"Richard Clark" wrote in message
...
Perhaps I should more blunt, but the quote I lifted only speaks to two
things: an antenna, and a claim for its signal to noise ratio.

60 dB ??????????????

Originally I almost added something like, "(assume you're standing next to the
transmitter)" :-)

60dB+ isn't unheard of for hilltop-to-hilltop microwave links though, is it?
And one might obtain 50dB with regular TV antennas if they have a good
line-of-sight to the transmitter and there aren't significant reflections,
right?

"Joel Koltner" wrote in
:

"Richard Clark" wrote in message
...
Perhaps I should more blunt, but the quote I lifted only speaks to
two things: an antenna, and a claim for its signal to noise ratio.

60 dB ??????????????

Originally I almost added something like, "(assume you're standing
next to the transmitter)" :-)

60dB+ isn't unheard of for hilltop-to-hilltop microwave links though,
is it? And one might obtain 50dB with regular TV antennas if they have
a good line-of-sight to the transmitter and there aren't significant
reflections, right?

It doesn't solve the problem.

You still haven't given enough information to determine the absolute
level of either signal or noise, and you need that to consider the impact
of the DUT's internal noise (which you know in absolute terms).

Owen

On Mon, 23 Mar 2009 10:11:31 -0700, "Joel Koltner"
wrote:

"Richard Clark" wrote in message
.. .
Perhaps I should more blunt, but the quote I lifted only speaks to two
things: an antenna, and a claim for its signal to noise ratio.

60 dB ??????????????

Originally I almost added something like, "(assume you're standing next to the
transmitter)" :-)

60dB+ isn't unheard of for hilltop-to-hilltop microwave links though, is it?
And one might obtain 50dB with regular TV antennas if they have a good
line-of-sight to the transmitter and there aren't significant reflections,
right?

This is comparing elephants to oranges. You haven't specified
anything that is noise related, you said nothing about antennas (exept
what might be presumed from vague associations), and receive and power
levels are wholly missing. As dB is a ratiometric relationship, you
have offered nothing to validate the ratio.

Hilltop-to-hilltop microwave links can be designed for a 60 dB snr
(one cannot call it gain, certainly); or 60 db directivity; however
hilltop-to-hilltop microwave links do not automagically qualify as
coming with that directivity if they are too close!

So, you came up with 60 dB, what was the noise level in? what was the
noise level out? What is the source of the noise in? What are you
loading the 1,000,000 * (S+N) into?

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Fri, 20 Mar 2009 19:46:53 -0700, "Joel Koltner"
wrote:
Say I have an antenna that I know happens to provide an SNR
of 60dB...
I've been following this saga for a while now, and I note no one seems
nonplused by the statement above. For as much that has been unsaid,
there must be a flood of presumptions that flowed from this detail.

It would have been much better off for me to state that, "Say I have a signal
generator that I know happens to provide an SNR of 60dB." I knew that
background radition temperatures were high, but not that even the quietest
parts of the spectrum are 4,000K!

On Fri, 20 Mar 2009 19:46:53 -0700, "Joel Koltner"
wrote:

Say I have an antenna that I know happens to provide an SNR
of 60dB...

Returning to one of the few quantifiables, it would be instructive to
judge why it is so astonishing as a point to begin a dive into the
discussion of noise figure. In other posts related to deep space
probe's abilities to recover data from beneath the noise floor, much
less cell phones to operate in a sea of congestion, I encountered the
economic objection that such methods cost too much - expense of
bandwidth.

Well, not having seen anything more than yet another qualification -
how much is "too much?" It is time to draw back and ask how much is
enough? What would NOT be too expensive? Replacing qualitative
objections with quantitative objections sometimes evokes a horse laugh
when the magnitude of the qualitative issue ceases to exhibit much
quality.

I won't open this round of enquiry with exotic Spread Spectrum which
portends the objection of phase issues with clocks (even knowing that
such modulation techniques automatically incorporate slipping to
adjust for just such problems). Instead I will slip back some 60
years to the seminal paper published by Claude Shannon who figured
this all out (with H.W. Bode) and quote some metrics for various
coding (modulation) schemes. Search for "Communication in the
Presence of Noise." When you google, search in its image data space
for the cogent chart that I will be drawing on, below. Obtaining the
paper may take more effort (or simply email me for a copy).

Starting with BPSK and a S+N/N of roughly 10.5 dB, the bit error rate
is one bad bit in one million bits. This is probably the most
plug-ordinary form of data communication coming down the pike; so one
has to ask:
"is this good enough?"
If not, then "SNR of 60dB" is going to have to demand some really
astonishing expectations to push system designers to ante up the
additional 49.5 dB.

Well, let's say those astonishing expectations are as wild as
demanding proof that you won't contribute to global warming if you
chip an ice cube off of a glacier - such are the issues of scale when
you chug the numbers for BPSK.

OK, so as to not melt down the planet, we step up the complexity of
modulation to better than the last solution for "good enough." Let's
take the Voyager probes of the deep planets where at a S+N/N of 2.53
dB (in what is called 8 dB coding gain) the same error rate of 1 bit
in 1 million is achieved. One has to ask:
"is this good enough?"
If not, then "SNR of 60dB" is going to have to demand some really
astronomical expectations.

OK, perhaps this is a problem demanding really deep pockets that
exceed the several $Trillion being spent on the past 8 years of
Reaganomic neglect. (Why else pound the desk for that extra 57 dB?)
Let's go the full distance to the Shannon limit. It will give us that
same 1 bit error for every 1,000,000 at -1.5 dB S+N/N. If this isn't
below the noise floor, then the problem demanding 60 dB will never
find the solution to positively answer:
"is this good enough?"

73's
Richard Clark, KB7QHC

Dear Group:

Three conclusions/observations:
1. Noise temperature is the unambiguous way of specifying/describing the
noise performance of a receiver.

2. The paper by Costas in December 1959 Proc of IRE is also valuable to
this discussion. Be sure to read the follow-up comments.

3. I heard with my own ears Shannon observe that, from an engineering point
of view, if one did not have an occasional transmission error one was using
a wasteful amount of power. Shannon was a Michigan boy. 60 dB SNR??? Not
in fly-over land.

73, Mac N8TT

--
J. McLaughlin; Michigan, USA
Home:
"Richard Clark" wrote in message
...
On Fri, 20 Mar 2009 19:46:53 -0700, "Joel Koltner"
wrote:

Say I have an antenna that I know happens to provide an SNR
of 60dB...

Returning to one of the few quantifiables, it would be instructive to
judge why it is so astonishing as a point to begin a dive into the
discussion of noise figure. In other posts related to deep space
probe's abilities to recover data from beneath the noise floor, much
less cell phones to operate in a sea of congestion, I encountered the
economic objection that such methods cost too much - expense of
bandwidth.

Well, not having seen anything more than yet another qualification -
how much is "too much?" It is time to draw back and ask how much is
enough? What would NOT be too expensive? Replacing qualitative
objections with quantitative objections sometimes evokes a horse laugh
when the magnitude of the qualitative issue ceases to exhibit much
quality.

I won't open this round of enquiry with exotic Spread Spectrum which
portends the objection of phase issues with clocks (even knowing that
such modulation techniques automatically incorporate slipping to
adjust for just such problems). Instead I will slip back some 60
years to the seminal paper published by Claude Shannon who figured
this all out (with H.W. Bode) and quote some metrics for various
coding (modulation) schemes. Search for "Communication in the
Presence of Noise." When you google, search in its image data space
for the cogent chart that I will be drawing on, below. Obtaining the
paper may take more effort (or simply email me for a copy).

Starting with BPSK and a S+N/N of roughly 10.5 dB, the bit error rate
is one bad bit in one million bits. This is probably the most
plug-ordinary form of data communication coming down the pike; so one
has to ask:
"is this good enough?"
If not, then "SNR of 60dB" is going to have to demand some really
astonishing expectations to push system designers to ante up the
additional 49.5 dB.

Well, let's say those astonishing expectations are as wild as
demanding proof that you won't contribute to global warming if you
chip an ice cube off of a glacier - such are the issues of scale when
you chug the numbers for BPSK.

OK, so as to not melt down the planet, we step up the complexity of
modulation to better than the last solution for "good enough." Let's
take the Voyager probes of the deep planets where at a S+N/N of 2.53
dB (in what is called 8 dB coding gain) the same error rate of 1 bit
in 1 million is achieved. One has to ask:
"is this good enough?"
If not, then "SNR of 60dB" is going to have to demand some really
astronomical expectations.

OK, perhaps this is a problem demanding really deep pockets that
exceed the several $Trillion being spent on the past 8 years of
Reaganomic neglect. (Why else pound the desk for that extra 57 dB?)
Let's go the full distance to the Shannon limit. It will give us that
same 1 bit error for every 1,000,000 at -1.5 dB S+N/N. If this isn't
below the noise floor, then the problem demanding 60 dB will never
find the solution to positively answer:
"is this good enough?"

73's
Richard Clark, KB7QHC

"J. Mc Laughlin" wrote in message
.. .
2. The paper by Costas in December 1959 Proc of IRE is also valuable to
this discussion. Be sure to read the follow-up comments.

Is that available publicly anywhere?

3. I heard with my own ears Shannon observe that, from an engineering point
of view, if one did not have an occasional transmission error one was using
a wasteful amount of power. Shannon was a Michigan boy. 60 dB SNR??? Not
in fly-over land.

I think the counterpoint is that, particularly in mobile environments, you
often needed huge fade margins, e.g., 20-40dB wasn't uncommon for pager
systems. Hence in systems designed to have, say, an "average" of 30dB SNR
(same audio quality as the telephone system, assuming 3kHz bandwidth as well),
it wouldn't be surprising to occasionally find you're actually getting 60dB
SNR in the most ideal scenario.

Although perhaps designing for an average of 30dB SNR is a little high for a
paging system... anyone know? (I'm thinking 20dB might be a bit more
realistic.)

---Joel

"Joel Koltner" wrote in message
...
Is that available publicly anywhere?

What I really meant here was, "Is that available *to download from the
Internet* publicly anywhere?"

Dear Joel Koltner (no call sign):

I know of no site where the classic paper may be downloaded. The paper
had a significant influence on how people thought about modulation and
frequency allocation. "Shannon, Poison (I can not think how to spell his
name) and the Radio Amateur" is the title of the paper. A good library
should be able to get you a copy. The same issue had a paper on small,
loaded cavities, which became the norm for front end selectivity in VHF
communication receivers.

Regards, Mac N8TT

--
J. McLaughlin; Michigan, USA
Home:
"Joel Koltner" wrote in message
...
"Joel Koltner" wrote in message
...
Is that available publicly anywhere?

What I really meant here was, "Is that available *to download from the
Internet* publicly anywhere?"

Joel Koltner wrote:
"Joel Koltner" wrote in message
...
Is that available publicly anywhere?

What I really meant here was, "Is that available *to download from the
Internet* publicly anywhere?"

Yes.

To get more than the abstract for free you have to be an IEEE member and
a member of MTTS or otherwise subscribed to the online system.

For the abstract start at:
http://ieeexplore.ieee.org/xpl/Recen...number=4547924

and for $29...
http://ieeexplore.ieee.org/guide/g_tools_apo.jsp

Happy trails!
- Galen, W8LNA