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Re: LF: RE: looking for first signals ...

To: [email protected]
Subject: Re: LF: RE: looking for first signals ...
From: "James Moritz" <[email protected]>
Date: Sat, 22 May 2004 09:57:53 +0100
References: <[email protected]> <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Hi Jim,

your PSK signs are audible in jo43sv. but qrn makes them almost
see attachment.

btw. what type of transmitter do you use for the PSK mode?

Dear Uwe, LF Group,

Thanks for the report - I transmitted CW/QRSS3 from 1900 - 2100 and 2200 -
2300, and PSK31 from 2100 - 2200. As you observed, the drawback of PSK31 on
LF is that every QRN impulse gives you a 50-50 chance of corrupting a bit,
and so losing the character. A mode using error correction works better -
like VE2IQ's "Coherent" program for example.

The TX in use here is the usual class D Decca PA - to get a clean signal, I
use an "envelope elimination and restoration" scheme, where the 136kHz drive
to the PA is phase modulated, and amplitude modulation is applied to the DC
feed to the PA. The phase keying signal is generated by the "Digimode
terminal" in DL4YHF's Spectrum Lab software, and the envelope waveform is
generated from the phase signal by external hardware.

Cheers, Jim Moritz

73 de M0BMU

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