[TenTec] THANK YOU AND APOLOGY

[Jim Brown]

On 7/27/2014 12:54 AM, K8JHR wrote:
> I was encouraged by ARRL Lab expert Bob Allison,  who reviewed the 
> same graphs and said,
>
>     "THEY HAVE NEARLY THE SAME COMPOSITE NOISE."

Several points. Mr. Allison is probably not a contester. He is looking 
as a lab tech, not as a user.

Second, they way the data are plotted with all the data at the bottom of 
the graph, it IS hard to see the differences. But when you look at the 
data with a reasonable scale, and plot multiple competing radios on the 
same graph, the differences jump out at you.

Third, I look at this data from the perspective of someone who must 
coexist with all of that noise produced by near neighbors, and others 
with strong signals with crummy radios.

My plot of Bob's data clearly shows the Eagle to be, on average, 5-6 dB 
cleaner than a TS590, depending on how far off frequency you are 
listening. 6 dB is an S-unit, and it corresponds to 4X the transmitted 
noise power. That sure matters to me if I'm trying to copy a weak signal 
buried by someone else's sideband trash!

James, as part of this discussion, I and others have on several 
occasions, observed that the interference between radios consists of 
multiple components, most of which are the result of how the radio is 
built. They are designed in characteristics, the result design decisions 
made by the engineering team to build a product for a defined set of 
functions and cost. That's what engineering is! Rick posted an email 
from N6KR that addressed some of the design decisions he made in 
designing the K3 and KX3 to make both their TX and RX as clean as possible.

Those mechanisms include, but are not limited to, (see, I can get 
lawyerly if I wanna) phase noise in the RX, distortion in the RX 
(measured as intermod -- IMD), and fundamental overload (the interfering 
signal drives the RX to its voltage limits); phase noise and distortion 
transmitted by the other station (composite noise in the ARRL tests), 
his IMD, his key clicks, and overdrive of his audio. The only one of 
these not the fault of the radio's design is the last one -- overdrive 
of audio.

What is phase noise?  It is a byproduct of the frequency synthesizer 
that determines the radio's operating frequency, how much of it is 
present depends strongly on its design. Again, see N6KR's email, which 
Rick has posted here at least twice. It originally ran on the Elecraft 
reflector. Read the ARRL Handbook to learn more.

What is distortion? It is the non-linear behavior of a system (what you 
get out of an amplifier is more than a perfect copy of what you put into 
it), and the "more" consists of harmonics and sideband trash.

Overdrive of the audio also creates distortion, thus sideband trash. 
Overdrive of a power amp also causes its distortion to increase.

ALL amplifiers create SOME distortion (harmonics and sidebands). Study 
the ARRL Handbook to understand why. HOW MUCH distortion is produced 
depends on the design and how it is driven. How much escapes as 
harmonics is determined by bandpass filters, both inside the amplifier 
and outside it.

In an earlier post, you made some snide, cheap lawyerly remarks about a 
radio that was not clean at rated power and had to be run at lower power 
to be clean. The distortion in ALL amplifiers varies with their supply 
voltage (close to their design voltage, more supply voltage = cleaner) 
and output power. Typical ham amplifiers are cleaner at half power than 
at full power. When I use the word "amplifier" here I'm also talking 
about the output stage of a ham transceiver.

And don't tell me that we have not tried to teach you. At least a month 
ago, I posted a link to an excellent tutorial on the topic by K6XX. It's 
still on my website. k9yc.com/publish.htm

73, Jim K9YC