From: lancelot@cruzio.santa-cruz.ca.us
Newsgroups: rec.radio.shortwave
Subject: Re: Radio Upgrade Help
Summary: Clarification of original post...and mucho thanks!
Keywords: Synchronous, Exalted Carrier, Recommendations
Date: 2 Sep 92 04:00:03 GMT
Reply-To: lancelot@cruzio.santa-cruz.ca.us
Distribution: usa



Thx to all for their help! My original question was, and I started 
this thread which has  meandered down a back road (or is that 
a sideband? ;@} ), how does Synchronous Detection (as Sony and 
the Drake say they use) differ from Exalted Carrier Selectable 
Sideband? (as the NRD-535 proportedly uses)...

According to Weik (COMMUNICATIONS STANDARD DICTIONARY), 
exalted carrier reception seperates the carrier from the 
sidebands, filters and amplifies it, and then combines (in a 
diversity combiner) the carrier again at a higher level prior 
to demodulation. 

Synchronous detection, as I understand it from the SONY lit 
and others (and my understanding of anything is open to 
question ;@} ) injects a pure carrier signal, with no level 
variation, perfectly synchronized with the original carrier, 
generated in the sychronous detector circuit and mixed with 
the received signal to compensate the attenuated carrier 
componant; thus reducing the distortion due to fading from the 
over-modulation caused by the attenuation of the carrier 
frequency on the way to the the receiver. Also, in the 
synchronous detector circuit, one of the sidebands can be 
received, this allows clear reception without interference 
from adjacent stations.

So, to rephrase my original question and clarify somewhat ;@}: 

1- I take it that in synch detection, the original carrier is
   filtered out at least somewhat completely and replaced with 
   a carrier generated in the synch detector, right? While this
   would eliminate most of the fading, there might be some 
   distortion due to the discrepancy between the "constant"
   locally generated carrier and sideband attenuation as it 
   travels to the receiver. I believe I hear this on my SONY
   2010, though it is minimal and using the synch detector
   improves things vastly! Or is there some feedback mechanism
   whereby the carrier level adjusts automatically to the changing
   signal strength of the sideband? Can anyone show me the actual
   circuit involved and how it works? ;@} Maybe I can get it
   into my thick noggin that way!

2- I take it that in E.C.S.S. the original carrier is preserved
   but vastly improved, correct? Again can anyone show me how the
   actual circuit works, especially the diversity combiner part?
   Why did NRD choose to go with this circuit rather than synch 
   detection? I have heard from one source, though another denies 
   it, that the NRD has a tendency to diminish audio output when
   the ECSS is kicked in, correct or no? It seems to me that this
   might be the case though it also seems to me that signal 
   intelligibility might be slightly better with the ECSS scheme...

Sorry to be so overbearing and ask so many questions, but does 
anyone out there want to set me straight please? Thanks very 
much for your help! 
   

-- 
Brett Breitwieser / KC6UPU @ N0ARY.#NOCAL.CA.USA / grid CM86XX
lancelot@cruzio.santa-cruz.ca.us   (...netcom!cruzio!lancelot)
425 Ninth Ave., Santa Cruz, CA. 95062-3915 / (408)475-9156 voice
"Volo ut syntaxis mea splendescat in litore, veniente aestate."      
Newsgroups: rec.radio.shortwave