Antennas aint equal, Joyse !!!

[gordon_s1942]

Today I replaced a Hills Hunter UHF phased array with a new dual phased array (commercialy made) and got a disapointingly bad result.
Markedly lower signal quality on all channels and SBS refused to display a picture at all.
I removed the Dual and tried a 97 element Yagi I had in use untill earlier this year and I got a BIG improvement all around, better even than the Hills Hunter.
I had recorded the signal/power readings before removing the Hunter and when I tried the Dual phased array.
My 'TEST' equipment is a 7 inch LCD Cobalt brand made in China SD digital TV.
The power/quality scale is NOT calibrated to an Industry standard and is just a guide.
Basically this is how I interperate the scale,
on antenna 1, if it has a picture,sound, no pixeling, scale says 48/50, Good.
antenna 2, 'Locked' but no pic, scale says 30, Not Good.
antenna 3, has picture,sound, scale very steady and showing 51/53,damn good.
Even 2 or 3 % as far as I am concerned is an improvement.
Each channel was checked individualy and recorded, but SBS is the one I use as the yardstick as its the hardest to receive.
I must say I have always liked Yagis even tho so many swear by the phased array.
I have no idea why this Dual phased seemed to perform so poorly compared to the old single Phased array or the Yagi.
I know phasing makes antenna's very directional and a mite touchy but I really didnt expect this poor a result.
All new cable between the MHA and the antenna, clean connections, no loose clamps or fine wires across any terminals, been caught that way before.

[Farmsky]

Vertical or horizontal reception?

Distance from transmitter?

Obscured path? Tree obstruction?

Optimised antenna location?

Lot's of things may favour one or the other.

Here's a quick graphic (you won't have seen ), which demonstrates one very fundamental difference.

[vk6xlr]

Vertical or horizontal reception?

Here's a quick graphic (you won't have seen ), which demonstrates one very fundamental difference.

Looking at the antennas, they seem to me to be horizontally polarized, so the radiation pattern should be effectively the same.
Whereas, the yagi's pattern seems to be vertical, in your diagram.

[Farmsky]

Both antennas are horizontally polarised in the diagram (or that is the intention ).

However notice the big difference in beam width between each antenna type.

So depending on the polarisation you are receiving, the two antennas have quite different characteristics.

A wide beam horizontal width is generally useful for obstructed path reception.

How 'bout the other questions?

[gordon_s1942]

Vertical, 12 kms roughly, view in front is clear BUT there is a ridge between me and the translator and ALSO, the damn translator is directional and I am behind the coverage lobe.
I have the coverage pattern maps issued when the translator went from VHF to UHF (circa 1988) and the ABC's Digital coverage and my location is some 45 degrees behind the projected pattern so what I get is purely fortuitous.
The signal is affected by heat and cold inversions, sunrise and sunset, the rise and fall of the Dollar and Galah's sitting on the antenna.
I have used both Yagi's and single phased arrays here over the years and I am very well aware phasing any antenna's, Yagi's or Phased Array types together makes them very directional.
I bought this dual phased Array already made up so I was very surprised by the loss in signal compared to the Hills Hunter single Phased array and now the 97 element Yagi.
For whatever reason I could not get the Dual Phased Array to receive as well as the other 2 antennas.
It literaly killed SBS and everything else had a lower signal quality.
I know I am going to have stong wind problems with the yagi on SBS unless I can work out a way of anchoring the long boom without affecting its reception.
Its on a 3 metre (10 foot) mast which make that a bit simpler.
This long boom Yagi has a support bar but its meant for Horizontal mounting rather than Vertical.
I only posted this because the big Digital day is getting closer and for those like me in poor to bad areas, we cant just assume that every antenna will work for us no matter how good it looks on paper.

While I was fiddling yesterday, a new neighbor stopped and asked me about the TV reception as he was unable to get it at his house.
He didnt even know he had to have the antenna Vertical for here.
He said he had called a local installer but they expressed no interest in doing anything for him because they consider here a No Signal area.
They will do Select or Aurora but not Terrestial TV.

[Farmsky]

A dual phased array has a theoretical gain of 3dB over a single yagi. So if it's two 12db yagis, then 15dB.

In your situation antenna gain is everything.

The big yagi clearly has most gain and a clear advantage in vertical polarisation (see the graphic) witha relatively wide beam width. You would notice this when aligning for best signal. This provides more tolerance as the very weak signal moves around a bit on the horizon with weather, temp inversions etc.

What is the theoretical gain of the three antennas and the desired channels?

Note: The Wisi EE06 style 4 di-pole phased arrays are typically used for horizontal diffused/obscured reception. If used in vertical mode the horizontal beam width is quite narrow and will perform poorly for this type of reception.

[gordon_s1942]

Farmsky, gain unlike size as the actress said to the Bishop is very important which is why I tried the commercialy made Dual Phased array.
Many years ago I put up a pair of Hills VHF Phased arrays using Hills Phasing harness for reception from Sydney. They worked fairly well untill they put an FM radio station a few miles away and the old Kingray MHA wasnt filtered for FM as there wasnt an FM station around back then so now they are used on my FM receiver.
You can phase 4 antenna but I doubt 3 would be very easy to configure.
I posted some pics of a 4 bay Yagi just recently.
Everything I have read on phasing antennas has said that while the gain increases in nearly all cases by 3db, it reduces the frequency coverage of the antenna and makes the antenna VERY directional, sometimes so directional that even the slightest movement of the antenna up on a mast can loose the signal.

That WISI EE06 looks like the Hills Hunter but uses a wire or rod for the bowtie configured elements rather than the pressed metal elements of the Hills Hunter.
the Dual Phased array I was trying is a wire element but it is closer to an Hour Glass continuous loop, so in effect it is a form of Folded dipole I guess.
Both connected by a form of etched circuit board balun to match them as a pair.

[mtv]

Vertical phased arrays are particularly good at rejecting multipath signals... excellent in SFN areas.

Changing an antenna often requires repositioning of the mounting location, particularly in difficult reception areas, which means, just because a 'sweet-spot' has been located for one particular antenna, doesn't automatically mean that will be the best spot for a different type of antenna.

This is where accurate instrumentation is required..... but you're already aware of that.

I haven't used the dual vertically-polarised phased array, but have had some very good results with the dual with horizontal signals, using balun preamps.

Once again, beamwidth characteristics play a big part.

Stacked vertical yagis may be more beneficial in both terms of gain and greater capture area for vertically polarised signals.

[gordon_s1942]

A few years ago I really seriously considered buying a quality FSM as I could have afforded it but common sense ruled against it on 2 substantial grounds.
One was I would have almost no use for it once I had done what I wanted for my self and the 2nd even more compelling reason was I didnt know how to use it correctly.
Because of those 2 reasons the cost then became a factor.
Even if it cost a dollar,as I couldnt use to its capability it became an excessivly expensive toy.
I had been lent one many years ago that had an analog scale on it and I was shown how to turn it on, tune in the TV channel and read the scale.
But what was I reading on the scale, was it noise, was it the TV signal, I didnt know.
I dont mind admitting I have limited knowledge and abilty but I dont like the idea of just sitting back and not at least trying and learning by my mistakes.
I will keep plugging away as I have the time albeit not always the energy and who knows what will happen as apart from that, I have had the pleasure of meeting and talking to some really fantastic people in these forums.

[gordon_s1942]

After 24 hours of gale force gusting winds,trees uprooted, branches ripped asunder, rain squalls,dust up to the waaazoo, Lightning, translator dropouts, power outs (7 hours), no hail or snow (yet), I still have TV so I must have done something right.
SBS gets the collywobbles everytime the wind blows hard enough to blow the house over but its only a few odd lines of pixels very briefly so the Yagi isnt bouncing around as badly as I thought it could.
Not a bad job for a bum amatuer I dont think.

[Farmsky]

Farmsky, gain unlike size as the actress said to the Bishop is very important which is why I tried the commercially made Dual Phased array......

It IS all about size ....

When gain is paramount the more metal in the air ... the better (as long as the damn thing is designed correctly). That's physics.

I suspect the increased Q of the Dual knocked the standard antennas frequency bandwidth down a bit.

Anyhow, tis good you have a happy ending.

[mtv]

After 24 hours of gale force gusting winds,trees uprooted, branches ripped asunder, rain squalls,dust up to the waaazoo, Lightning, translator dropouts, power outs (7 hours), no hail or snow (yet), I still have TV so I must have done something right.
SBS gets the collywobbles everytime the wind blows hard enough to blow the house over but its only a few odd lines of pixels very briefly so the Yagi isnt bouncing around as badly as I thought it could.
Not a bad job for a bum amatuer I dont think.

That's a pretty damn good test.

If the antenna itself is still there after all that and better still..... working... an excellent effort there Gordon.

[gordon_s1942]

MTV, if you get up into this or the Sydney area soon you will see just how much dust there was.
I am 66 years old and I have lived here for the last 46 years, Katoomba and Sydney before that and I have NEVER experienced the dust we had.
We have had a bit of dust overnight before some years ago but that was a grain compared to the volume yesterday.
It is simply incredible where it has landed, covered trees, in the twist of bundled cables, sides of houses, the grass.
I could taste it in the air early yesterday morning.
There is a set of Wet Pavement flashing warning lights on the highway and today in clear sunshine, they were going lickety split so I guess the rain/dust now mud has fouled the sensors. It also affected smoke alarms in some locations as the detector couldnt tell between smoke and fine dust.
Apparently the Particulate count went off the scale in Sydney.
A normal reading on a smoggy day is 500 to something, this passed 15,000 for 10 hours when the count fell as rapidly as it began.
I might have to rethink my thoughts on Global Warming if this occurs again as is being forecast.

[mtv]

Experienced a similar dust storm in Melbourne in the 80's.

Probably back in Sydney & BM next week.

[Jason_dinAlt]

The signal is affected by heat and cold inversions, sunrise and sunset, the rise and fall of the Dollar and Galah's sitting on the antenna.

I know I am going to have stong wind problems with the yagi on SBS unless I can work out a way of anchoring the long boom without affecting its reception.

My 91 element yagi is aimed at Mt Sugarloaf in Newcastle (despite being told it was impossible to get MT Sugarloaf here) and is occasionally effected by winds but they have to be huge gusts to effect it, I get the odd pixelation when it happens, never loss of pics though, Prime seems to be the worst offender here. I have braced mine not for wind but for bloody galahs, there are hundreds of the buggers here in Dungog. As you can see in the pic a bloody galah broke off one of the elements. The dip in the antenna at the front when galahs would take off or land on it would be enough to pixelate the picture and it really was pissing me of but I havent had any problems since puttting in the brace.

[mtv]

The problem with bracing with a metal stay in Gordon's case, would interfere, as his yagi is vertically polarised, so the support would be in the elements' path.

One solution could be to use a non-metallic support.... fibreglass rod, or possibly even some PVC conduit.

[OSIRUS]

This is my setup ATM



I know they are all too close together, but they all work OK

I am in the country about 250km north of Sydney

From the Top down

1 & 2 VHF for Sydney reception

3 & 5 UHF for Newcastle reception

4 & 6 VHF & UHF for Local reception

[gordon_s1942]

I did think of making up a brace for the boom if it bounced around too much.
At the moment the antenna is barely 10 feet off the ground so it would be reletively easy to place 2 suitable poles say 4 feet apart and use a 1/2 inch thick fibre glass mining roof bolt between them with the boom JUST sitting on it.
Like the top of a Letter "T"
As MTV says, I am vertical and it is a pain in the arse with long boom antennas as any metal then becomes part of the antenna.
But, so far its not needed.

Osirus, thats one busy little mast. I hate to think how that would look if you were chasing VHF.

[mtv]

Osirus, thats one busy little mast. I hate to think how that would look if you were chasing VHF.

The top two and the fourth one down are VHF.

The top two looks like Hills DY14's.

How are you combining the stacked arrays, Osirus?

[OSIRUS]

The top two and the fourth one down are VHF.

The top two looks like Hills DY14's.

How are you combining the stacked arrays, Osirus?

My Setup is not a very professional setup mtv,

One Sydney VHF aerial (1) is straight though to a Digital STB (most digital channels are on VHF)

One Newcastle UHF aerial (3) is straight though to a Digital STB (All digital channels are on UHF)

One Sydney VHF aerial (2) & one Newcastle aerial (5) are combined using a VHF/UHF diplexer for analog TV reception,

& the Local VHF aerial (4) & Local UHF aerial (6) are combined using a VHF/UHF diplexer for analog TV reception,

It works, but it is not a professional setup,

I would have liked to have done it using a meter & get the correct metered values, especially for the Digital Reception,

I am open to suggestions as to how it could have been done better,



P.S. I'm better with Satellite's (I think)