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  #172   Report Post  
Old November 3rd 14, 09:24 PM posted to rec.radio.amateur.antenna
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Default No antennae radiate all the power fed to them!

On 11/3/2014 3:48 PM, wrote:
rickman wrote:
On 11/3/2014 3:09 PM,
wrote:
rickman wrote:
On 11/3/2014 1:07 PM,
wrote:
rickman wrote:
On 11/2/2014 4:11 PM,
wrote:
Lostgallifreyan wrote:
wrote in news
The only external heat source in space is the Sun; solution, sun shade.


Maybe not. I just did a bit of Googling for 'superconductors in space' minus
quotes. There's a lot of statements abotu space missions ended because
required helium or hydrogen coolant ran out,

Yeah, the coolent ran out for the things that GENERATE a lot of heat
and need to be cooled more than radiation can provide. Radiative cooling
does not provide for a lot of cooling.

and also of space having latent
temperatures up to 100K, so a sun shade won't help a lot there with current
materials.

There really is no such thing as temperature in space as it is a vacuum.

That is a gross oversimplification. The temperature of space is the
temperature of the background radiation, even in a near vacuum.

That is also an simplification.

But not a gross oversimplification.

True.

Shall we go into why an ordinary thermometer exposed to the Sun at about
Earth's distance from the Sun allowed to stabilze will read the
tempurature of space as about 7 C and what are the unstated assumptions
for this to happen?


The number I found was about 4 °C. I believe it was posted with all the
assumptions...


I didn't see that post.

If it has already be done, so be it.


It is just the assumption that the object is a round, highly conductive,
black body so that it absorbs all radiation hitting it and spreads the
heat so it is isothermal and re-radiates it at that temperature the same
in all directions. Sort of an inside out integrating sphere.

This was the post where I quoted a formula that said the energy from the
sun would produce 77 °K at about 13 AU.

--

Rick
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Old November 3rd 14, 09:26 PM posted to rec.radio.amateur.antenna
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Default No antennae radiate all the power fed to them!

On 11/3/2014 4:05 PM, wrote:
On Monday, November 3, 2014 2:01:21 PM UTC-6, rickman wrote:
On 11/3/2014 12:13 PM,
wrote:
On Monday, November 3, 2014 11:05:11 AM UTC-6, gareth wrote:
"Lostgallifreyan" wrote in message
. ..
How many other people who are not engineers or scientists do you see
posting around here?

In discussions about short antennae, quite a few from Yankland.

I'm just a regular ole ham here. Never studied any of this stuff
in school, and don't work in any related field.
Everything I've learned, I learned on my own. Mainly from books,
of which I have several. I trust good textbooks a lot more than I
trust usenet jibber jabber. Usenet jibber jabber is only as good
as the qualifications of the one jabbering. Some info is good, some
is bad, and some is pure unadulterated bafflegab.


Will you do us *all* a favor and stop replying to him? You keep feeding
the tosser... er, I mean troll.

--

Rick


Why don't you kiss my differential. If I want to reply to him I will,
and I don't care if chaps the ass of every "Rick" on the planet.
No one is holding a pistol to your head making you read it.


Exactly, and the same goes for your rants to Gareth. No one is making
you read his nonsense. But both of you make this group a less pleasant
group.

--

Rick


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Old November 3rd 14, 09:27 PM posted to rec.radio.amateur.antenna
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Default No, antennae radiate all the power fed to them!

On Sat, 01 Nov 2014 15:32:03 -0400, rickman wrote:

On 11/1/2014 11:26 AM, gareth wrote:
Ignoring, for the moment, travelling wave antenna, and restricting
discussion to standing wave antennae ...

A wave is launched, and radiates SOME of the power, and suffers
both I2R losses and dielectric and permeability losses associated
with creating and collapsing the near field.

At first, there is no standing wave, until the wave reaches the point of
reflection
in the antenna and heads back the way it has come (because not all has been
radiated*****)
On the way back, it againn suffers the losses described above, as well as
radiating a
bit more.

It then reaches the other end and suffers further reflections ad infinitum.

An interesting conclusion is, therefore, that the I2R losses are repeated,
each tiome with a smaller loss, as the wave decrements.

***** Without the remnants of non-radiated power, there could NOT be
a standing wave!


I think the subject says it all.


Yes, antennae radiate all the power fed to them.
The larger part as electromagnetic wave,
the smaller part as infrared radiation.

w.
  #178   Report Post  
Old November 3rd 14, 09:28 PM posted to rec.radio.amateur.antenna
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Default No antennae radiate all the power fed to them!

wrote in message
...
About what? I read what I need to read in order to do whatever it is
I need to do. I don't need to read any more about small antennas in order
to deal with the likes of you. As you recall, I was probably the first one
to jump on you when you falsely claimed that small radiators are
inefficient.
Anyone that has actually read up on the subject knows that that is not
true.
If anyone needs to invest in some good textbooks on the subject, it's you.


Based upon what you write, I suspect that your textbooks were written by
Dr.Seuss. The most advanced of my textbooks, which was a course textbook
back in the early 1970s was, "Fields and Waves in Communications
Electronics"
by Ramo, Whinnery and Van Duzer; Ramo and Whinnery being the R and the W
in TRW.

Short antennae are poor radiatiors. I refer you to the book, "Antennas" by
"Those Engineers Ltd", a Yank book from 1948 that discusses that issue.


  #179   Report Post  
Old November 3rd 14, 09:29 PM posted to rec.radio.amateur.antenna
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Default No antennae radiate all the power fed to them!

On 11/3/2014 3:43 PM, Lostgallifreyan wrote:
rickman wrote in :

The reason why cooling something gets harder as it approaches
absolute zero is because the heat flow is proportional to the difference
in temperature. Even if your pump is perfect and acts as if you put the
thing being cooled in contact with a heat sink at 0 °K, the rate of heat
flow decreases as that temperature delta diminishes.


Ok, that helps. It's close to what I had in mind, though my reasoning may
still be bad. For what it's worth... if a superconductor is very cold,
needing to be so, then because there is no way to go below zero K, there are
more things hotter, than colder, so they have more effect than the shaded
space conditions. That balance might favour a need for forced cooling just to
play safe in many cases, but I accept that isolation might be fairly easy to
do, and I also accept that 77K is likely far enough above shaded space
conditions that it gives a wide margin to prevent small leaks from nearby
heat sources causing failure.


There is nothing at all in your posts that is based on any facts.
Science and engineering don't work on "might favor". Get the equations
and do the math. Otherwise it is just waving hands and flapping gums.

--

Rick
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Old November 3rd 14, 09:32 PM posted to rec.radio.amateur.antenna
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Default No antennae radiate all the power fed to them!

"rickman" wrote in message
...
Get the equations and do the math.


Physician, heal thyself.


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