Thanks for the additional detail, Joe.
Between you and Bill, maybe I will soon be "educated" enough to totally
understand these modes. Ed, K0KC
[email protected]http://k0kc.us/
From: Joe Taylor <[email protected]>
To: WSJT software development <[email protected]>
Sent: Saturday, January 2, 2016 11:09 AM
Subject: Re: [wsjt-devel] WSJT-X 1.7.0 r6333 Decoder Performance
Hi Ed,
K0KC wrote:
> I am currently testing WSPR-2 with WSJT-X 1.7.0 r6333 on 30 meters.
> I am getting multiple decodes at -30 dB. Seems like all of the
> hard work that the development team has put into this release
> has paid-off.
> I wonder how this performance translates to JT65 and JT9; I can
> see improvement, but nothing as good as -30 dB.
It should hardly surprise you that WSPR can be decoded at lower S/N than
JT65, JT9, or JT4. WSPR conveys 50-bit messages in approximately 111
seconds, while the other modes convey 72-bit messages in 47 s. If other
things were equal, this suggests already an advantage for WSPR of
10*log(72/50) + 10log(111/47) = 5.3 dB.
Of course, other things are not precisely equal in these four modes. In
return for using significantly more bandwidth, JT65 gains nearly 2 dB by
using a more efficient modulation: 65-FSK, vs 4-FSK for WSPR and JT4.
JT9 gains a slightly smaller amount by using 9-FSK modulation, but it
gains additionally by using only 19% of transmitted energy to establish
time and frequency synchronization. The other modes all use 50% of Tx
energy for this purpose.
-- 73, Joe, K1JT
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