Bob,
I rarely quote an entire email, but your post says so many important
things, and says them so well, that I want to emphasize them.
I have an Elecraft P3, which is a very nice, calibrated spectrum
analyzer, looking at the IF on both of my K3s. I often see signals
that are so broad that they are in violation of FCC Rules for spurious
emissions by a wide margin. I've also got an HP spectrum analyzer.
IMO, it is advertising dollars that cause ARRL to ignore this in their
product testing, and I think it's long past time that we call them on
it. I'd guess that more than half of the rigs they have tested fail to
meet FCC Rules when driving power amp.
73, Jim K9YC
On 4/23/2014 4:55 PM, Bob McGraw - K4TAX wrote:
I too found that I got great audio or great signal reports with one of
my radios. Those glowing audio reports are "on frequency"
reports. I looked at the real output of a radio on my desk and saw
all the crap being generated and transmitted some 20 kHz to 30 kHz
away. I find it is the "off frequency" thus adjacent noise and IMD
products that create a lot of unnecessary noise and pollution on the
bands. And as users, it is difficult to find the source in many
cases. For normal operation I use a spectrum analyzer connected to
the receiver bandpass filter. With that configuration one can see
much of the noise being generated as a certain signal appears and
disappears thus correlating the noise change.
As and example, look at the numbers. Take a given strong signal that
is S-9 + 20 dB at your receiver. Then presume his IMD products are
only 35 dB down. That then says his IMD products are equivalent to a
S-6 signal. I realize that in many cases our local noise level is
S-6 but be assured, that stations presumable IMD products contribute
to the local noise level as well.
I own one current production and very popular brand/model radio. When
this radio is in transmit the noise on all HF bands increase 10 dB to
20 dB. That's right, transmit on 160M and the noise on 10M increases
10 dB. Put it in a Field Day environment and you'll likely learn some
new vocabulary words from other operators. Put that radio on the same
band as another radio and when it is transmitting the other radio on
the same band is totally deaf.
Yes, it is time to start a clean up of our spectrum. Unfortunately,
many of the older radios are major contributors and even some of the
new current technology ones aren't much if any better. And then
there's the operator issues, taking a marginally spectrally clean
radio and adding 10 dB to 12 dB of gain via a linear amp that may not
be tuned correctly thus amplifying and generating more pollution.
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