[HCARC] Fwd: [cwops] Signal Cleanliness

[Don Murray via HCARC]

Hello all...
 
A VERY GOOD presentation on SIGNAL CLEANLINESS
from K6XX and K9YC...
 
A "MUST" read....
 
 
73
Don
W4WJ
 
 
  
____________________________________
 From: k9yc at audiosystemsgroup.com
Reply-to: k9yc at arrl.net
To:  cwops at yahoogroups.com
CC: cwops at yahoogroups.com
Sent: 4/27/2014 2:08:35  P.M. Central Daylight Time
Subj: [cwops] Signal Cleanliness



 
 
On 4/25/2014 10:26 AM, k6rb at baymoon.com wrote:
> and one uses an  IC-7600.

Rob,

KE1B is the guy with the 7600, and the combination  of phase noise and 
clicks chews up about 5 kHz of any band where he is  working CW, at least 
twice that on SSB. He's 8 miles from me, K6XX is  three miles away, with 
K3s and tube amps. K6XX and I can work 500 Hz apart  on CW, and if we 
hear each other at all, it's as a high pitch signal  outside our passband 
-- no clicks, no phase noise, no IMD products.  Looking on a P3, Bob (XX) 
is -60dBc at 350 Hz. KE1B is only 30 or so down  at 500 Hz. I use my K3s 
with a pair of the original Ten Tec Titans. On  KE1B's signal, I see (and 
hear) clicks, phase noise, and IMD.

There  are HUGE differences in the cleanliness of popular rigs. The 
IC7600 is a  terror, thanks to phase noise, IMD, and the fact that CW 
rise time is  adjustable by the user, with the factory default setting 
being pretty  fast. K6XX is an engineer at Elecraft, has worked on their 
amps, and as  part of the preliminary design work, studied many existing 
power amps.  Last fall, Bob gave a presentation to NCCC about "clean 
signals," to which  I contributed with on-air P3 traces to illustrate the 
concepts he  presented, and a short section on audio.

Since I knew from experience  that the 7600 was pretty bad, I arranged 
some on-the-air tests with  another neighbor who owned one, KW6S. We did 
it on 10M, so that QRM and  band noise would not skew the results. They 
are part of the presentation.  You can download it at 
http://k9yc.com/K6XXAmpTalk.pdf

One of the  things Bob showed with bench testing is that most rigs, 
including the K3,  are much cleaner (6 dB typically) at 50W as compared 
to 100W. That comes  into play when we reduce drive power from the rig 
when running a tube amp  -- my Titans need 40-50W for legal limit out, 
and that's how I run them.  My on-air P3 traces of the 7600 also show it.

73, Jim  K9YC


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