On 26/10/18 09:44, Graeme Fitzpatrick wrote:
& to throw another spanner in the works :-), what do you call
satellite dishes, either bubby ones for home use
https://goo.gl/images/qaDzSX or big commercial versions
https://goo.gl/images/44ZhNd?
They're certainly not towers, but they definitely are for
communication purposes.
Err the first one could be for reception only, so not communication.
They usually receive TV signals. They are fairly frequent in remote
areas, and with ex-pats who want to look at their home TV stations.
There is little to distinguish between the reception only and two way
communication types.
Thanks
Graeme
On Fri, 26 Oct 2018 at 07:45, Kevin Kenny <kevin.b.ke...@gmail.com
<mailto:kevin.b.ke...@gmail.com>> wrote:
On Thu, Oct 25, 2018 at 4:46 PM Warin <61sundow...@gmail.com
<mailto:61sundow...@gmail.com>> wrote:
On 25/10/18 23:56, Paul Allen wrote:
BTW, these days few radio telescopes are dishes. Most of
them are phased arrays and not on towers
or masts.
That depends on the frequency of operation.
New dish reflecting ones are being build. They simply perform
the best for the intended frequencies.
And there are dishes with phased arrays at the feed point, for
beam forming, and phased arrays of dishes, for long-baseline
interferometry. It all depends on what frequency, SNR,
polarization and angular resolution you need. Paul is right that
larger phased arrays are now practicable because of better
electronics, giving dishes less of an advantage, but phased arrays
are as old as radio astronomy.
Arrays of dishes are being used too, over very large distances. But
they can also be used individually, so each one needs to be tagged as a
separate antenna.
Where it is known that they are in some way combined for use then
perhaps a relation could be used to signify this.
See Way: Murchison Widefield Array (607964749)
Tags:
"antenna"="2048 dual-polarization dipoles"
"area"="yes"
"website"="http://www.mwatelescope.org/";
"man_made"="radio_telescope"
"name"="Murchison Widefield Array"
"description"="when combined from each antenna forms a single
telescope"
"frequency"="80 - 300 MHz"
This encompasses the area, but does not link the individual antennas
nor any other infrastructure. Maybe a site relation could be used.
Jansky built his "merry-go-round" Bruce antenna (20.5 MHz) in
1932, while Reber didn't build his first dish until 1937. Jocelyn
Bell discovered pulsars on a phased array built at Cambridge by
Ryle and Hewish (which also produced the 3C catalog of radio
sources - including 3C273, the first known quasar).
The conclusion is either, "Life is full of tradeoffs," or "you
really don't want to know!"
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