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Re: [amsat-bb] Re: Why FULLDUPE On is good? (Re: iss)

Bob Bruninga wrote:

> Its not that the congestion is preventing the TNC from Transmitting, its
> that the congestion is preventing it from Receiving.

"Vince Fiscus, KB7ADL" wrote:

> I know Bob APR disagrees, but the TNC on the ISS won't transmit until the
> uplink frequency is clear.  This is built into AX25 to prevent packet
> collisions. Since the ISS is transmitting on a separate frequency there is
> no need for it to wait as its packets won't be colliding with anyone
> else's. The result of all of this is that we get more packets from the
> ISS.  With full duplex on, the ISS will transmit even if DCD on the uplink
> channel.

What Vince says makes sense to me...in fact, is there some reason why an earth
station shouldn't transmit on the uplink even though the downlink is busy? I'm
assuming here that the ARISS TNC actually can recieve and transmit at the same

The uplink congestion is clearly preventing the ARISS TNC from *hearing* as many
good packets as it could, because of collisions. 

But am I mistaken to think that: 

--Even when it has heard and decoded a good packet that it *could* digipeat back
down, it *won't* as long as there's a signal on the uplink...even if that signal
is actually a collision between two carriers?  

--That the ARISS TNC will hold that packet in memory until it thinks it's clear
to send? Which right now means "when there's nothing heard on the uplink"?

--and that while it's holding that decoded packet, waiting to digi it, it won't
store any more? Or can there be several packets queued in the TNC waiting to
digi outbound?   

73 de Maggie K3XS, who has more questions than answers

-----/___.   _)   Margaret Stephanie Leber    / "The art of progress  /
----/(, /|  /| http://voicenet.com/~maggie   / consists of preserving/
---/   / | / |  _   _   _    `  _AOPA 925383/ order amid change and /
--/ ) /  |/  |_(_(_(_/_(_/__(__(/_  FN20hd / change amid order."   /
-/ (_/   '  K3XS  .-/ .-/    ARRL 39280   /___ --A.N.Whitehead ___/
/____ICQ 7161096_(_/_(_/__AMSAT 32844____/ <maggie@voicenet.com>

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