Rod Speed wrote:
John - KD5YI wrote:

Rod Speed wrote:

Geoffrey S. Mendelson wrote


Rod Speed wrote


Is one transmit and the other receive?
Or are they both transmit and receive?


They're normally both transmit and receive.


That's a shame. Here in Israel we are limited to 100mw EIRP, which
severly limits the transmit antenna. There is NO limitation on the
receive antenna.


A receive antenna has no EIRP, it doesnt radiate any real power.




Actually, when properly matched, it radiates half the received power.


Wrong.


Wrong.

On Sun, 9 Jul 2006 09:30:46 +1000, "Rod Speed"
wrote, in part:

What you may or may not be inclined to believe in spades.

That assemblage does not appear to be a sentence.


Anyone with a clue considers the facts, not the style stuff, ****wit.

But it is distracting when you choose to code your message content in
the style of an illiterate A-hole. I also think you should have said
"content" rather than "facts." Most of what you have been posting here
recently seems to be opinion rather than fact.

On Sun, 9 Jul 2006 09:30:46 +1000, in alt.internet.wireless , "Rod
Speed" wrote:

You have always been, and always will be, completely and utterly irrelevant.

Oh, I've just recognised your name. Conversation over, I don't waste
my time talking to the sort of fool who thinks that because they're
hiding on usenet they can emit language which would get them a severe
slapping in real life.

Nobody cares what you think. Not even you.

*plonk*
--
Mark McIntyre

xray wrote:
Rod Speed wrote

reams of your puerile **** flushed where it belongs

Most of what you have been posting here
recently seems to be opinion rather than fact.

Best get your seems machinery seen to then.

Its a fact that even when a receiving antenna does radiate back
half of what it recieves, THAT IS NOT RELEVANT TO WHAT WAS
BEING DISCUSSED, THE LEGISLATED EIRP LEVEL ALLOWED.

Not a shred of opinion involved what so ever.

Some terminal ****wit claiming to be
Mark McIntyre
wrote just the puerile **** thats all it can ever manage.

On Mon, 10 Jul 2006 04:10:46 +1000, "Rod Speed"
wrote:

xray wrote:
Rod Speed wrote

reams of your puerile **** flushed where it belongs

Most of what you have been posting here
recently seems to be opinion rather than fact.

Best get your seems machinery seen to then.

Its a fact that even when a receiving antenna does radiate back
half of what it recieves, THAT IS NOT RELEVANT TO WHAT WAS
BEING DISCUSSED, THE LEGISLATED EIRP LEVEL ALLOWED.

Not a shred of opinion involved what so ever.


Look at this part of the thread...

[John said:]
If the receiver matching is for optimal noise figure, there may be
some reflection and reradiation, but there's nothing pinning it to
be half the received power.

[Roy said:]
John is correct.

[Rod said:]
Nope.

[Roy said:]
A receiving antenna, when matched, reradiates half the power it
receives.

[Rod said:]
Yes but that ISNT ANY REAL POWER in the EIRP restriction sense.

---
So John made a factual statment. Roy agreed. Your opinion was to
disagree with the simple factual statment.

Roy added a clarifying statment. You started to go off the hook and
SHOUT because you were fixated on EIRP. When I read it I never saw any
direct implication about EIRP or legalities in the explanation; it was a
simple explanation about antennas.

Your *opinion* was involved in deciding you knew the exact intent of the
posting and that it had implications in the EIRP thing, just because
that is the interpretation that passed through your mind.

Ok, I'm done here. Not sure why I took the time for this one last post.

Rex wrote
Rod Speed wrote
xray wrote
Rod Speed wrote

Most of what you have been posting here
recently seems to be opinion rather than fact.

Best get your seems machinery seen to then.

Its a fact that even when a receiving antenna does radiate back
half of what it recieves, THAT IS NOT RELEVANT TO WHAT WAS
BEING DISCUSSED, THE LEGISLATED EIRP LEVEL ALLOWED.

Not a shred of opinion involved what so ever.

Look at this part of the thread...

[John said:]
If the receiver matching is for optimal noise figure, there may be
some reflection and reradiation, but there's nothing pinning it to
be half the received power.

[Roy said:]
John is correct.

[Rod said:]
Nope.

Not about that particular para of John's. I was saying that John was
not correct on the original point about whatever the receiving anntenna
radiates BEING RELEVANT TO THE LEGISLATED EIRP LEVEL.

No opinion there, just fact.

[Roy said:]
A receiving antenna, when matched, reradiates half the power it
receives.

[Rod said:]
Yes but that ISNT ANY REAL POWER in the EIRP restriction sense.

---
So John made a factual statment. Roy agreed.

It wasnt relevant to what was actually being discussed,
WHETHER WHATEVER THE RECEIVING ANTENNA
RADIATES HAS ANYTHING TO DO WITH THE LEGISLATED
EIRP WAS ACTUALLY BEING DISCUSSED.

Your opinion was to disagree with the simple factual statment.

It wasnt an opinion, it was a statement of fact that that
comment John made WAS NOT RELEVANT TO THE
LEGISLATED EIRP LEVEL THAT WAS BEING DISCUSSED.

Roy added a clarifying statment. You started to go off the
hook and SHOUT because you were fixated on EIRP.

The legislated EIRP level WAS WHAT WAS BEING DISCUSSED
WHEN JOHN MADE SUCH A SPECTACULAR FOOL OF HIMSELF
RABBITING ON ABOUT WHAT THE RECIEVING ANTENNA RADIATES.

When I read it I never saw any direct implication about EIRP or legalities
in the explanation; it was a simple explanation about antennas.

Pity it was a comment made WHEN THE LEGISLATED EIRP LEVEL WAS
BEING DISCUSSED WITH REFERENCE TO THE RECEIVING ANTENNA.

Your *opinion* was involved in deciding you knew the exact intent of the posting

Wrong again. It is a FACT that John's comment had no
relevance what so ever to what was being discussed,
whether the receiving antenna has any relevance what
so ever to the legislated EIRP level. It doesnt.

and that it had implications in the EIRP thing, just because
that is the interpretation that passed through your mind.

Nothing to do with my mind, it was what was being discussed.

Ok, I'm done here. Not sure why I took the time for this one last post.

Yeah, you just made a VERY spectacular fool of yourself, yet again.

[misc.consumers.frugal-living dropped from distribution list.]

Roy Lewallen hath wroth:

Don K wrote:
"John - KD5YI" wrote in message news:XLQrg.2896$bd4.372@trnddc01...
Rod Speed wrote:
A receive antenna has no EIRP, it doesnt radiate any real power.
Actually, when properly matched, it radiates half the received power.


How do you get that?
If the receiver input impedance is matched to the antenna, all the
received power is absorbed. There is no reflection. There is no radiation.

If the receiver matching is for optimal noise figure, there may be
some reflection and reradiation, but there's nothing pinning it to
be half the received power.

John is correct. A receiving antenna, when matched, reradiates half the
power it receives. An impinging field induces current in the antenna.
This causes radiation, just like the current in a transmitting antenna.
As it turns out, when the antenna is matched, the amount of power
radiated equals the amount of power delivered to the load, and that's
the best you can do. If you'd like a more in-depth and mathematical
explanation, you can find it in any antenna text, often discussed as
"scattering".

If a receiving antenna did absorb all the impinging power, it would be a
lot easier to make a shield or a stealth aircraft.

Roy Lewallen, W7EL

I'm not so sure. I couldn't find any specific references to this
effect in several books I skimmed. Same with internet searches. If
true, then the concept of converting solar power in an orbital
satellite, converting it to microwaves, beaming it down to an antenna
array in the middle of the desert, and converting it back to
electricity, isn't going to work if the array re-radiates half the
power. That's going to ruin quite a few nifty science fiction stories
and innovative business plans.

I also note that the common microwave path analysis calculations don't
take re-radiation into account. For example, if I start with an EIRP
of perhaps XX dBm from a transmit antenna, -YY dB of path loss, and ZZ
dB receive antenna gain, the power delivered to the receiver (ignoring
coax losses) is calculated at (XX - YY + ZZ) dBm without any mention
of the -3dB that would need to be subtracted if half the receive power
is re-radiated from the rx antenna. It would seem that the common
formula and web forms for link calculations are -3dB off.

I trust your judgement in such matters and you have far more expience
than me, but something seems wrong or I'm missing something. Can you
point me to any books or refernences? I just skimmed Chapter 2
(Fundamentals of Antennas) in "Antenna Engineering Handbook" by Jasik
(1961) and found no obvious mention of this effect.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
[misc.consumers.frugal-living dropped from distribution list.]

Roy Lewallen hath wroth:


Don K wrote:

"John - KD5YI" wrote in message news:XLQrg.2896$bd4.372@trnddc01...

Rod Speed wrote:

A receive antenna has no EIRP, it doesnt radiate any real power.

Actually, when properly matched, it radiates half the received power.


How do you get that?
If the receiver input impedance is matched to the antenna, all the
received power is absorbed. There is no reflection. There is no radiation.

If the receiver matching is for optimal noise figure, there may be
some reflection and reradiation, but there's nothing pinning it to
be half the received power.

John is correct. A receiving antenna, when matched, reradiates half the
power it receives. An impinging field induces current in the antenna.
This causes radiation, just like the current in a transmitting antenna.
As it turns out, when the antenna is matched, the amount of power
radiated equals the amount of power delivered to the load, and that's
the best you can do. If you'd like a more in-depth and mathematical
explanation, you can find it in any antenna text, often discussed as
"scattering".

If a receiving antenna did absorb all the impinging power, it would be a
lot easier to make a shield or a stealth aircraft.

Roy Lewallen, W7EL


I'm not so sure. I couldn't find any specific references to this
effect in several books I skimmed. Same with internet searches. If
true, then the concept of converting solar power in an orbital
satellite, converting it to microwaves, beaming it down to an antenna
array in the middle of the desert, and converting it back to
electricity, isn't going to work if the array re-radiates half the
power. That's going to ruin quite a few nifty science fiction stories
and innovative business plans.

I also note that the common microwave path analysis calculations don't
take re-radiation into account. For example, if I start with an EIRP
of perhaps XX dBm from a transmit antenna, -YY dB of path loss, and ZZ
dB receive antenna gain, the power delivered to the receiver (ignoring
coax losses) is calculated at (XX - YY + ZZ) dBm without any mention
of the -3dB that would need to be subtracted if half the receive power
is re-radiated from the rx antenna. It would seem that the common
formula and web forms for link calculations are -3dB off.

I trust your judgement in such matters and you have far more expience
than me, but something seems wrong or I'm missing something. Can you
point me to any books or refernences? I just skimmed Chapter 2
(Fundamentals of Antennas) in "Antenna Engineering Handbook" by Jasik
(1961) and found no obvious mention of this effect.



Antennas For All Applications by John D. Kraus and Ronald J. Marhefka
Third Edition
Page 746, Paragraph 21-15

"Prec=(Rr/(Ra+Rr))Pa

where

Rr=receiver impedance, ohms
Ra=antenna radiation resistance, ohms


For a perfect match, Rr=Ra, so that

Prec=(Rr/(Rr+Rr))Pa=0.5Pa (W)

and the receiver gets 1/2 the power collected by the antenna. The other half
is reradiated."

Also see "TV and Other Receiving Antennas" by Arnold B. Bailey published in
1950 by Rider Publishing. Beginning on page 235 near the bottom:

"In radio receiving antennas the predominant resistance is, strangely
enough, largely due to the fact that no electrons can move on the antenna
surface *without also sending radio energy back out into space*. So here we
have the paradox of a receiving antenna, having the prime function of
collecting or extracting energy from space, but unable to do so *without
itself returning radio energy of like kind* into space. The amount which it
returns is one-half of the total that it extracts under properly matched
conditions. In a good installation, with the antenna properly connected to
its receiver load, the receiving antenna will be able to *deliver to its
load one-half of the energy* it extracts from the oncoming radio wave but,
by necessity, *must return the other half to free space*. A receiving
antenna, then, is itself a *new source* of radiation. This is not so
surprising, since *any* reflecting surface, as we have seen, establishes a
new source of radiation"

(Note: The emphasis in the book was italics)

Cheers,
John

Jeff Liebermann wrote:
[misc.consumers.frugal-living dropped from distribution list.]

Roy Lewallen hath wroth:


Don K wrote:

"John - KD5YI" wrote in message news:XLQrg.2896$bd4.372@trnddc01...

Rod Speed wrote:

A receive antenna has no EIRP, it doesnt radiate any real power.

Actually, when properly matched, it radiates half the received power.


How do you get that?
If the receiver input impedance is matched to the antenna, all the
received power is absorbed. There is no reflection. There is no radiation.

If the receiver matching is for optimal noise figure, there may be
some reflection and reradiation, but there's nothing pinning it to
be half the received power.

John is correct. A receiving antenna, when matched, reradiates half the
power it receives. An impinging field induces current in the antenna.
This causes radiation, just like the current in a transmitting antenna.
As it turns out, when the antenna is matched, the amount of power
radiated equals the amount of power delivered to the load, and that's
the best you can do. If you'd like a more in-depth and mathematical
explanation, you can find it in any antenna text, often discussed as
"scattering".

If a receiving antenna did absorb all the impinging power, it would be a
lot easier to make a shield or a stealth aircraft.

Roy Lewallen, W7EL


I'm not so sure. I couldn't find any specific references to this
effect in several books I skimmed. Same with internet searches. If
true, then the concept of converting solar power in an orbital
satellite, converting it to microwaves, beaming it down to an antenna
array in the middle of the desert, and converting it back to
electricity, isn't going to work if the array re-radiates half the
power. That's going to ruin quite a few nifty science fiction stories
and innovative business plans.

I also note that the common microwave path analysis calculations don't
take re-radiation into account. For example, if I start with an EIRP
of perhaps XX dBm from a transmit antenna, -YY dB of path loss, and ZZ
dB receive antenna gain, the power delivered to the receiver (ignoring
coax losses) is calculated at (XX - YY + ZZ) dBm without any mention
of the -3dB that would need to be subtracted if half the receive power
is re-radiated from the rx antenna. It would seem that the common
formula and web forms for link calculations are -3dB off.

I trust your judgement in such matters and you have far more expience
than me, but something seems wrong or I'm missing something. Can you
point me to any books or refernences? I just skimmed Chapter 2
(Fundamentals of Antennas) in "Antenna Engineering Handbook" by Jasik
(1961) and found no obvious mention of this effect.



Antennas For All Applications by John D. Kraus and Ronald J. Marhefka
Third Edition
Page 746, Paragraph 21-15

"Prec=(Rr/(Ra+Rr))Pa

where

Rr=receiver impedance, ohms
Ra=antenna radiation resistance, ohms


For a perfect match, Rr=Ra, so that

Prec=(Rr/(Rr+Rr))Pa=0.5Pa (W)

and the receiver gets 1/2 the power collected by the antenna. The other half
is reradiated."

Also see "TV and Other Receiving Antennas" by Arnold B. Bailey published in
1950 by Rider Publishing. Beginning on page 235 near the bottom:

"In radio receiving antennas the predominant resistance is, strangely
enough, largely due to the fact that no electrons can move on the antenna
surface *without also sending radio energy back out into space*. So here we
have the paradox of a receiving antenna, having the prime function of
collecting or extracting energy from space, but unable to do so *without
itself returning radio energy of like kind* into space. The amount which it
returns is one-half of the total that it extracts under properly matched
conditions. In a good installation, with the antenna properly connected to
its receiver load, the receiving antenna will be able to *deliver to its
load one-half of the energy* it extracts from the oncoming radio wave but,
by necessity, *must return the other half to free space*. A receiving
antenna, then, is itself a *new source* of radiation. This is not so
surprising, since *any* reflecting surface, as we have seen, establishes a
new source of radiation"

(Note: The emphasis in the book was italics)

Cheers,
John