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RE: iss packet

There is another possible reason for using the splits.

Firstly, by having a single downlink frequency, we only have to listen on
the one frequency on the ground so will be able to hear whichever mode is in
use. We then just switch to the appropriate uplink to call them in that

Having 2 separate uplink frequencies means that if they decide to switch
from one mode to another, they won't have people still trying to call on the
original mode now blocking those trying to work on the new mode from being
heard by them. As most will probably realise, the space station can see a
footprint of some 1500kM radius or more so they can hear literally hundreds
of stations. It must be a real dog pile for them.

73....Eric VK2VE.

-----Original Message-----
From: owner-SAREX@AMSAT.Org [mailto:owner-SAREX@AMSAT.Org]On Behalf Of
Larry Faehling
Sent: Saturday, 27 December 2003 13:00
To: 'sarex@AMSAT.Org'
Subject: Re: [sarex] iss packet

That's the way it appears to me.  I can see altering the xmit freq from
the ISS to suit the area covered, but on semi-duplex usage, what 's the
point of splitting the t/r freqs?  Not that it makes any real
difference in the  long range of things, as long as we know what it is.
  This would make a real difference if it was full duplex.  I 'spose
that if there are a lot of satellite ops in your immediate area that
aren't set up correctly, it might make a difference in your recieve


On Friday, December 26, 2003, at 08:48 AM, Christensen, Eric wrote:

> Yeah, but it isn't full duplex.  When it is transmitting, it isn't
> listening
> on the up freq.  So it might as well have been a collision because the
> radio
> didn't hear it.
> 73s,
> Eric KF4OTN
> At 02:31 AM 26/12/2003, Christensen, Eric wrote:
>> Why go with the frequency pair?  I am hoping for more time on the
>> digipeater
>> (-4) and I think the duplex is just added "stuff" to have to deal
>> with.  Is
>> there a bonus for having the split?
>> Eric KF4OTN
>      Cuts the traffic (and hence the probability of colliding packets)
> in
> half.  I would think the "hidden transmitter syndrome" is greatly
> enhanced
> when trying to work a moving target with just a 12-15 minute window.
> Split
> operation helps this.
> 73/DX Paul VE1DX (QSL via VE1YX)
Larry Faehling
Amateur Radio KL7IBV in Wisconsin
Wondering about Wisconsin weather? Visit
Nothing is foolproof to a sufficiently talented fool.
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