Re: LF: RE: something for the weekend ??

[DL4YHF@aol.com]

Hi Steward, Andy and group,


> I am not sure about the physics of this.
>
> The 90deg phase shifter has to be some sort of dispersion
> device (propagation time varies with frequency), and this
> will operate on the fourier components of the waveform.
>
> The fourier components present are sin(a+b) and sin(a-b),
> not the complex waveform cos(a)*sin(b).
>
> Therefore the phaseshift will apply individually to
> sin(a+b) and to sin(a-b).
>
> Can we go back to the physical device itself, and confirm
> that the IF phase shifter is shifting by 90deg (as opposed to
> say 270deg) and that you can select both sidebands
> properly with the add/subtract?
>
> Stewart G3YSX


Thanks for the correction, accepted ! To delay a 'broadband' signal 
    cos(a) * sin(b)

by simply substituting it with
    cos(a+90°) * sin(b+90°)
was a mistake by myself; it would be ok if there wasn't that multiply thing in between ;-)

However, Andy's 2nd diagram does work, it is also shown in the ARRL handbook. Think I'll have to find my old math textbook, pre-heat the brain with a good cup o' coffe and make another attempt..

Cheers,
 Wolf.