I wonder about that too. I've got 3 different receivers. Recently while
using the same antenna and switching each receiver on line at a time I can
clearly tell there is a difference in the way a single CW signal sounds.
Tuning off of the signal some 100 or so Hz again I here clicks but different
from one receiver to another. I attribute this to differences in filters,
band flatness, slopes and shape factors. Also, I can hear that AGC
attack/release times have some effect. This was proven by turning off the
AGC on each receiver and adjusting the RF gain for a "common" signal level
as best the ear could tell. At the same time it makes me wonder why the
receivers are sounding different on the same signal. Oh yes, I can use the
same speaker or headphones on each one. No difference in results......but
do observe different sounds. May be BFO purity or jitter in the receivers.
Then there's IM which is an artifact of the mixer products. Something else
to consider in the receiver.
So now I wonder. Just how do I give a truthful and meaningful CW report.
I'm now not sure. Should that be a 598.5 or maybe a 598.7 or maybe a 597.9.
And then do I add a C or maybe K to it? But surely somewhere out there is
a 599.0 X signal.
In tuning between signals I do hear clicks but I'm beginning to wonder if
part of that is not receiver artifacts based on the above. Some of them
almost just have to be. On the other hand, clearly some are transmitter
generated.
73
Bob K4TAX
----- Original Message -----
From: "Steve Ellington" <n4lq@iglou.com>
To: "Carl Moreschi" <n4py@earthlink.net>; <tentec@contesting.com>
Sent: Thursday, January 31, 2002 7:47 PM
Subject: Re: [TenTec] Re: FYI - key click thread on Ten-Tec reflector
> I'm not sure about the 340 but certainly, DSP filtering has given us the
> ability to really hear those clicks. This was mentioned in a QST review of
> one (IF) DSP reveiver. At first listen, they though the filtering was
> somehow creating the clicks but later decided that the clicks were
actually
> there and had been overlooked while using standard crystal filtering. On
the
> TS-870, I can set the filter at 100 or 50hz, get in between signals and
hear
> nothing but clicks.
> So what I'm asking is: Are rigs clicking more these days or are we just
able
> to hear them better with the brick wall dsp?
> Steve Ellington
> N4LQ
> ----- Original Message -----
> From: "Carl Moreschi" <n4py@earthlink.net>
> To: <tentec@contesting.com>
> Sent: Thursday, January 31, 2002 7:30 PM
> Subject: Re: [TenTec] Re: FYI - key click thread on Ten-Tec reflector
>
>
> > I would just like to add that last weekend I listened a lot to
> > the 160 meter CW contest. Using the Rx340 filters even down to 100
> > hertz, I found key clicks were all over the band. It was easy to find
> > places where there were no CW tones, but impossible to find places
> > where there were no key clicks. It seems as though most rigs now
> > generate excessive clicks.
> >
> > Carl Moreschi N4PY
> > Franklinton, NC
> > ----- Original Message -----
> > From: "Tom Rauch" <w8ji@akorn.net>
> > To: <tentec@contesting.com>
> > Sent: Thursday, January 31, 2002 2:47 PM
> > Subject: [TenTec] Re: FYI - key click thread on Ten-Tec reflector
> >
> >
> > > > >From W9AC:
> > > > "Correct to the extent that CW bandwidth may be minimized. I don't
> > > > necessarily agree with Tom's view that the "correct" CW waveform is
> > > > one in which the transmitted bandwidth is minimized by extending the
> > > > rise and decay of the envelope and turning the wave edges into a
> > > > sine-slope characteristic. The problem with Tom's approach is that
in
> > > > minimum signal conditions and at relatively high CW speeds, his
> > > > preferred wave form becomes difficult read. In essence, the
"correct"
> > > > CW wave form is purely subjective.
> > >
> > > That is not true by any observation I have gathered in well over 50
> > > tests when my signal was weak on 160 meters.
> > >
> > > I now use a waveshape that is similar to a sine rise and fall, and no
> > > one so far can tell any difference at all when I "square it" except
> > > the people up or down a few kHz.
> > >
> > > I work just as much DX when my signal is marginal, and when I do
> > > an A-B test no one so far can tell the difference unless I AM
> > > strong.
> > >
> > > What proponents of wide bandwidth-wasting clicking CW signals
> > > forget is that the ear and the receiver system up to your ear, unlike
> > > a power meter, does not measure or store "average power" or
> > > accumulated power. Until the accumulated rise and fall time
> > > approaches the width of a "dit", it makes no difference at all in
> > > weak signal copy.
> > >
> > > We have to have some respect for other people on the bands. As
> > > far as I am concerned, people can click and clack all they like as
> > > long as they respect my space, and stay a few kHz away from all
> > > other operators on the band...especially weak signals.
> > >
> > > > "My preference is for a fast leading edhe in the order of 1.5 mS,
and
> > > > a trailing decay in the order of 5-6 mS, much the same as is often
> > > > shown in the older ARRL handbooks when grid-block keying is used.
> > >
> > > That will click, and occupy excessive and unnecessary bandwidth.
> > > The closest possible sideband would be almost 700Hz away, no
> > > matter what speed you are sending. Even if you used a filtered sine-
> > > shaped envelope, your signal would be 1.5 kHz wide. With a
> > > normal single pole R/C filter, which gives the poorly filtered
> > > waveshape the handbook calls "ideal", you would have garbage out
> > > a few kHz each direction every time the envelope rose. That
> > > garbage would be there no matter if you sent one word per minute,
> > > or a hundred words per minute.
> > >
> > > While you may "like hearing" an excessively-short clicking rise
> > > time, it is poor engineering and wasteful of spectrum to transmit
> > > that way on crowded bands. It is poor form to promote something
> > > that will cause all CW signals to be well over 1.5kHz wide.
> > >
> > > > This produces a percussive CW note with a slight "bell-sound." No,
it
> > > > is not as spectrally pure as what Tom suggests, but the note is very
> > > > distinctive and easy to copy. A bit of extra bandwidth can
sometimes
> > > > be a good thing."
> > >
> > > I'm sure it is a "good thing" for some of us when we are dishing it
> > > out. For one thing it ensures others can't stand operating within a
> > > kHz or two of you. When we are on the receiving end of the
> > > needless clicks, it isn't so wonderful!
> > >
> > > My goal is to have a click-less signal that occupies no more
> > > bandwidth than necessary.
> > >
> > > There is no logical reason in the world for a CW signal to occupy
> > > more than a few hundred Hz of bandwidth.
> > > 73, Tom W8JI
> > > W8JI@contesting.com
> > > _______________________________________________
> > > 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
>
|