Do I Need Amplification?

[Slayer]

Hi Guys

Basically I'm after you're advice on whether I need to add amplification to my tv signal whether it be masthead or and amplified splitter.

Location: Glenfield, Sydney 2167

Format: Digital

Aerial: Can't remember the exact model but it was purchased from laceys and it's something along the lines of a Fracarro 34? (I know I purchased it specifically for digital reception as it filters out some frequencies like abc analog, it's also physically a very small aerial)

Cabling: RG6 quad shield + f type connectors.

Usage: Currently I have one wall outlet which I run a fly lead from into a connection on my belkin isolator power board http://catalog.belkin.com/PureAV_detail.pr...oduct_Id=184722 I then run a small fly lead from the output of the powerboard into an unpowered 2 way splitter which has 2 more fly leads that run into the inputs on a HDTV card in my htpc.

Problems: I seem to get pausing and stuttering of the signal fairly regularly. More often than not it happens exactly when a light is switched, the fridge is opened etc. Now this happens whether I'm running it with a single fly lead directly from the wall or setup in my usual setup above. I should mention that I only started running the first fly lead into the belkin board recently before that it was straight into a splitter then to the htpc. Since the belkin has been in the chain the stuttering appears to be more regular.

Signal Strength: My hdtv card lets me monitor the signal via a piece of software. Strangely the results are pretty much identical whether I run it directly with one fly lead from the wall or through the splitters and powerboard (I was expecting a drop atleast from the splitting!)

An example of the signal strength using Channel 9 is

Signal strength = 84%

Signal quality = 96%

SNR = 26.5db

So that's the situation... Yesterday on a whim I picked up a cheap amplifier splitter from Big W for $28 it's a Alvin ASA122P specifications

Input Level = 45-90dBuV

Frequence = 50-900MH z

Gain = 20dB

Gain control = 15db

max output = 105dbuv

So I've just plugged this in adding it to the chain straight after the power board. After adjusting the gain control it seems to of made very little difference to the monitoring tools results except for the SNR going up to 27db (.5 increase) However after watching tv for 40mins I havn't had a single stutter! the house is empty so theres minimal interference so tonight will be the big test but for what reason would this be helping?

I had all the intentions to try this unit and more than likely return it to big W and the lack of improvement in signal strength confirmed this however strangely the stuttering hasn't kicked in since plugging it in.

I never really intended on using one of these amplified splitters I was planning on going to a suitable masthead amp however now I'm not sure what I should do. To throw another spanner in the works I'd really like to connect a 3rd device up meaning the signal would be split again if possible.

Thanks in advance

[wahroonga farm]

It all comes down to 'signal vs noise', which your card measures as 26.5dB (probably not terribly reliable).

However the viewing results indicate that your operating right on the 'digital cliff'. This is not helped by the Belkin board which is simply adding mains power impulse noise.

So the only way to improve the signal level is:

# Bigger antenna and/or

# Better antenna location

with the shortest feed.

The feeder losses are best overcome by a modest gain, low noise figure Band 3/4 (only) masthead amplifier. It must be mounted at the mast, otherwise noise gathered along the feeder is also amplified.

Something like this from Laceys:

Masthead Distribution Amplifiers

High output 118dBµV @-60dB IMR mast amp, with +19dB

gain, <1.8dB nf, >10dB R.L., 12-24V DC @100mA.

MDA20H 174-860MHz with 174MHz High Pass flt. R126.

The 'Fraccaro LP34' is probably a band 3/4 model, with 9/10 dB antenna gain, but good external electrical noise rejection. I guess suitable for your area (depending on your actual location), but only modest gain.

Everything else is fiddling at the edges, without really solving the root problem.

[bellotv]

Slayer

Masthead amps should only be used as a last resort.

The MOST important thing is to position your antenna so it picks up the most signal.

It is pointless having the best you beaut antenna if its mounted where there is bugger all signal.

You should get out an antenna installer with a digital meter to at least find the best position for your antenna.I say this time and time again.Only when you use a meter do you realize how hit and miss it is not to use one.

The 18dB gain that a masthead amp may give you can very often simply be obtained by moving tha antenna to a different position.Not only have you saved $126 dollars but also increased your fade margin and overridden your impulse noise.

Amplifiers definitely have their place but they should never be used as a band-aid.

As an after thought,Have you correctly terminated the coax to the antenna ?I,ve seen these where the plastic insulation of the coax was clamped instead of the braid .It kind of worked but not very well

[wahroonga farm]

Yes I agree 100% re amps (it wasnt part of the S/N solution) ....... but unless I'm reading wrongly it's a 'deaf' PC card (not a 'real tuner'); so a modest gain low NF amp cud be part of the overall answer particularly if multiple points are required (the amp is simply doing wot a quality STB wud do in any case).

[bellotv]

Yes I agree 100% re amps (it wasnt part of the S/N solution) ....... but unless I'm reading wrongly it's a 'deaf' PC card (not a 'real tuner'); so a modest gain low NF amp cud be part of the overall answer particularly if multiple points are required (the amp is simply doing wot a quality STB wud do in any case).

I fail to see the difference between a STB tuner and a tuner card in a PC.What is a deaf PC card ? If it can display signal strength/quality readings (even if not calibrated) then it must have a digital tuner in it.

RE-reading slayers original post I was drawn to "SMALL FLY LEADS AND SPLITTERS"

This may well be the weakness.Spot soldered plastic injection moulded fly leads are utter crap and should never be used for digital.Must be replaced with Quad shield PAL CRIMPED leads .READ HERE NOT F-F lead with PAL - F adapters (as these are the most un reliable product on the market)

Also what kind of splitter ?

Is it a proper all F type fully metal type or a plastic Y type splitter ?

The above respond appauling in situations where there is impulse noise

[wahroonga farm]

The majority of consumer PC based tuners (Analogue, DVB-T, DVB-S) are deliberately rf deaf (poor sensitivity), so that they don't pick up and amplify signals from the extremely noisy environment in which they operate.

They rely on good signal strength at the card input. Poor signal strength means competition with internal card noise.

Then again, not all STB's are equally sensitive (just like analogue tv's).

Sensitivity is something the Strong range of DVB-T boxes are good at.

[bruiser333]

This is not helped by the Belkin board which is simply adding mains power impulse noise.

Out of interest, is it generally accepted that running your antenna signal through the filter of such a device (eg antenna in/out on a Belkin powerboard) only serves to add noise to the signal?

[Slayer]

Thank you for the replies guys most appreciated.

After watching some more tv last night it started to breakup and stutter again, whether this was because of the electrical storm we had or more electrical interference from lights/appliances I'm not 100% sure but obviously this cheap amp/splitter hasn't fixed that problem.

To answer some of the questions

The MOST important thing is to position your antenna so it picks up the most signal.

I'm pretty sure we've got the aerial as well positioned as we can. Basically when setting up the new aerial I was monitoring the results from my hdtv cards monitoring tool as I had someone angle the aerial in different directions, so we ended up settling for an angle where every channel had the best results.

As an after thought,Have you correctly terminated the coax to the antenna ?I,ve seen these where the plastic insulation of the coax was clamped instead of the braid .It kind of worked but not very well

I'm pretty sure this is fine, we were pretty careful when setting it all up and particularly noted how the connection on this aerial was different to the previous aerial (rg6 goes directly into the aerial nothing in between)

This may well be the weakness.Spot soldered plastic injection moulded fly leads are utter crap and should never be used for digital.Must be replaced with Quad shield PAL CRIMPED leads .READ HERE NOT F-F lead with PAL - F adapters (as these are the most un reliable product on the market)

I have absolutely no idea what this means basically all leads are black rg6 quad shield with the little exposed bit of copper in the middle from there they are screwed onto the female points (wall outlet, powerboard and splitter and then into adaptors so they plug into the back of the hdtv card)\

Also what kind of splitter ?

Is it a proper all F type fully metal type or a plastic Y type splitter ?

It's a dse metal f type splitter 1 in port and two out ports. Strangely enough I don't see any change in measured results when using the splitter and when not using the splitter.

This is not helped by the Belkin board which is simply adding mains power impulse noise.

Hmm so would you suggest I don't use this feature on the belkin board? it supposedly filters and protects anything connected to the aerial. I beleive it has dropped the signal strength as it has added another device in the chain but I thought that was the only downside.

So in summary do my measurements indicate that my problems may be caused by a weak signal which I'm only making weaker by splitting and filtering? I obviously don't have a lot of knowledge when it comes to aerials and amplification so rely on your experience and knowledge and purchase from there. I can easily return the big w amp/splitter so that's not a big deal I guess it was wishful thinking that it would be an easy solution.

I should also note that even running directly from the wall outlet into one of my cards inputs (single fly lead from wall) that I get the electrical interference, but it does seem to stutter less.

If you need me to take any more measurements with the monitoring tool please let me know and I will get it done

Thanks again guys

[wahroonga farm]

Yes. Everything indicates that the signal is too weak when it arrives at your PC card. My guess is that the PC card is also not the most sensitive receiver. But (disclaimer), stranger things have happened

Basically my guess is that it will all come down to signal strength at the antenna.

It's not just precise antenna direction ... you need to do the 'antenna dance' up down and all around the roof. You need the best spot for the best signal on all viewed channels.

If someone has a digital stb you can grab, you could try that and note any differences in performance & sig/qual levels.

Have you an analogue television?

How does it receive the analogue channels (not Ch 2)? Have a look at this reception guide, for typical problems. This may help analyse wots going on with your digital reception. If any analogue channels (adjacent to digital channels) are snowy, then it's probably signal strength.

[Slayer]

Yes. Everything indicates that the signal is too weak when it arrives at your PC card. My guess is that the PC card is also not the most sensitive receiver. But (disclaimer), stranger things have happened

Basically my guess is that it will all come down to signal strength at the antenna.

It's not just precise antenna direction ... you need to do the 'antenna dance' up down and all around the roof. You need the best spot for the best signal on all viewed channels.

If someone has a digital stb you can grab, you could try that and note any differences in performance & sig/qual levels.

Have you an analogue television?

How does it receive the analogue channels (not Ch 2)? Have a look at this reception guide, for typical problems. This may help analyse wots going on with your digital reception. If any analogue channels (adjacent to digital channels) are snowy, then it's probably signal strength.

Hi

thanks again for your reply, ahh ok I'm limited to where the aerial is currently mounted on the roof, it's not my house so I'm lucky enough to of been able to mount the extra digital aerial just for my room

Funny you mention the analog signal, as just the other night when I was setting up the new tv I had the analog plugged in, from one of the fly leads off the splitter (before I plugged in the belkin) the picture was perfect (Well as good as analog gets) from the 2nd fly lead it was a bit snowy which I thought was quiet weird as I thought it was the higher quality cable out of the two. Anyways I switched that fly lead for another one I had lying around and the analog from that cable was no longer snowy. So in summary my analog signal is pretty much perfect. Whether the snowyness with the fly lead indicates that the cable was shoddy or I'm right on the borderline of clear analog and snowy I'm not sure.

[wahroonga farm]

Clearly indicates shoddy cable connection. Re-check everything (using the analogue tv/snow indication test technique). This IS the most likely problem!

Complete abscence of analogue snow is a reasonable 'wet finger' signal to noise test for reliable Digital reception.

Analogue goes progressively snowy as you lose signal. No step affect.

[beeblebrox]

Thank you for the replies guys most appreciated.

After watching some more tv last night it started to breakup and stutter again, whether this was because of the electrical storm we had or more electrical interference from lights/appliances I'm not 100% sure but obviously this cheap amp/splitter hasn't fixed that problem.

To answer some of the questions

I'm pretty sure we've got the aerial as well positioned as we can. Basically when setting up the new aerial I was monitoring the results from my hdtv cards monitoring tool as I had someone angle the aerial in different directions, so we ended up settling for an angle where every channel had the best results.

I'm pretty sure this is fine, we were pretty careful when setting it all up and particularly noted how the connection on this aerial was different to the previous aerial (rg6 goes directly into the aerial nothing in between)

I have absolutely no idea what this means basically all leads are black rg6 quad shield with the little exposed bit of copper in the middle from there they are screwed onto the female points (wall outlet, powerboard and splitter and then into adaptors so they plug into the back of the hdtv card)\

It's a dse metal f type splitter 1 in port and two out ports. Strangely enough I don't see any change in measured results when using the splitter and when not using the splitter.

Hmm so would you suggest I don't use this feature on the belkin board? it supposedly filters and protects anything connected to the aerial. I beleive it has dropped the signal strength as it has added another device in the chain but I thought that was the only downside.

So in summary do my measurements indicate that my problems may be caused by a weak signal which I'm only making weaker by splitting and filtering? I obviously don't have a lot of knowledge when it comes to aerials and amplification so rely on your experience and knowledge and purchase from there. I can easily return the big w amp/splitter so that's not a big deal I guess it was wishful thinking that it would be an easy solution.

I should also note that even running directly from the wall outlet into one of my cards inputs (single fly lead from wall) that I get the electrical interference, but it does seem to stutter less.

If you need me to take any more measurements with the monitoring tool please let me know and I will get it done

Thanks again guys

You cannot rely on anything a tuner card or STB tells you when it comes to signal.. they only do very very basic estimations and do not have the capacity to measure the signal properly.

You need a digital field Strength meter that can measure CBER and PvBER and you need to measure the signal around the whole roof (not just in different directions) and also at different heights to get the best possible signal.

If you have impulse noise like this you will not resolve it by tinkering around the edges.. you need to get an expert in with the right tool.... or go and do a training course on how to use a PRomax or Unaohm meter and then rent one for a couple of hundred bucks per day from tech rentals...

then when you've captured all the information from that come back here with your measurements from a reliable source and we can help you... measurements from PC cards and STB's are meaningless .

[wahroonga farm]

Hi Slayer,

Dont' let the grumpy old pro's rattle your tree. You've got enough tools there to resolve the problem (and I suspect without moving the aerial .... which u can't in any case).

# The Analogue Tv = poor man's S/N meter by checking all adjacent analogue channels for reception

# The PCcard = it's at least a 'good/bad' meter

# Multimeter = DC check all your leads/terminations for connectivity.

# begged /borrowed /(stolen) 2nd stb = u mite be surprised

# ....... If all tests ok and a 2nd stb works ok, fit the masthead.

[beeblebrox]

It's not about signal strength.... it's about Bit Error rates and whilst signal strength is a factor it is by far not the only factor to consider.

I'd be triying another tuner.... a good qulaity STB rather than a PC card that is notoriously unreliable due the the hardware and software interaction involved.

You can't measure Bit error rates accurately with a normal tuner (PC CARD or STB) so you can only guess what is wrong. and my point is you can spend a lot of time and money tinkering around the edges for no result.

By all means use the tools available but if you've got the right antenna and good quality RG6 that's not running near any power and you're still getting the problem maybe it's time to be actually looking at what the signal is really doing..

[alanh]

Slayer.

I suggest that there are problems in your area as you will see in the Sydney Viewers' Forum

Read Get the Best Reception, Sydney and read the links.

As you will see the most likely cause for your problem is AM interference from the ABC transmitters in Prestons.

I would like to add that the Log Periodic you have is not particularly sensitive.

Please reply in the Sydney Viewer's Forum.

AlanH

[Slayer]

Hi Guys

Wow a bit of information overload, I appreciate everyones input!

Hmm doesn't look like its a simple answer though.

A bit more information to add since last post.

I found what looked to be a rg6 flylead with crimped connectors (one f-type female the other end pal with no adaptor) So I tried this cable directly from the wall outlet straight into the tuner (nothing inbetween)

Even with this setup there was stuttering and pauses (mostly when electrical devices in the house were activated but not limited to them) So this pretty much rules out the fly leads and cabling?

I then tried another suggestion of testing the signal with analog, I did this with the full setup i.e fly lead to filter, filter to splitter, flyleads from splitter to tv. The analog signal was actually pretty good, no snow at all a tiny bit of ghosting but barely noticable. So this would suggest my signal is good enough?

Alanh I noticed glenfield was listed in the areas of possible interference, I referred to that thread a year or so ago and chose the fracarro in hope it would filter out the frequencies.

It looks like I have issues with electrical noise in the house but I've run out of ideas after purchasing a special aerial to avoid this and the usage of rg6 with f-type connectors seems to be the right choice. I guess I was hoping a boostage of the signal might help overcome some of these issues especially if I'm now looking to split the signal 3 ways. I should mention I've been using a htpc hdtv setup for more than 2-3 years now so I can definately persevere with the stuttering and pausing I guess I'm more concerned the splitting will make it worse

[mtv]

A major key to sucessful digital reception is locating the best mounting position for an antenna.

As others have said, the only way to do this is with a professional meter designed to measure channel power and most importantly, bit error rate (BER). Without one, it's all pure guess work and often results in time, money and frustration experimenting.

Once you have the best possible signal, this will reduce the interference as the signal will be more robust.

Just moving an antenna a few centimetres in any direction can make a huge difference. If you can't acurately measure what the signal is doing, then you are unlikely to obtain the best possible result.

Good analogue reception does not necessarily indicate digital reception will be good from the same antenna/position.

[wahroonga farm]

Perhaps the RG6 feed from antenna to wall plate is still possibly suspect?

If your were to short the RG6 connector (centre to earth braid) at the antenna and if you had a mulitmeter, you should measure open cct (no short) and 5-10 ohms (guess) with the short. This is only a DC test and doesn't test for crushed cable etc.

I'd still try a stand alone stb (you can still feed the PC card at video) to see if there is any change. In reality an external stb + video capture card is a more robust solution.

[bellotv]

Perhaps the RG6 feed from antenna to wall plate is still possibly suspect?

If your were to short the RG6 connector (centre to earth braid) at the antenna and if you had a mulitmeter, you should measure open cct (no short) and 5-10 ohms (guess) with the short. This is only a DC test and doesn't test for crushed cable etc.

I'd still try a stand alone stb (you can still feed the PC card at video) to see if there is any change. In reality an external stb + video capture card is a more robust solution.

Wahroonga

he has a Fraccarro LP34 log periodic.

These have the coax connected direct to antenna.No F connector.

There are two parallel aluminium booms connected together at the mast/U/bolt end and separated at the other by a plastic insulator.

Coax threads though the lower boom and exits at the insulator end.Braid connects to lower boom,centre conductor connects to upper boom.

If you measure coax at TV end it should be a short curcuit due to antenna booms being joined at mast end.

Fraccarro are converting their log periodics to F connector and this will make installation easier.

[wahroonga farm]

Tks Bellotv.

Forgot 'bout the Fraccaro log periodic termination method. Good to know it'll be remedied.

Poltec get it right though

[bellotv]

I,m at two mind about it.

1) F connection is quick and easy and a good connection point to attach meter during alignment and means if facia mounted ,you don't have to lean 1 metre out to end of antenna to make connections after alignment.

2)Direct connection to antenna elliminates another potential problem connection remembering that the new F connection is simply a short piece of coax connected to the usual termination point and ending in a female F socket.

These have been a common weakness in other fraccaro clones.

Hopefully Fraccaro have it right

[longshot]

I would like to add that the Log Periodic you have is not particularly sensitive.

Just happens to work very well though.

One day Alan, you will take up gclarke8's antenna challenge. Shootout in the wild west