Tiny spherical antennas

Skip Channel

Just been reading about these tiny dishes perfected by an Egyptian guy. I've heard about these before but not seen them as small as this. These could be ideal for us indoor reception enthusiasts!

__hXXp://farragsat.33host.com/

Channel Hopper

Parabolics ?

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Skip Channel

Sorry? Not sure what you're asking.

Jeff_19341

No CH, spherical objects .

Orthoclipse

They look like a Luneberg lens design.

spiney

yep, it's just another "dielectric lens" antenna, can't collect any signal outside its diameter, and with additional losses due to absorbtion, so note the required high field strength mentioned, as they rightly say it's "not for dx"!

Skip Channel

I'm perplexed again! I feel like the dopey kid in the top science/maths class (strangely that was me - never could quite figure out why I wasn't at least in the next class down!).

What does CH mean? A Google won't help as that'll bring up tens of thousands of links to pages about central heating and Switzerland!

Ahh! Now I see - Channel Hopper! The perils of using abbreviations in such a thread with such an OP.

Skip Channel

Well, not all of us can do anything other than direct-to-home! (Can't find a tearful smilie!)

But if these things can be made more efficient (I'm a dummy but if I take what's been published at face value...) and cheap enough then people like myself can put 'em on their windowsills! Newer, more powerful birds will help (of course that all goes out the window(!) if these newer birds are more focused on another part of Europe!)

Jeff_19341

@ Skip Channel

CH = Channel Hopper one of the posters on this thread
Parabolics and spherical objects = play on words.

JuMbuCk

spiney

I don't see how it could possibly be "more efficient"! The "aperture" of a sat antenna - how much signal it can collect, and then focus on the lnb horn - can be no greater than the lens or dish cross sectional area. Anything else just isn't physics. It would be nice if somebody found a way to get a big signal from a small dish, but there's just the tiny snag that it's impossible (if you could do that, then somebody else would have, ages ago!).

Presumably, the lens special design makes it easier to "space" several different lnbs, which would seem to be the point, but the local field strength for each one must still be fairly high.

(It would be nice if they gave actual performance (gain) figures!).

Skip Channel

I'm no mathematics expert (I think that's quite obvious!) but I thought that a magazine such as TSI wouldn't just print an article without checking it out first. Having said that, I'm not sure what those in the know here think of that particular magazine. Are they considered good journos?

spiney

Well Skip, looking again at the article, it says the 30cm version "starts working" at around 47dBW (transponder power, at "footprint" centre), which is around the same as a Sky minidish (at 40cm, the minidish has a higher gain, allowing a "safety margin" for cable and bad alignment and variable rain attenuation losses, etc.

I think suggesting this is "more efficient" than a conventional dish is a bit misleading!

Skip Channel

So, what's your take on TSI magazine in general? Are they a well respected reviewer of satellite equipment/technology or are they a bit like the satellite world's 'Which?' magazine?! ;o)

spiney

Sorry, never read TSI, was just going by article from your link.

Spherical antenna's an interesting idea, maybe better than a dish if you want to easily set up for receiving several close-together strong-signal satellites, but I'm afraid there's no "magical" way to increase sensitivity, other than by increasing size (of dish or lens), or by lowering lnb noise. We all wish there were, it would make things a lot easier, but there just isn't

Skip Channel

There's theory and then there's practice. Of course at the end of the day it all boils down to physics but a lot of experts would've said I'd have no chance of getting Hispasat indoors, behind glass on a dish considerably smaller than Sky's minidish.

Llew

Well, I've taken it on and off for several years, and they do have some interesting technical articles, together with early reviews of the latest receivers (the Triple Dragon was the only English review I've seen). A blessed relief from the S*y-saturated bumpf in Wotsat.

A recent change has been the flight of the magazine's original editorial staff, including Dr. Dish, who now uses his website to promote almost every European satellite magazine . I say almost - TSI is noted for its absence.

Llew

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spiney

If it works, then it works! But, why does it work?

Skip Channel

That's what I want to know spiney! Of course there has to be a technical reason behind these things (even if they seem highly improbabe - like my indoor setup!).

Llew, interesting - That's another puzzle, why are all those staff jumping ship?!

Llew

Christian Mass (Dr.Dish) posted this and similar statements on various satellite boards -

Drdish-Team left TELE-satellite International

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"TELE-satellite International Magazine lost the whole editorial team. The chief editor Christian Mass (aka drDish) and the editorial manager Kinga Szentesi left the company on April 21th, 2005. Meanwhile some of the external writers of the magazine followed.
TSI was once the leading magazine when it came to satellite communications. In the autum of 2004 the publisher fired the ads-manager Claudia Spaeth to do this job by himself. In the 13 years of Claudias work for the magazine, the ads revenue was quite high. After the take over by the publisher A.Wiese this important source of income broke down to a half. to prove that he could sell ads, he offered them for fraction of the old prices. Yes, he got more pages, but the revenues went down. The work situation went from bad to worse. Censorship, influencing the editorial people to write test report in the favor of the ads-clients and delivering false circulation information could not be tolerated.
TSI has no riight the use the name DrDish anymore. All of us are working on a new project. Many of you enjoyed (more or less) DrDish@TV. No panic, we will be back on short notice."

Llew

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Skip Channel

Don't really need to read between the lines there then! D'oh! I've just taken out a year's sub! ;o) It's not that expensive but there's not a great deal in it, and now it appears the reviews are more promotional than critical to keep the advertisers happy!

From that I guess they didn't even bother checking out whether Farragsat's dishes work or not - all their technical staff have gone AWOL!

spiney

Well, Skip Channel was asking about that particular magazine. I assume the editor only accepts valid stuff, but obviously can't check eveything, and of course any articles published aren't "scientific papers", of the type that would be peer reviewed in technical "journals".

I'm sure the spherical antenna's inventor is sincere, I don't wish to suggest otherwise, but I'm also fairly certain there's no "magical" technique that "bypasses" known physical laws (if there were, money and patent lawyers would quicly follow .....). But, there might be a "niche market" for what he's done, if it fulfills some particular local need.

Receiving where you "shouldn't"? Mght be all sorts of reasons. I use a 40 cm Sky minidish - from behind a double glazed window! - and can get Hotbird, although I'm "not supposed to" (always the stronger transponders, and sometimes most of them, depending on weather!).

Skip Channel

My Hotbird reception depends on which window I point the dish at! Two identical sized panes offer almost two different sets of frequencies.

I get many of the low band channels (and not much in the high band) if my dish is looking through the left pane. I get many of the high band channels (and not much in the low band) if it's looking through the right.

The middle pane is wider but shorter so to get good reception of any satellite the dish has to be upside down - and that gets results like the right pane.

FWIW the left pane has been replaced after the local kids broke it, so possibly different type of glass!

spiney

Yeah, also get variable results here ("it's a pane", ha ha ha .... oh dear!).

Window glass does seem unpredictable on hi band, agreed, it must somehow depend on the glass exact composition, but I don't know what!