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Old July 30th 03, 01:57 AM
Dave Shrader
 
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Default BPL pollution - file reply comments by August 6

One of the technologies we have ignored in the BPL discussion is the use
of coherent detection in the BPL circuitry. It provides very high common
mode rejection. For example, high rejection to amateur and commercial
HF/VHF transmissions, and high signal to noise integrity on the desired
frequencies.

Coherent detection can very easily pull a signal out from under the
noise level. For example, I have used systems where the signal can be 20
dB below the noise and still be recovered.

It may just be possible that interference TO the BPL system will not be
severe, but interference FROM the BPL system ... well that has been
discussed.

Deacon Dave, W1MCE
+ + +

Dave Platt wrote:

In article ,
Ryan, KC8PMX wrote:


Don't know if anyone has considered this, but if the BPL lines are going to
radiate intereference, would it not stand to reason that the lines would be
(not by choice) accepting outside RFI sources???



Correct... and there have been some very pithy statements concerning
this issue submitted to the FCC.

[SNIPPED}


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Old July 30th 03, 02:23 AM
Dave Platt
 
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Default

In article [email protected],
Dave Shrader wrote:

One of the technologies we have ignored in the BPL discussion is the use
of coherent detection in the BPL circuitry. It provides very high common
mode rejection. For example, high rejection to amateur and commercial
HF/VHF transmissions, and high signal to noise integrity on the desired
frequencies.


My understanding is that the BPL systems being proposed, use various
spread-spectrum techniques - I believe they're based on discrete-
multitone / orthogonal frequency division multiplexing modulations,
similar to what's used for most ADSL systems these days. There won't
be a single carrier frequency... there will be dozens or hundreds in
use in any given transmission.

That's how they can get a lot of bandwidth over the wires, provide
some resistance to narrow-band interference, and still manage to keep
the radiated energy in any given band-slice to within the FCC
emissions limits.

Coherent detection can very easily pull a signal out from under the
noise level. For example, I have used systems where the signal can be 20
dB below the noise and still be recovered.


That works nicely with narrowband signals, and at low data rates.

Doesn't seem to me that it will work at all well with wideband
multi-carrier systems such as DMT, operating at high data rates.

Also, achieving high common-mode rejection is nice, but since power
lines are a long way from being electrically-balanced at HF/VHF
frequencies, there's going to be a whole howling lot of
differential-mode signal on the lines any time a licensed transmitter
keys up in the neighborhood.

Also, getting good common-mode rejection (for coherent detection or
otherwise) requires that you have adequate dynamic range and
resolution in your front-end electronics... if the interference
saturates the receiver chain at any point _before_ the common-mode
portion of the signal is eliminated, you're screwed. That's one of
the problems one commenter discussed on the FCC page.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
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Old July 30th 03, 02:23 AM
Dave Platt
 
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Default

In article [email protected],
Dave Shrader wrote:

One of the technologies we have ignored in the BPL discussion is the use
of coherent detection in the BPL circuitry. It provides very high common
mode rejection. For example, high rejection to amateur and commercial
HF/VHF transmissions, and high signal to noise integrity on the desired
frequencies.


My understanding is that the BPL systems being proposed, use various
spread-spectrum techniques - I believe they're based on discrete-
multitone / orthogonal frequency division multiplexing modulations,
similar to what's used for most ADSL systems these days. There won't
be a single carrier frequency... there will be dozens or hundreds in
use in any given transmission.

That's how they can get a lot of bandwidth over the wires, provide
some resistance to narrow-band interference, and still manage to keep
the radiated energy in any given band-slice to within the FCC
emissions limits.

Coherent detection can very easily pull a signal out from under the
noise level. For example, I have used systems where the signal can be 20
dB below the noise and still be recovered.


That works nicely with narrowband signals, and at low data rates.

Doesn't seem to me that it will work at all well with wideband
multi-carrier systems such as DMT, operating at high data rates.

Also, achieving high common-mode rejection is nice, but since power
lines are a long way from being electrically-balanced at HF/VHF
frequencies, there's going to be a whole howling lot of
differential-mode signal on the lines any time a licensed transmitter
keys up in the neighborhood.

Also, getting good common-mode rejection (for coherent detection or
otherwise) requires that you have adequate dynamic range and
resolution in your front-end electronics... if the interference
saturates the receiver chain at any point _before_ the common-mode
portion of the signal is eliminated, you're screwed. That's one of
the problems one commenter discussed on the FCC page.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
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Old July 30th 03, 03:10 AM
W5DXP
 
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Default

Dave Shrader wrote:
Coherent detection can very easily pull a signal out from under the
noise level. For example, I have used systems where the signal can be 20
dB below the noise and still be recovered.


Let's bring back coherent CW.
--
73, Cecil http://www.qsl.net/w5dxp



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Old July 30th 03, 03:10 AM
W5DXP
 
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Default

Dave Shrader wrote:
Coherent detection can very easily pull a signal out from under the
noise level. For example, I have used systems where the signal can be 20
dB below the noise and still be recovered.


Let's bring back coherent CW.
--
73, Cecil http://www.qsl.net/w5dxp



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Old July 30th 03, 03:48 AM
H. Adam Stevens
 
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Default

It's decades too late for coherent thought.



"W5DXP" wrote in message
...
Dave Shrader wrote:
Coherent detection can very easily pull a signal out from under the
noise level. For example, I have used systems where the signal can be 20
dB below the noise and still be recovered.


Let's bring back coherent CW.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 80,000 Newsgroups - 16 Different Servers! =-----



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Old July 30th 03, 03:48 AM
H. Adam Stevens
 
Posts: n/a
Default

It's decades too late for coherent thought.



"W5DXP" wrote in message
...
Dave Shrader wrote:
Coherent detection can very easily pull a signal out from under the
noise level. For example, I have used systems where the signal can be 20
dB below the noise and still be recovered.


Let's bring back coherent CW.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 80,000 Newsgroups - 16 Different Servers! =-----



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Old July 30th 03, 05:25 AM
CW
 
Posts: n/a
Default

Hey, I am coherent.

CW
KC7NOD


"W5DXP" wrote in message
...
Dave Shrader wrote:
Coherent detection can very easily pull a signal out from under the
noise level. For example, I have used systems where the signal can be 20
dB below the noise and still be recovered.


Let's bring back coherent CW.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 80,000 Newsgroups - 16 Different Servers! =-----



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Old July 30th 03, 05:25 AM
CW
 
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Default

Hey, I am coherent.

CW
KC7NOD


"W5DXP" wrote in message
...
Dave Shrader wrote:
Coherent detection can very easily pull a signal out from under the
noise level. For example, I have used systems where the signal can be 20
dB below the noise and still be recovered.


Let's bring back coherent CW.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 80,000 Newsgroups - 16 Different Servers! =-----





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