Recomend masthead amp please

PyeContinental

I realise that there's probably no straightforward answer, but would welcome some informed opinion. I'm looking at masthead amps here http://www.tvaerials.com/shop.aspx?categoryid=104
and wondering which is the best. What kind of DB gain should I look for?
Is this Vision model good?
http://www.tvaerials.com/product.aspx?productid=1380
Is this one better because it has higher gain with lower noise?
http://www.tvaerials.com/product.aspx?productid=1101
What amp should I get to use it with?

I'm on the south east coast and want to make an improvement to the reception of DTT from Preseli. I'm using a roof mounted Televes Dat 75 wideband aerial, with a standard masthead amp in a plastic box and Triax indoor 12volt power amp.

byte

What gain does your current amp have?

I've seen the FTE's in action before and they seemed OK, but I'd reckon having the jumper on 40dB a bit overkill unless you've a very very long downlead.

PyeContinental

I don't know is the honest answer. The masthead amp seems like a fairly generic one and I don't remember seeing any model info on it.
The indoor power amp is a Triax 100/2 model. The label on it says insertion loss is <4.0db but doesn't give a gain figure.

Is there any disadvantage to "overkill" as such? DTT reception has never been fully consistent, although perhaps a bit more so since the analog switchoff and power increase from Preseli, but channels like Virgin1 and Dave are still the weakest and I'd like to do as much as I can to try to improve their consistent reception.

Rippy

The triax p100/2 is not an amplifier at all. It is simply a power supply unit to provide 12v up the cable to the masthead amp.
Because it has two outputs it is ,in effect,a 2 way splitter and you would be better to replace it with a single output psu.
Also look at your cable, particularly if it is old replace it with a decent copper -on copper cable , such as Triax TX100 or philex PF100.
I have no experience of the FTE amp, but 40 db gain does sound excessive.
Particularly with a wideband amp. such a high gain could lead to problems with co-channel interference and oscillation, from carriers both inside and outside the band.
The Vision amp is excellent.
Whatever amp you buy make sure it is a f connector type in a fully shielded enclosure (metal box).

stevethesatguy

Proception 16db amp and 12v power supply great for analogue not really neccessary for RTE digital

PyeContinental

Thanks for the correction Rippy - I didn't know whether it was an amp or just a power source for the amp on the masthead. I wasn't sure if the masthead amp was equivalent to a pre-amp or not, if you see what I mean.

Anyway, yes I will use one with F-connectors. I have read on other threads here that they give better shielding. There is good quality cable in use already, but I will be replacing it with satellite type cable which I used with my sat dish. The type I have is RG6. If there is a higher grade type though I would be willing to pay for the best quality I can get. (I believe in doing the best job possible if I'm going to do a job)

If I had known about the different types of aerials before I bought the Televes wideband one I would have tried a Group B one instead, but only recently learnt of their existence - through reading threads on this forum again.

I'm glad to hear the vision amp and power source are good, but I see that the specs for the FTE says that the signal noise is less. Could I not turn down the gain if I find that it amplifies too much and gets interference from Mount Leinster on a co-channel? Is the gain level only selectable from a switch on the masthead amp itself? I'm taking on board what you're saying about the possible downside of over-amplification, but am just trying to figure out what is likely to work best before buying. It will end up being a case of just taking a punt on one of them otherwise.

stevethesatguy wrote: »

Proception 16db amp and 12v power supply great for analogue not really neccessary for RTE digital

I have a separate UHF roof aerial pointed at Mount Leinster which I use to pick up the Irish DTT channels. I'm not interested in analogue channels any more though as I've been too spoiled by digital quality reception via satellite and DTT for too long now!

mrdtv

PyeContinental wrote: »

Thanks for the correction Rippy - I didn't know whether it was an amp or just a power source for the amp on the masthead. I wasn't sure if the masthead amp was equivalent to a pre-amp or not, if you see what I mean.

Anyway, yes I will use one with F-connectors. I have read on other threads here that they give better shielding. There is good quality cable in use already, but I will be replacing it with satellite type cable which I used with my sat dish. The type I have is RG6. If there is a higher grade type though I would be willing to pay for the best quality I can get. (I believe in doing the best job possible if I'm going to do a job)

If I had known about the different types of aerials before I bought the Televes wideband one I would have tried a Group B one instead, but only recently learnt of their existence - through reading threads on this forum again.

I'm glad to hear the vision amp and power source are good, but I see that the specs for the FTE says that the signal noise is less. Could I not turn down the gain if I find that it amplifies too much and gets interference from Mount Leinster on a co-channel? Is the gain level only selectable from a switch on the masthead amp itself? I'm taking on board what you're saying about the possible downside of over-amplification, but am just trying to figure out what is likely to work best before buying. It will end up being a case of just taking a punt on one of them otherwise.


I have a separate UHF roof aerial pointed at Mount Leinster which I use to pick up the Irish DTT channels. I'm not interested in analogue channels any more though as I've been too spoiled by digital quality reception via satellite and DTT for too long now!

I think you have several issues: firstly the COM muxes are lower ERP than the PSB stations by 3dB in the case of SDN and Arqiva A (Virgin, Dave respectively) and currently 8dB in the case of Arqiva B (going up to 10kW like the other COM muxes currently are operating at in 2011). The other problem is Arqiva A is cochannel with RTE Mount Leinster and there must be some leakage in your area.

Personally I would use a Group B aerial and prefer other vendors such as Fracarro, Antiference, Blake etc. You can see very interesting measurements of the DAT wideband versus grouped aerial performance at www.aerialsandtv.co.uk

This is also of interest:

http://www.digitaluk.co.uk/__data/assets/pdf_file/0005/34925/Installer_Newsletter_Preseli__1_month_out_FINAL_2_revised_relay_times.pdf

See also this curve on comparative performances of various aerials including the DAT 75 genre:

http://www.aerialsandtv.co.uk/gaincurves.html#WidebandCurves

It will be interesting to see how it works for you...

maxg

First the OP should check if he got an DAT 75 with Televes MRD 5050 preamplifier. The DAT aerials are sold with fitted preamplifier and without.

PyeContinental

Can you pick out a specific Group B aerial that you would be happy to spend your own money on? I'm willing to dump the wideband Televes aerial if I can optimise the reception. I'm only interested in those channels (Virgin1, Dave, and the plus 1s, Fiver, Five US, Quest etc) which are on the weaker muxes, as I get the BBCs, ITVs and CH4 channels via freesat.

I still have a roll of RG6 cable, but what is the best grade that I could buy?
What are your opinions on the best masthead amp and power source, mrdtv?

maxg wrote: »

First the OP should check if he got an DAT 75 with Televes MRD 5050 preamplifier. The DAT aerials are sold with fitted preamplifier and without.

No, I don't think so maxg, but will check when possible. Where would the MRD 5050 be located if it was there? On the masthead or integrated onto the aerial itself?

mrdtv

PyeContinental wrote: »

Can you pick out a specific Group B aerial that you would be happy to spend your own money on? I'm willing to dump the wideband Televes aerial if I can optimise the reception. I'm only interested in those channels (Virgin1, Dave, and the plus 1s, Fiver, Five US, Quest etc) which are on the weaker muxes, as I get the BBCs, ITVs and CH4 channels via freesat.

I still have a roll of RG6 cable, but what is the best grade that I could buy?
What are your opinions on the best masthead amp and power source, mrdtv?


No, I don't think so maxg, but will check when possible. Where would the MRD 5050 be located if it was there? On the masthead or integrated onto the aerial itself?

This looks to me like you have a composite system. Personally I love the Fracarro range ( very compact, excellent F/B ratio, and their Gold range has fully integrated mastheads.) That UK site I gave you is very highly regarded ( look at the testimonials... I would ring him.) Other alternatives include Antiference, Unix etc. I prefer compact aerials because of the windloading: tribooms have a nasty habit of coming down in the storms. CT100 or similar satellite grade cable is the business. You can research this nicely. I also understand there is a new very high spec log periodic ( Vision Ghost or supreme) which is apparently excellent (again very compact): the broadcasters always prefer logs on their relay and RBL sites. You are up against CCI from Mount Leinster and the lower power transmissions on those COM muxes from Preseli especially Arqiva B which is 2kW till 2011.

maxg

The MRD 5050 is part of the aerial design.
http://www.tvaerials.com/product.aspx?productid=274

PyeContinental

I will examine the aerial when I can get a chance so, maxg.
Even if it does have one, I know it goes into a masthead amplifier regardless though.

mrdtv, I'm looking for a bit of spoonfeeding here and asking for you to pick a specific aerial, because it would be a random choice for me.
The only Group B aerial that I can see on the site is this Televes one, at least I'm presuming it is, as the plastic is yellow.
http://www.tvaerials.com/product.aspx?productid=2446&product=Televes%201495%20-%20DAT%20HD/DATHD%20TV%20Aerial
Annoyingly, on that site, it doesn't always say the frequency range for each aerial.

I know that there is a certain amount of interference on one of the muxes from Mount Leinster (666MHz). I've always been able to get the channels intermittently though (weather conditions etc, and ususally more often in summer, but not consistently). What I'm trying to achieve is to raise the threshold, perhaps even just a little bit, which could make the reception of these channels much more consistent.

mrdtv

PyeContinental wrote: »

I will examine the aerial when I can get a chance so, maxg.
Even if it does have one, I know it goes into a masthead amplifier regardless though.

mrdtv, I'm looking for a bit of spoonfeeding here and asking for you to pick a specific aerial, because it would be a random choice for me.
The only Group B aerial that I can see on the site is this Televes one, at least I'm presuming it is, as the plastic is yellow.
http://www.tvaerials.com/product.aspx?productid=2446&product=Televes%201495%20-%20DAT%20HD/DATHD%20TV%20Aerial
Annoyingly, on that site, it doesn't always say the frequency range for each aerial.

I know that there is a certain amount of interference on one of the muxes from Mount Leinster (666MHz). I've always been able to get the channels intermittently though (weather conditions etc, and ususally more often in summer, but not consistently). What I'm trying to achieve is to raise the threshold, perhaps even just a little bit, which could make the reception of these channels much more consistent.

Better sites are www.aerialsandtv.co.uk AND [url]www.fracarro.co.uk:[/url] download the entire catalogue.Its fully specified. The BLU series look rather impressive to me but make sure you get a compatible variable gain masthead. I think a few phone calls are what is needed after a bit of Internet research. The Fracarro aerials are very good: you need to find a UK, NI or ROI distributor.

maxg

PyeContinental wrote: »

I will examine the aerial when I can get a chance so, maxg.
Even if it does have one, I know it goes into a masthead amplifier regardless though.

The MRD 5050 has 13db gain and your current mast amp is blocking the electrical power for the preamp if there is one.

byte

Assuming he currently has a Triax amp (he said it's blue, and has a Triax PS to match), some of them had the option to add a screw for power pass, making it act like a line amp. Still though, it'd seem strange to me to have two amps so close together (assuming his aerial has an integrated amp).

mrdtv

If I was going to buy an antenna today this is what I personally would get:

http://sigma.fracarro.co.uk/download/datasheet_SIGMA_6HD_eng_UE.pdf

Its not cheap, is available on the web, and has a gain of 17dB (vs DAT 75 of 19dB) and use it with a Fracarro variable gain amp up to 20dB). Its the successor to the Fracarro digital gold antennas and because of its revolutionary design its a fraction of the length of the DAT75 so its going to stay up in storms. Others are bringing out similar new designs. You could also look at grouped Unix 52's or the very high performance Antiference log with built-in variable gain masthead. (30dB in total...)

Also remember,you will not get dave,sky news or anything on ch45 only rarely as its co channel with mt leinster-no loss though tbh and that ch42 for the moment is on 10kws ie half what the psb muxes are on-so on the rare occasions that weather upsets the signal-ch 42will be the one under pressure.
It's happened about 3 times briefly here since july,twice before aso which shows how rare it is.

PyeContinental

Black Briar, yes I'm aware of the co-channel issue with Irish DTT on channel 45 (666MHz), and am willing to write off the possibility of getting Dave or Sky3.
Dave Ja Vu can be received though, and Sky3 doesn't have much worth watching, so it's no real loss.

It's really channels 42 and 49 with Fiver, Fiver US, Virgin1, Virgin1+1, Quest mainly that I'm interested in. They can be received, but my aim is to improve the consistency of their reception.

mrdtv, why would you chose that aerial? It says it's a wideband one, shouldn't I be looking for a Group B aerial? If I had seen that without your recommendation I would have assumed the circular elements were a gimmick.

The existing Televes DAT 75 is big, but it has stayed put for a few years now and so I think it has already seen the worst storms it's ever going to. What I want to avoid doing is spending money on replacing that aerial and then feeling like it was for no good reason when I see no appreciable difference.

Byte and maxg, I'm going to have to investigate that MRD 5050 possibility later when I can get up on the roof again.

I've had no problems with either of those using twin fringe group b's.
Ch49 on a group b will be weaker in any event as it's on the edge of the band that group works best with.

Typically with me,it's about 15% weaker than say 43.
ch 42 I've only had brief drop outs on once as it behaves well even at 10kw erp because of it's location in the b band.

Take mrdtv's advice and concentrate on the aerial aswell as the amp.
Lots of elements in a good group b - they are your friend if you want consistent reception.

Why not twin your existing aerial-that will increase gain for you.

just to answer your question on mrdtv's recommendation.
That wide band would pull in ch49 for you a lot better than a group b.

You'll also have the plus of having regular summer visits from caradon hill dtt in cornwall and other faraway tx's..

mrdtv

I have now seen two of these Fracarro Sigma's locally in the last two hours and called an installer who I have known for years and who does a lot of contract work: he's fussy but thinks they are now the bee's knees. If you continue with the DAT 75 make sure you have a properly working MRD unit ( its quite possible yours isn't by the sounds of it): then you'll also need to make sure you have decent modern cabling.

If your receiver (you don't say what it is...) gives signal state information (and some do it all now) I'd like to know:

a) Signal strength

b) Quality

c) Pre and post- Viterbi BER

d) C/N ratio

e) COFDM AGC

That would be most interesting.

PyeContinental

mrdtv wrote: »

See also this curve on comparative performances of various aerials including the DAT 75 genre:

http://www.aerialsandtv.co.uk/gaincurves.html#WidebandCurves

It will be interesting to see how it works for you...

Does that demonstrate that the peak gain is high for the DAT75, but that overall gain across the full channel spectrum is not as good as other aerials?

Deleted User wrote: »

Take mrdtv's advice and concentrate on the aerial aswell as the amp. Lots of elements in a good group b - they are your friend if you want consistent reception.

There are 18 elements on each of the three booms on the existing wideband Televes DAT 75.

http://www.aerialsandtv.co.uk/gaincurves.html#Bgroups

If I'm interpreting this graph correctly, then this XB16 seems to have the largest gain across all the Group B frequencies.
http://www.aerialsandtv.co.uk/onlineaerials.html#XB16B
Out of stock though apparently.

I am prepared to change the aerial, but I feel like I'm being given conflicting advice. I want to be sure of the reasoning for changing the aerial before I do.

I know that the amp can be improved because the existing one is definitely not the best available and is not the solid type with F connectors as in the Vision or others linked to earlier on in the thread.

Deleted User wrote: »

That wide band would pull in ch49 for you a lot better than a group b.

I'm getting confused because you also said I should get a good Group B aerial instead of my wideband aerial. Why would that Fracarro Sigma wideband aerial be better than the existing wideband Televes Dat 75 I have already?

Deleted User wrote: »

Ch49 on a group b will be weaker in any event as it's on the edge of the band that group works best with.

So even though Group B aerials are designed for channels 35 to 53, it won't pick up channel 49 as good as a wideband aerial? I have a wideband aerial already.

Deleted User wrote: »

Why not twin your existing aerial-that will increase gain for you.

It would probably be an expensive experiment. I don't know enough about the procedure or likely benefit. As I understand it, they need to be mounted at the same level a specific distance apart. I would be concerned about the stability of that setup in strong winds alright.

Deleted User wrote: »

You'll also have the plus of having regular summer visits from caradon hill dtt in cornwall and other faraway tx's..

It actually was a kind of a thrill to occasionally receive (analogue) ITV Westcountry and some other faint snowy signals from who knows where during high pressure weather in the summer months, but I'm not trying to do DXing. All I want to do is to receive Virgin1, +Virgin1, Dave Ja Vu, Fiver, Five Us and Quest consistently. If those channels moved to Freesat, I would take down the aerial.

mrdtv wrote: »

I have now seen two of these Fracarro Sigma's locally in the last two hours and called an installer who I have known for years and who does a lot of contract work: he's fussy but thinks they are now the bee's knees.

Can you say why he thinks they are so good? What makes them so good?

mrdtv wrote: »

If you continue with the DAT 75 make sure you have a properly working MRD unit ( its quite possible yours isn't by the sounds of it):

Have you any advice as to how I can check this? Bypass the masthead amp and connect straight to a 12v power source?

mrdtv wrote: »

then you'll also need to make sure you have decent modern cabling.

Absolutely ready and willing to do this! Please tell me what is the best grade? I have a roll of sat cable with RG6 marked on the reel. What is the best grade? CT125?

mrdtv wrote: »

If your receiver (you don't say what it is...) gives signal state information (and some do it all now) I'd like to know:

a) Signal strength

b) Quality

c) Pre and post- Viterbi BER

d) C/N ratio

e) COFDM AGC

That would be most interesting.

I use a Windows 7 Media Centre HTPC with two Hauppauge HVR4000s as my main tuners.
I also have a Sony VTXD800U DTT box and an LG LF7700 TV which has both Sat and DTT tuners built in.

I can get you some kind of info on a and b, but you'll have to explain the rest!

mrdtv

PyeContinental wrote: »

Does that demonstrate that the peak gain is high for the DAT75, but that overall gain across the full channel spectrum is not as good as other aerials?


There are 18 elements on each of the three booms on the existing wideband Televes DAT 75.

http://www.aerialsandtv.co.uk/gaincurves.html#Bgroups

If I'm interpreting this graph correctly, then this XB16 seems to have the largest gain across all the Group B frequencies.
http://www.aerialsandtv.co.uk/onlineaerials.html#XB16B
Out of stock though apparently.

I am prepared to change the aerial, but I feel like I'm being given conflicting advice. I want to be sure of the reasoning for changing the aerial before I do.

I know that the amp can be improved because the existing one is definitely not the best available and is not the solid type with F connectors as in the Vision or others linked to earlier on in the thread.


I'm getting confused because you also said I should get a good Group B aerial instead of my wideband aerial. Why would that Fracarro Sigma wideband aerial be better than the existing wideband Televes Dat 75 I have already?


So even though Group B aerials are designed for channels 35 to 53, it won't pick up channel 49 as good as a wideband aerial? I have a wideband aerial already.

It would probably be an expensive experiment. I don't know enough about the procedure or likely benefit. As I understand it, they need to be mounted at the same level a specific distance apart. I would be concerned about the stability of that setup in strong winds alright.


It actually was a kind of a thrill to occasionally receive (analogue) ITV Westcountry and some other faint snowy signals from who knows where during high pressure weather in the summer months, but I'm not trying to do DXing. All I want to do is to receive Virgin1, +Virgin1, Dave Ja Vu, Fiver, Five Us and Quest consistently. If those channels moved to Freesat, I would take down the aerial.


Can you say why he thinks they are so good? What makes them so good?

Have you any advice as to how I can check this? Bypass the masthead amp and connect straight to a 12v power source?


Absolutely ready and willing to do this! Please tell me what is the best grade? I have a roll of sat cable with RG6 marked on the reel. What is the best grade? CT125?


I use a Windows 7 Media Centre HTPC with two Hauppauge HVR4000s as my main tuners.
I also have a Sony VTXD800U DTT box and an LG LF7700 TV which has both Sat and DTT tuners built in.

I can get you some kind of info on a and b, but you'll have to explain the rest!

Because Fracarro is an excellent brand ( I have used them myself) and this is generally recognised by the professional and SMATV community across the EU. The Sigma is a clever new design and has its competitors, the curves I posted show you how good its performance is. However if you have 'sunk costs' in the DAT 75 then I suggest that you get the matching MRD unit working properly, its gain is 19dB without amplification. All you need is satellite grade cable, F type connectors. The Sony box, alas now discontinued, gives you signal strength and quality only. It does handle multiple transmissions very well but is only MPEG2. I would not choose the DAT 75 from a standing start because as that site shows the Grouped aerials are better. But some of the widebands are very close. The biggest gains will be in the quality of the mast head amp and your cabling along with careful positioning of the antenna: a difference of 2dB is statistically not big between antennas before amplification.

maxg

PyeContinental wrote: »

Byte and maxg, I'm going to have to investigate that MRD 5050 possibility later when I can get up on the roof again.

From the satcure page:

How can I tell whether my existing DAT aerial has an MRD fitted?

The standard DAT aerial comes with an H shaped dipole which has exactly the same moulding and "F" connector as the version that has the MRD electronics inside. Unfortunately, the only way to tell is to borrow a telescope and look for the letters "MRD" or the number "5050" on the label on the dipole box.

PyeContinental

Thanks maxg, I got up on the roof today but no reference to MRD or 5050 on the label of the dipole box.
This was exactly what was written on it:
1597 ANT UHF DAT 75 ESPEC UK
DAT 75 ANTENNA UHF BLACK

Checked out the mast head amp again while I was there and found it is also a Triax, model 333501 with 25db gain
http://www.triax.com/AntennaSystems/TerRec/TerrElectronics/MastAmps/Wideband.aspx?productId={F34D4392-EEC1-4C44-A518-6AF6D807F941}&Tab=0

Anyway, I bypassed the masthead amp and wired the DAT75 directly to the tuner. Actually got a picture on BBC, at the threshold of breaking up though and signal strength and quality varying between 20 to 30% and 30 to about 60% respectively.
I tried then routing the cable through the triax power source, but got no picture at all. Tried without it again and still no picture. Don't know if I've damaged the aerial or it was just because bad weather coming in had affected the signal detrimentally.

mrdtv, I feel like I'm getting conflicting advice from you. Earlier you said you would get a Group B aerial but this Fracarro Sigma is a wideband aerial. You say that grouped aerials are better, but some of the widebands are close. Is this Fracarro the one wideband aerial that is better than group B aerials? So grouped aerials aren't necessarily better?
If I have now damaged my existing aerial it will mean I'll definitely be buying a new one, so I would like to know what exactly makes this aerial so good? If it's the circular design of the elements then why do circular elements work so well?
There aren't many elements so this goes against what was said before about more elements being better.

I see that Fracarro PDF gives a flat curve across the signal range but that is the manufacturer's data, and so isn't directly comparable to the independent tests of the aerialsandtv website.
The PDF also says that it is preassembled and easy to install - so who knows if that's not the main reason why your installer friend likes them so much.

I might just have to take a punt on that Vision masthead amp now and use new cabling and then see where I am before buying another aerial. Is CT125 the best cable grade?

Where on the south east coast are you roughly?
I'm up in arklow using twin group B's and have about 99.5% consistency in reception from presely.
In fact losing any channels is so rare I can't remember offhand when it last happened.

The low power mux carrying davejavu for instance is hitting 70% signal strength this evening despite wind and rain.
The BBC a mux is over 80%
I'm thinking there must be something else wrong at your location that we/you are missing.
You do have an uninterupted line of sight towards presely/and you are certain the aerial is peaked for presely direction wise?

Twins aren't that difficult to set up,they're attached by brackets to an 18" horizontal bar and have survived 70 mph winds.
The biggest problem is bird vandalism :mad:

PyeContinental

The aerial has a view of the sea, but obviously the Preseli transmitter is too far away to actually see. It is pointing in the right direction. Peaking, I don't know about.

If having twin aerials is what it takes to achieve 99.5% consistent reception, even on the lower powered muxes, then I suppose I'd be prepared to do this. I do think that having the weight of two aerials extended either side of the pole is a legitimate concern though.

I will improve on the known weakness first - the masthead amp, and I will replace the cabling for the best grade possible. After that, if consistent reception isn't achieved I'll be looking for a new aerial.

What is the best grade of cable? Is it CT125?

GoGoBoss

Hi Pyecontinental,
Just had a look through this thread, I was interested to see how you were all getting along with receiving the UK DTT. I think the others here are giving you good advice. I will try to help if I can, a second areial after combining will only give you an extra 2.3dB gain approx. I would be careful with your money here, if you can provide a few figures for your existing reception, I may be able to let you know if you could expect much of an improvement in picture quality. As for your co-channel interference...alot of the time this can be eliminated if you use the correct aerial for your location. You need to look at the polar diagrams (make sure there benchmarked) and your position between the 2 transmitters, the idea is to pick an arial where the unwanted signal will arrive at the arials "null point". Also bear in mind your masthead amp will usually perform better using a grouped arial as it will not be amplifing as much unwanted siganls, also this will help reduce intermodulation products that may occur, the net result is this will improve your all important C/N

I'm using ct100 afair.
You didn't say where you are [a rough guide..I hope it's not coastal west of Rosslare or the parts of north waterford that are blinded somewhat from presely due to welsh terrain in the way]..if you don't want to say ok

To be honest,My hunch is that as we don't have sight of your set up , I'm guessing theres a cabling issue or an amp issue.
Replacing both of those will tell the tale.

Can you get yourself a digital signal meter and let us know what you are receiving db wise.
It will allow you to tweak the aerial position.
You're getting some of the muxes even without an amp so thats a good sign that replacing what you had and putting in a new good cable run.

I did all that and had twins anyway as in the days of analogue,twins used clean up reception very well.
The same gain is not needed obviously for digital unless you are in very marginal territory.
I can't advise what amp I'm using as I left the install up to a professional.
I can find out if you wish.
The twins are definitely giving me a lot more gain than I need and I'm not for turning it down as it's been a great sucess so far

maxg

PyeContinental wrote: »

The aerial has a view of the sea, but obviously the Preseli transmitter is too far away to actually see. It is pointing in the right direction. Peaking, I don't know about.

If having twin aerials is what it takes to achieve 99.5% consistent reception, even on the lower powered muxes, then I suppose I'd be prepared to do this. I do think that having the weight of two aerials extended either side of the pole is a legitimate concern though.

I will improve on the known weakness first - the masthead amp, and I will replace the cabling for the best grade possible. After that, if consistent reception isn't achieved I'll be looking for a new aerial.

What is the best grade of cable? Is it CT125?

CT100 should be good enough. I you have already RG6 and you cannot give it back use that cable.
You wrote at the first page your PSU for the mast amp has a througput loss of 4db. Thats too much. Modern PSU's have maximum 1db loss.
If I where you I would a buy a adjustable mast amp 7db to 22 db and a good power supply for it.
It is maybe also a good idea to place the amp in the attic and not at the pole.

mrdtv

maxg wrote: »

CT100 should be good enough. I you have already RG6 and you cannot give it back use that cable.
You wrote at the first page your PSU for the mast amp has a througput loss of 4db. Thats too much. Modern PSU's have maximum 1db loss.
If I where you I would a buy a adjustable mast amp 7db to 22 db and a good power supply for it.
It is maybe also a good idea to place the amp in the attic and not at the pole.

Pyecontinental: the key parameters in any aerial are its gain, F/B ratio and sidelobe pattern. Your DAT is quite a good aerial but I think you have amplifier problems or some connection issues ( just google MRD problems and you'll see what I mean.) The point about the Sgma is that its a new design ( Televes has a similar one coming out): they are all very compact and don't have to be very large to have similar performance. BTW I have never had any problem with Fracarro data sheets and always found them to be very accurate. The others have advised you to sort out your masthead (issues: I fully agree with sticking it in the loft for ease of maintenance). That way you minimise any additional expenditure.

maxg

It makes no sense to replace a DAT 75 wideband aerial with a weaker wideband aerial from Francaro.
Btw the graph at the aerialsandtv site is for a DAT45 like aerial not for a DAT 75.

mrdtv

maxg wrote: »

It makes no sense to replace a DAT 75 wideband aerial with a weaker wideband aerial from Francaro.
Btw the graph at the aerialsandtv site is for a DAT45 like aerial not for a DAT 75.

The gain difference between the DAT 75 and the Sigma is 2dB which is pretty insignificant. Justin over at aerialsandtv.co.uk makes the point that the DAT75 is very unwieldy ( I have just seen one downed here in the storms last night). I think much greater headway can be made with low loss satellite cable and making sure that a variable gain LNA is properly mated with the DAT75. In Pye Continental's case he should go with what he has got and see where it takes him: he doesn't indicate where his approximate location is despite prompting from black briar. With new installations I would be more inclined to go down the compact modern aerials installation and Televes are bringer out a similar gadget to the Fracarro Sigma as are others.

maxg

Are you kidding. People stacking 2 aerials to get around 3db better gain and you say 2db is not important.

mrdtv

maxg wrote: »

Are you kidding. People stacking 2 aerials to get around 3db better gain and you say 2db is not important.

You must be. Buy Freesat if you are going down the stacking route...

GoGoBoss

I know in the days before DTT 2 and 4 aerials were common enough, for every doubling of aerials you could expect a gain of about 2.3dB after combining. This could make all the difference between a poor picture and a good picture in marginal areas along the irish coast. DTT presents different problems. Typically in the uk there was a 17dB difference between analogue and digital broadcasts. You could get a good picture from an analogue signal at the aerial with about 55dB assuming the noise levels were ok. With DTT if you previously had an analogue signal of around 55dB you would expect to be receiving a DTT signal of around 38dB assuming the noise levels are within the limits this is sufficient for a reliable reception, but you would obviously need a masthead amp. I have got DTT working reliably with a signal strength of 22dB at the aerial, obviously the quality of the signal was very good. The point is that using high powered masthead amps and higher gain aerials is not always the solution for DTT. Typically the components in a system with the most losses are the downlead, wall plate and fly lead also this is where you can pickup alot of interference which can dramatically increase noise levels. What I am trying to get accross is that I think some on the forum are paying to much attention to signal strength when they should be giving atleast as much attention to the quality of the signal and what effects the other components are having between the aerial and the tv tuner.

PyeContinental

mrdtv, from what I've read now over the last while, the key thing seems to be the average gain, rather than the peak gain, which can be misleading, and apparently the DAT 75 is a case in point.
However, the sensible order of things seems to me to replace the amp and power source with a new one (I might as well try that Vision model) and see what that achieves before replacing the aerial.
Always best to change one thing at a time anyway when looking for a solution.

I have the DAT75 disconnected since I last experimented with it. If I've damaged it by connecting it directly to the power source then I'll be in the market for a new aerial but I'll wait and see what happens with the new amp first.
I don't care about wind loading or size, at least they are minor issues compared to the performance of the aerial. I'm looking for technical reasons as to why the Fracarro is a better aerial at receiving signals - that's the only attribute I want to focus on. The manufacturer's gain curve across the relevant spectrum is quite flat which does look to be a good thing though.

As for the masthead amp location, everything I have read says that it should be as close to the aerial as possible so that the signal is amplified as soon as possible. That way the amount of noise is at a minimum before amplification. There was something about not making the cable from the aerial to the amp shorter than the wavelength of the frequency you want to receive though. In general that would mean not to make the cable any shorter than half a metre between aerial and amp.

From what the guy on the aerialsandtv website says, a gain of 2db at the aerial would be a significant increase:
From http://www.aerialsandtv.co.uk/tvaerialtests.html

Differences in the test results of one dBμV on any individual frequency should be disregarded, manufacturing tolerances or a truck going over a hill somewhere between the test site and the TX could easily account for those ! Furthermore the response of any aerial is not linear, its gain curve will have bumps and dips in it. That said, a 1dB difference
across the whole band is significant, and an increase (or decrease) of two or three dB is
very significant. It should be remembered that 3dB is a 40% higher signal level, and such
an increase at the aerial (as opposed to through an amplifier) is very difficult to achieve.

Thanks for everyone's input on this so far. I do appreciate the theoretical discussion, but I'm trying to be focused on solving my particular issue which for me I think is improving the efficiency of each component of the system - amp, cable, and aerial, to get above a certain threshold for consistent reception. GoGoBoss, I agree of course with what you're saying about signal quality as oppossed to strength, but I hope to achieve an increase in both.

Right, well I suppose the best thing for me to do is to get back to you all with an update when I have the new amp and power supply.

One last thing - can someone please just let me know if CT125 is the best grade of cable that can be used?
I always approach a project with the intention of using the best components that I can get. I want to give myself the best chance of success with this. If I cut corners or even use something that should be "good enough" and don't see any difference, it will have been all a bit of a waste. For me, the "buy cheap, buy twice" adage has often proven itself to be true.

PS - I have freesat and I'm still delighted with it. For a total of 80 quid, I put the dish up and ran the cables myself and was surprised how easy it was. All this aerial stuff is just for the few channels that aren't on freesat (yet, at least).

maxg

mrdtv wrote: »

You must be. Buy Freesat if you are going down the stacking route...

Once more are you kidding. What has freesat to do with signal strength in fringe reception areas for DTT.
Do you think wasting signal strength is the way to go for getting a better picture?

PyeContinental

PyeContinental wrote: »

All this aerial stuff is just for the few channels that aren't on freesat (yet, at least).

And multi-room multi-channell tv of course...

As for ct125 being better than ct100-a simple google tells me it is...but hard to work with.

http://www.letsautomate.com/10012.cfm

However I don't know anyone that uses it.
The pest person to as would be via pm to Tony of satelite.ie

If anyone here would know he'd know

http://www.boards.ie/vbulletin/member.php?u=3111

mrdtv

GoGoBoss wrote: »

I know in the days before DTT 2 and 4 aerials were common enough, for every doubling of aerials you could expect a gain of about 2.3dB after combining. This could make all the difference between a poor picture and a good picture in marginal areas along the irish coast. DTT presents different problems. Typically in the uk there was a 17dB difference between analogue and digital broadcasts. You could get a good picture from an analogue signal at the aerial with about 55dB assuming the noise levels were ok. With DTT if you previously had an analogue signal of around 55dB you would expect to be receiving a DTT signal of around 38dB assuming the noise levels are within the limits this is sufficient for a reliable reception, but you would obviously need a masthead amp. I have got DTT working reliably with a signal strength of 22dB at the aerial, obviously the quality of the signal was very good. The point is that using high powered masthead amps and higher gain aerials is not always the solution for DTT. Typically the components in a system with the most losses are the downlead, wall plate and fly lead also this is where you can pickup alot of interference which can dramatically increase noise levels. What I am trying to get accross is that I think some on the forum are paying to much attention to signal strength when they should be giving atleast as much attention to the quality of the signal and what effects the other components are having between the aerial and the tv tuner.

The points you raise are excellent and well worth implementing. This was studied in detail by DTG in the UK in the early days of DTT where the biggest sources of loss were the components you identified: in my experience old wall plates are the biggest enemy of reliable DTT reception and lead to significant loss of margin. Recent measurements of the high power Winter Hill BBC PSB1 at 85 miles distance indicate that the new UK DTT stations are putting signal strength down just 3-5dB below their analogue counterparts as expected (100kW DTT vs 500kW analogue.) As you remark the use of amplifiers in noisy systems has adverse consequences and steps should be taken all the way along the chain to minimise noise ingress as this raises the C/I ratio.

mrdtv

Deleted User wrote: »

And multi-room multi-channell tv of course...

As for ct125 being better than ct100-a simple google tells me it is...but hard to work with.

http://www.letsautomate.com/10012.cfm

However I don't know anyone that uses it.
The pest person to as would be via pm to Tony of satelite.ie

If anyone here would know he'd know

http://www.boards.ie/vbulletin/member.php?u=3111

I used CT100 when DTT first started in an area where early postcode predictors indicated no reception and ran the cable direct to the fplug: it worked straightaway and has had no impulse noise problems to this day. CT100 is standard satellite grade cable and is very easy from a materials handling perspective. At UHF the advantage of CT125 is about 3dB but this can be overcome by an amplifier (if needed)..

We were getting well above 70db's from the twins with the amp here on analogue in very good reception conditions and we'd be considered fairly near the northern extreme of Presely's SE Ireland reach.

I'm thinking the op needs a meter up at the aerial and if he's not getting greater than 40db there,then somethings wrong with the location/aerial.

Mind you that was analogue testing-I'll let Mrdtv comment on the digital equivalent requirements.

Also that signal was strong enough for dtt on low power pre aso except in wet weather.

mrdtv

Deleted User wrote: »

We were getting well above 70db's from the twins with the amp here on analogue in very good reception conditions and we'd be considered fairly near the northern extreme of Presely's SE Ireland reach.

I'm thinking the op needs a meter up at the aerial and if he's not getting greater than 40db there,then somethings wrong with the location/aerial.

Mind you that was analogue testing-I'll let Mrdtv comment on the digital equivalent requirements.

Also that signal was strong enough for dtt on low power pre aso except in wet weather.

What I have not seen so far on this reflector is a systematic measurement of the signals in Ireland.

As a sample of what would be really interesting to know :

Here's what was actually measured by aerialman on ukfree.tv at 85 miles from Winter Hill:

Some interesting early results,of signal strengths in dB scale,of the Winter Hill Transmitter,at an elevated position in South Shropshire.85 miles 'as the crow fly's'.
Analogue:
BBC 1.North West 46dB
ITV Granada 47dB
Channel 4 45dB
Channel 5 35dB {12.5kw}

Digital:
BBC A PSB 1 43dB {100kw}
Mux 2 29dB
Mux A 28dB
Mux B 29dB
Mux C 30db
Mux D 34db

BBC 1,Granada,Channel 4,analogue channels at 500kw.

All Digital muxes radiate at 10kw

What stands out here,is that BBC A/PSB 1,signal levels are only 3 to 5dB down on the analogue services,which i find encouraging,about the eventual robustness of all Digital signal levels!after complete switch-over.

Test result,consisted of Televes High-gain Aerial,with 14 meters of coaxial cable downlead/coax plug connection,at roof level.

The Wrekin Transmitter is same line of site as Winter Hill,but only 15 miles away.For example Mux C 39dB,Mux D 37dB,at 1kw each.
Analogue channels,58-66dB range.1ookw each.


In further comments on that thread he noted that the DTT signal could work well down into the 30dB level (and 22dB was reported in this thread earlier): this means that the fringe area coverage is quite extensive. And unlike analogue its perfect reception.

Black Briar if you were getting 70dB on PAL, you are probably getting 65dB on Preseli DSO DTT. This corresponds to a more or less bombproof signal which has been your experience to date and the main problem will be CCI in lift conditions which is a hazard in all RF systems but intermittent.

GoGoBoss

Hi all,
Pye I see your considering using a vision amp and PSU, is this the vision optima range of amp? if so I have fitted about 50 to 60 of these over the past few months. They are generally OK, but they do seem to produce more noise than one would expect at higher frequencies around 700MHz upwards, bear in mind too that DTT from three rock is in this area. Also I have 8 power supplies that did not work out of the 50 - 60 I bought. I personally find a Triax amp performs better.
It is good practice to leave about one wavelength of the lowest frequency been used for the lead from the aerial to the amp, note the dipole will be about half the wavelength, so you can work out the length of cable quite easily. Also you should always place the masthead amp as close to the aerial as possible, you can never improve the signal after the aerial and your down lead will add directly to your noise levels, weak signals are more vunerable to noise than a strong sigal, amping early is always best. As for CT125 it is generally used for system installations, I wouldn't use it for a domestic installation unless your cable run was more that about 40m and the signal was marginal. CT100 or similar is good enough for your purposes.
I see you quoted "It should be remembered that 3dB is a 40% higher signal level" and I said previously that a gain of 17dB is an increase of 50 times the power......I guess most of you will think one of us is wrong..but were both right your quote is refering to microvolts and I am refering to power. A 3dB increase is a doubling of power and a 6dB increase is a doubling of voltage. Anyway good luck with your quest.....

maxg

@GoGoBoss
How should a downlead add noise. Can you explain it?
If you place an amp in the loft and you use say 3 meter cable you will lose around 0.3db SNR. That is it.

Satdog

mrdtv wrote: »

I used CT100 when DTT first started in an area where early postcode predictors indicated no reception and ran the cable direct to the fplug: it worked straightaway and has had no impulse noise problems to this day. CT100 is standard satellite grade cable and is very easy from a materials handling perspective. At UHF the advantage of CT125 is about 3dB but this can be overcome by an amplifier (if needed)..

Slighty off topic but as it's a cable issue....... I wanted to replace all my coax cable and ordered CT100 and got MF100 (copper braid and sheilding and foam dialectric) €32 for 100m from local electrical supplies - much cheaper than online. I haven't come across MF100 in any of the threads or posts. Performance wise is it on a par with CT100? Thanks in advance.

GoGoBoss

maxg wrote: »

@GoGoBoss
How should a downlead add noise. Can you explain it?
If you place an amp in the loft and you use say 3 meter cable you will lose around 0.3db SNR. That is it.

Hi Maxg,
I understand where you are coming from and it can be difficult to explain but I will try [FONT=&quot]hypothetically, obviously you would not do this in real life... . If you can imagine running several hundred metres of cable with the aerial at one end and an amp at the other, firstly there will be a huge loss and you could typically expect at UHF frequencies to end up with less than 1% of the signal that was originally at the aerial. Also the cable itself has copper and is therefore a conductor which will pickup unwanted signals along the length of cable and mix them with your aerial signals adding to the noise levels. After amping at the end of the cable you may have a strong enough signal strength but you will also have amplified the noise pickup too. Your noise levels at this point would probably be so severe that your C/N would be so low the tuner at the receiver could no longer distinguish between the carrier and the noise resulting in no picture. The point is you don't want to amplify the noise the cable picks up on route to the reciever, this can be achieved by placing the amp as close to the aerial as possible. Note that a strong signal level is far less vunerable to noise than a weak signal. Usually the cable most vunerable to signal ingress is around the aerial. In commercial systems sometimes it can help to amp up to 120dB microvolts for long cable runs and back the signal off along the line before it arrives at the receiver. This helps reduce unwanted signal ingress along the cable interfering with the wanted signal.
SNR (S/N) is a measurement of signal to noise ratio after demodulation ie. baseband signal after the carrier is removed within the tv or stb tuner, this is not the same as C/N which is generally measured at the aerial or along the cable. The loss in C/N varies on the enviroment and the components being used. I have seen the term S/N been misused alot which can make it confusing to people. Bear in mind that a reduction of 1dB in C/N can result in no picture, there is very little margin in C/N and S/N compared with the margins a system could cope with regarding signal strength. For example a satellite signal strength of anywhere between 50 and 80dB at the receiver will work perfectly well, however the C/N typical from a sky dish kit around 11dB will work very well and be reliable but if the C/N drops to around 9dB at this point the stb will struggle to distinguish the carrier from the noise and you will probably end up with picture break up. I hope I explained this ok......
[/FONT]

whizbang

IF: you are only looking for a UK Digital signal, then you can use massive gain. Even so much that any analog is going to be totally unusable. i have tried it myself, using a really crappy aerial, and multiple amps until even vhf was obscured by the noise. Digital signal quality still good. Put the biggest damn thing you can find on the mast, and a variable attenuator near to your distribution point, tweak it for best overall.
Try to keep anything analog away tho..

mrdtv

whizbang wrote: »

IF: you are only looking for a UK Digital signal, then you can use massive gain. Even so much that any analog is going to be totally unusable. i have tried it myself, using a really crappy aerial, and multiple amps until even vhf was obscured by the noise. Digital signal quality still good. Put the biggest damn thing you can find on the mast, and a variable attenuator near to your distribution point, tweak it for best overall.
Try to keep anything analog away tho..

An unorthodox approach! Are you using Arfon or Preseli?

PyeContinental

Very interesting, Whizbang. The FTE maximal I asked about at the beginning of the thread would have given a maximum of 40db gain. I went for the Vision amp (up to 27db) but if it doesn't work out, I might try the FTE as part of my experiments.

GoGoBos, of course you explained that well. I have a feeling that maxg was looking for an argument rather than an explanation though! :pac:

Well anyway, I can't give you any updates until the new masthead amp arrives.

GoGoBoss

whizbang wrote: »

IF: you are only looking for a UK Digital signal, then you can use massive gain. Even so much that any analog is going to be totally unusable. i have tried it myself, using a really crappy aerial, and multiple amps until even vhf was obscured by the noise. Digital signal quality still good. Put the biggest damn thing you can find on the mast, and a variable attenuator near to your distribution point, tweak it for best overall.
Try to keep anything analog away tho..

Glad to hear that approach worked for you whizbang......your right that you can amp the hell out of a signal and have excellent quality at the other end even after several amps. However every amp has a maximum input and maximum output level, if you exceed these figures it can all go terribly wrong. Generally the noise figure of the first amp is the most significant and the noise added by further amps along the line can a lot of the time be disregarded as there noise contribution is not adding as much as you would expect. If you can imagine a channel going down a cable is like a spike and it is say at 90dB and the maximum input to the next amp is 80dB and output is 100dB and has a gain of 30dB. Basically the amp is goinig to cut the top off the input signal and reduce it to 80dB and at the output instead of getting 80dB + 30dB gain the amp is going to cut the spike again because its maximum output is only 100dB. This can produce a corrupted output signal that is no good.
Anyway glad to hear it worked for you, but do be careful you could waste money with this approach. Best practice is to amp at the aerial and only as much as is neccessary. Also bear in mind alot of DTT receivers cannot cope with a signal of more than 75dB if you exceed this there is a risk that you will overload the tuner in the receiver and it will show as if you had a bad signal....no signal.....or something similar.