LF: Re: WOLF??

["James Moritz" <james.moritz@btopenworld.com>]

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