Newer Model Instrumentation Amp
in [Design]
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From: JosephKK on 23 Jun 2010 02:05 On Mon, 21 Jun 2010 13:01:50 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Sun, 20 Jun 2010 17:07:12 -0700, Joerg <invalid(a)invalid.invalid> >wrote: > >>Spehro Pefhany wrote: >>> On Sun, 20 Jun 2010 15:28:53 -0700, the renowned John Larkin >>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>>> On Sun, 20 Jun 2010 22:01:24 GMT, paulhendersen(a)qualcomm.com (Paul >>>> Henderson) wrote: >>>> >>>>> On Sun, 20 Jun 2010 07:38:00 -0700, John Larkin >>>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>> >>>>>> On a current design, I had to make my own. I wanted lots of >>>>>> overvoltage protection, logic-switchable gains from 0.05 to 256, high >>>>>> precision, and at least +-12 volts of common-mode range, 120 dB CMRR >>>>>> at high gain. I wound up with a classic 3-opamp diffamp, using an >>>>>> LT1124 dual opamp, four Supertex depletion mode fets for protection, a >>>>>> discrete string of thinfilm resistors, one DPDT gain switch relay, two >>>>>> analog muxes, and an INA154 as the second stage. Two tiny trimpots >>>>>> tweak cmrr. Times 16 on one board. I'd love to get all that in a SO-8! >>>>>> >>>>> If that's not a proprietary design John, any chance of posting a link >>>>> to the schematic? >>>>> >>>>> Paul Hendersen >>>> >>>> Yes, it is proprietary but, hell, I *am* the boss, so here it is: >>>> >>>> ftp://jjlarkin.lmi.net/22S490B_ch12.pdf >>>> >>>> in hopes that it will invoke an entertaining flurry of pecking and >>>> clucking. >>>> >>>> I don't totally like the style of the schematic; I drew it on D-size >>>> vellum "my way" and The Brat entered it into PADS. It would be too >>>> much work to push 16 channels of stuff around at this point. >>>> >>>> John >>>> >>> >>> That bipolar relay driver is a thing of beauty. >>> >> >>Sure is. >> >>But John calls them "K", as in kontactor or kool kampground :-)) > >K is the ANSI/Mil designation for a relay. OK, I'm old fashioned and >don't just make up stuff like LED2, TR5, RLY12, CON2, RV7, RN8, ZEN15, >or other abominations. > >John And a lot of it comes from translations from Mandarin or Cantonese.
From: Paul Keinanen on 23 Jun 2010 02:08 On Tue, 22 Jun 2010 20:45:29 -0500, "krw(a)att.bizzzzzzzzzzzz" <krw(a)att.bizzzzzzzzzzzz> wrote: >On Tue, 22 Jun 2010 18:27:51 -0700, "Joel Koltner" ><zapwireDASHgroups(a)yahoo.com> wrote: >>You can probalby do OK if you get people to weat hardhat-mounted antennas, >>like this: http://www.ka7exm.net/Dayton2007/IMG_3791.JPG . :-) (From the "odd >>headgear" section here: >>http://www.ka7exm.net/Dayton2007/hamvention_photos.htm ) > >I suggested a beanie with an automatic antenna rotator to solve our multi-path >problem in domed stadiums. ;-) In that picture, there appears to be three different length antennas, so probably for different frequency bands and hence frequency diversity could be used to combat multi-path. An array of four antennas if often used in electronic direction finding application, so mechanically rotation is not needed. A helmet is sufficiently large for spatial diversity or even MIMO systems down to lower UHF and possibly even upper VHF.
From: krw on 23 Jun 2010 18:59 On Wed, 23 Jun 2010 09:08:44 +0300, Paul Keinanen <keinanen(a)sci.fi> wrote: >On Tue, 22 Jun 2010 20:45:29 -0500, "krw(a)att.bizzzzzzzzzzzz" ><krw(a)att.bizzzzzzzzzzzz> wrote: > >>On Tue, 22 Jun 2010 18:27:51 -0700, "Joel Koltner" >><zapwireDASHgroups(a)yahoo.com> wrote: > >>>You can probalby do OK if you get people to weat hardhat-mounted antennas, >>>like this: http://www.ka7exm.net/Dayton2007/IMG_3791.JPG . :-) (From the "odd >>>headgear" section here: >>>http://www.ka7exm.net/Dayton2007/hamvention_photos.htm ) >> >>I suggested a beanie with an automatic antenna rotator to solve our multi-path >>problem in domed stadiums. ;-) > >In that picture, there appears to be three different length antennas, >so probably for different frequency bands and hence frequency >diversity could be used to combat multi-path. > >An array of four antennas if often used in electronic direction >finding application, so mechanically rotation is not needed. A phase array wouldn't have nearly the visual effect of a beanie on the head of a 350# football lineman. >A helmet is sufficiently large for spatial diversity or even MIMO >systems down to lower UHF and possibly even upper VHF. Spacial diversity doesn't help.
From: Paul Keinanen on 24 Jun 2010 00:59 On Wed, 23 Jun 2010 17:59:39 -0500, "krw(a)att.bizzzzzzzzzzzz" <krw(a)att.bizzzzzzzzzzzz> wrote: > >>A helmet is sufficiently large for spatial diversity or even MIMO >>systems down to lower UHF and possibly even upper VHF. > >Spacial diversity doesn't help. If you have severe multipath problems, one of the worst modulations is narrow band AM/FM, since it is quite likely that a single antenna is at the multipath null, where the multipath signals cancel each other completely. The area at which the signals cancel each other is quite small and gets smaller with higher frequencies. Having two or more antennas at some distance from each other (e.g. on different part of your body), it is unlikely that _all_ those antennas would be in multipath nulls. With multiple antennas and multiple receivers, just sum the audio outputs, but squelch those receivers that have a weak (noisy) signal at the moment. Of course some more sensible modulation method, such as DSSS, TDMA or OFDM would make more sense in an environment with heavy multipath even with a single antenna.
From: JosephKK on 24 Jun 2010 07:47
On Tue, 22 Jun 2010 19:03:38 -0700, "Joel Koltner" <zapwireDASHgroups(a)yahoo.com> wrote: ><krw(a)att.bizzzzzzzzzzzz> wrote in message >news:mep2261ikogmiem55eq9mkeo40g5m9qcj6(a)4ax.com... >> On Tue, 22 Jun 2010 18:27:51 -0700, "Joel Koltner" >> <zapwireDASHgroups(a)yahoo.com> wrote: >>><krw(a)att.bizzzzzzzzzzzz> wrote in message >>>news:9rm226tc7dr29jev59desa4ripunn02c5j(a)4ax.com... >>>> We don't do our own RF, so our needs in that area are much smaller. >>>Gee, some day perhaps you could become a customer then, if you guys decide >>>to >>>aggressively pursue certain markets where at least some people believe the >>>"all-digital in the ISM bands" approach isn't the best choice. Heh, heh... >>>:-) >> The problem with that idea is that it indeed seems to be the *right* choice. > >Given some time you might decide that there are additional markets out there >that it isn't currently the right choice for. :-) > >Heck, nothing you have nor anything we would is probably the right choice for, >say, a small venue like a church that has limited funds and is going to be >looking at more budget-priced options. I'm kinda surprised that companies >like Shure -- who seems to make endless varieties of wireless microphone >systems at very attractive price points -- don't get into wireless intercoms. >Besides the pro-audio guys, the only other major players seems to be >restaurant-oriented where you have the likes of HME and 3M. > >---Joel None seem to be trying to cover very cost conscious markets, but for smaller venues; traditional PA vendors, manufacturers of Assisted Listening devices (that is the first stage search string, it gets the manufacturers, then you look at their full lines) seem to be plentiful. |