Polands answer to Bowtie Grid ("Colour King") aerials

Mike 1972

Saw these while on holiday in Poland recently.

An enhanced version of the grid/colourking/billboard aerial with four booms on front with a set of three directors on each giving something more akin to a stacked yagi than a grid.

Presumably these have slightly more gain than the grid aerials which are fairly ubiquitous in many parts of Ireland ?

watty

yes, they are.

You can extend the principle till you have 4 x 16/17 dbi yagis on a pole with three combiners.

Four of any kind aerial gives roughly 6dB more gain

Sam the Aerialman

Is it my imagination or is the balun mounted vertically? The captive area of that array is damaged by having those directors squashed together in that fashion, any forward gain is nulled by those pointless twigs. The short backfire array is designed as a low gain aerial which can eliminate ghosting or from what looks like a CCI problem from an intervening tx.

If you placed an 8inch diameter aluminium disc, 10 inches away with an X dipole half way between the short backfire aerial, it's effectiveness lies in the build up of energy bouncing between the two reflectors with the dipole sitting nicely in the centre of this energy build up. Never mind the wind loading but that looks absolutely pointless.

Mike 1972

watty wrote: »

Four of any kind aerial gives roughly 6dB more gain

Assuming of course its set up properly and one doesnt make a complete hash of the phasing/positioning/impedance matching

Sam the Aerialman wrote: »

Is it my imagination or is the balun mounted vertically?

Photo is taken from a kinda awkward angle but Its basically a "colourking" Grid aerial with the director bits added on.
I saw them on sale boxed in Saturn (big retail chain in much of Europe) of course Im well aware that just because something is widely used/available in shops doesnt mean its actually any good.

Havent seen the claimed specs for these things but I thought it a bit odd having straight directors with X type "dipole" elements (strictly speaking not the same as bowties but similar). Thought the whole point of an X (or a bowtie) was to increase bandwidth. Surely the straight directors negate this ?

Im really not sure whether the directors enhance the design or not. I do know a lot of the the basics of aerial design/theory but I suspect yourself and Watty know a bit more ?

Sam the Aerialman

Mike 1972 wrote: »

Assuming of course its set up properly and one doesnt make a complete hash of the phasing/positioning/impedance matching

Surely the straight directors negate this ?

Im really not sure whether the directors enhance the design or not. I do know a lot of the the basics of aerial design/theory but I suspect yourself and Watty know a bit more ?

It's nothing more than a gimmick, what that thing is a large aerial deployed to combat co-channel interference. When you stack any 4 aerials in that fashion what you usually find is two are duds. Reason being to null any unwanted signals in front of the aerial and force it over the side lobe of the aerial. I would hedge a fairly good guess there's a piece of fairly high intervening ground, hill or small mountain between the aerial and it's Tx causing a reflection. I don't know if that's the aerials design or the rigger realised by getting the reflector to stand off the pole he could something useful. Phasing is your enemy here, a boxed off the shelf aerial is going to have nothing more than a pressed bit of copper running parallel with the feed point.

Sam Russell

The picture makes it hard to see what is going on. It looks like the 'yagi' elements are the wrong shape and the length shortens too rapidly to be yagi elements. They look to be out of band.

The look more like bird perches to me. Perhaps birds are a problem round there.

Tom Slick

Mike 1972 wrote: »

I saw them on sale boxed in Saturn (big retail chain in much of Europe)

Was there a brand name on the box? Even a rough idea. Looked up Saturn but couldn't find it in their products.

12 element

Alcad's grid aerial have added directors, not as many at that yoke though!

Mike 1972

Tom Slick wrote: »

Was there a brand name on the box? Even a rough idea.

Dont remember unfortunately

Probably not all countries branches of Saturn do them though

Sam the Aerialman

A proper set of 4 bayed yagi's - 4x Jaybeam Parabeam circa mid 80's. This setup is implemented when co-channel interference (CCI) puts down unwanted signal strength in front of the aerial. The cross polar rejection of the two outside yagi's shield the two inside, this is a great system when intervening terrain causes image displacement or ghosting.

Note the phasing harness on the left leg of the tower, each downlead must be exactly the same length or when the output leaves the harness usually coupled to 7/8 feeder and run through a pre-amp you will get bugger all end product.

Also note how each aerial is spaced and is flush with each corner of the tower very important when setting up such a system that each additional piece
of metal doesn't come a part of the array.

byte

Ah, Strathyre. I've witnessed that little tower in person. Tidy wee job so it is!

Tom Slick

12 element wrote: »

Alcad's grid aerial have added directors, not as many at that yoke though!

Don't a lot (if not most) 'X-Beam' Yagis have (usually 1 of) those short pieces (for want of a more technical term) in front of the balun?

Sam the Aerialman

byte wrote: »

Ah, Strathyre. I've witnessed that little tower in person. Tidy wee job so it is!

You didn't happen to venture up the hill and check out the active deflector by any chance.

watty

Tom Slick wrote: »

Don't a lot (if not most) 'X-Beam' Yagis have (usually 1 of) those short pieces (for want of a more technical term) in front of the balun?

bit behind the active element is a Reflector

Wires connecting active elements are "transmission line"

Balun is inside the box the coax connects to. Coax is unbalanced. Dipoles (folded, straight or X) and twin wire "transmission lines" are Balanced
Balun = Balanced to Unbalanced convertor.

The wires, rods, spikes >< or X in front of active elements are "Directors"

Manufacturers now commonly count ever spiky piece of metal as an "element". Strictly the Elements are "number of Directors" + Active element (e.g. dipole) + Reflector, so an 100 element aerial might be 21 to 25 elements really.

Actually what counts for well designed Yagi is simply the ratio of boom length in Meters / Wavelength. Above a ratio of 2 there is little increase even doubling length. Boom length is a more accurate comparison than number of elements.

Then "Stacking" aerials roughly doubles the signal (Obvious that two aerials will give twice signal if not interfering!).

So since a Doubling is 3dB in "dB" terms, you have to double the aerials to get 3dB more gain...
2 = 3dB
4 = 6dB
8 = 9dB
16 = 12dB

In practice it doesn't work as well as that due to losses. But Interference picked up experiences the same loses. So even if a 4 aerial stack only gives 4.5dB due to losses rather than 6dB, it may increase the SNR margin by 6dB.

The SNR margin is the REAL limitation as Modern tuners and amplifiers are very low noise.

byte

Sam the Aerialman wrote: »

You didn't happen to venture up the hill and check out the active deflector by any chance.

No, sadly not.

I will try the next time I'm in the village, but that won't be til next year probably.

Richie Blackmor

I spotted one of those strange aerials in Kyrgyzstan in 2009. Thought it unusual enough to photograph ....

https://us.v-cdn.net/6034073/uploads/attachments/104700/96201.JPG

Mike 1972

Richie Blackmor wrote: »

I spotted one of those strange aerials in Kyrgyzstan in 2009.

In that particular case their method of attaching it to the mast/pole is even more (ahem) interesting !

ADDS: On closer inspection is that TWO downleads I see ?

Peter Rhea

I knew I'd seen a thread about Polish aerials here . . .

These seem to be the same (or v.similar).

Sam Russell

Interesting. I have no Polish whatsoever, so can only interpret what I see.

I cannot imagine who thought up that design. I think it is installation art. The bits that protude from the 'bowties' are too small with respect to the wavelength to do anything much to the signal other than give the aerial watchers something to talk about. I like the colour scheme.:)

Peter Rhea

As far as I can make out . . . the ones at the top are 'wideband with amplifier', the others are 'wideband with balun'.
The gain ('zysk') figures would seem to bear this out . . .
They all claim to do VHF, although some seem more suited (look like coiled elements).

Mike 1972

Peter Rhea wrote: »

They all claim to do VHF

Bit confused about that one myself.

Also I notice the Band 1 aerials are listed as covering channels 2-4 while Band 3 aerials cover channels 6-12 but what about Channel 5 ?