Is this UHF aerial worth buying?

leex

Located in Nth Galway - Maghera transmitter. Would I need a mast amp or anything?

http://www.argos.ie/webapp/wcs/stores/servlet/ProductDisplay?storeId=30001&catalogId=1500002501&langId=-1&productId=1500833277

watty

It's too much flimsy plastic. Avoid. Ice or Wind will destroy it.

savemejebus

How would it fare in an attic?

PauloMN

Wonder what this means:

Amplifies up to any dB.

Fine in an attic - assuming you've a strong enough signal. Outside though they are not strong enough. The elements on those are very light and bend easily, even with birds landing on them.

Personally though I would imagine a grouped UHF aerial - even a basic contract one - would perform better than the above. The above is a wideband.

danjo

Take a look at the details

"Amplifies up to any dB."

Would not put it in the attic in case the house burned down with the strong signal.

mossym

PauloMN wrote: »

Personally though I would imagine a grouped UHF aerial - even a basic contract one - would perform better than the above. The above is a wideband.

actually, you remind me of something i meant to ask, what would be better for reception...one of these:

http://www.amazon.co.uk/SLx-27884K-Element-Digital-Aerial/dp/B0026600CY/ref=sr_1_6?ie=UTF8&s=electronics&qid=1283355310&sr=8-6


or one of these

http://www.tvtrade.ie/red-group-a-uhf-aerial.html

STB

mossym wrote: »

actually, you remind me of something i meant to ask, what would be better for reception...one of these:

http://www.amazon.co.uk/SLx-27884K-Element-Digital-Aerial/dp/B0026600CY/ref=sr_1_6?ie=UTF8&s=electronics&qid=1283355310&sr=8-6


or one of these

http://www.tvtrade.ie/red-group-a-uhf-aerial.html

The first one.

48 element vs 10 element.
Full kit - pole etc.

mossym

STB wrote: »

The first one.

48 element vs 10 element.
Full kit - pole etc.

that's what i thought, but then questioned if a group specific aerial would be better...cheers

STB

Well a group aerial would be better than a wideband of course.

But there is not even a kit with the Blake Group A ? Mounting pole ? Just a bracket.

You realise that the Wideband one (the first one) is for loft mounting only and not suitable for outdoors ?

Why not have a look at other yagis besides the tv trade one (sorry Ronan).

Sam Russell

STB wrote: »

You realise that the Wideband one (the first one) is for loft mounting only and not suitable for outdoors ?

Why not have a look at other yagis besides the tv trade one (sorry Ronan).

Well, I've tested one of these Argos aerials mentioned by the OP.

It gives 53% signal vs 43% for a bent coathanger, as measured on my Picnic box. It also gives 43% when incorrectly polarised. So it is a bit better than a coathanger. I cannot tell if it has a balun. It is not very directional, as it did not matter much which direction I pointed it. I'm sure most aerials would be better, as it is very flimsy. The directors are just bacofoil and very fragile, and it is not a yagi, as the directors are not bars as I would expect them to be. It would appear to be designed to look more technical than it is, as it is descibed as having 21 elements - that must include the mounting screws.

But at €9 I suppose it is more useful than a coathanger, but only just.

watty

Blake make good aerials and their proception gear is good.

Re: Bacofoil Argos
It's not an 48 element. That's just counting spikes. It's got a reflector, driven element and I think 10 directors. = 12 Elements.
They are Yagi. Just poor. Using an X instead of -- bar widens the bandwidth, but makes directivity and gain poorer. Yes very badly made.

I compared Blake 18 element (i.e. Reflector, driven element and 16 directors) with the BIG DX aerials, the Fragile Hershman, Kathrein and Unix 100 etc (Not 100 Elements, closer to 21) The fact is that a pair of 18 Element was more robust, fraction of price and within 1dB of same gain when using quality combiner.

I tested SR18A, B and C/D group aerials.
http://www.blake-uk.com/page/aerial_range/aerial_sr
WB is 12.5dB
A is 13dB and of course the C/D is higher gain due to higher frequency is 14.8dB

A Blake 10 element group aerial will be about SAME gain as that so called 48 element wideband that would be wrecked in 1st blow or bird landing.

There has been almost no advance in yagi design since late 1970s. The "modern" and "Digital" style ones are cosmetic marketing and dishonest counting of "elements".

Basically for any well designed Yagi, the "boom length" is the important parameter anyway and at about 2.5 times wavelength any increase has very little increase in performance. Doubling the number of smaller identical aerials however gives about +3dB

So two 14dB aerials = 17dB (realistic limit for any yagi and 1dB to 2dB more than most)
Four 14dB aerials = 19dB (2dB to 3dB more than any yagi).

My opinion is the SR10, SR13 or SR18 are the ones to buy. If you are "fringe" or want UK DX reception then use 2x or 4x of the SR18 of correct group stacked at correct spacing.

The "Contract" model Blake is cost reduced version, hence small reflector and poorer interference rejection.

mossym

STB wrote: »

Well a group aerial would be better than a wideband of course.

But there is not even a kit with the Blake Group A ? Mounting pole ? Just a bracket.

You realise that the Wideband one (the first one) is for loft mounting only and not suitable for outdoors ?

Why not have a look at other yagis besides the tv trade one (sorry Ronan).

sorry, i didn't mean those exact aerials, i was using them as an example. i guess hte question was really would a wideband with more elements do better than a smaller group specific aerial

Sam Russell

watty wrote: »

Re: Bacofoil Argos
It's not an 48 element. That's just counting spikes. It's got a reflector, driven element and I think 10 directors. = 12 Elements.
They are Yagi. Just poor. Using an X instead of -- bar widens the bandwidth, but makes directivity and gain poorer. Yes very badly made.

A bit more testing.

With the full aerial, 53% is the best I got. Just the active aerial element on its own, 51%, so the 21 elements claimed add almost nothing. The directors are two seperate pieces of tinfoil, not connected to each other. The dipole is not a folded dipole atall which it resembles, just a bow on each side. Now this is important for impedance matching and because I could not open the plastic box and verify whether there was a balun. Therefore I could not check the impedence match, and given its performance, I doubt that there is one.

This aerial is junk, not designed to any principles that I know of, more show than go.

If it is good enough for a job, then so is a coathanger properly shaped.

PauloMN

watty wrote: »

Blake make good aerials and their proception gear is good.

Re: Bacofoil Argos
It's not an 48 element. That's just counting spikes. It's got a reflector, driven element and I think 10 directors. = 12 Elements.
They are Yagi. Just poor. Using an X instead of -- bar widens the bandwidth, but makes directivity and gain poorer. Yes very badly made.

I compared Blake 18 element (i.e. Reflector, driven element and 16 directors) with the BIG DX aerials, the Fragile Hershman, Kathrein and Unix 100 etc (Not 100 Elements, closer to 21) The fact is that a pair of 18 Element was more robust, fraction of price and within 1dB of same gain when using quality combiner.

I tested SR18A, B and C/D group aerials.
http://www.blake-uk.com/page/aerial_range/aerial_sr
WB is 12.5dB
A is 13dB and of course the C/D is higher gain due to higher frequency is 14.8dB

A Blake 10 element group aerial will be about SAME gain as that so called 48 element wideband that would be wrecked in 1st blow or bird landing.

There has been almost no advance in yagi design since late 1970s. The "modern" and "Digital" style ones are cosmetic marketing and dishonest counting of "elements".

Basically for any well designed Yagi, the "boom length" is the important parameter anyway and at about 2.5 times wavelength any increase has very little increase in performance. Doubling the number of smaller identical aerials however gives about +3dB

So two 14dB aerials = 17dB (realistic limit for any yagi and 1dB to 2dB more than most)
Four 14dB aerials = 19dB (2dB to 3dB more than any yagi).

My opinion is the SR10, SR13 or SR18 are the ones to buy. If you are "fringe" or want UK DX reception then use 2x or 4x of the SR18 of correct group stacked at correct spacing.

The "Contract" model Blake is cost reduced version, hence small reflector and poorer interference rejection.

This is very interesting and answers some questions I have on an install I'm considering. Most houses near me have large UHF aerials pointed north for reception from Divis. Some of these are missing elements/reflectors etc.. I was wondering if 2 x more solid aerials (like the Blake ones) combined would give a similar (or possibly better) results than the single large aerials I see around.

Your post prompts a few more questions (don't mean to hijack the thread, but this info is probably useful to the OP also):

- How far apart should 2 aerials be spaced? I'm thinking of 2 x group K aerials (for future reception of DTT from Divis after ASO).
- Can they be mounted across from each other or stacked one on top of the other or either way?
- How are they combined, and fed into a preamp?

Also one thing I've noticed is that many grouped aerials are not CAI benchmarked, whereas their wideband counterparts are.... anyone know the reason for this? Is it purely a marketing thing i.e. lots more widebands will be purchased?

Any links for calculating gain of combined aerials and stacking distances would be good.

watty

You use a quality F-Connector splitter as a combiner. Make lengths the same from each aerial.

Combine a pair.

if you need more gain combine two pairs

I've seen up to 32!

Each time you want 3dB more you have to double the number of aerials.

Subtract the loss of the splitter (used as combiner). Cheap ones are about 1dB to 1.5dB (subtract 3dB from splitter quoted loss as 3dB is inherent in splitting signal). Only really expensive ones are 0.5dB loss
(Cheap spiltters http://www.blake-uk.com/page/amplifiers_distribution/proception_protaps )
So rarely worth having 8 aerials. Due to splitter loss you either have 2, 4 or 16!

http://www.directivesystems.com/STACKING.htm

See http://www.techtir.ie/radio-tv/uhf-aerials

12 element

watty wrote: »

You use a quality F-Connector splitter as a combiner. Make lengths the same from each aerial.

Combine a pair.

if you need more gain combine two pairs

I've seen up to 32!

Each time you want 3dB more you have to double the number of aerials.

Subtract the loss of the splitter (used as combiner). Cheap ones are about 1dB to 1.5dB (subtract 3dB from splitter quoted loss as 3dB is inherent in splitting signal). Only really expensive ones are 0.5dB loss
(Cheap spiltters http://www.blake-uk.com/page/amplifiers_distribution/proception_protaps )
So rarely worth having 8 aerials. Due to splitter loss you either have 2, 4 or 16!

http://www.directivesystems.com/STACKING.htm

See http://www.techtir.ie/radio-tv/uhf-aerials

Interesting stuff watty, where did you see the 32 aerial array?

watty

Keeper hill


Not been used for years for Brougher rather than Divis since Chorus got the first private Microwave link licence from Cavan to that site. Now a UPC site.

It's possibly 1 x16 for Brougher and 1 x16 for Divis. Very smashed up (by snow!) and poor camera phone picture maybe 6 years ago?

[EDIT]
Had a search. We did discuss this TWICE before... At least.

http://www.boards.ie/vbulletin/showthread.php?p=51963059&highlight=keeper#post51963059

mossym

watty wrote: »

[EDIT]
Had a search. We did discuss this TWICE before... At least.

yup, not the first time i saw that pic,we discussed it another thread as well, not the one you linked to