At 11:24 PM 2/11/2004 -0800, you wrote: > >>I think that we differ here. I find the logic circular, so maybe you care > >>to expand. The standing wave is a result of the reflection. So, there is > >>no way that I see to add or remove a short. It was intrinsic. Surely if I > >>put a pin through coax, I am going to heat the heck out of the drive > >>amplifier. I don't see why you believe that a rectangular cavity is > >>fundamentally different. > > > >Then think about this. I once worked on a television station project > >where the > >nitrogen filled 6 1/8" dia hardline coax carried over 200KW of video power > >through a > >short section of t-line that had a huge, deliberately placed metal slug > >between the > >center conductor and the outer tube (shield) essentially an RF short > >designed to > >protect the transmitter from lightning strikes. This section fed a large > >rectangular cavity > >which is otherwise known as a diplexer. By using your explanation, it > >would seem to > >stand to reason that the transmitter would have been destroyed upon > >applying power > >to this t-line section or at least the metal slug would have been > >disintegrated. > >Not at all, because the reactance of that plate did not interfere with the >tuned circuit driving the cable. A 6MHz television channel is a whole lot >different than the broadband of a PWB, or a broadband CATV >amplifier. Aren't bandpass filters wonderful? This actually goes right >back to the guy with his 400MHz radio and "Bob's" inductor. Sorry, you don't have the winning number.... please play again. <grin> ... not 6 MHz... that's the bandwidth. Try up around 600 MHz.... these pitiful little boards have nothing of the energy that stuff had... and you made my point. > >>I hope you do well with the patent. In the meantime I take it that you > >>agree that the planes don't provide a lot of CM reduction for HF currents > >>in the ICs. > > > >Patent? Phooey. Take a look at all the RF devices out there already doing > >a form of it. That's what I meant by the technology already being there. > >But, if it can be done and it isn't, you really should go do something and >make money at it. Ok. Noted. > >>Follow the field lines West young man!!! Due to the higher permittivity, > >>the field concentration close to the top of the trace is much greater than > >>for a surface trace. Consequently, it doesn't take a lot of the stuff to > >>knock 15db or more off of the signal versus a surface microstrip. > > > >Take a look at the gray hair and you'll know that "young" isn't quite the > >right > >description. Hey, but I think young! <grin> Also, I've been "West" ... and > >chose not to be there, at least for now. > > >You mean you don't look forward to lala land, the "Capital of the Third >World". Although all the industry is north and south of the basin. Been there, done that and wondered what was so special... definitely different but I wouldn't call it special. > >Seriously though, after helping folks on EMI stuff for a long time, large > >quotes on dB > >reduction make me smile and say "yeah, right." I'm sorry but that's just > >a bit much > >to swallow (an 83% reduction?). > >Microstrip to buried microstrip that is the idea. It is not an 83% >reduction of the overall assembly. I hope the experiment was consistent enough such that the microstrip was the same distance from the plane in both cases... still that much change doesn't make sense. I agree it'll help some but not that much. I would believe it if the distances were different like in a stackup like: surface microstrip dielectric (distance A) embedded microstrip dielectric (distance A) plane reference >Well, as much as we disagree on this point, the best way to get everyone on >the same page is to do controlled measurements and publish them. Could we >agree to set this up using two boards built with just an SMA launch and a >single microstrip trace? > >Regards, > > >Steve. Yep. And agree on the measurement method... Regards, Michael ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu