# Forum Home Renovation Television, Computers & Phones  Upgrading or Downgrading an Antenna?

## Salem

Hi, since buying our home 2 years ago it was always on the cards to replace our aerial which had pieces missing and bits dangling around in the wind. I've recently bought RG6 cabling, ftype connectors and wall plates and keen to get started to give this all a bit of an overhaul. I also just bought an antenna from Jaycar that I thought would be safe and the specs looked good for my area. 
The only bit thats made me stop and question the job at hand is the size of the existing antenna. I live in the Penrith region and I currently have a rather large antenna on a 10 metre mast. There's also other homes around the are that have similar antennas. I know the signal strength/quality is only as good as the antenna itself and dont want to muck this up. I want to do this once properly.  
Without understanding the specs does anyone know whether going from something like this:    
to something like this is a disadvantage to me?  Digimatch VHF/UHF X-type Colinear 27 Element Receives Band 3, 4, and 5 (Channel 6-12 and 28-69) - Jaycar Electronics 
FYI - after a bit of tweaking I've got the signal strength to be really good and considering its on a 4 way splitter I'm really happy. Would just seem backwards to upgrade all the cabling and leave an old tattered aerial up on the roof as well. Keen to replace but not if its at a loss to me.  
Thanks - appreciate any input.

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## SirOvlov

Change the whole lot over, you have a 4 way splitter but ar 
e all ends connected? each one that is lowers db by 5, so you may be ok now but not when you use all.

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## oldtrack123

> Hi, since buying our home 2 years ago it was always on the cards to replace our aerial which had pieces missing and bits dangling around in the wind. I've recently bought RG6 cabling, ftype connectors and wall plates and keen to get started to give this all a bit of an overhaul. I also just bought an antenna from Jaycar that I thought would be safe and the specs looked good for my area. 
> The only bit thats made me stop and question the job at hand is the size of the existing antenna. I live in the Penrith region and I currently have a rather large antenna on a 10 metre mast. There's also other homes around the are that have similar antennas. I know the signal strength/quality is only as good as the antenna itself and dont want to muck this up. I want to do this once properly.  
> Without understanding the specs does anyone know whether going from something like this:    
> to something like this is a disadvantage to me?  Digimatch VHF/UHF X-type Colinear 27 Element Receives Band 3, 4, and 5 (Channel 6-12 and 28-69) - Jaycar Electronics 
> FYI - after a bit of tweaking I've got the signal strength to be really good and considering its on a 4 way splitter I'm really happy. Would just seem backwards to upgrade all the cabling and leave an old tattered aerial up on the roof as well. Keen to replace but not if its at a loss to me.  
> Thanks - appreciate any input.

  
HI 
One little problem
They are for different SIGNAL polarities [horizontal or vertical]as shown, but  simple to change orientation
You should check the signal polarity when the change to DIGITAL is made in your area 
I would expect it will be the same polarity as you now have !!. 
However looking at the mast you needed, you are not in a good reception area 
Perhaps just see how the current one goes first, then if problems look at what others around you have put up or seek proffesional LOCAL opinion
Remember with  digital, unlike anologue , you either get a good enough signal for good reception or it is hopeless  unlike anologue which could tolerate weak signals with minor degradation.  
PeterQ
PeterQ

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## Salem

Hi thanks for the feedback. I can confirm that both the Sydney and new Kurrajong transmitters that take care of my area are using Horizontal polarization. I dont know if/when that changed at some point however I do know that scanning around the area shows both types of aerials in use. I dare say that some of the older homes (30 years) seem to have the same vertical aerial as myself. The other thing that I noted was that a lot of homes have a satellite dish. I always assumed this would have been for pay TV but I did read recently about those homes that have difficulty are entitled to a satellite dish (VAST). Maybe I was wrong about the sat dish. 
My vague understanding of the aerial is that the vertical antenna will continue to work as it does however there would be significant signal drop running in a vertical configuration of the transmitters broadcast a horizontal signal. 
I think thats on the money. SirOvlov for the moment the 4 way splitter and cabling is connected however is only connected to one TV at the moment while we tidy up our reno's.

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## michael_sa

> Change the whole lot over, you have a 4 way splitter but ar 
> e all ends connected? each one that is lowers db by 5, so you may be ok now but not when you use all.

  This is not correct. 
A four way F type splitter will decrease the input signal strength by approx 8.5dB, irrespective of how many TV's are plugged in.   

> HI 
> One little problem
> They are for different SIGNAL polarities [horizontal or vertical]as shown, but  simple to change orientation
> You should check the signal polarity when the change to DIGITAL is made in your area 
> I would expect it will be the same polarity as you now have !!.
>  PeterQ
> PeterQ

  Both antennae as displayed in the photos are mounted for horizontal polarity.
The original antenna is a VHF co-phased array, the new antenna is a VHF/UHF combination antenna   

> However looking at the mast you needed, you are not in a good reception area 
> Perhaps just see how the current one goes first, then if problems look  at what others around you have put up or seek proffesional LOCAL opinion
> Remember with  digital, unlike anologue , you either get a good enough  signal for good reception or it is hopeless  unlike anologue which could  tolerate weak signals with minor degradation.
> PeterQ
> PeterQ

  Visit the mySwitch website and enter your street address, it'll give you a reasonable idea of the signal level to expect at your location.
If there are multiple transmitters available to you, that information is also available on that page, including channel frequencies and polarity.
Your antenna selection should be made dependant on which transmitter site offers the best signal quality at your location. Some transmitters may be UHF, others may be a combination of VHF and UHF (which would make the antenna you have already purchased the correct one.)
- Bear in mind that there are many other things that can affect the signal quality at your location.   

> Hi thanks for the feedback. I can confirm that both the Sydney and new Kurrajong transmitters that take care of my area are using Horizontal polarization. I dont know if/when that changed at some point however I do know that scanning around the area shows both types of aerials in use. I dare say that some of the older homes (30 years) seem to have the same vertical aerial as myself. The other thing that I noted was that a lot of homes have a satellite dish. I always assumed this would have been for pay TV but I did read recently about those homes that have difficulty are entitled to a satellite dish (VAST). Maybe I was wrong about the sat dish. 
> My vague understanding of the aerial is that the vertical antenna will continue to work as it does however there would be significant signal drop running in a vertical configuration of the transmitters broadcast a horizontal signal. 
> I think thats on the money. SirOvlov for the moment the 4 way splitter and cabling is connected however is only connected to one TV at the moment while we tidy up our reno's.

  Cross polarity will severely attenuate the TV signal power. Visit the myswitch website for info on your local situation.
I would expect that most or all of the sat dishes you are seeing in your area are (or were) for pay TV, not VAST. 
Regards, 
Michael

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## Salem

Thanks Michael, I feel a bit more at ease with my antenna selection now. I did reference the myswitch site previously which was very helpful. Apparently I can get kurrajong however 2 doors door id have to aim it at Sydney which shows the requirement for VHF & UHF. Considering I'm likely a bit borderline I bought the combination. 
I know other factors could intervene but happy I'm a step in the right direction. Cheers

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## SirOvlov

Adding the splitter will take -8ish db off once connected to one tv, each there after can takr another -5db depending on length and tuner being connected. If you use a powered splitter you wont loose the -8ish but for each connection there after you will.

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## michael_sa

> Adding the splitter will take -8ish db off once connected to one tv, each there after can takr another -5db depending on length and tuner being connected. If you use a powered splitter you wont loose the -8ish but for each connection there after you will.

  Rather than hi-jack this thread, I'm quite happy to take this up with you via PM or email as what you are saying is simply not correct and I'm more than happy to demonstrate that to you.
I'm actually quite interested to know what your experience was that led you to believe this and how you measured the results.
 - I'm presuming you have accurate professional test equipment and have actually seen the signal decrease (as you suggest) as other outlets are terminated by TV's.
When you did this test, did you also measure the pre & post BER? What about the MER? as it's not just about the digital signal power. 
I have brand new stock in my work bus to recreate your example and in the interests of some friendly education, I'd be happy to email you (or post publicly) photos displaying results that show your belief is misguided. (PM your email if you are interested) 
Regards, 
Michael

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## oldtrack123

> Rather than hi-jack this thread, I'm quite happy to take this up with you via PM or email as what you are saying is simply not correct and I'm more than happy to demonstrate that to you.
> I'm actually quite interested to know what your experience was that led you to believe this and how you measured the results.
> - I'm presuming you have accurate professional test equipment and have actually seen the signal decrease (as you suggest) as other outlets are terminated by TV's.
> When you did this test, did you also measure the pre & post BER? What about the MER? as it's not just about the digital signal power. 
> I have brand new stock in my work bus to recreate your example and in the interests of some friendly education, I'd be happy to email you (or post publicly) photos displaying results that show your belief is misguided. (PM your email if you are interested) 
> Regards, 
> Michael

  Hi Michael  
Why go by PM?? 
I am sure no one would mind knowing the right ANSWERS 
I perrsonally think PMs on subjects such as this defeats the whole purpose of a forum.
After all it is a special forum section allocated for that purpose
Those that find it too deep simply do not have to bother reading :Biggrin:  
PeterQ

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## SirOvlov

No hijacking, I think the op's question has been awnsered and now it is a discussion, exactly what a forum should be. If I'm wrong, fine, not a drama but to do it by PM's is a little high school! 
It's been 5yrs since I was on tools and now in a completely different field (conveyancing) so my memory is a little off. I would love for you michael to bench say a 4 way unpoweredsplitter with 10-20 metre runs on each and see the loss and I think the forum would too. -5db is what I remember and we are talking power, not quality but feel free to show the results of both.

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## michael_sa

I'm not sure from where this myth originates. I've heard it a few times before and unfortunately, the internet is not only a great source of information, but it's also pretty effective at spreading misinformation. 
Perhaps it's the (incorrect) presumption that signals in a coaxial cable behave like water in a pipe...perhaps someone's experience where other faults existed in their system and gave them similar symptoms - whatever the reason/s, here are the results of a simple test I carried out to disprove the original pretence - being that connecting multiple TV's to outputs of a correctly configured splitter, will decrease the signal level at the other outlets. 
My background:
I am an open registered telecommunications cabler. I am a DBCDE approved TV antenna installer with just short of 15 years experience working in some of the most 'interesting' (read: challenging) reception areas in the state.
I'm a licensed amateur radio operator and have been messing about with antennas and electronics for about 30 years. Antenna theory, feed-lines and RF propagation is something I consider myself to have a reasonable grasp of.  
The following test involved measuring the COFDM digital signal power (only) from channel 12, (226.5MHz) broadcast from SA's Mount Lofty transmitter, about 60 km from my home location.
The channel 12 multiplex broadcasts ABC's content from this transmitter site. 
The results:   http://s24.postimg.org/76dpllsjn/image1.jpg
Image 1: Digital signal power available from antenna = 66.5 dBµV    http://s11.postimg.org/nypoi4a1t/image2.jpg
Image 2: 4 way splitter inserted in line. Spare outputs unterminated. Digital signal power at splitter outputs = 57.6 dBµV    http://s22.postimg.org/auhcqv9q8/image3.jpg
Image 3: TV1 connected. Spare outputs unterminated. Digital signal power = 57.8dBµV     http://s16.postimg.org/nfiw84at0/image4.jpg
Image 4: TV1 connected. Spare outputs fitted with 75 ohm terminators. Digital signal power = 58.6dBµV     http://s24.postimg.org/b13s2bohw/image5.jpg
Image 5: TV1 & TV2 connected. Spare splitter output terminated. Digital signal power = 58.6dBµV    http://s17.postimg.org/ivg3pkmta/image6.jpg
Image 6: TV1 connected, TV2 disconnected. One splitter output unterminated. Digital signal power - 57.6dBµV     http://s22.postimg.org/ktc0bqrcw/image7.jpg
Image 7: TV1 connected, TV2 reconnected. Spare splitter output terminated. Digital signal power = 58.4dBµV   
As is probably obvious, this is by no means an exhaustive test. It is just a very, very simple test measuring nothing more than the digital signal power - since that was the point ' SirOvlov' was making - that the signal 'level' decreased with the connection of other TV's into a system.
 By his logic, we connect the splitter and lose about 8dB, surely then when we connect the signal meter we'd lose 5dB as well, since it is a receiver/decoder/load - call it what you want. So with his theory, we should have 66.5dBuV -5 -5 -5 -5
Quite clearly not the case. 
So what do those results mean. 
As the splitter outputs were terminated (either by a TV or a terminator) the signal level actually increased marginally in my example. So the exact opposite happened to that which was claimed by  SirOvlov.
If his theory were true, as each output of my splitter was terminated - either by a TV or a terminator (as this presents the same 'load' to the system as aTV) - the signal level would have dropped by his expected 5 dB for each 'load' connected - this simply was not proven to be the case. Essentially, the level did not change one iota.
Adding cable length to each splitter output would change nothing, other than having a decreased signal level at the far end. About -2.75dBuV for 25 metres at 226.5MHz, it's interaction or effect on other outputs will remain unchanged. (I can see already that this is the next thing I'll need to provide evidence of ;-) 
This example/test serves to highlight that there are many aspects to measuring the digital TV signal in an antenna system, it's really quite a complex thing and is definitely not just about the signal power. Digital TV signal quality measurements also involve measuring noise margins, modulation error ratios and pre/post Viterbi bit error ratios. The element of being able to correctly interpret what your test equipment is telling you, is also involved. Something which is beyond the scope of this post.  
Regards, 
Michael

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## SirOvlov

Great write up Michael, thanks for that. Very interesting as you pointed out, there are a few around that work on that same theory that I had. Now it makes me think on those few problem jobs I had, what wad actually causing the drop...

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## barney118

I ran my RG6 cable and had the experts finish it off with new aerial, terminate it and test it best ~300 spent.

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## michael_sa

> Great write up Michael, thanks for that. Very interesting as you pointed out, there are a few around that work on that same theory that I had. Now it makes me think on those few problem jobs I had, what wad actually causing the drop...

  No problem. The most common reason for one TV socket affecting another (as described above), would be no splitter (ie; the coax cables just being "twitched" together) or a failed splitter (not so common with F type splitters but it can happen) - of course there are plenty of other situations that can result in similar problems, particularly in the digital environment.
I'll dig out some pics of some of the cr@p I've come across and post them up, you'll get a laugh from a few of them - one example off the top of my head: there used to be a local electrician here in town who never used splitters, he and his workers just twisted the coax conductors together and taped them up. They did that for years, I can't remember how many of those things I've removed, affectionately (not!) we referred to them as a Lxx's Electrical Splitters - Over time, subsequent occupants of the property would do things like fit mast head amps in an attempt to improve their TV reception. Of course with the power supply inside the house plugged into a TV outlet, the power is going to the twitched wire 'splitter' up to the amp on the antenna mast and out to all TV outlets. Not a problem if no other TV's are plugged in, but as soon as a TV is plugged in, it drags down or kills the power to the amp - hey presto - no TV...
I'll track down a few pics... 
Regards,
Michael

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## michael_sa

> ...
> I'll track down a few pics...

  I probably should start a new thread for this... but here's a few to get started: 
The dreaded "Lxxx's Electrical Splitter" Looks like it's been installed for some period of time, then had another TV outlet fitted by a similarly knowledgeable rocket scientist who has just wrapped the new RG6 coax around the old coax cables.  
Yes this really is how some people join their cables:  
Both of these plugs virtually fell off the end of their cables:  
How not to crimp an F connector:  
More 'splitter' fails:  
Speaking of fails... how not to fit a side entry plug on a power-board:  
The husband of the house DIY'd this thing onto a power-board behind their TV.
- Friendly cable guy (moi) comes along to test the signal at the antenna socket (which is located next to the power socket this thing is plugged into) - moves TV unit which moves power-board which moves cable inside the plug... !!BOOF!! 
A light & sound show of a few milliseconds follows... I remember feeling the heat flash on my arm and face. Scary stuff. 
This bit of ineptitude not only tripped the house breaker, but also took out the service breaker in the estates cabinet across the street. 
(I'm certain this kinda thing never happens in NZ) /sarcasm 
Regards, 
Michael.

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