"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

"Owen Duffy" wrote in message
...
"Joel Koltner" wrote in
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.

I thought Richard's main problem was that 60dB is (relatively) unheard of in
wireless systems. I agree with you 100% that not enough information was given
to determine the absolute signal or noise levels.

Perhaps , might be related to the old dB Rnco Standard, in analog
microwave paths (for setting Muting (squelch)) with a 30 dB S/N ratio,
at a specified freq slot or channel in the bandwidth (think 1.8 MHz )?

Think gave close to 52 dB s/n ratio at the lowest frequency in the
baseband (order wire) . Jim NN7K




Joel Koltner wrote:
"Owen Duffy" wrote in message
...
"Joel Koltner" wrote in
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.

I thought Richard's main problem was that 60dB is (relatively) unheard of in
wireless systems. I agree with you 100% that not enough information was given
to determine the absolute signal or noise levels.

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

Hi Richard,

"Richard Clark" wrote in message
...
This is comparing elephants to oranges.

Not intentionally; I misunderstood your objections.

The whole point of the exercise was that just starting with an SNR doesn't
provide enough information to do anything useful relating to noise figures,
although I didn't realize when I posted it that specifying "an antenna" is way
too vague.

So, you came up with 60 dB, what was the noise level in?

To be consistent with what I was trying to concoct, the noise level would have
been kTB with T=290K.

Here's a question for you: What's the noise output power of your
run-of-the-mill RF signal generator (e.g., an HP 8594A/B/C)? I'm thinking the
noise output power is *well* in excess of kTB (where T is the room temperature
you're operating the generator in)?

---Joel

Joel Koltner wrote:
Hi Richard,

"Richard Clark" wrote in message
...
This is comparing elephants to oranges.

Not intentionally; I misunderstood your objections.

The whole point of the exercise was that just starting with an SNR doesn't
provide enough information to do anything useful relating to noise figures,
although I didn't realize when I posted it that specifying "an antenna" is way
too vague.

So, you came up with 60 dB, what was the noise level in?

To be consistent with what I was trying to concoct, the noise level would have
been kTB with T=290K.

Here's a question for you: What's the noise output power of your
run-of-the-mill RF signal generator (e.g., an HP 8594A/B/C)? I'm thinking the
noise output power is *well* in excess of kTB (where T is the room temperature
you're operating the generator in)?



This can be answered by looking at the specs for the generator.

For example, an Agilent N5181 looks like the noise floor is around
-160dBc/Hz well away from the carrier (e.g. 10MHz). That's probably
representative of the overall noise floor with the carrier at some level
like 0dBm. If we take that level, then it's 14 dB above kTB of -174 dBm/Hz

"Jim Lux" wrote in message
...
For example, an Agilent N5181 looks like the noise floor is
around -160dBc/Hz well away from the carrier (e.g. 10MHz). That's probably
representative of the overall noise floor with the carrier at some level
like 0dBm. If we take that level, then it's 14 dB above kTB of -174 dBm/Hz

Thanks. Presumably then if you dial the carrier power down much below -14dBm
you're then going to have a -174dBm/Hz noise floor due to the output
attenuators as Owen mentioned...

---Joel

"Joel Koltner" wrote in
:

....
Here's a question for you: What's the noise output power of your
run-of-the-mill RF signal generator (e.g., an HP 8594A/B/C)? I'm
thinking the noise output power is *well* in excess of kTB (where T is
the room temperature you're operating the generator in)?

Most SSGs will have a large attenuation at the output, and as the output
level is reduced (attenuation increased), the noise power density away from
the carrier approaches kT/Hz.

Owen