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PA2AGA > HDDIG 05.12.99 13:58l 216 Lines 7391 Bytes #-9661 (0) @ EU
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To: hd_broadcast@pa2aga
Subject: HamDigitalDigest 99/304D
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depths, etc) are approved. The choice of which to use at any given time is at
the
broadcaster's option. In this town, the three broadcasters currently
transmitting
DTV are each using a different standard. (We can even change standards for
different programs.)
This isn't a problem, however, since any of the receivers can decode and
display any of the various standards. That's possible because the protocol
headers notify the receiver which particular standard is being received at
the moment, and its firmware then adapts that to the capabilities of the
display hardware.
(Low end receivers might show a high definition show in a low resolution
format, for example, because its hardware is incapable of showing the
higher resolution, while a high end receiver might show it in all its glory.
This is a bit like the way a X Window display server behaves.)
We can also choose to transmit up to 4 different standard definition signals
at
the same time instead of one high definition signal. The receiver chooses
which
one it will display, or all 4 at once at the viewer's option. (This is likely
to be widely
used since it effectively quadruples the broadcaster's programming options,
and
doesn't require a large inventory of HD programming, which doesn't yet exist.)
We
can also choose to transmit non-visual data in part of the bandwidth instead
of
either a high definition program or multiple standard definition programs. As
long
as we deliver at least one standard definition program to the audience, the
FCC
doesn't care, and your receiver won't care either.
Gary
Gary Coffman KE4ZV | You make it |mail to ke4zv@bellsouth.net
534 Shannon Way | We break it |
Lawrenceville, GA | Guaranteed |
>.
------------------------------
Date: Sat, 20 Nov 1999 06:12:16 -0600
From: "Charles Brabham" <n5pvl@texoma.net>
Subject: FCC reallocates Ham Band
NV Jims <nvjims@aol.com> wrote in message
news:19991120000400.08924.00000191@ngol03.aol.com...
> Charles has shown his usual contempt for new modes and progress, and,
called me
> a "bastard" in the process..............
>
> Can't we get him banned from this newsgroup?
No, you can't.
By the way, what "new mode" were you referring to? Using The telephone
instead of Radio?
Call that "progress", do you?
Moron.
--
73 DE Charles Brabham, N5PVL
N5PVL @ N5PVL.#NTX.TX.USA.NOAM
http://www.texoma.net/~n5pvl
>.
------------------------------
Date: Sat, 27 Nov 1999 01:15:07 +0100
From: Nico Palermo <nicopal@microtelecom.it>
Subject: German packet radio
Gary Coffman wrote:
>
> On Fri, 19 Nov 1999 22:50:09 -0800, "Cathryn Mataga"
<cathryn@junglevision.com> wrote:
> >"Gary Coffman" <ke4zv@bellsouth.net> wrote in message
> >news:6WM5OBGfkbX71SImHGfukMwE9Zgj@4ax.com...
> >> On Thu, 11 Nov 1999 18:16:33 -0600, "Steve Sampson"
> ><ssampson@usa-site.net> wrote:
> >> >There's probably a chart somewhere (I'm not that much of an expert) that
> >> >shows the optimum deviation. I suspect it should be at an index
slightly
> >> >greater than one, or about 6 sidebands of the modulating frequency.
> >>
> >> The optimum is an index of 0.5. It is called MSK.
> >
> >Does that mean 9600 baud should have a 4.8khz deviation then? That is
> >2.4khz up and 2.4khz down from the center frequency -- right?
>
> Right.
>
> >Is MSK better also than PSK too? Or is MSK just better than
> >all FSK with higher deviation? Is MSK just what it sounds like? FSK with
> >that specific deviation?
>
> Better is a slippery word. MSK does have a smaller occupied spectrum
> than ordinary PSK for signals of the same baud. OTOH, BPSK has a larger
> Hamming distance than MSK, so it can offer a weak signal detection
> advantage if coherent detection is employed. Which one is better is a
> matter of particular spectral circumstance and system objectives.
No! MSK performs even better than BPSK. Since MSK is a modulation with
memory, you can demodulate it with a Viterbi decoder (or alternatively
with a matched filter with 2T integration period) and get the same BER
performance of BPSK ( BER=10^-5 @ Eb/No = 9.6dB).
MSK performance is worse than BPSK only if demodulated by a coherent
detector which takes symbol-by-symbol decisions (3 dB penalty), either
by an incoherent one (6 dB penalty), or by a frequency discriminator. In
the latter case the optimum modulation index is 1.25 (not 0.5) and there
is a ~7 dB penalty over Viterbi decoding.
Furthermore, MSK requires smaller bandwidth than BPSK and, beeing its
envelope constant, it can be nonlinearly (C class) amplified. Filtered
BPSK envelope is not constant and the power amplifier should be operated
far below saturation.
Only more complex phase modulation systems, i.e. PI/4 DQPSK, can compete
with MSK and its gaussian derivatives.
Nico Palermo, IV3NWV
___________________________
http://www.microlet.com/yam
>.
------------------------------
Date: Fri, 26 Nov 1999 17:53:14 -0500
From: Gary Coffman <ke4zv@bellsouth.net>
Subject: German packet radio
On Fri, 19 Nov 1999 22:50:09 -0800, "Cathryn Mataga"
<cathryn@junglevision.com> wrote:
>"Gary Coffman" <ke4zv@bellsouth.net> wrote in message
>news:6WM5OBGfkbX71SImHGfukMwE9Zgj@4ax.com...
>> On Thu, 11 Nov 1999 18:16:33 -0600, "Steve Sampson"
><ssampson@usa-site.net> wrote:
>> >There's probably a chart somewhere (I'm not that much of an expert) that
>> >shows the optimum deviation. I suspect it should be at an index slightly
>> >greater than one, or about 6 sidebands of the modulating frequency.
>>
>> The optimum is an index of 0.5. It is called MSK.
>
>Does that mean 9600 baud should have a 4.8khz deviation then? That is
>2.4khz up and 2.4khz down from the center frequency -- right?
Right.
>Is MSK better also than PSK too? Or is MSK just better than
>all FSK with higher deviation? Is MSK just what it sounds like? FSK with
>that specific deviation?
Better is a slippery word. MSK does have a smaller occupied spectrum
than ordinary PSK for signals of the same baud. OTOH, BPSK has a larger
Hamming distance than MSK, so it can offer a weak signal detection
advantage if coherent detection is employed. Which one is better is a
matter of particular spectral circumstance and system objectives.
Gary
Gary Coffman KE4ZV | You make it |mail to ke4zv@bellsouth.net
534 Shannon Way | We break it |
Lawrenceville, GA | Guaranteed |
>.
------------------------------
Date: Sat, 27 Nov 1999 11:46:17 +0200
From: Paul Keinanen <keinanen@sci.fi>
Subject: German packet radio
On Mon, 22 Nov 1999 10:44:32 -0500, Gary Coffman <ke4zv@bellsouth.net>
wrote:
>Sure. A bandpass wider than the signal lets in excess noise, so your
>SNR is sharply degraded, and your BER goes through the roof.
What exactly do you mean by sharply degraded ?
Assuming 10 % larger receiver filter bandwidth than the transmitted
signal to compensate for filter tolerances and receiver and
transmitter frequency error/drift, I get only a less than 1 dB
To be continued in digest: hd_99_304E
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