Return to KLUBNL.PL main page

rsgb_lf_group
[Top] [All Lists]

Re: LF: COHERENT BPSK ON MF

To: [email protected]
Subject: Re: LF: COHERENT BPSK ON MF
From: Paul Nicholson <[email protected]>
Date: Mon, 16 Nov 2015 20:36:39 +0000
In-reply-to: <[email protected]>
References: <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
User-agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130106 Thunderbird/17.0.2
Nice work.

The 22:00 message Eb/N0 is 13.8dB calculated from the symbol
error rate, but when the decode is used to reverse the
modulation so as to reconstruct a steady carrier, its S/N
corresponds to only Eb/N0 = -3.3dB.   Was there a signal on an
adjacent frequency, within the bandwidth of the baseband I/Q but
far enough away from the EbNaut signal not to upset the decode?

Two of the other messages also have suspiciously weak S/N of
the reconstructed carrier.

Adjacent signals wont upset the decoder but will give incorrect
(low) carrier S/N measurements.

The carrier S/N is used to estimate percentage of capacity,
maybe this estimate should instead use the Eb/N0 derived
from the BER so that it's not affected by signals on nearby
frequencies.

There's a big range of signal levels during this QSO, is that
normal for MF?  The phase looks pretty steady on these short
messages so I guess the amplitude should be too.

Perhaps you will try some weaker transmissions. Some of the
signals are 3dB to 15dB too strong to be a challenge
for EbNaut, it is not even having to use list decoding.

--
Paul Nicholson
--

<Prev in Thread] Current Thread [Next in Thread>