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[Linrad] Re: Linrad network connections

Hi Joe,

Unfortunately the convention conflicts with our annual vacation, so I can't
be there.

Since we last spoke I've got a SDR-IQ and SDR-1000 which makes JT65 via the
moon a lot easier.
But still waiting, and hoping, for MAP65 being able to function with JT65C
for 1296Mhz work.


-----Original Message-----
From: linrad@xxxxxxxxxxxxxxxx [mailto:linrad@xxxxxxxxxxxxxxxx]On Behalf
Of Joe Taylor
Sent: 24 July 2008 22:02
To: linrad@xxxxxxxxxxxxxxxx
Subject: [Linrad] Linrad network connections

Today I've been playing with the Linrad+MAP65 combination, in
preparation for making some demonstrations at the EME Conference in

I noticed something that may be interesting to others on this list.

You'll recall that Linrad serves as a "front end" to MAP65.  Digital
data in the Linrad "timf2" format, taken after the first inverse FFT,
are sent over an ethernet connection to MAP65.  The default Linrad code
does this transfer in the form of multicast UDP packets.  Multicast
means that there is one source of packets -- Linrad -- and in principle
there may be many receivers.  Many months ago I changed my working copy
of Linrad (version 02.34) so that instead of multicast it uses
"unicast".  That is, data are sent explicitly to a single IP address,
that of the machine running MAP65.  This resulted in more reliable data
transfer -- and also, even more importantly, it prevented swamping my
local network with Linrad traffic so that my wife could not use the
network to check her email, etc.

Today I discovered another big advantage of sending unicast rather than
multicast packets.   On my network, at least, multicast transfers make
*much* more RFI.  Every packet transfer is clearly audible on an HF
receiver tuned to the 30 m band.  I don't hear anything at all when I
switch to making transfers to a single IP address.

	-- 73, Joe, K1JT

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