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LF: Re: WOLF??

To: <[email protected]>
Subject: LF: Re: WOLF??
From: "James Moritz" <[email protected]>
Date: Mon, 30 Jan 2012 00:40:07 -0000
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Dear Stefan, LF Group,

Hmmmmmmmmmmmm, so what about a WOLF VLF test? Can the program easily be
configured to transmit at 8970 Hz? I.e. does it generate a tone at that
frequency? Please confirm that no linear mode PA is needed. Wolf 10,
means 10 Hz bandwidth?

Wolf is binary phase shift keying at 10 bits per second. This does not *require* a linear PA, provided the PA does not explode when the phase in the tank circuit is reversed abruptly. But to achieve the 10Hz bandwidth, envelope shaping is required in the same way as PSK31, which is also BPSK.

Leaving out the envelope shaping results in "key clicks" when the phase transitions occur, and a wider bandwidth. One can ask the question "does this matter?" Probably yes it does if you are running 1kW on 136k. But there are plenty of clicks on VLF already, so I doubt anyone would notice at 9kHz ;-) Certainly, the US "Lowfer" LF stations with their 1W TXs used Wolf successfully with class D or E amplifiers and no envelope shaping.

You could use a linear PA to generate the envelope-shaped signal. In the 2001 tests I used the Decca class D PA with the DC supplied via a high level series modulator, in conjunction with a phase modulated carrier, to generate the amplitude-modulated BPSK. The transmitter used dedicated waveform-generating hardware, with the binary message code burned onto an EPROM. With WOLF GUI, at least changing the transmitted message should be quicker...

Cheers, Jim Moritz
73 de M0BMU



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