Not to confuse the issue, but the original topic of what to change when
adding or changing filters suggested to me that the questioner was concerned
about "carrier oscillator insertion frequency" rather than "carrier
balance."
Carrier insertion in a conventional - not an IF-DSP - rig concerns the
placement of the (suppressed) carrier frequency relative to the passband of
the filter used for transmit and receive. Since the same filter is used for
USB and LSB, the filters are made with the passband flanks as nearly
identical as possible.
The frequency range of the baseband audio signal recovered from the received
signal as it is passed through the filter depends upon where the insertion
oscillator frequency is placed relative to the passband of the filter.
Similarly on transmit, the "pitch" of the voice signal depends upon where
this oscillator frequency is located on the slope of the filter response
curve.
If the frequency is too high or too far up on the slope, the signal will
sound "bassy" compared to having the insertion frequency lower on the slope.
Usually the insertion frequency is critical in another respect: having the
USB and LSB transmit and receiver audio sound the same. To the extent that
the filter slopes are symmetrical and the insertion frequency is correct,
the two modes will sound very nearly the same. If the oscillator is too high
or too low, one mode will sound higher pitched than the other and
conversely.
A great advantage of the IF DSP architecture is that none of these signal
generation and demodulation operations is done with analog oscillators and
filters. Everything is done by software calculations. The phasing method of
ssb is used and no filters are involved in either generating or demodulating
an SSB signal. One less set of problems!
Hope this helps.
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: <tlogan7@cox.net>
To: "Mike J Maloney" <ac5p@juno.com>
Cc: <tentec@contesting.com>
Sent: Tuesday, April 15, 2003 10:17 AM
Subject: Re: Re: [TenTec] Re: inrad filters
> Mike -
> That's what I needed - a place to start! Thanks very much. I do appreciate
it and I will check the handbook now :-)
> 73/Tim NZ7C
> >
> > From: Mike J Maloney <ac5p@juno.com>
To: <tentec@contesting.com>
> > Date: 2003/04/15 Tue AM 10:53:06 EDT
> > To: tlogan7@cox.net
> > Subject: Re: [TenTec] Re: inrad filters
> >
> > It is associated with the balanced modulator. This device mixes the
> > audio from the speech amp to create the RF sidebands and also balance
out
> > or null the carrier which is not desired. The carrier balance is
> > adjusted for optimum carrier suppression. Check your handbook chapter
> > Single Sideband, under carrier oscillator and balanced modulator for
> > greater details.
> > 73, Mike, AC5P
> >
> > On Mon, 14 Apr 2003 19:33:25 -0700 <tlogan7@cox.net> writes:
> > > Barry -
> > > What exactly - in very simple terms - does "adjust carrier balance"
> > > mean?
> > > Or, what topic should I look under in the Handbook to teach myself?
> > > Sorry
> > > I'm so ignorant about this.
> > > Thanks and 73/Tim NZ7C
> > > ----- Original Message -----
> > > From: "Barry N1EU" <n1eu@yahoo.com>
> > > To: <tentec@contesting.com>
> > > Sent: Monday, April 14, 2003 7:29 PM
> > > Subject: [TenTec] Re: inrad filters
> > >
> > >
> > > > I believe Inrad specifically advises to check/adjust
> > > > the carrier balance when installing the Inrad 2.8Khz
> > > > filter in the 9Mhz i.f. I own an oscilloscope so this
> > > > was very easy to do.
> > > >
> > > > Many folks also like to adjust the carrier offset in
> > > > order to optimize the hi/lo cutoffs of the audio
> > > > passband.
> > > >
> > > > And then some folks who aren't as concerned about
> > > > optimal performance probably just drop in the filter
> > > > and forget about it. If you do this you should at
> > > > least solicit signal reports for the presence of
> > > > unsuppressed carrier.
> > > >
> > > >
> > > > 73,
> > > >
> > > > Barry N1EU
> > > > www.n1eu.com
> > > >
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> >
> >
>
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