EQUIPMENT TO STACK AERIALS

Galway

What apart from the aerials, vertical mast pole, brackets etc which I have, do I need for stacking (horizontally) two UHF Unix 52 or similar?

many thanks

Sam the Aerialman

Galway wrote: »

What apart from the aerials, vertical mast pole, brackets etc which I have, do I need for stacking (horizontally) two UHF Unix 52 or similar?

many thanks

You will need the appropriate grouped diplexer with a combined leg - Fringe do an excellent set. You will need good double screened downleads (PF-CT100) exactly the same length from balun to diplexer, no short cuts. You may need to look at a masthead or attenuators to ensure the signals remain balanced and to avoid signal mismatches. Remember also that diplexers only carry one thru leg important when setting up a stacked array.

Galway

But the diplexer surely must not be groupised as I am stacking the same group side by side. Fringe have a simple combiner that just combines two aerials, is that it? The only problem is that the Fringe stuff tends not be screened so I tend to avoid them. I would be using a johansson 35 db UHF masthead amp. The cable is not a problem, but how do I mount the aerials horizontally side by side?

Sam the Aerialman

Galway wrote: »

But the diplexer surely must not be groupised as I am stacking the same group side by side. Fringe have a simple combiner that just combines two aerials, is that it? The only problem is that the Fringe stuff tends not be screened so I tend to avoid them. I would be using a johansson 35 db UHF masthead amp. The cable is not a problem, but how do I mount the aerials horizontally side by side?

That is exactly it - The decision you need to make is what group the transmissions are to match the diplexer. I would strongly recommend Fringe i have been using their grouped combiners for these types of installations for many years. There is the ordering codes below -

FRI70 FRINGE (GROUP A) 21 to 34 pass filter
FRI71 FRINGE (GROUP 35 to 53 pass filter
FRI72 FRINGE (GROUP C/D) 48 to 68 pass filter

You will require a parallel clamp that simply clamps 1 length of pole perpendicular to the vertical. Some refer to them as shelley clamps and is pictured below.

Two types of previous installations below -

mullingar

Traix do a 100 element aerial too, but the GroupA may be discontinued for some reason. These are 2.4m long!

There was a good thread on "stacking aerials" from a few months ago here:

http://www.boards.ie/vbulletin/showthread.php?t=2056008658

Sam the Aerialman

mullingar wrote: »

Traix do a 100 element aerial too, but the GroupA may be discontinued for some reason. These are 2.4m long!

There was a good thread on "stacking aerials" from a few months ago here:

http://www.boards.ie/vbulletin/showthread.php?t=2056008658

As far as i'am aware Triax stopped production of the Unix 100 due to complaints and wind loading problems. There is still a limited number of C/D and Wideband versions in circulation from various dealers.

Galway

Sam the Aerialman wrote: »

As far as i'am aware Triax stopped production of the Unix 100 due to complaints and wind loading problems. There is still a limited number of C/D and Wideband versions in circulation from various dealers.

I have now had 4 of the UNIX 100 A downed by winds, 3 of which were totally destroyed, hence now the need to try a different route. Pity Antiference have stopped making the XG 16 A.

Galway

Sam the Aerialman wrote: »

That is exactly it - The decision you need to make is what group the transmissions are to match the diplexer. I would strongly recommend Fringe i have been using their grouped combiners for these types of installations for many years. There is the ordering codes below -

FRI70 FRINGE (GROUP A) 21 to 34 pass filter
FRI71 FRINGE (GROUP 35 to 53 pass filter
FRI72 FRINGE (GROUP C/D) 48 to 68 pass filter

You will require a parallel clamp that simply clamps 1 length of pole perpendicular to the vertical. Some refer to them as shelley clamps and is pictured below.

Two types of previous installations below -

Thanks Sam but I will need an inductive coupler to combine the 2 group A aerials prior to amplification.

Sam the Aerialman

Galway wrote: »

Thanks Sam but I will need an inductive coupler to combine the 2 group A aerials prior to amplification.

No just keep the downleads from the baluns exactly equal and you'll eliminate any phasing problems pre-amplification.

Galway

Sam the Aerialman wrote: »

No just keep the downleads from the baluns exactly equal and you'll eliminate any phasing problems pre-amplification.

And they can then be combined with a f type splitter/combiner?

How do I know how far to space the group A aerials from each other on the horizontal pole?

From whom can I order the Fringe band pass filters?

mullingar

Galway wrote: »

And they can then be combined with a f type splitter/combiner?

Yes, but make sure its an outdoor type!

Galway wrote: »

How do I know how far to space the group A aerials from each other on the horizontal pole?

Use the lowest channel in the group for your calculation. Group A is Ch21 = 470Mhz.

300/470Mhz = 0.64cm,

However, RF can be a black magic, best do do a trial and error.

From here:
http://www.kyes.com/antenna/stackluge.html

For optimum performance, stacked antennas must be properly spaced. If you do not space vertically and horizontally stacked antennas more than ½ wavelength apart, they will adversely load each other. Loading is caused by the elements of one antenna re-radiating some of their received energy into the element of the other antenna, with consequent reinforcement and cancellation of fields and voltages. 0ptimum and minimum spacing is 0.94 and 0.60 wavelength, respectively, at the lowest frequency received. Spacing exceeding one wavelength reduces the performance of the stack.

So according to that statement the best distance is 64cm x0.94 = 60cms. But this seems too close as those extra high gain aerials are over 2 meters long, I would multiply that by 2 = 120cms to maximize the signal

Sam the Aerialman

Galway wrote: »

And they can then be combined with a f type splitter/combiner?

How do I know how far to space the group A aerials from each other on the horizontal pole?

From whom can I order the Fringe band pass filters?

Mullingar is spot on but as he says because the high gain aerials are of much larger size and capture area of an average contract aerial. A trial and error approach is required unless you have the use or hire of a spectrum analyser.
Remember a key point the pole, mount and aerials must be flush, exactly in line with each other. Flush and at right angles to their mountings - You do not want support metal becoming part of the array and blowing your chances of decent field strength.

You can order your combiner unit/ pass filter from any decent trade supplier or website. Sat Cure - CHC any number of places.

Galway

Sam the Aerialman wrote: »

Mullingar is spot on but as he says because the high gain aerials are of much larger size and capture area of an average contract aerial. A trial and error approach is required unless you have the use or hire of a spectrum analyser.
Remember a key point the pole, mount and aerials must be flush, exactly in line with each other. Flush and at right angles to their mountings - You do not want support metal becoming part of the array and blowing your chances of decent field strength.

You can order your combiner unit/ pass filter from any decent trade supplier or website. Sat Cure - CHC any number of places.

As the aerials will be either Triax Supergain 14A or Unix 52 A or Diamond Colour Quad 11A I am considering rear mounting them rather than using the support boom. As regards the splitter combiner Johansson do an external one in a plastic housing with accompanying pole tie. There is no way I am putting up two Unix 100 A or Hirschmann FESAs with the wind at this location! I have a Horizon terrestrial meter but not a spectrum analyser so I am not sure that will be of any use. Thanks for all the help & advice!

Sam the Aerialman

Galway wrote: »

As the aerials will be either Triax Supergain 14A or Unix 52 A or Diamond Colour Quad 11A I am considering rear mounting them rather than using the support boom. As regards the splitter combiner Johansson do an external one in a plastic housing with accompanying pole tie. There is no way I am putting up two Unix 100 A or Hirschmann FESAs with the wind at this location! I have a Horizon terrestrial meter but not a spectrum analyser so I am not sure that will be of any use. Thanks for all the help & advice!

In broadcast circles it's been well known to rear mount an aerial to make sure it's the first point of contact before any metal support. However as broadcast gear is extremely low profile and built like a tank. Those rigs have huge reflectors and additional wind loading factors i would support on a boom were ever possible.

Nothing wrong with the HDTM have one myself, but when phasing and checking separation of an aerial the ability to check standing waves, tetra interference and the old screwdriver trick a signal meter just doesn't cut it.