[TenTec] AM, was "Just noticed ..."

[geraldj]

Some SW AM Broadcasters have been running SSB AM for years.

73, Jerry, K0CQ


---------- Original Message -----------
From: Ken Brown <ken.d.brown at hawaiiantel.net>
To: Discussion of Ten-Tec Equipment <tentec at contesting.com>
Sent: Mon, 12 Jun 2006 17:07:23 -1000
Subject: Re: [TenTec] AM, was "Just noticed ..."

> Joel,
> 
> Yes I see what you mean. Using the same amount of power in the remaining 
> sideband as was in that sideband before would result in the same SNR. I 
> wonder about doubling the power in one sideband and eliminating the 
> other. Same total amount of sideband power, just not two sidebands. 
> Would the same carrier level be sufficient for demodulation? It may be 
> that with DSB the two opposite sideband's power peaks occur in opposite 
> phases of the modulating audio, not simultaneously. If all that power 
> were put into a single sideband the total instantaneous peak power level 
> in that one sideband would be twice what you had with DSB, requiring 
> twice as much carrier for proper demodulation. Someone better versed in 
> the mathematics of modulation could clarify this.
> 
> DE N6KB
> 
> joel hallas wrote:
> > Ken,
> >
> > I guess it depends on what you assume about the way the signal power is 
> > generated. You assume that the sideband power will be twice as high as 
> > the power in each sideband of a DSB-AM signal. I assumed that the signal 
> > power in the remaining sideband would be the same as it was in the 
> > DSB-AM case, that is that the DSB-AM signal was generated at 100% 
> > modulation and then one sideband was loped off by the filter. Thus the 
> > noise power (by going from 6 kHz to 3 kHz BW) and signal (sideband) 
> > power are both cut in half so the SNR remains the same.
> >
> > I guess if the transmitter were peak power limited, you could increase 
> > the remaining sideband power by a factor of two and keep the same 
> > carrier, but I suspect that the receiver would have some problems 
> > demodulating without distortion.
> >
> > Regards, Joel
> >
> >
> >   
> >
> 
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------- End of Original Message -------