= = = Greg wrote in message
= = = ...
Interesting how my original post about the Military Affiliate Radio System
turned into a discussion on communications in space. Interesting stuff!
This is a very lively group. And thanks all for avoiding any discussion of
signals radiating from Uranus!

Greg


GREG,

Good Come Back :o)

Just a Thought - Isn't there a book that was written:
Women are from Venus
.. . . Men are from Mars !

Considering that the majority of posters here are Men,
it is easy to see why "MARS" became 'Mars' :o]

Although the Men may have originated from Mars, I believe
that you are right that a few of then must have been raised
on Uranus because they are such ***-***** at times ;-

Just for the Fun of It ~ RHF

..

From: (RHF)
Organization: http://groups.google.com
Newsgroups: rec.radio.shortwave
Date: 10 May 2004 14:49:05 -0700
Subject: MARS?

= = = Greg wrote in message
= = = ...
Interesting how my original post about the Military Affiliate Radio System
turned into a discussion on communications in space. Interesting stuff!
This is a very lively group. And thanks all for avoiding any discussion of
signals radiating from Uranus!

Greg


GREG,

Good Come Back :o)

Just a Thought - Isn't there a book that was written:
Women are from Venus
. . . Men are from Mars !

Considering that the majority of posters here are Men,
it is easy to see why "MARS" became 'Mars' :o]

Although the Men may have originated from Mars, I believe
that you are right that a few of then must have been raised
on Uranus because they are such ***-***** at times ;-

Just for the Fun of It ~ RHF

My wife teaches middle school science and her kids love it whenever she
mentions Uranus!

Greg

Harris wrote:
JJ wrote:

Arthur Harris wrote:


The signal will decrease by 6 dB every time you double the distance. MIR was
about 250 miles above Earth, and you could establish communicaion with
fairly low power when it was overhead. On the other hand, Mars is about 35
million miles away! You'd need a LOT more power and antenna gain to contact
Mars.



Voyager 1 is just over 90 Astronomical Units or 8.4 billion miles from
the sun, transmitting with approximately 2 watts and signals are still
being received here on earth. How do you account for that?


A steerable 12-foot dish on the spacecraft, and HUGE antenna arrays on
Earth.

So you don't need a LOT of power to contact Mars.

JJ wrote:
Arthur Harris wrote:

The signal will decrease by 6 dB every time you double the distance. MIR was
about 250 miles above Earth, and you could establish communicaion with
fairly low power when it was overhead. On the other hand, Mars is about 35
million miles away! You'd need a LOT more power and antenna gain to contact
Mars.


Voyager 1 is just over 90 Astronomical Units or 8.4 billion miles from
the sun, transmitting with approximately 2 watts and signals are still
being received here on earth. How do you account for that?

A steerable 12-foot dish on the spacecraft, and HUGE antenna arrays on
Earth.

See:
http://www.spectrum.ieee.org/pubs/tr...c06-stone.html

The article says in part:

"The science data from this 12-year journey of exploration completely
altered our understanding of these planetary systems. A number of
first-time telecommunications achievements made this possible, including
the first operational X-band (8.4-GHz) system. During the course of the
mission, there were a number of significant changes to the communications
system on the spacecraft and on Earth which provided in aggregate a factor
of six higher data return at Neptune than was possible at launch. Data
compression programmed into the flight data system gave the largest single
increment, and switching from a Golay code to a Reed-Solomon code helped
enable the use of the data compression. The other major contribution came
from increases in effective receiving area by arraying of multiple Deep
Space Network (DSN) antennas and increasing the size and efficiency of the
largest DSN antennas from 64 m to 70 m. For the Neptune encounter, an
array of 29 antennas consisting of 70- and 34-m antennas in California and
27 additional 25-m antennas (comprising the National Science Foundation's
Very Large Array in New Mexico) provided fully steerable equivalent
aperture of 150 m."

Art N2AH

"JJ" wrote in message
...
Harris wrote:
JJ wrote:

Arthur Harris wrote:


The signal will decrease by 6 dB every time you double the distance.
MIR was
about 250 miles above Earth, and you could establish communicaion with
fairly low power when it was overhead. On the other hand, Mars is about
35
million miles away! You'd need a LOT more power and antenna gain to
contact
Mars.



Voyager 1 is just over 90 Astronomical Units or 8.4 billion miles from
the sun, transmitting with approximately 2 watts and signals are still
being received here on earth. How do you account for that?


A steerable 12-foot dish on the spacecraft, and HUGE antenna arrays on
Earth.

So you don't need a LOT of power to contact Mars.

It takes lots of ERP (Effective Radiated Power). You can get high ERP by
using high power or a high gain antenna (or both). The 12-foot dish on
Voyager has over 40 dB of gain at X Band. In conjuction with Voyager's 20
watt (not 2 watt) transmitter, that produced over 200,000 watts of ERP.

See:
http://www.spacetoday.org/SolSys/Voyagers20years.html


The statement I took issue with was:

"Very little power is necessary in space. I had a QSO with an astronaut on
MIR with a 3 watt ht. With nothing in the way, it will go on virtually
forever."

That implied that a simple low power transceiver and mediocre antenna could
communicate over unlimited distances in space. That is simply not true. The
Mars missions and Voyager mission used very sophisticated engineering to
accomplish what they did.

Art N2AH

Arthur Harris wrote:
"JJ" wrote in message
...

Harris wrote:

JJ wrote:


Arthur Harris wrote:


The signal will decrease by 6 dB every time you double the distance.

MIR was

about 250 miles above Earth, and you could establish communicaion with
fairly low power when it was overhead. On the other hand, Mars is about

35

million miles away! You'd need a LOT more power and antenna gain to

contact

Mars.



Voyager 1 is just over 90 Astronomical Units or 8.4 billion miles from
the sun, transmitting with approximately 2 watts and signals are still
being received here on earth. How do you account for that?


A steerable 12-foot dish on the spacecraft, and HUGE antenna arrays on
Earth.

So you don't need a LOT of power to contact Mars.


It takes lots of ERP (Effective Radiated Power). You can get high ERP by
using high power or a high gain antenna (or both). The 12-foot dish on
Voyager has over 40 dB of gain at X Band. In conjuction with Voyager's 20
watt (not 2 watt) transmitter, that produced over 200,000 watts of ERP.

The Voyager's power is now down to 2 watts and has been for some time to
conserve power. So you don't need a LOT of power to communicate long
distances in space. Real power from the transmitter and ERP are two
different things.