The best we had until Collins introduced the noise blanker was noise
limiters. But usually they produced some distortion. A few had a means of
self adjustment so that they would not produce much distortion but clip the
noise pulses. Drake's early noise filters did not work very well because
they followed the crystal filter (8Khz or so) or after the first 50 KHz IF
transformer in earlier models.
Either way the bandwidth was much too small for them to be very effective.
But the Argonaut V's noise blanker (DSP) follows the last IF filter which
is not so wide either.
73
Bill wa4lav
At 10:54 AM 7/17/2003 -0500, you wrote:
>It is interesting to recall that the Collins and Drake rigs, noted for
>excellent noise blankers for the times, both used separate 40 MHz receivers
>to obtain the noise signal through a wide passband and then use the derived
>blanking pulse in the actual receiver narrow IF chain. Modern receivers try
>to do this prior to the first narrow IF filter, but most do not seem to do
>as well as the old timers.
>
>But, the next time you feel like complaining, come with me back to the
>mid-40's when ignition noise would eat 10 meters alive if there was a car
>within a mile. Then came the Twin Noise Squelch and the other noise limiters
>as they were called back then. My National HRO-5TA1 had a Noise Limiter knob
>on it, a simple peak amplitude limiter - miraculous! I don't recall that we
>had any true blankers prior to the Collins and Drake rigs, but those days
>are dim now . . .
>
>I'll take today . . .
>
>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: "Bill Fuqua" <wlfuqu00@uky.edu>
>To: <tentec@contesting.com>
>Sent: Thursday, July 17, 2003 10:30 AM
>Subject: RE: [TenTec] field day from hell
>
>
> > The Human ear and its associated processor (the human brain) works very
> > well. I wonder if there has ever been a real study on the usefulness of
>DSP
> > in communications situations where adaptive noise reduction is used. It
> > perhaps may reduce strain and fatigue by performing some pre-filtering for
> > the operator.
> >
> > By the way. I never got an answer about the "noise blanker" in the new
> > Argonaut V.
> >
> > I was wanting to hear from someone who has been able to compare the noise
> > blanking function of the Argonaut V with some other radio with an
>effective
> > noise blanker. The one in the Argonaut V is not a real noise blanker. It
> > uses the DSP. And by doing the noise pulses have been passed thru a fairly
> > narrow bandpass filter that convolutes the high amplitude narrow pulses
> > into low amplitude, long pulses that are difficult if in not impossible
> > to to actually blank out.
> >
> > If someone can do a side by side comparison of the Argonaut V and another
> > radio with a good noise blanker and email the results to me, I would
> > appreciate it. This is one reservation I have about buying an Argonaut V.
> >
> > 73
> > Bill wa4lav
>
>
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