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Re: Condensed Guide lines for Mir PMS







Mir Minimum ERP.

The Minimum about of Power required to work the Mir 2-meter PMS is a very
elusive calculations.
There are many variables to consider and the most important variable is, How
many people are calling at the same time.
If the 2-meter channel is perfectly clear, and there is NO other traffic on the
Channel, and there is no one transmitting
on an adjacent channel (plus or minus 25 Khz from the Mir RX channel within 1500
 miles).  Then you can probably come up
with an ERP rating of much less than one (1)  watt.
Unfortunately reality says, you will not find very many of those types of clear
days.
(Except from 1:00 am - 5:00 am, weekdays).
Since were are dealing with an FM signal, the signal you need to transmit needs
to be approximately 10 times stronger than
the average noise level begin heard at the FM satellite
 ( I am not being exact with the numbers, rounding is good enough for this memo)

I prefer to base my calculation on experience and the term (Reliable
Communication).
A one watt HT can ping Mir on a Good day.  However this is mostly luck and
should be considered
Un-reliable communications.
A 45 watt ERP station will have Reliable Communications with the Mir FM system
more than 50% of the time.
(Except at noon on weekends, when everyone is calling at the same time, etc.)
The  "minimum ERP requirements" to close the link under nominal conditions for
Mir is in the range of 25-50 watts ERP.
Yes, it can be done with less ERP on a good day.  Should you try it with lower
power, Sure, Go for it.  Your success
will depend on how may people are using the channel within 1500 miles of Mir,
and how many people are on adjacent channels.
And your success will also depend on Where Mir is located.
Example:
My QTH is in Boston Mass.
When Mir is over Chicago, I need to add more power to reliably upload a message
to the Mir crew.
When Mir is over the North Atlantic, I find excellent results with an ERP of 10
watts.

Note: FCC Law
§ 97.313 Transmitter power standards.
(a) An amateur station must use the minimum transmitter power necessary
to carry out the desired communications.

So you may choose your desired communicaitons power level
Reliable
or
Un-reliable



Note: the power suggestions for Mir do not apply to Transponder based
satellites.

good luck

Miles WF1F
MAREX-NA

The most efficent satellite club in the world.




To:  Miles Mann/PicTel
cc:  Ray Soifer <71331.1337@compuserve.com>, "Bob Bruninga, WB4APR"
<wb4apr@AMSAT.Org>, Hans van de Groenendaal <zs5akv@AMSAT.Org>,
amsat-bb@AMSAT.Org, sarex@AMSAT.Org
Subject:  Re: Condensed Guide lines for Mir PMS



On Mon, 26 Jul 1999, Miles Mann wrote a short condensed guide line for
using the Mir Personal Message System listing Mission and minimum ERP
requirements:

>   * FREQUENCIES:       145.985 FM Simplex
>   * RECOMMENDED ERP:   45 W
<snip>

As one of the sysops for the PMS system, Mile's recommendations are
whatever he thinks is best....  in this case 45 watts.  But what I meant
to ask for from all satellite owner/operators was the "minimum ERP
requirements" to close the link under nominal conditions.  This would
estalbish the minimum station baseline.

During the first week of June APRS/MIR Handheld tests we demonstrated near
100% reliable MIR communications using 5 watt Handhelds and rubber duck
antennas.  THus, approximately 5W ERP.  These were not just flukes.  We
did it consistently, repeatedly, and frequently over the USA.  I am
overdue for posting the results to the SIG, but I had a student working on
the summary and he was on vacation...

So, in my opinion, the "minimum ERP requirment" for MIR is 5 watts for
individual UI packets.  Miles recommendation is from a different
perspective and that is to complete a CONNECTED QSO with a BBS and all the
attendant overhead packets in the presence of QRM...   I'm not arguing
with his recommendation.  Just clarifying the issue..

bob, WB4APR



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