George -
Thank you. Is the insertion frequency the same thing as the center frequency?
In my original question I mentioned that there were TWO Inrad 400Hz filters -
one with a 9000.6 center freq - and the other with 9000.7. I completely
understood your note, but I do not know if the center freq is the same as
insertion freq. PS - you sly dog - had to slip in a mention of one of the
benefits lost when I sold the PRO II hi hi! As always, thanks George - much
appreciated!
Regards, Tim
>
> From: "George, W5YR" <w5yr@att.net>
To: <tentec@contesting.com>
> Date: 2003/04/15 Tue PM 01:12:25 EDT
> To: <tentec@contesting.com>, "Mike J Maloney" <ac5p@juno.com>
> CC: tentec@contesting.com
> Subject: Re: Re: [TenTec] Re: inrad filters
>
> 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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