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Re: LF: WOLF bandwidth suggestions

To: [email protected]
Subject: Re: LF: WOLF bandwidth suggestions
From: "Stewart Nelson" <[email protected]>
Date: Tue, 17 Apr 2001 11:37:36 +0200
Organization: SC Group
References: <[email protected]>
Reply-to: [email protected]
Sender: <[email protected]>
Hi Rik and all,

The real loss is indeed worse than 0.8 dB, but is extremely unlikely to
come anywhere near 3 dB.  That's because the message data is interleaved
with a pseudo-random stream which is known to contain 240 zeros and 240 ones.
Also, one message bit affects more than 40 coded bits.  If you flip 40
coins, the chance of getting say, fewer than 10 heads is only about 1 in
3000.  The WOLF web site gives the degradation for '-t 1' as 1.5 dB, which
I believe is conservative.

73,

Stewart KK7KA

----- Original Message ----- From: "Rik Strobbe" <[email protected]>
To: <[email protected]>
Sent: Tuesday, April 17, 2001 8:58 AM
Subject: Re: LF: WOLF bandwidth suggestions


Hi Marcus & group,

>1. WOLF is using cosine-shaped zero-crossings with a risetime of only 5 ms, >which causes a few extra sidebands on each side of the spectrum. I'd prefer >to extend the cosine-envelope to the full symbol duration (like in PSK31), >then ideally only the 10 Hz wide main spectral lobe would persist. At a given >PEP level and with 50% phase transitions, on average we'd lose only 0.8 dB >SNR while saving 24% transmitted energy.
You are right about the average value, but for a '0101' sequence the signal
will be 3dB down. And as it is of very little use if you can decode
sequences like '111000111' but you cannot decode a '010101010' sequence I
believe that that the effective loss of SNR is 3dB, even if the average
power is only 0.8dB down.

73, Rik  ON7YD




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