You have described one of the several heartburn areas in the R&O.
Determining compliance with the "50 watts ERP" with an arbitrary antenna
setup is another.
I think that the intent of the language is to state that the available
channel bandwidth that can be used is a maximum of 2800 Hz, centered on a
specified frequency for each channel. It is up to each operator to figure
out where to set his dial for each channel so that *his* SSB sideband will
lie within the channel.
I also think that you hit the nail on the head about stations with different
equipment working one another on these channels. The primary service
probably uses essentially identical equipment and thus, per government
convention, when they set their transmitter to Channel X, the USB suppressed
carrier frequency is set to the same value for all such transmitters.
But, in the ham case, we each have slightly different occupied bandwidth
characteristics and so it is highly likely that there will be frequency
errors if one simply follows the math and sets his dial according to his own
transmitter passband, as in your example.
I have made spectral plots of the occupied bandwidth of each filter setting
I use on my equipment, so I can estimate what dial frequency to use with,
say, my 2.4 KHz filter setting. But even there, *my* 2.4 KHz filter (being
DSP) may have different characteristics than *your* 2.4 filter, so chances
are we would end up on two different suppressed-carrier frequencies.
Carl, maybe the answer is this simple:
Forget about where our equipment has its transmit bandwidth (how
measured: -6 dB?) placed with respect to the carrier frequency. Let's just
all use the same frequency, calculated by subtracting 1.4 KHz from the
"channel center frequency." By keeping the bandwidth conservatively below
the allowed maximum of 2.8 KHz we would all at least be on the same
frequency.
This "band" is going to be a real problem with people changing their dial
settings so that Charlie sounds more natural and in so doing they can slide
right out of the channel.
What do you think?
73/72, George
Amateur Radio W5YR - the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
"In the 57th year and it just keeps getting better!"
<mailto:w5yr@att.net>
----- Original Message -----
From: "Carl Moreschi" <n4py@earthlink.net>
To: <tentec@contesting.com>
Sent: Friday, May 16, 2003 6:24 AM
Subject: Re: [TenTec] 60M
> Don't forget that most radios don't start the bottom end of the passband
at
> 0. It is usually 200 hertz . So if you are using a 2800 hertz filter and
> the bottom of the passband is 200 hertz, then your desired frequency is
200
> + 2800/2 or 1600 above the dial frequency. It seems like everyone would
be
> on a slightly different frequency depending on how their radio passband is
> designed and transmit filter they are using in order to center their SSB
> emission at in the prescribed channel.
>
> Carl Moreschi N4PY
> Franklinton, North Carolina
> n4py@earthlink.net
> ----- Original Message -----
> From: "George, W5YR" <w5yr@att.net>
> To: <tentec@contesting.com>
> Sent: Friday, May 16, 2003 6:33 AM
> Subject: Re: [TenTec] 60M
>
>
> > The government and the military, in short.
> >
> > They specify frequency in terms of the center frequency of the occupied
> > bandwidth or channel width. Hams use the transmitted frequency for all
> > carrier-present modes and the suppressed carrier frequency for SSB,
SSTV,
> > etc.
> >
> > So, if a channel is 2.8 KHz wide and the FCC defines the center
frequency
> > for the channel - and the R&O clearly says "center frequency" - then the
> way
> > our rigs are set up, we have to set the dial to that specified center
> > frequency and then lower the reading by 1400 Hz to put our
> > suppressed-carrier frequency on the lower-frequency edge of the channel
> such
> > that our occupied bandwidth will run from that edge upward 2.8 KHz.
> >
> > It *is* different! <:}
> >
> > 73/72, George
> > Amateur Radio W5YR - the Yellow Rose of Texas
> > Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
> > "In the 57th year and it just keeps getting better!"
> > <mailto:w5yr@att.net>
> >
> >
> >
> >
> >
> > ----- Original Message -----
> > From: "Kip Glunt" <kipg@yorkinternet.net>
> > To: <tentec@contesting.com>
> > Sent: Friday, May 16, 2003 1:15 AM
> > Subject: Re: [TenTec] 60M
> >
> >
> > > I'm curious, when did the center of a Single Sideband signal
(presuming
> it
> > could have an upper or lower sideband) become the specified frequency
plus
> > or minus 1400 KHz.? Where did this come from?
> > >
> > >
> > > ... Kip, WB3AFL
> > >
> > >
> > >
> > > _______________________________________________
> > > TenTec mailing list
> > > TenTec@contesting.com
> > > http://lists.contesting.com/mailman/listinfo/tentec
> >
> > _______________________________________________
> > TenTec mailing list
> > TenTec@contesting.com
> > http://lists.contesting.com/mailman/listinfo/tentec
>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
|