Hi, Steve--
Here ya go. For years I used first a Heathkit HW-101 and then an
SB-102. My friends kept urging me to get into the modern world, so
about a year after it came on the market, I bought a Yaesu FT-757. It
was everything a ham could want -- a QSK rig with a CW filter and
built-in keyer. . . But the keyer wouldn't go over 25 wpm and even at
that speed the dots were all choppy. I used the rig with an external
keyer.
As time went on, I noticed that I was operating less. One day when I
turned the rig off, I noticed that my body seemed to relax.
Investigation showed several things, first that the rig was not able to
hear weak signals on 10 meters (even with the RF pre-amp switched on)
that my SB-102 could hear. The biggest thing I noticed was that on a CW
signal, there was a fuzziness -- a weak hashy noise -- modulating the CW
note. With most rigs, as the signal gets stronger the noise diminishes
but not so with this noise, the stronger the signal the stronger the
noise.
Listening to that rig would make the muscles in my body begin to tense
until I would wind up with a headache. I drop-kicked the rig out the
shack window and replaced it with a Triton 544 -- no more headaches, no
more choppy dits.
I know that since that time the manufacturers have gotten better with
the noise problem -- the "phase noise" perhaps. But I question whether
they have gotten rid of it. The thing to remember is that the human
ears and eyes are able to discern things that instruments often can not
measure and the human brain can discern things that we are not aware of.
The ARLL can run all the tests in the world comparing rigs but the only
true test is to sit two rigs side by side in the shack and use them.
After a while, I notice that I tend to use one rig much more than the
other. I often don't know why and can't articulate a reason, but
something about the way the rig sounds or the ease of operation will
lead me to use it instead of the other.
73, Mike
----- Original Message -----
From: "Steve Ellington" <n4lq@iglou.com>
To: <al_lorona@agilent.com>; <tentec@contesting.com>
Sent: Sunday, April 07, 2002 9:39 AM
Subject: Re: [TenTec] Rig Chart
| I had a choice of 50khz or 20khz and chose the 20khz spacing. As for
"phase
| noise", I've heard it discussed for years and I'm still not sure what
it
| sounds like unless it sounds like the transmitter products emitted by
the
| Pegasus/Jupiter.
| Steve Ellington N4LQ.
| ----- Original Message -----
| From: <al_lorona@agilent.com>
| To: <n4lq@iglou.com>; <tentec@contesting.com>
| Sent: Sunday, April 07, 2002 1:53 AM
| Subject: RE: [TenTec] Rig Chart
|
|
| >
| > In the last few years I have become convinced that the two-tone 3rd
order
| > dynamic range numbers in ARRL reviews measured with a 20 kHz tone
spacing
| > are absolutely irrelevant in demanding amateur radio conditions. The
two
| > tones have to be much closer together in order to get a better idea
of
| what
| > the receiver will tolerate. I'm glad to see that the ARRL is
apparently
| > getting the message, as I heard recently they were going to start
| measuring
| > it with something like a 5 kHz spacing. We should publish the 5 kHz
specs
| > for each of the receivers in Steve's chart.
| >
| > I define 'demanding conditions' as similar to those in a contest
where
| there
| > are lots of very strong signals very close to the frequency your
receiver
| is
| > tuned to.
| >
| > I'm going to assume that the rest of the DR specs were all measured
with
| the
| > same receiver bandwidth, although Steve's chart does not explicitly
state
| > this. If not, the numbers don't mean anything to me.
| >
| > Every one of the receivers listed has way more than enough
sensitivity for
| > any of the HF bands. Since about 1980, MDS numbers have been
rendered
| > irrelevant.
| >
| > An important spec missing from the chart is that of local oscillator
phase
| > noise, which is difficult to measure and even more difficult to
explain
| > exactly what it does to the way a receiver sounds. In general, the
more
| > phase noise, the more problems that poses to a receiver. One of the
| > by-products of phase noise is reciprocal mixing. You can definitely
hear
| it,
| > but describing what it sounds like is hard. That's why during the
recent
| > thread about which receiver was 'quieter' I kept telling myself one
of the
| > parameters going into such a qualitative spec has to be the effects
of a
| > receiving system's phase noise; hence the difficulty in quantifying
the
| > receiver's 'quietness'.
|