RadioBanter - View Single Post - European Mars probe to use 80meters to look for Martian water?

August 10th 04, 01:45 AM

In article ,
(N2EY) writes:

(N2EY) wrote in message
...
In article , Robert Casey
writes:

Contests working Earth-Mars contacts should be interesting, when
you remember that speed'o light means that radio signals take
about 5 to 15 minutes one way to make the trip...

If my math is right, the one-way transmission time works out to between 188
seconds at closest approach to 688 seconds maximum.

Well, it's not correct. The 188 seconds is pretty close but the 688 is
way off because I added the Earth orbit radius rather than diameter.

Oh, my! Had anyone else come up with those numbers you
would have sent many a multi-screen message accosting
them of error-prone perfidy! :-)

Here's a more exact calculation:

Per NASA website, the Earth's orbit varies from 149.5 to 149.7 million
kilometres and Mars' orbit varies from 204.52 to 246.28 million
kilometres.

The closest the two planets approach is 204.52 - 149.7 = 54.82 million
kilometres
The farthest apart they get is 246.28 + 149.7 = 395.98 million
kilometres

Using 0.3 million km/sec (that's 300,000,000 metres/sec) as the speed
of light, we get:

54.82 / 0.3 = 183 sec (3 minutes 3 seconds)

395.98 / 0.3 = 1320 sec (22 minutes 0 seconds)

give or take......

What, no EXACTNESS? Speed of light isn't EXACTLY
that nice round figure. Tsk, tsk.

But you can count on contest ops to figure a way to make that work. Use the
transmission time as a 'buffer' of sorts. Not a problem.

Ingenious use of the delay interval would permit pretty good contest
rates. Of course the ability to work duplex would be a plus.

I am non-plussed. With a 44 minute round-trip time you wouldn't
need any sort of T/R switch, just solder some lands on a PCB to
do the same job to go from Rx to Tx and back again. :-)

For rag chewing, contacts between fixed nonpolar stations on each
planet up to about 12 hours long are possible if the locations are
just right at both ends.

You could WEAVE the rag material, cut it to shape, sew it up
in the time of those contacts... :-)

SO2R is just the beginning.

Of course the reason no one - professional or amateur - has been
awarded the Elser-Mathes Cup is because it requires operators at both
ends of the QSO. Human space programs won't be in a position to do
that for decades yet.

Ah! One of the remarkable OBVIOUS statements! :-)

I hearby nominate you for three or four votes in the Department of
Redundancy Department.

Okay, now what is the PATH LOSS and what kind of Tx power is
needed at each end for a given S:N ratio?

Can you get by on amateur radio power levels? Without violating
any of the regulations?

How about Doppler Shift? How much?

Interplanetary denizens want to know! :-)

LHA / WMD