Rod antennas can be either passively matched or active. Most antenna sold today are active. This makes them easier to use (no band-switching) but they are easier to overload. There were a couple remotely controlled passive antennas where the band-switching was controlled by the receiver as it tuned, but these systems are somewhat obsolete, although still in use.
The two best active rod antennas ever made, the Stoddart/Singer/Ailtech 95010-1 and the Honeywell model (can't recall the model number) are no longer made, but if you find one latch on to it. The 95010-1 used a special FET that had huge dynamic range. It can measure to several Volts per meter, and the sensitivity is as good as anything out there. The FETs are obsolete however, so I have a couple of these antennas in case the worst happens. The Honeywell unit used a capacitive voltage divider at the rod base to provide frequency independent attenuation in front of the sensitive FET. No modern antennas have the dynamic range of these old dinosaurs. You can get new rod antennas from ETS/Lindgren (http://www.ets-lindgren.com/), Electro-Metrics (http://www.electro-metrics.com/), Com-Power (http://www.com-power.com/) and AH Systems (http://www.ahsystems.com/). Also Raven Engineering in San Diego will work on the older 95010-1 antennas, if you find one. All of these outfits will also sell you biconicals and double ridge guide horns that meet the mil-std requirements. I think Rohde & Schwarz (http://www.rohde-schwarz.com/), the test equipment manufacturer also sells some antennas, but I know for a fact that their rod antenna doesn't look like the mil-std's, so I shy away from stuff like that (see my last two paragraphs below). Same comment for Antenna Research Associates (http://www.ara-inc.com/) - they make a whole spectrum of special purpose very sensitive active antennas, but for MIL-STD-461E test purposes, I would only purchase those that are per the mil-std. I have not mentioned Amplifier Research (http://www.ar-worldwide.com/). They used to be an amplifier house and sold some transmit antennas to augment their amplifier sales, but they (like ETS/Lindgren) have bought and merged and subsumed so many other companies that it is difficult to keep track of the product line. Also they tend to private label other company's products, so it is usually less expensive to figure out who the OEM is and get it from them. I don't disagree with the facts as stated in Mr. Price's reply, but I want to emphasize something I feel he did not address as vigorously as he might have. It is critically important to use antennas that precisely meet the mil-std requirements - these measurements are made in the near field and the physical characteristics of the antennas - their physical apertures - must be tightly controlled in order to get test results that are meaningful. For instance, I feel that the older log-conical or log-spiral antenna was a better choice than the double-ridge guide horn used today, but that does not mean I can use one in place of what is mandated for -461E. Even accounting for the appropriate antenna factors will not yield results that correlate >from one antenna to the other. Ken Javor > From: "Charles Blackham" <charles.black...@sulisconsultants.com> > Date: Wed, 28 Feb 2007 11:41:08 -0000 (GMT) > To: emc-p...@ieee.org > Subject: MIL-STD-461E RE102 Antennas > > Group > > MIL-STD-461E section 5.16.3.2 specifies very detailed dimensional > requirements for Antennas used for emissions testing to RE102. > > With the exception of the 30-200 MHz Bi-Conical, I'm having difficulty > locating suitable antennas: > > - can anyone recommend specific Rod and Double-ridge Horn antennas that > meet exactly the requirements. > > - or are tests typically done with antennas that don't meet exact phyical > requirements? > > regards > Charlie > > - > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to emc-p...@ieee.org > > Instructions: http://listserv.ieee.org/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > > Scott Douglas emcp...@ptcnh.net > Mike Cantwell mcantw...@ieee.org > > For policy questions, send mail to: > > Jim Bacher: j.bac...@ieee.org > David Heald: emc-p...@daveheald.com > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
