Ed, I've always called them "Parallel rod E-field generators". Emco sells one: <http://www.ets-lindgren.com/page/?i=3107B> http://www.ets-lindgren.com/page/?i=3107B Note that this one contains the termination load internally, some similar products from other manufacturers leave the termination load external. This model also has a band switch at 5MHz, although the one I used was more efficient if it switched around 7MHz. It also worked much better if I ran a bonding strap from the bottom elements to the floor. The field is generated between the elements. The bottom elements are connected to ground (cable shield) while the top elements are driven through a network. With the elements horizontal, the e-field is vertically polarized. I believe the Mil-Std RS103 test only requires vertical polarity below 30MHz. You are absolutely right about driving power into a biconical. I've also witnessed the problem of harmonics becoming dominant due to the poor factors at low frequencies. Emco makes a biconical with a high-power balun, and they have optional extended elements that make it much more efficient at the lower frequencies (down to 20MHz I believe). I'm not trying to sell any one brand, just giving some info on products I've had experience with. Bob Richards, NCT.
"Price, Ed" <[email protected]> wrote: Be careful about driving biconicals; be sure the one you are using is rated for the power you are putting into it! There are various balun designs for biconicals. Some shouldn't see more than about 0 dBm, while other have such a "high-power" capability that the balun housing needs perforations for air flow cooling. (That tells you something about total efficiency.) Some military tests require illumination to begin as low as 10 kHz, where a biconical is totally hopeless. There is another antenna design that, although being relatively inefficient, can produce significant electric fields over the 10 kHz to 200 MHz range. I don't know what to call it, other than an electric field generator. Of course, it's a transducer, not really a generator, but an example of the design is the IFI EFG-3 Antenna; see: http://www.ifi.com/web/html/antennas/antmain.html You will also want a hefty RF power amplifier; for military work, I would suggest something on the order of a 1 kW rating. And, with that EFG example, you also need a 50-ohm termination for the antenna, so that has to be rated for the amplifier capacity too. Ed Price <http://us.f565.mail.yahoo.com/ym/[email protected]> [email protected] NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (FAX) Military & Avionics EMC Is Our Specialty - ---------------------------------------------------------------- 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 [email protected] 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 [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] 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 [email protected] 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 [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] 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 ______________________________________________________________________
