Randy: First, there's the old Polarad CA-L, CA-S, CA-M & CA-X covering, respectively, 1-2, 2-4, 4-8 & 8-12 GHz.
Then there's the old Singer EMA 910 series, with 1010 & 1020 horns for 1-2.5 & 2.5-4.5 GHz. Then the 1030 horn + 1001 reflector for 4.3-7.3 GHz and the 1040 + 1001 reflector for 7.2-10.5 GHz. And finally, the 1050 horn + 1001 reflector for 10-17 GHz and the 1060 horn + 1001 reflector for 17-26 GHz. To find those "antiques", you have to follow the surplus market and keep track of the Ebay auctions and the Usenet "boatanchors" discussion group. Narda makes a line of antennas, the 640 (8-12 GHz), the 639 (12-18 GHz) and the 638 (18-26 GHz). Unfortunately, these are small horns, with AF's of about 34, 37 and 41 dB, respectively. I think Continental Microwave also has a similar series. For emission testing, you might be able to get around high AF's by using a high-gain, very low-noise pre-amp. See Miteq Corp for pre-amps. I think the best route to go is to build your own horns as needed. OTOH, I am currently waiting for delivery of two custom-built horns, with low AF's, for the 18-26 GHz band and the 26-40 GHz band. For custom-built horns, I suggest you contact: Larry Caney Raven Engineering PO Box 2300 Valley Center, CA 92082 760-751-8853 Regards, Ed :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-) Ed Price [email protected] Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Services Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-) > -----Original Message----- > From: Flinders, Randall [SMTP:[email protected]] > Sent: Tuesday, March 07, 2000 12:41 PM > To: Zhong Chen; [email protected] > Subject: Re: Horn Antenna > > > Is anyone aware of any Tuned Horn sets that use multiple Horns to cover > the > frequency Range? I use a broadband Horn antenna for Radiated Emissions > testing > and I am finding that as our products move in to higher frequency regions > of the > spectrum, the Broadband Horn (1-18 GHz) offers too high of an AF. > > Regards, > > Randy Flinders > EMC Engineer > Emulex Corp. > (714) 513-8012 > (714) 513-8265 Fax > [email protected] > > aka... > > Chairman > Orange County Chapter > IEEE EMC Society > [email protected] > > Zhong Chen wrote: > > > Just a quick comment, > > the relationship between AF(dB/m) and G(dB) is > > > > AF(dB/m)=20*log(f_MHz)-G(dB)-29.79 > > > > As you can see, if you have an antenna with a constant gain, it is a > > physical law that the AF goes up with frequency. Now, of course you can > > design an antenna with a extremely large gain (small AF). But, for most > > cases, it is not desired, because the higher the gain, the narrower the > > beam. For immunity test, you really want a moderate gain antenna to > cover a > > reasonable area. EMCO 3115 has a gain between about 7 and 14 dBi > accross > > the band. I do not know if you really want the gain to go any higher > than > > that. > > > > Zhong Chen > > > -----Original Message----- > > > From: Price, Ed [SMTP:[email protected]] > > > Sent: Tuesday, March 07, 2000 9:03 AM > > > To: [email protected] > > > Subject: RE: Horn Antenna > > > > > > > > > Derek: > > > > > > Excellent comments on horns from Robert. > > > > > > I have a couple of EMCO 3115 Double-ridged horns. This design > sacrifices > > > efficiency for bandwidth, which means time saved not swapping > antennas. > > > Although the design is rated to 18 GHz, I found the antenna factor > became > > > intolerably high (for my needs) above around 14 GHz. > > > > > > So I built a horn for the 12-18 GHz band. The easy technique for this > is > > > to > > > use a section of waveguide, cut off square at one end and flanged at > the > > > other. Just use sheet metal (brass) to extend a flared horn out from > the > > > cutoff end. Use fairly heavy gauge metal sheet, and you can either > solder > > > or > > > braze all the seams. Now, just use a coax to waveguide adapter to make > > > your > > > connection. There are designs available for flare angle and length of > the > > > horn everywhere from the ARRL Antenna Handbook to Reference Data for > Radio > > > Engineers to the classic textbooks. > > > > > > Most of us already have octave band amplifiers, so it's not that much > > > extra > > > hassle to change an antenna along with the amplifier for each band. > > > > > > If you really need to squeeze out every dB of performance from your > > > immunity > > > setup, then consider mounting the antenna directly off the output > > > connector > > > of your TWT amplifier. Zero cable loss. Of course, it's nice then to > have > > > a > > > "stupid" amplifier, that is, one which has nothing but a TWT tube and > a > > > brute force power supply. All those fancy microprocessor controls and > IO > > > are > > > likely to prove susceptible to the RF field. You can use a small > pre-amp > > > to > > > boost the signal on the relatively long amplifier input cable, if you > need > > > to. Also, a long, low-loss, low-power coax is much cheaper than a > long, > > > low-loss, high power coax. And very much cheaper than a long flex > > > waveguide. > > > > > > There's another benefit to using a waveguide to coax adapter to feed a > > > horn. > > > If you do manage to damage the system, through arcing from high SWR > (like > > > maybe the antenna falls over and lands throat down on the enclosure > > > floor), > > > the adapter is easily replaceable. Also, rarely, you will encounter a > > > badly > > > assembled Type N male coax cable connector, with the male center pin > > > sticking out too far. It's much better to damage the female connector > on a > > > replaceable adapter, than a female connector built into the antenna. > > > (Let's > > > all check our coax cables today. <grin>) > > > > > > Now wait a minute! How big was that enclosure you described? One meter > by > > > 0.7 meters?! That sounds more like a waveguide than a chamber! > > > > > > Regards, > > > > > > Ed > > > > > > > > > > :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):- > > > ) > > > Ed Price > > > [email protected] > > > Electromagnetic Compatibility Lab > > > Cubic Defense Systems > > > San Diego, CA. USA > > > 858-505-2780 (Voice) > > > 858-505-1583 (Fax) > > > Military & Avionics EMC Services Is Our Specialty > > > Shake-Bake-Shock - Metrology - Reliability Analysis > > > > :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):- > > > ) > > > > > > > -----Original Message----- > > > > From: Robert Macy [SMTP:[email protected]] > > > > Sent: Monday, March 06, 2000 2:30 PM > > > > To: [email protected]; [email protected] > > > > Subject: Re: Horn Antenna > > > > > > > > > > > > Derek, > > > > > > > > The horn antenna is an impedance matching device for getting between > 50 > > > > ohm > > > > lines and 377 ohm free space while launching TEM mode wave fronts. > > > > > > > > You could use the commercially available one which has an awful > antenna > > > > factor. It's broadband as a result of the ribs placed in the horn. > > > > > > > > Just guessing, but if you want 1 V/m which is around 2.7mW in free > space > > > > (4.3 dBm, 0.367Vac in a 50 ohm system) and your antenna factor is > around > > > > 34dB, you'll have to power the antenna with 38.3 dBm (6.8W, > 18.4Vac) > > > > > > > > The antenna will probably take that. > > > > > > > > However, if you want to get to 3V/m you'll then need (61W, 55Vac) > and > > > > might > > > > be overpowering the antenna. > > > > > > > > For 10V/m you need (680 W, 184 Vac) Wow! Assuming 1 dB drop in your > > > > cabling > > > > and you dissipate 70W there! > > > > > > > > Sorry, don't know antenna design enough to tell you if you can > improve > > > > that > > > > antenna factor but my guess is no, or the EMC supply houses would > have > > > > been > > > > supplying those antennas already. The best bet is to go for octave > band > > > > antennas with only 10-16dB antenna factors and change the antenna a > lot. > > > > > > > > - Robert - > > > > > > > > Robert A. Macy, PE [email protected] > > > > 408 286 3985 fx 408 297 9121 > > > > AJM International Electronics Consultants > > > > 619 North First St, San Jose, CA 95112 > > > > > > > > -----Original Message----- > > > > From: [email protected] <[email protected]> > > > > To: [email protected] <[email protected]> > > > > Date: Monday, March 06, 2000 12:55 PM > > > > Subject: Horn Antenna > > > > > > > > > > > > > > > > > >Hi, > > > > > > > > > > I'd like to construct a wide band horn antenna covering from about > 1 > > > GHz > > > > to 10 GHz or so. > > > > > > > > > > This is used only to generate a field inside a small EMC Chamber ( > > > about > > > > 1 > > > > metre by 0.7 metres ), so I'm not worried about gain flatness > etc.... I > > > > just > > > > want field;-) > > > > > > > > > > Any thoughts about: > > > > > > > > > > 1) How these things work > > > > > > > > > > 2) The best way to go about modelling this > > > > > > > > > > 3) The best way to make one > > > > > > > > > > Thanks in advance > > > > > > > > > > Derek Walton > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
