40 replies to this topic

[alanh]

For more detail read Antenna Design Basics + Amplification

This list is selected on the basis of the channels covered only and quotes the appropriate website’s antenna gain.

The higher the number of dB the larger the antenna, the more sensitive and more directional it is. It is also more expensive. The advantage of getting gain from the antenna rather than an amplifier, is that the antenna becomes more focussed thus rejecting delayed signals and interference sources. Amplifiers can become overloaded which antennas cannot. Thus amplifiers can make reception worse.

If the antenna signal is too strong at the receiver, a low cost attenuator can be used. The advantage of this method is that any interference picked up by the cabling is also reduced.

Yagi – Band 3 Channels 6-12 and Band 4 Channels 27-36
Horizontally polarised local reception and medium distance)
Vertically polarised diffuse reception (either long distance or blocked by terrain)

Matchmaster catalog
Nil

Hills
HD1 Platinum Band 3 gain 4 - 6 dB Band: 4: 9 - 11.5 dB
HD2 Platinum Band 3 gain 3.8 - 6.6 dB Band 4: 10.4 - 11.6 dB

Laceys TV - Fracarro
Nil


WISI
Nil


Nationwide Antenna Systems
Nil

Phased Array - Band 3 Channels 6-12 and Band 4 Channels 27-36
Vertically polarised local reception and medium distance)
Horizontally polarised diffuse reception (either long distance or blocked by terrain)

Nil


AlanH
Please post errors and omissions here

Edited by alanh, 19 March 2009 - 11:21 PM.

[bristolmark]

Hi Alan,

Just wandering around the Hills website and stumbled across this range (Spectramax UHF/VHF Antenna) which would seem to fit into this group.  http://www.hillsante...oducts/A1201SPE.

FYI.  The link you have in the post pointing to a pdf on the Hills website doesn't seem to work.

Cheers,
Mark.

Edited by bristolmark, 19 December 2007 - 05:26 PM.

[M'bozo]

Hills also have a new F connect log periodic antenna BC71498 covering B3/4/5 a la Fracarro log periodics. I can't find it on the Hills site to link to, so I've taken the liberty of scanning the bit of paper that came with it - see here.

Had the chance to use one of these a couple of weeks ago when my stock of Fracarros ran out and this was in the local electrical distributors store.

It's been installed in a high windy area.

[bellotv]

Alanh
What are you specifically looking for here ?
Matchmaster have high gain Band3 antennas and band4 and band4+
So do Hills .
And so do Laceys.Tv.
Infact Laceys have the CAI certification on certain Fraccarros.

Some manufacturers also make combos with the VHF and UHV combined by an integral Diplexor .

What about Log periodics ?

[alanh]

Guys,
What I am looking for is a single antenna designed for just band 3 & 4 only. Ie channels 6-12, 27-35.
The Hills Spectramax4+ is designed for channels 6-12, 27-50. or the WB model is ch 6-12, 27-69
I have links for single antennas of band 3 only and band 4 only. I have a link to band 3 & 4+ which includes the B4+ Spectramax

The reason I have not specified the log periodics  band 3 & 4 is that they are designed for channels 6-36. this includes 230 - 519 MHz which the above ones do not.

The advantage of a narrow bandwidth is higher and flatter gain on the channels you want and less signals that you do not wantl

Does it say where BC71498 is made?!

I will fix the link.

AlanH

[bristolmark]

Thanks Alan,

I realise I should have phrased my post more like the question I thought I was asking.  I had only just stumbled upon the page yesterday and having been to this forum many months ago I remembered that there were no links to actual antennas for this Band 3 & 4 group.  Given the 1st line on the Hills website (link I posted) only states Band 3 and 4 (not 4+) I had hoped this antenna fitted this thread.  I know a 4+ antenna would not be required in this thread.

I suspected the antenna was a 4+ based on the model number description at the bottom of the page.  As neither of the electrical or mechanical construction jpegs on the Hills website was working for me I had no more information to go on.

Thanks you for clearing it up.  The hunt continues...

Cheers,
Mark.

[dig2all]

Allan,

You wrote "The reason I have not specified the log periodics band 3 & 4 is that they are designed for channels 6-36. this includes 230 - 519 MHz which the above ones do not."

For the Fracarro log periodic antennas that is not true.  Check the element sizes and spacings and you will see a discontinuity between the band 3 and 4 sections of the antennas indicating a plan to suppress response between bands 3 and 4.

By excluding Fracarro's LP34HV and their new improved F connector LP34F models your list excludes some very good antennas that were designed for Australia and are widely available here.

[bellotv]

Dig2all
I was just in the middle of typing the same response to Alanh  regarding obvious element lengths when we had a power cut.
I would also like to point out that  Fraccaro Log Periodics have very low pick-up of frequencies below their design band width.The same can not be said for Yagi or phased array antennas that can pick up considerable amounts of Band 1 /2.

[alanh]

dig2all,
I have a .pdf of the gain, front to back and polar graphs. Unfortunately the original document is not scanned with enough resolution to be able to read the numbers on the axes.
I agree that log periodics have sharp cutoffs at either end of their design bandwidths. However in these antennas they are designed for the European frequency range and not Australia.

All antennas will pickup signals outside their design range, the point is how strong does this signal have to be? The narrower the frequency range of design the higher the Q and hence the received signal level when compared to other antennas designed for a wider frequency range.

AlanH

[dig2all]

Allan,

If a few MHz this way or that effected their performance why are so many of them sold to professional installers?

Obviously you have not tested one.

You wanted antennas designed only for bands 3 and 4, kindly add the Fracarro LP34HV and LP34F to your list!

These antennas were designed for Australia.

[alanh]

dig2all,
Fracarro, Italy These antennas are designed in Europe for the 174-230, 470 - 900 MHz market. They make no mention of Australian models only UK. I have recommended their phased arrays and their Band 3 antennas.

AlanH

[dig2all]

AllanH,

Fracarro's LP34HV and LP34F were designed by Fracarro with Australia in mind.  The fact that they don't mention that in their European catalogue is not the point.  Australian catalogue info. is provided by their distributor, Laceys.tv

OK, most Log Periodics compromise by working across all of bands 3, 4 and 5 - these ones don't.

Not including those 2 models in your list seems an unreasonable omission that is not balanced out by the Fracarro antennas you do recommend.

[bristolmark]

Hi,

According to the Fracarro catalogue (2006 version), Page 18 has the bandwidth specified for those antenna's (LP34HV and LP34F) as 174 -230, 470-606 MHz for both units.


Cheers,
Mark.

Edited by bristolmark, 21 December 2007 - 03:57 PM.

[bellotv]

alanh, on Dec 20 2007, 11:15 PM, said:

All antennas will pickup signals outside their design range, the point is how strong does this signal have to be? The narrower the frequency range of design the higher the Q and hence the received signal level when compared to other antennas designed for a wider frequency range.

AlanH

AlanH
You are assuming that all antennas behave like an LC resonant curcuit.
From what I have measured ,comparing band4/5 antenna's (just to keep the Q the same for all intents and purposes ) the band 1 pickup is around -30dB on a log periodic (only tested fraccarros) compared to similar gain phased arrays or yagis where the band 1 pick up is -15 dB.

You maintain that an antenna should have minimal pick up of band 1/2 and below  to reduce pick up of impulse noise.
I am saying that fraccarro log periodics(and possibly other logs) have better rejection of lower frequencys than phased arrays or yagis From what I have measured and therefore are a more ideal antenna to satisfy your quest for minimal low frequency pick up.

[alanh]

digi2all
I do not see any changes in model numbers
What is the difference in dimensions between the European model and ours.
Where is the readable frequency response graph? I wish to know where the -3dB and the -20 dB points are.

You might have also noticed that I have not recommended the wideband log periodics from other outlets. either.

bellotv
Log periodic antennas are designed on the principle of use each element as a dipole. The dipole behind it acts as a reflector which gives a good front to back ratio. The bandwidth hence the Q of the dipole depends on the frequency range to be covered and the number of elements.
The Q for a European UHF wideband antenna is 1.59 (0dB)
For an Australian UHF wideband antenna is 2.22 (6.9dB)
Australian Band 5 is 2.95 (9.4 dB)
Australian band 4+ (ch 27 - 49) 3.72 (11.4 dB)
Australian band 4 (ch 27 - 35) 8.74 (18.8dB)
Band 3 3.61 (11.1 dB)

Q = frequency/bandwidth

As a comparision the Q for channel 9A only is 29.36 (29.4 dB)
Channel 30 77.64 (37.8 dB)
Channel 52 99.64 (40 dB)
However I agree that to get Q's of such a high value would be difficult to get the surface resistance low enough.

To prevent impulse interference upsetting reception is a matter of signal to interference ratio. To make a valid comparison, the gains in the designed channel range should be compared with the amount of element length. So if an antenna has 18 dB of gain as compared with one of 10 dB and the pick up of interference is the same, the 18 dB antenna will make the receiver much less troubled by interference including that picked up in the cabling.

I was not comparing band 1 reception into UHF antennas. Firstly the radiated power of UHF transmitters is 6 dB higher than for the equivalent VHF transmitter. I was comparing reception of frequencies in the 1 MHz range and below to that of the types of antennas. Try measuring the signal strength of 2NR (ABC Local Radio) on 738 kHz at a power of 50 kW located at Lawrence. The antenna cable here could be a major contributor so it must be kept short.

My main point however is to stop people installing antennas designed for band 1 & 2, which will never be used for Digital TV. After GWN 3 Bunbury goes digital early next year, there is only 8 low powered sites left who need a band 1 or 2 antenna.

AlanH

[dig2all]

AlanH,

The model numbers are the same because the antennas are the same.  I don't have a frequency response graph, but if element positions and sizes matter to you, please measure them.  Performance is what it is all about, but if you have never tried one - you will never know.

Fracarro LP34HV and LP34F are band 3 and 4 ONLY antennas.  From what I have seen all other commercially available TV Log Periodics include band 5, making their band 4 performance less than it could be.  But the wideband competitors I know don't work as well as even the wideband Fracarro's as their design and production methods have introduced compromises.  The fact that several are also European does not mean their quality is the same.

By not including Fracarro LP34HV and LP34F in your band 3 & 4 antenna list you effectively compromise your plan "to stop people installing antennas designed for band 1 & 2" as the information you offer is incomplete.

[IsDon]

Question for AlanH If I may.

Been doing some research on antennas since I have started having channel 10 and ABC problems over the last few weeks.

I live in Bangor NSW (Sutherland Shire) and have my antenna pointed at the Sydney city transmitters.

I printed out your scale antenna diagrams and it appears I have a dipole but it also has a what I beleive to be a UHF antenna incorporated into it (short horizontal bars arranged in a sort of arrow formation).   I inheritted it with the house so I'm not sure what brand it is.

I seem to be getting reasonable signal strength but poor quality on 10 and ABC and reading your notes on the dipole diagram it appears that the two longest dipoles (which don't receive digital signals anyway) may be contributing to interference.   It also says on the notes that "this rod could be cut into 5 directors for channels 6-12 to give a stronger signal to reduce the chance of pixellation and sound chirps".

Now just to clarify before I climb onto my roof with a hacksaw.   Does this literally mean I can cut of these superfluous dipoles to reduce interference?

Failing that what antenna would you recommend replacing it with?   There seem to be none listed in your list which are an ideal solution.

Edited by IsDon, 26 December 2007 - 11:54 AM.

[digitalj]

IsDon, on Dec 26 2007, 12:49 PM, said:

Question for AlanH If I may.

Been doing some research on antennas since I have started having channel 10 and ABC problems over the last few weeks.

I live in Bangor NSW (Sutherland Shire) and have my antenna pointed at the Sydney city transmitters.

I printed out your scale antenna diagrams and it appears I have a dipole but it also has a what I beleive to be a UHF antenna incorporated into it (short horizontal bars arranged in a sort of arrow formation).   I inheritted it with the house so I'm not sure what brand it is.

I seem to be getting reasonable signal strength but poor quality on 10 and ABC and reading your notes on the dipole diagram it appears that the two longest dipoles (which don't receive digital signals anyway) may be contributing to interference.   It also says on the notes that "this rod could be cut into 5 directors for channels 6-12 to give a stronger signal to reduce the chance of pixellation and sound chirps".

Now just to clarify before I climb onto my roof with a hacksaw.   Does this literally mean I can cut of these superfluous dipoles to reduce interference?

Failing that what antenna would you recommend replacing it with?   There seem to be none listed in your list which are an ideal solution.

you have a band 1/3/4 combination antenna, the band 3 part probably only does VHF 6-10.

you need one that does Band 3/4, make sure the Band 3 part does VHF 6-12 (6=7 digital, 8=9 digital, 11=TEN Digital, 12=ABC Digital).

It's possible that it's just the antenna that needs updating.

[M'bozo]

IsDon, on Dec 26 2007, 12:49 PM, said:

Now just to clarify before I climb onto my roof with a hacksaw.   Does this literally mean I can cut of these superfluous dipoles to reduce interference?

Most likely not.

The design of wideband yagis for TV reception is difficult to optimise owing to complex interactions from parasitic elements, required to achieve adequate gain and/or front to back ratios over a broad range of frequencies.

In NW Tassie a large number of Hills 215/2710 (VHF channel 2-10 inclusive) antennas were and are still being used, they are basically a 3 element band 1-2 with folded dipole & 5 element band 3 with folded dipole on a common boom with the dipoles paralleled. Originally their use was for reception of ABC3 & SCTV9 analogue from Mt Barrow.

I experimented by removing the 3 long elements (including a folded dipole), this changed the contrast of the received picture on C9, suggesting some reflections were now occurring. Removing the 5 short elements to use the remainder as an FM antenna stuffed up the front to back ratio and hence the directivity. So the interaction of all the elements is greater than the sum of the parts.

However, as digitalj notes, I suspect you will be up for an antenna changeover anyway, so nothing is to be lost by experimenting. I won't recommend one as I have no local knowledge, I'm sure someone else here will be able to.

[IsDon]

Thanks for your replies.   Looks like I'll dispense with the hacksaw.   Wasn't really looking forward to balancing on the roof of the second story anyway.

I had a bit of a tinker today and bypassed the mast head amp which was recently installed by an antenna "professional".

As soon as I removed it I was rewarded with 70% signal and 100% quality on all channels.   Maybe 10 and ABC have boosted their signals recently resulting in my mast head amp overboosting the signal.   In any case they all seem to work OK at present.   It will be interesting to see what happens tonight as this seems to be the time the channels start to play silly buggers.

Once again thanks for your help guys.

[mtv]

Regardless of what is on spec sheets, or in theory books, in practice, the Fracarro (and probably similar) log periodics work extremely well in most circumstances.

Isn't that what this is all about, recommending antennas that actually provide a good result?

I'm sure those among us who regularly install log periodic antennas will agree on how well they perform.

Granted, they are not suitable for every application, however, no single antenna is!

Whilst theory and a thorough knowledge and understanding of RF transmission characteristics is greatly advantageous, it's providing reliable digital reception for the customer, that really counts.

Realistically, how we achieve that is usually of no interest to the end-user.

We just have to do whatever it takes to provide.... what works.

[IsDon]

Thanks Col,

I thought I had it skun.   100% signal quality on all channels at 4pm today.

7pm tonight ABC and 10 have dropped to 70% with associated dropped frames and pixelisation.   Had enough of this ****.       Time for a new antenna optimised, as much as possible, for digital in Sydney.

Col, if I assume correctly your recommending the Fracarro LP34HV.   Where's the best place to get one and what are they worth.   I'm getting one tomorrow.

Thanks in advance,

Wayne.

[mtv]

Wayne,

I was making a general comment about log peridic antennas, in the context of this thread, not specifically replying to your post.

However, I'll do so now.

I'm familiar with Bangor and the 'Shire" in general and it's a complete mixed bag as far as digital reception goes.

If you are in a part of Bangor which is elevated, with clear views towards the main transmitters, then you should be fine.

If you are in one of the lower areas, with trees, gullies, buildings or other obstructions in the signal path, then it's a different story.

Yes, a Fracarro LP34HV may be ok for you, but it is totally dependent on what your signal measurements are.

By this I mean 'accurate' measurements from a digital field strength meter/analyser with Bit Error Ratio readings.

The figures given from STB 'meters' are notoriously inaccurate and are indicative only.

My suggestion would be to have the 'pro' installer who installed the amplifier return and sort out your reception issues, although, if he didn't recommend a suitable antenna replacement and just installed the amp, then perhaps he isn't the best 'pro' around.

As you suspect, the amp may well have been amplifying 'too much' causing overload.

An amplifier should only be used to compensate for distribution losses, such as splitting to several outlets, not to try & boost a poor signal.

This is the key to reliable digital reception, capturing a strong signal with low errors, by selecting the correct antenna for the location, and most importantly, mounting it where the best possible signal is obtained.

Did the 'pro' installer conduct a site test to determine the best mounting position for your antenna?

Whilst the Fracarro LP34HV generally has a very low BER across it's range, it isn't a high-gain antenna, so it works best in strong to medium signal areas.

Certainly, there are parts of Bangor where they will work very well and others not so well.

Given you mentioned 100% quality without the amp, you probably have a pretty good chance of success with a simple change of antenna, to one which is designed for the digital channels.

If you want to try the Fracarro, I don't know of any retail outlets near you, however, Lacey's TV are at 1/18 Alfred Rd, Chipping Norton, 2170 Ph 9755 5026

Once again, I can't guarantee the Fracarro LP34HV will be the ideal antenna without a site test, however I have had success with installations of them at Miranda, Barden Ridge, Lucas Heights and Menai.

Hope this helps.

[IsDon]

Thanks once again Col you're a wealth of information.

I live in an elevated position in Bangor but I'm on the side of the valley that faces Menai.   The valley itself points towards the city and from the city end of the highest part of the roof on my 2 storey house (where the antenna is mounted) looking along the valley I have an almost uninterupted view of the city.   I'm in Belarada Close Bangor with the backyard facing North West to the valley and the valley running roughly NE/SW.   I'm just around the face of the valley along which Belbowrie Close runs.   They have direct views to the city from road height.   Pretty clear on a map like "whereis" to determine my situation.

I feel certain that if the Francaro worked in Barden Ridge or Lucas heights it should be ideal.   I'm a little reticent to get another so-called pro to come out as if he looked at the signal in the middle of the day he would say I didn't have a problem.   I suggest the reason the previous installer went for the easiest solution of an amp instead of replacing the antenna in the first place is one look at how high up it was and didn't feel like getting up there.

I guess if he didn't get up on the roof then he didn't do the site test you mentioned.   Just interested in charging as much as he could for as little time at my home as possible.   Should have taken one look at his brand new shiny black Crewman "work" ute to realise that.

Chipping Norton is not so far away so I might drop out there today for a chat if they're open.

Once again thanks for your help Col.

Wayne.

[mtv]

Wayne,

I'm a little confused when you say the installer didn't get on the roof, but he installed a mast head amplifier?

Just a couple more questions for you..... how high (approx) is the antenna above your roof?

How is it mounted eg: on the ridge with guy wires?

How many outlets are there?

If there is a splitter, is it a fully-shielded 'F' type?

Is the coax RG6 quadshield or dualshield?

FYI, the LP34HV works fine in Menai, just a few blocks away from you to the west, although it's a general indication, as signals can vary greatly even between houses next door to each other.

Unfortunately, a lot of homes I've seen around your area had crappy 'air-spaced' open-braid coax installed, which is very effective at killing otherwise good digital signals, with high signal loss, and extremely prone to picking up interference.

If you need to replace your coax, RG6 Quadshield is the best to use.

Also, replace any 'plastic box-type' screw & saddle splitters with fully shielded 'F' type splitters and connectors.

Remember, your signals can only be as good as the weakest-performing link in your antenna/distribution system.

The Fracarro LP34 should cost around $70