loss in the setup.

You mentioned the bad diplexor, that will be much of the problem along with a bad run of coax.

[kiwisteve]

something really wrong if you need an amp and line of site !! I can get lock on all 3 muxes not line of site and at 71km with a test antenna sitting on the back porch !!
Dont always go by the neighbours antenna direction . I knew of a case where they had it wrong and the other neighbour copied !

What make and model is the antenna ? I have come across one brand that wont work properly on the top channel group !!

[rjbathgate]

humz as soon as you said I shouldn't need a mast head amp when I can see the tower (and it's only about 5km away) i started to think...

another trip up the roof to take that diplexer off i think....! that would explain why we've had bad reception on analogue since we moved in a few years ago too!!!

will let u know how i get on!

Thanks all

[kiwisteve]

My final suggestion is to check the UHF analogue channels they should all be noise free at that range If they are not then you have an antenna / feeder or plug problem

[rjbathgate]

I am currently the happiest man around!

Fixed!!

Bypassed the old diplexer on the roof, and volia, great reception on everything! 100% on CH51!

Going to see if I need the mast head amp in at all now... although it's not doing any harm in is it?

Thank you all for all your help, much apprecaited :)

Rob

[rjbathgate]

Yeah, do need the amp - loose a fair amount of signal without out... guess the line of sight isn't enough... still, I'm happy, got the amp, and it's all working now...

Thanks again

[kiwisteve]

Be careful with AMPS they can overload , cause intermodulation between channels and in worse case re radiate back out the antenna to other Non Tv services :D

[herbie_g]

Question?

You said you were really happy because you removed the diplexer and got ch51 @ 100%, right? So, why would you want to put in an amp?

If it's to improve the loss of VHF analogue channels, then you're asking for trouble. Install another diplexer capable of digital instead.

[rjbathgate]

Sweet, cheers kiwisteve - everything seems to be good around the house with the amp on :)

[rjbathgate]

Question?

You said you were really happy because you removed the diplexer and got ch51 @ 100%, right? So, why would you want to put in an amp?

If it's to improve the loss of VHF analogue channels, then you're asking for trouble. Install another diplexer capable of digital instead.

I got ch51 at 100% when the amp was installed.

I got only about 60% when the amp wasn't installed.

On analgue, without amp I get heaps of noise. With amp, I get chrystal clear analogue too (on UHF). Although my VHF aerial is currently unplugged until I get a new dixplexer up there.

Cheers

[Apsattv]

It sounds like you also need to replace the coax it must be extremely lossy.

[kiwisteve]

yes probably some of that horrible stuff with nearly no braid and a centre conductor the diameter of a hair !! l Use some Good Quality RG6 such as Belden or TimesFibre
beware of some Asian coax with little braid and a very dull outer black plastic jacket the UV in NZ kills it in months not years

:D:D:D

[rjbathgate]

Cheers, but now I can get 100% signal, i'm happy with it, happy to use the current set up - not sure i've got it in me to spend anymore time in my loft!

[kiwisteve]

Yes too hot in the roof this time of year !

[herbie_g]

Having had been in the installation industry for many years, I would strongly advise that you replace the co-ax as others have suggested asap.

The reason I say this is that all too many times people have claimed to have poor signal, bought an amp which has temporarily 'cured' the problem. Only to find that their signal gradually gets worse again.

If your existing cable has either had water in it, or has water in it, it tends to create an electrical short which has been known to burn out amps.

What you have done, in essence, is remove the web without killing the spider first.

Hope this helps.

[rjbathgate]

Having had been in the installation industry for many years, I would strongly advise that you replace the co-ax as others have suggested asap.

The reason I say this is that all too many times people have claimed to have poor signal, bought an amp which has temporarily 'cured' the problem. Only to find that their signal gradually gets worse again.

If your existing cable has either had water in it, or has water in it, it tends to create an electrical short which has been known to burn out amps.


Oh dear... so we talking all the coax right from the aerial connection down to the wall sockets? Or just external ones that have the chance of water?

What would the connections be to the actual aerials? There are big chunky black plastic connections - these easy to replace the coax in?

Thanks again

[herbie_g]

Oh dear... so we talking all the coax right from the aerial connection down to the wall sockets? Or just external ones that have the chance of water?

What would the connections be to the actual aerials? There are big chunky black plastic connections - these easy to replace the coax in?

Thanks again

I would run a test cable to start with from the aerial directly into your stb, then look at the sig/quality on the stb. If the quality is 80+% then you definitely have a prob in your cabling somewhere.

Next stop would be to check your splitter (if you have more than one outlet in the house. Note I said outlet, not TV's). If that looks good, ie: no sign of corrosion or all metal parts look shiny, then any water hasn't reached that far. So, it would just be a matter of replacing the lead from the aerial to the splitter.

The other thing to check would be the age of the cable. This can be done by looking on the side of the cable for writting. If it says RG6 or similar, chances are the cable is relatively new. RG59 would indicate it was installed sometime in the 90's - this probably would be OK too. 2002 or 2006 was designed in the days of VHF only TV, and is not suitable for UHF at all.

Might sound a bit complex, and it is for a newbie, but once you get the hang of it it'll all make sense.

Cheers.

[rjbathgate]

Hey,

Cheers Herbie... it does all make sense, cheers

All the cable is RG6 (from aerial, into splitter, and then down to outlets).

The splitter in the loft (had been there for as long as house was built I think) is in good condition, no signs or corrosion or rust.

Will run a new cable from aerial to stb to see what I get. If I get bad signal even with that, I can put signal quality down to poor reception rather than cabling.

If I get goodish signal with new cable and nothing else connected, then yes, I will replace the roof to loft cable...

Thanks heaps for your help

Rob

[kiwisteve]

And of course you have any un-used outlets terminated with a 75ohm termination plug !!

[rjbathgate]

Out of interest, where does 3c-2v cable lie in the quality scheme of things? Google tells me it's Chinese..... got a short length of it which would be ideal for some small lengths between a splitter...

cheers

edit: just realised it's very narrrow, too narrow for f type at least, so not very handy

[herbie_g]

Sorry bout the delay, basically the thinner the cable the more lossy it'll be. RG6 is the industry standard these days... Also, the splitter can be rather lossy as well. I would suggest getting an F-type one to replace your existing one, if you feel your existing one maybe more than 8 years old.

Cheers.


Out of interest, where does 3c-2v cable lie in the quality scheme of things? Google tells me it's Chinese..... got a short length of it which would be ideal for some small lengths between a splitter...

cheers

edit: just realised it's very narrrow, too narrow for f type at least, so not very handy

[kiwisteve]

It should be done properly Herb , under pressure from a dehydrator plant
!!!! :D:D:D:D