Content-Transfer-Encoding: 8bit
Message-ID: <3.0.1.16.20010327082941.2dc732c6@mail.cc.kuleuven.ac.be>
Date: Tue, 27 Mar 2001 08:29:41
To: rsgb_lf_group@blacksheep.org
From: "Rik Strobbe" <rik.strobbe@fys.kuleuven.ac.be>
Subject: Re: LF: RE: WOLF (BPSK) modulation continuous phase modulation.
In-reply-to: <25798.200103261700@gemini>
References: <3.0.1.16.20010326144713.21b765b2@mail.cc.kuleuven.ac.be> <65AECDF1F89AD411900400508BFC869F9C03FA@pdw-mail-1.dera.gov .uk>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii; format=flowed
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Sender: <majordom@post.thorcom.com>

Hello Jim & LF group,

That is indeed another way to have a look at it. But I would't try to make
a perfect envelloped BPSK signal (that would take a filter with a Q of many
1000) but a signal that has a bandwidth that is approximately the same as
that of a normal CW signal.
The same way as the key clicks are surpressed by soft keying (avoiding
steep slopes) I would try to avoid the 'steep' phase jumps and spread the
180 degrees phase change over a few milliseconds.

73, Rik  ON7YD

At 18:05 26/03/01 +0000, you wrote:
>Dear Rik, LF Group,
>
>Another way of looking at this modulation method is that the high Q 
>tuned circuit acts as a narrow filter which removes the unwanted 
>sidebands of your "rude" BPSK - the signal will certainly be 
>amplitude modulated at the output of the tuned circuit; in fact it will 
>look very similar to the "ideal" envelope-modulated BPSK signal. 
>This is effectively another way of generating the BPSK signal, 
>analagous to generating SSB by the filter method. But 
>unfortunately, any clipping or AGC will distort the amplitude 
>envelope, which in turn will re-introduce unwanted sidebands. 
>
>Of course, if the filter was placed at the transmitter output, this 
>criticism would not apply. But although it is probably possible, 
>producing an antenna tuning network with a loaded Q of 700 would 
>be quite difficult.
>
>Cheers, Jim Moritz
>73 de M0BMU
>
>
>
>