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alanh

Antenna Design Basics + Amplification

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:ph34r: Dear mr AlanH

I live in Perth (Connolly) and have read your extensive information about antenna,s.

Being 65 + it goes a bit over my head.

Could you recommend an antenna man in the Perth area who knows all those things you write about and could give me advice  and possible install the best antenna for my area ?

Regards

Ewoud

Did you get your antenna system sorted out? I also am in Perth - i had installed my antenna system myself and have had excellent result. PM if you would like some more information.

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Carlton

Meters generally give two BER measurements,The first is the channel BER which is the BER of the signal as arrives at the input.This is sometimes referred to as B BER on some brands of meter as it is the BER BEFORE viterbi correction.

The second BER measurement is the post viterbi BER or PV BER sometimes referred to as A BER or AFTER VITERBI BER.

People are always looking for the magic pass/fail  good /bad type of figures.

STB,s will just show a perfect picture with Channel BER as low as 1e-02 and a PV BER just under 1e-04 but these are absolute minimums.

A Channel BER of 1e-04 or higher would be a realistic value for reliable service.This would generally relate to PV BER of 1e-06 - 1e-08

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thanks for your help bellotv appreciate it !!! is there anywhere where i can get more info on understanding the formulas for ber some of the readings are a bit strange to me like "1x10-4" etc

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Ewoud,

I have been away without contact with the forum. I am now reading the 27 pages of new posts!

Have you read WA Geographic Viewers' Forum. WA subforum Select your geographic subforum and then open Get the best reception. Which transmitter and which antenna

Connelly is also subject to salt spray not only on antennas but also on the power lines which can cause the picture to break into blocks and the sound to chirp.

Depending on your location (can you see the Darling Range in the Bickley area) or not. If you can use one of the first recommendations for the Main transmitter, if not I would use the weak signal recommendations.

Any further posts should be in the Perth Viewers' forum.

AlanH

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I'm looking at trying one of the TF160 high pass filters. Given it's a "trade" filter it probably won't come with much in the way of instructions. I'm sure I can figure it out but one thing I want to check is should it be installed before or after the masthead amplifier?

I'd prefer to put it after to save getting up on/in the roof until I see if it actually works if that possible.

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HP filter needs to be installed before masthead to stop lower frequencies (and hopefully the impulse noise) from even being amplified and more likely in the case of impulse noise from overloading the amp.

Fitting it after the masthead is like shutting the gate after the horse has bolted.

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HP filter needs to be installed before masthead to stop lower frequencies (and hopefully the impulse noise) from even being amplified and more likely in the case of impulse noise from overloading the amp.

Fitting it after the masthead is like shutting the gate after the horse has bolted.

But will it work (at all) after the amp? Just as a temporary test to save me the time of climbing up into the roof just to test. It's only the outlet that has the STB on it that I'm concerned with. If it works, even only as a reduction rather than complete cure I can then look at installing it permanently.

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It will work to an extent, however if you have already amplified the offending signals/interference it may be totally useless.

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is there an amp avail to cover the entire uhf range as mt tamborine on the gold coast hinterland trans mits from uhf 36 - sbs to uhf 68 nbn digital.

thanx

7seven

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apsilon,

You have not said where you are. Click on Geographical Viewers' Forums. Subforums Select your geographic subforum and then open Get the best reception. Which transmitter and which antenna

Post any further posts on this topic in your geographic viewers’ forum.

The some masthead amplifiers come with filters included. Anything which is not wide band .

7seven

Kingray MHU44G B1-3 -1 dB, B4-5 44 dB

AlanH

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thanks for your help bellotv appreciate it !!! is there anywhere where i can get more info on understanding the formulas for ber some of the readings are a bit strange to me like "1x10-4" etc

Carlton,

In order to understand BER, please use the following example:

BER = Bit Error RATIO (NOT RATE!) Rate is Incorrect terminology and means something totally different.

It is the ratio of errors present within the incoming data stream.

And is measured before and after viterbi / error correction.

Then... Usually a BER meter/instrument would normally display the 1x10-4 as a 1E-5

In any case, 1E-4 would mean

1 Error in every 10,000 Bits of Information (data) received.

Notice the (-4), you can make this the NUMBER OF ZEROS you must add to the initial number.

If your instrument is displaying a 10 before the Bit number, then it would equate to 10 + 0000 zeros. Ie: 100,000 but you will need to check on this from your user manual but logically I would bet it to be like this.

The same goes for 5E-3.

This would equate to: 5 errors in every 1,000 Bits received.

or 3E-2 would equate to 3 errors in every 100 bits received.

Of course, the less number of zeros (or you could call it the order of magnitude) the worst your signal is.

A bad signal would be 1E-2 and probably your signal is on the border line of falling off the cliff edge.

A fantastic signal would be 1E-8 (ie: a perfect incoming signal)

However, be aware...if you are getting 1E-8 AFTER viterbi (error correction) and a lower reading like 1E-3, then you would have to look at your antenna setup to try and get a better signal.

You really should aim for the best possible incoming signal measured BEFORE viterbi (error correction).

I hope this is easy enough for you to understand. If you still have trouble, please let me know and I will explain in a different way. But I am pretty sure you will understand now.

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apsilon,

You have not said where you are. Click on Geographical Viewers' Forums. Subforums Select your geographic subforum and then open Get the best reception. Which transmitter and which antenna

Post any further posts on this topic in your geographic viewers’ forum.

The some masthead amplifiers come with filters included. Anything which is not wide band .

7seven

Kingray MHU44G B1-3 -1 dB, B4-5 44 dB

AlanH

AlanH,

Is there a reason why you always refer to Kingray?

They are not the best solution for the above problem!

There are many other Mast Head Amplifiers that will do the job better and WITH RF shielding for a much lower price and higher quality.

The MHU44G is NOT RF SHIELDED. IT IS IN AN ENTIRELY PLASTIC CASE! And very inviting for Impulse noise.

Maybe you can try a Fracarro JS2RT or even the Fracarro MAP series.

It all depends on the incoming signal.

If it is too strong and you use a high gain mast head, you will over drive the amplifier and destroy/clip the signal.

In your case you mentioned an MHU44G which has 44dB gain on UHF right?

However, if the incoming signal is very high like...say...70dBuV and because the MHU44G has a final output of 108dBuV, you will actually overload the amplifier because:

70+44=114dBuV (this is 6dB over the MAXIMUM Input allowed)

So sure, now you can say you will just turn down the input attenuator and sure that is fine.

You will need to attenuate by 6dB to get to the maximum allowed, but will you have minimum noise?

And remember that the MHU44G is an INPUT stage Amplifier, Not Mid stage so there is NO gain control! Just input attenuator so your noise factor is increased.

But what if the person in question has a huge signal like 85dBuV off the antenna straight to the TV outlet?

Many people make the mistake of thinking that because the set top box doesn't work or the analogue picture is bad, it must be because of low signal... Then by adding a masthead you actually make the problem even worse.

7seven, can you supply a CHANNEL POWER & CARRIER TO NOISE READING?

This would help greatly in solving your problem.

Sure you can also say that the signal received by the person in question might be very low, then that is a different story to a certain extent. But remember that the Kingray Masthead that you have recommended is NOT shielded but in a plastic case. For digital, this is NOT recommended!

Then, if you are using the mast head as a filter...well then there is something wrong with your thinking.

Filtering is done by filters, not mast heads unless you want to perform a multitude of operations at once which includes amplification.

Also, AlanH, I am not sure why you are saying that Salt spray will make digital reception pixelate and the sound to chirp. Among the many reasons why this could be happening, most of the time it is because of two things. Either too little or too much channel power or impulse noise but I am betting it would be impulse noise more than anything.

Digital TV is present in MANY countries INCLUDING countries that have a coast line like Australia, Italy or Vietnam for example. In both cases, salt spray is NOT a factor. It is usually Impulse noise or other reception factors.

But salt spray...that would have to be the most silly thing I have ever heard... sorry :blink:

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Digital Docktor,

The reason I have been recommending Kingray is because of the internal filtering. I am looking a band pass filter of 174-230 MHz for band 3, 526 - 589 for band 4, 526 - 680 for band 4+ and 680 - 820 MHz for band 5.

In particular I do not want gain in the 45-174 MHz band.

This minimises interference and allows the maximum gain to be set. The only source of overload is other analog TV transmissions in that band. If yoiu can find others, then I will certainly recommend them.

As for shielding, the amount of metalwork in antennas particularly band 1 - 3 is considerably more than the input wiring to the first transistor of the masthead amplifier, so I would rather have a filter than shielding if I had to chose. So the antenna is a much better antenna than the wiring in the masthead amplifier.

I agree that overloads are a possibility These amplifiers contain gain controls. I also agree that an antenna which is restricted to the frequency range of interest and has adequate gain is preferable. Getting sufficient signal level from the amplifier through long cables is also important to minimise interference and overcoming cable loss. You will notice I have said this is general advice in the Geographic Viewers' forums. Here I have only recommended them for diffuse and weak signal areas.

The fact that masthead amplifiers can make the situation worse has come up many times on this forum.

Filtering can be anywhere but it must be prior to any amplifer and as close as possible to the input. Otherwise you get intermodulation . This will then "transfer" the interfering signal to the frequency of the channel being amplified. Then no filter can remove the interference. Putting the filter in a separate shielded box then makes is much more expensive because of the extra weather proof case, pcb, dicast box and connectors.

Salt, Australia is an island surrounded by ocean where most of the population live. The Mediterranean is a sea so is smaller.

The problem with salt is that it accelerates the corrosion of the steel screws (which connect to the down lead) and the aluminium they screw into. The oxides in rust are a semiconductor and as a result will cause the intermodulation mentioned above. I have seen analog pictures from a corroded antenna with the windscreen wiper effect. So for digital the inpulse interference will worsen as the corrosion increases.

The other problem with salt is that it gets on high voltage power line insulators. This causes them to arc when there is moisture. Typically at tea time! The arc will produce many frequencies gradually reducing in power as the frequency rises. However the power line is the aerial! Where I live the power company washes the salt from the insulators to prevent blackouts.

One poster lives near a 225 kV power line and can tell you all about it, even the acoustic noise you can hear from the power line.

AlanH

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And remember that the MHU44G is an INPUT stage Amplifier, Not Mid stage so there is NO gain control! Just input attenuator so your noise factor is increased.

Oh give me a break please!

MHU44G pdf

I must be using a different product, there seems to be a midstage gain control in this model :blink:

Edited by marcj

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Oh give me a break please!

MHU44G pdf

I must be using a different product, there seems to be a midstage gain control in this model :blink:

Marcj,

Yes I have clearly made a mistake in my comment. I did not see this pdf before I made that comment so I will give you that, but it doesn't change the gist of what was said.

It is funny you have pinpointed this particular thing though... No problem...

I will now be extremely alert and include some quotations of particular persons in the future :P

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AlanH,

Sure you have selected the Kingray because of the band pass filtering...However, this doesn't change the fact that if you might have too much signal and you will over drive the amplifier and make the situation worse.

The first thing that should always be done before anything else would be to KNOW the ACTUAL signal received. I have never seen anyone ask a question on what type of Channel Power, CNR or BER this particular person is receiving at the outlet point.

Ie: the Channel Power and CNR of each individual carrier in the particular bands.

ONLY THEN can one make an informed decision of which type of mast head amplifier to use. And no one can argue with that. Without proper measurements, we are all flying blind.

Then...about shielding on mastheads and that you stated "As for shielding, the amount of metalwork in antennas particularly band 1 - 3 is considerably more than the input wiring to the first transistor of the masthead amplifier, so I would rather have a filter than shielding if I had to chose. So the antenna is a much better antenna than the wiring in the masthead amplifier." Sorry mate, that is absolutely rediculous!

Do you not know that many impulse noise problems ingress at the mast head and connection point and many times because of non existent shielding or even impedence missmatching... Even the masthead you recommended, it is a saddle and screw type. Not even F-Connector and also just plastic cover with NO SHIELDING. http://www.gme.net.au/matv/mhu_series.php

Also your comment QUOTE:"Filtering can be anywhere but it must be prior to any amplifer and as close as possible to the input. Otherwise you get intermodulation . This will then "transfer" the interfering signal to the frequency of the channel being amplified. Then no filter can remove the interference. Putting the filter in a separate shielded box then makes is much more expensive because of the extra weather proof case, pcb, dicast box and connectors."

Well actually I agree with you, the filtering must be before the amplifier, but usually always at the headend. Imagine you have ingress at the headend but you insert a filter before a trunk amplifier down the network. That is just wasting time. However sometimes the interference is BEHIND the actual carrier that you are trying to reticulate and therefore not possible to filter with normal filtering. But this is very important because when it comes to Impulse noise or other similar type of interference, the problem occurs BEHIND the actual carrier that you are trying to reticulate and by using equipment that has NO shielding, you are making the probability much higher. And when you are mentioning about metal boxes etc... if you compare the fracarro product pricing to Kingray pricing, and remember that the Fracarro product is Shielded, the fracarro pricing is much lower in cost than Kingray and you get a better product anyway. And no I do not work for Fracarro.

Finally, about the salt issue. I'll have you know that I have lived on an island and other countries on the coast not far from Australia for many years and some of these places have digital and very salty atmosphere with high and low humidity. I can tell you that what you are saying is rediculous and extreme. Yes, the salt causes corrosion etc... but the actual problem here is IMPULSE noise. But sure, you can say that arcing is what is generating the impulse noise and I will give you that, but to say it in this context is quite silly. There could be 10s of different reasons why there is impulse noise present.

In the islands and other countries that I have lived in, and have both sat and terrestrial digital, problems were generally because of impedence missmatching, ingress, poor connections/connectors, poor quality cable, non earthing of headend or antennas, mercury vapour lighting and dirty motors... the list goes on and on. Not once has there been an incident which was caused by overhead high voltage electrical cables arcing when there is moisture unless of some extreme scenario.

Even the poster that lives near a 225kv power line can talk about the Audible acoustic noise that they can hear, doesn't mean that this is the reason for the pixelisation. In the end, BER, Channel Power and CNR (all together) are extremely important. If all parameters are comfortably correct and you have pixelisation problems, then you can start looking at impulse noise etc... but I would be starting with the house lighting, any motor driven equipment even nearby, or even checking the actual TV system if that is the case... Has this person checked every single RF connector? Are all connections F-Type? What type of antenna?, what type of mast head (if any)? what type of cable used?, what type of outlet wall plate used?, what type of fly lead? Is there an impedence missmatch in the system? etc... The electrical power lines would be the last thing that would be looked at. Could even be that the signal received is just hanging off the edge of the cliff. But without actually Measuring the channel power, CNR & BER, no one can say what the cause is, not even myself. Sorry :blink:

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