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Content preview:  TU emails from Gaj Kumar and Bob Riese.  RRR.         Re google info, see various coherer designs: https://en.wikipedia.org/wiki/Coherer  Principle of operation:  microwelding in some coherer designs.   I’d think attraction of oppos [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [74.6.130.121 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (mrsocion[at]aol.com) 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: 80dfd4418e586cee7526d670ae10acbc Subject: Re: LF: 160 years of Popov birthday Content-Type: multipart/alternative; boundary="----=_Part_6833228_992845348.1552927227938" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: *** X-Spam-Status: No, hits=3.1 required=5.0 tests=FORGED_MUA_MOZILLA,HTML_50_60, HTML_FONTCOLOR_BLUE,HTML_FONTCOLOR_UNKNOWN,HTML_MESSAGE autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false ------=_Part_6833228_992845348.1552927227938 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable =C2=A0TU emails from Gaj Kumar and Bob Riese.=C2=A0=C2=A0RRR.=20 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0Re google info, see various= coherer designs: https://en.wikipedia.org/wiki/Coherer =C2=A0Principle of = operation:=C2=A0 microwelding in some coherer designs.=C2=A0=C2=A0 I=E2=80= =99d think attraction of opposite charges andsame-directed currents might a= lso be involved with ratio of particle surfacearea to mass this extreme.=C2= =A0 The articlerecognizes that a coherer simply detects presence or absence= of RF so it=E2=80=99s notan AM detector which isn=E2=80=99t used in ham LF= anyway. =C2=A0Presumably, a coherer creates some noise ofits own as the pa= rticles change their constellation of electrical contacts witheach other. =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0Because a coherer is not fr= equency-sensitiveand does undesirably respond to noise peaks, a lot of filt= ering, noiserejection and AGC tied to noise level could need to come ahead = of it. =C2=A0=C2=A0For CWsignals spaced quite some way apart, no problem.= =C2=A0 For FSK and MSK, the filtering would need to bemore exacting.=C2=A0= =C2=A0 Perhaps rake RX as you say.=C2=A0=20 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 With all that, suppose acoherer = could detect presence of signal voltage down to 10% of noisevoltage.=C2=A0 = That would be SNR =3D -20dB -10log10(2500/b.w.)=C2=A0 in a 2.5KHzbandwidth = where b.w. is filter bandwidth in Hertz.=C2=A0=C2=A0=C2=A0=20 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0At the end of the day, why not ju= st use adiode detector or and forget all this.=C2=A0=C2=A0Or do FFT (fast F= ourier transform) and deep error correction like wehave now. =C2=A0No matte= r how you simulate acoherer, it still just detects whether electricity exce= eds some threshold. =C2=A0=C2=A0Pretty solid objections, right?=C2=A0=20 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0Software could simulate particle = sizes evenfiner than any realizable in known coherers.=C2=A0=C2=A0Software = could simulate particle shapes in a more systematic way thanthe randomly gr= ound particles in a hardware coherer.=C2=A0=C2=A0=C2=A0 Software could repr= esent particle responsesindividually to electrical currents and magnetic fi= elds in the coherer thatmight depart from F=3Dma and usual electrodynamics-= -perhaps even diversely as to some particles vis-=C3=A0-vis others. =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0In thisage of nanostructure= s, nanoparticles and quantum mechanical insights, I doubtwe have fully prob= ed the properties and capabilities of colossal numbers ofindividual particl= es to respond collectively to signal and not noise. =C2=A0=C2=A0While there= =E2=80=99s no need to get carried awayover this topic, I think the coherer = concept deserves a seat at the table of LFtopics occasionally, hi. GL & 73, Jim H=C2=A0=C2=A0 W5EST ------=_Part_6833228_992845348.1552927227938 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
 
TU emails from Gaj Kumar and= Bob Riese.   RRR.
      = ;  Re google inf= o, see various coherer designs: https://en.wikipedia.org/wiki/Coherer  Pri= nciple of operation:  microw= elding in some coherer designs. &nb= sp; I=E2=80=99d think attraction of opposite charges and same-directed currents might also be involved with ratio of particle surfac= e area to mass this extreme.  = The article recognizes that a coherer simply detects presence or absence of RF so it=E2= =80=99s not an AM detector which isn=E2=80=99t used in ham LF anyway.  Presumably, a coherer creates some noise of its own as the particles change their constellation of electrical contacts = with each other.
      = ;  Because a coh= erer is not frequency-sensitive and does undesirably respond to noise peaks, a lot of filtering, noise rejection and AGC tied to noise level could need to come ahead of it.   For CW signals spaced quite some way apart, no problem.  For FSK and MSK, the filtering would need to be more exacting.   Perhap= s rake RX as you say.  =
      = ;  With all that, suppose a coherer could detect presence of signal voltage down to 10% of noise voltage.  That would be SNR = =3D -20dB -10 log10(2500/b.w.)  in a 2.5KHz bandwidth where b.w. is filter bandwidth in Hertz.   
       At the end of the d= ay, why not just use a diode detector or and forget all this.&n= bsp;  Or do FFT (fast Fourier transform) and deep error correction like we have now.  No matter how you= simulate a coherer, it still just detects whether electricity exceeds some threshold. =   Pretty solid objectio= ns, right? 
       Software could simulate particle sizes even finer than any realizable in known coherers.   Software could simulate particle shapes in a more systematic way tha= n the randomly ground particles in a hardware coherer.    Software could represent particle res= ponses individually to electrical currents and magnetic fields in the coherer that might depart from F=3Dma and usual electrodynamics--perhaps even diversely = as to some particles vis-=C3=A0-vis others.
      = ;  In this age of nanostructures, nanoparticles and quantum mechanical insights, I dou= bt we have fully probed the properties and capabilities of colossal numbers of individual particles to respond collectively to signal and not noise.   While there=E2=80=99s no n= eed to get carried away over this topic, I think the coherer concept deserves a seat at the table o= f LF topics occasionally, hi.
GL & 73, Jim H   W5EST
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