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Re: Crossband repeat on ISS



The way I see it, there are really two problems here:  One is that there are 
too many stations competing for the channel's bandwidth.  The other is that 
the there is no way to prevent the stations that are competing from 
colliding with each other.  The solution to both is to reduce the number of 
stations transmitting at any one time, to increase the odds of success.

One factor at work with the ISS repeater is that it's a relatively scarce 
resource.  AO-51 was utterly useless for the first few weeks it was open for 
use.  Now, it's possible to actually use it.  Make the ISS repeater more 
available, and I bet the congestion will decrease dramatically.

But, when it is open, there is still the collision problem, and I'm not sure 
that a Net Control station is going to be very effective.  Unlike on SSB HF, 
when stations collide on FM the control station is going to hear nothing.  
With HF, Net Control is usually able to pick out a letter or two of the call 
sign, to winow out the next round of calling.  Another problem is that the 
pass duration is very short compared to the typical net, and even shorter 
when you consider that it's the mutual window that counts, not the pass for 
any one station.  The winowing process can be slow, and stations with short 
windows are less likely to be patient.

We need another way to coordinate the calling traffic.  How about including 
a CW "traffic signal" in the downlink?  Everybody can hear the downlink, 
independent of what is happening on the uplink.  Run it on a timer, cycling 
every few seconds through the letters of the alphabet.  To access the 
transponder, a station would use the traditional 1st letter of their call 
sign suffix as their access key.  When their letter comes up, they can 
transmit.  Replies to the calling station, of course, would transmit when 
addressed (not waiting for their letter to come up).  That should thin out 
the competition at any point in time enough for a station to get through.

We can't run this way all the time, because it pretty much eliminates rag 
chewing, round tables, and other formats.  But when you hear the letters 
merged into the downlink traffic, you'd know that the system is operating in 
the coordinated mode.

Just a thought...

Greg  KO6TH


----Original Message Follows----
From: "Edward R. Cole" <al7eb@acsalaska.net>
To: Robert Bruninga <bruninga@usna.edu>
CC: amsat-bb@AMSAT.Org, morsesat@optonline.net
Subject: Re: [amsat-bb] Crossband repeat on ISS
Date: Sun, 01 Jan 2006 14:26:00 -0900

HAPPY NEW YEAR SATELLITE FOLKS!

I deleted the prior text on this topic but guess those interested have been
reading along.

I do not have much to add to Bob's suggestion other than we should try it!
The current Leo "free-for-all" is not working well, obviously!

I would point to the HF DX manager stations that "run a list".  i.e. a
strong Net station coordinates stations calling a rare DX station by asking
for callers from different call zones, countries, states, whatever way to
breakdown the number fo callers.  They then list the calls in order
received and give permission to call the DX station.  They work pretty well
with everyone waiting their turn.

Leo Net Controls or ISS Net Controls can work out a procedure as well (as
Bob explains).  I would guess that it would work on satellite when the word
gets out.  Net needs to have "horse power" to overwhelm any "cowboys" or
"free soles" that wander on frequency.  We have enough seasoned operators
with Big-Gun capability to act as Net Control.

One list might be that once you contact ISS you move to the end of the
list; that way more stations get a chance over time.

Since ISS only peeks above horizon for about ten minutes for Alaska and
less on the few other passes...chances to work ISS are far and few.  Since
I go to work daytime, the odds are nearly zero for me to work them.  The
good passes are about 0900-1100 utc in the middle of the night.  A NC List
would work really good for me as I could schedule my attempt loosing less
sleep!

Who will volunteer to be NC?  Someone needs to step forward to coordinate
this.
Give it a Try!
73's,
Ed - KL7UW
===================================
BP40iq,  Nikiski, AK      http://www.qsl.net/al7eb
Amsat #3212
Modes: V - U - L - S
===================================
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