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Reception Issue In New Home


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#1 Chris Dowling

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Posted 05 September 2012 - 08:26 PM

Hey guys, Recently installed 3 points in a house, one splitter and one phased array antenna.

When i'm testing the signal with my meter it shows 30mer and 75db (too high i think) from the antenna i check the actual tv program through the meter and works fine.
However there is always an issue during **** weather. mainly losing abc and win.

I am coming off Warrnambool City transmitter and less than 1km from the transmitter, mySwitch says its great coverage however we have the highway in between the antenna and the tower so there are a few cypress trees half way, but they dont look to be a problem as this house is very high.

I'm stumped as to whats going on here. Any ideas or tips where i can look?

regards
Chris


PS, not amplified and its windy and raining. roughly 20m below the transmitter line of sight

Edited by Chris Dowling, 05 September 2012 - 08:40 PM.


#2 debruis

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Posted 05 September 2012 - 08:57 PM

Hi Chris,

I do a lot of installations close to the towers in Sydney. I have found that higher signal will cause you problems when the installation is very close to the towers. I can only suggest to antenuate the incoming signal from 15db -20db below the current level and see if that makes a difference.

#3 beeblebrox

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Posted 05 September 2012 - 09:04 PM

Chris is that at the wall outlet or at the antenna?

#4 Chris Dowling

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Posted 05 September 2012 - 09:25 PM

At the antenna, i will have to re check at the actual tv point. sorry James, also recently sent you an email regarding the issue

Edited by Chris Dowling, 05 September 2012 - 10:15 PM.


#5 M'bozo

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Posted 05 September 2012 - 10:23 PM

one phased array antenna.


My usual choice for a vertically polarised transmitter with possible obstructions in the way.

shows 30mer and 75db (too high i think) from the antenna


75dB from the antenna is fine. This should be giving around 65dB at the outlets. Presumably all cabling/flyleads is/are quadshield, the splitter is F shielded, etc etc.

More important measurements for me would be cBER and dropped packets - when things are fine, and then when they go pear shaped, to get an idea of the variation in the received signal quality between the two states.


i check the actual tv program through the meter and works fine.


Even when the problem is evident on the TV?

The channels that don't appear to have a problem may still be affected in these conditions, just not be going below the error correcting capabilities of the television.


However there is always an issue during **** weather. mainly losing abc and win.


If you can look at the spectrum of the individual channels when this is happening, that may give a clue. Vertical objects (eg trees) moving between your receiving antenna and a vertically polarised transmitter can give some interesting frequency dependent effects, which would be visible on a spectrum display. (depending on your meter's resoution.)

Is it wind & rain combined, or does wind only have the same effect?

A reception path problem may require optimising the location of the antenna, when the fault is evident.

Edited by M'bozo, 05 September 2012 - 10:24 PM.


#6 Chris Dowling

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Posted 05 September 2012 - 10:32 PM

Both wind and rain as far as I have been told. I will do more checks tomorrow night and hopefully rectify the problem.

Changing the location of the antenna wont help in the slightest and the path will always be the same due to the location of the house and whats inbetween it and the transmitter.

The only thing i can do in regards to moving the antenna is pointing it towards tower hill (listed as Warrnambool transmitter currently its pointed at Warrnambool city transmitter)

I will get ber measurements in its current state and then see what i can do to change it. i will check it late tomorrow night and hopefully this crap weather is still around for me to see whats happening.

Out of curiosity is it possible the problem during rain/wind can't be fixed? I have always assumed tv reception can always be fixed unless in really bad locations or something

#7 Tazzy2Heads

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Posted 05 September 2012 - 10:34 PM

Chris
Post the signal measurements taken at the end of the respective flyleads.
Tazzy

#8 Tazzy2Heads

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Posted 05 September 2012 - 10:47 PM

I wouldn't have thought you would have weather related issues with the signal at those measurements at the antenna and so close to the transmitter unless they are trees with very thick foliage reducing the signal when wet.It maybe something in the system.
Tazzy.

#9 M'bozo

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Posted 05 September 2012 - 11:19 PM

Changing the location of the antenna wont help in the slightest and the path will always be the same due to the location of the house and whats inbetween it and the transmitter.


Can't speak for your specific problem, but I have several similar here that have required repositioning the antenna, for similar reasons, over the years, as vegetation changes have occurred. Sometimes by only a small amount of antenna movement in the x/y/z axis, (or points in-between.)

Others have required complete antenna relocation. It's the nature of the beast.


Out of curiosity is it possible the problem during rain/wind can't be fixed?


Sometimes. You have to know when to pull the pin and choose an alternative method (eg VAST.)


I have always assumed tv reception can always be fixed unless in really bad locations or something


It helps if you have an alternative transmitter to choose from.


The only thing i can do in regards to moving the antenna is pointing it towards tower hill (listed as Warrnambool transmitter currently its pointed at Warrnambool city transmitter)


Which you do, so don't stuff around. I would try the alternative site. It's higher powered, and may be more suitable.

#10 mtv

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Posted 06 September 2012 - 12:11 AM

.... Changing the location of the antenna wont help in the slightest and the path will always be the same due to the location of the house and whats inbetween it and the transmitter.

The only thing i can do in regards to moving the antenna is pointing it towards tower hill (listed as Warrnambool transmitter currently its pointed at Warrnambool city transmitter)


Chris,

You've provided more info in your forum post than in your PM and the answers received so far are all pertinent, so I'll reply here.

Your quote above rings alarms for me, when you say "Changing the location of the antenna wont help in the slightest".... this may be quite wrong, as even moving an antenna position even a few centimetres in any direction, including up/down, can make a huge difference.

This would be the very first thing I would be doing, searching for a more-suitable antenna location.

As mentioned, trees/foliage moving in the wind and chages in moisture content can alter signal paths, absorbing, refracting and reflecting signals.

As a result, signal may be decreasing, increasing, adding multipath signals, all of which can upset DCP, BER/MER.

Different frequencies may be affected to varying extents.

Also as mentioned, I would also be checking options like using a different transmission site. EG: Tower Hill, which has a max power of 8KW as oppsosed to Warrnambool City, which is only 630W.

I also agree cBER and RS dropped packet readings (if your meter shows RS) provide better indications of issues than just MER.

Elevation between your antenna and the TX can be an issue with antennas reasonably close to TX as often the signals can be going over the top of you, with insufficient downtilt from the TX antenna array. (I've seen this quite a bit).

Tilting the receive antenna upward often helps in these situations.

Without being there, it's very difficult to advise.... you just need to go through all the standard processes a good installer would do... the most important, is test numerous antenna mounting positions.

Testing with different antenna types... often one antenna type will work better than others... and it's not always the type you may expect in theory to work best, or the one that worked best at the house next door.

#11 bellotv

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Posted 06 September 2012 - 12:52 PM

M'Bozo said it, MTV said it and I will also say it.

Try a different antenna location.On UHF its critical.

I don't know what meter you use.I've got a T40 .It has histogram which is gold when it comes to finding position least affected by trees moving in the wind.

Just thinking out of box .Is there any electric fence nearby that may be arcing in the rain ?

#12 nbound

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Posted 06 September 2012 - 01:02 PM

Is the balun connection waterproofed?
Is there any outside joins?
Was the cable used new?
Was the meter used to align the aerial or just to test after the fact?

Ideally we need signal measurements while the faulty is occuring... A massive drop in DCP/BER would likely indicate water ingress. Drops mainly in BER would lean more towards the trees or some other envirmonmental issue.

#13 Chris Dowling

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Posted 10 September 2012 - 07:27 PM

Think i sorted it out, had a chat to beeblebrox over the phone and it turns out the problems are most likely

1: too close to the roof (around 400mm from the base of the antenna)
2: there is about 30 meters of roof before the edge of the building and then its clear air from there
3: possible trees over the highway in between the antenna and signal.

at this stage all i did was move it higher and i will see how it goes from there.

thanks for the help guys. this is def the place to ask when those niggle little things i cant quiet work out.

#14 Tazzy2Heads

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Posted 10 September 2012 - 11:19 PM

Hi Chris
Beeblebrox is on the money I think with point 1- antenna height from roof .
I had a job back in the Analog only days fitting a combo antenna on a metal roof where the sparky had brought the cable through, there was clear line of sight to Mt Wellingtons 1000+ kw UHF transmitters. I did a quick check of the signals with my trusty Promax
meter thinking it was all theoretical by holding the antenna by hand and all seemed ok, when I checked the pictures at the finish thinking again it was all theoretical I found Southern Cross to be horrible , I thought the sparky had stuffed up the wall plate but all four had the same dodgy Southern Cross so I thought the antenna must have been crook so I replaced it with another new one only to find no change. Then the penny dropped after a bit of head scratching , lowered the antenna 200mm in my case and all was as it should be. Put it down to reflected signals off the roof cancelling out the main signals owing to roof angle, antenna height and channel frequency etc.Have had it happen once or twice since then with a crook Digital channel in a LOS situation with UHF signals.
Its not uncommen to have one or two channels with weaker UHF signals than the others in low power TX areas with line of sight to the towers. Thats why all the earlier posters were saying you have to carefully check the roof etc for best quality of the weak ones and also try different antenna types as theory and reality can be very much different.
Cheers Tazzy

#15 andrewlace

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Posted 02 October 2012 - 08:39 PM

Hi Chris,
It sounds like you're going down the right path as far as using a phased array antenna. Usually is a customer has problems on UHF during inclement weather this is a good place to start. I would assume the cypress trees are your big issue. I have seen it several times where moving the antenna inches can make a huge difference. Detuning the antenna can make a difference also. Some may also have run accross the issue with fast growing tree foliage during the spring times. This seems to be the time of year in very well treed areas where tv reception is affected I believe due to the season. A nice feature of a higher resolution and faster spectrum analyser is the ability to see the distortion in the signal. Having bought an AP01 some three years ago, it's a really nice feature to have.