As Ken says, with a short wire you need to match the antenna to the receiver, which means a tuning unit - otherwise try an active rod amplifier is a mosfet with Hi-Z input and (in the case of the EATON) matched 50Ohm output. The EATON 1m active rod antenna has an AF of 8dB without the "top hat" or 0dB with it (an 8" diameter disc of brass if I remember) You should be able to put together a simple amplifier - but watch the capacitive loading of the input to avoid "shorting" the signal to earth. Regards Tim
************************ Tim Haynes A1N10 Electromagnetic Engineering Specialist SELEX Sensors and Airborne Systems 300 Capability Green Luton LU1 3PG ( Tel : +44 (0)1582 886239 7 Fax : +44 (0)1582 795863 ) Mob : +44 (0)7703 559 310 * E-mail : tim.hay...@selexgalileo.com P Please consider the environment before printing this email. There are 10 types of people in the world-those who understand binary and those who don't. J. Paxman ________________________________ From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Ken Javor Sent: 05 May 2009 14:38 To: Untitled Subject: Re: AM antennas *** WARNING *** This message has originated outside your organisation, either from an external partner or the Global Internet. Keep this in mind if you answer this message. I believe the preference is a matter of personal needs – there is no absolute “best choice.” A vertical wire cut to a quarter wavelength over a ground plane at least a quarter wavelength in radius will give the best sensitivity, but unless you have lots of money and room, and one favorite station to listen to, that is not a practical solution. A shorter wire with a tuner can offset some of the losses associated with an electrically short wire, but most tuners are built for the shortwave, not medium wave bands. An untuned loop will have relatively poor sensitivity, which is why built-in AM loops are wound on a ferrite rod core. Also they are very small and fit within the radio enclosure. But they are hardly efficient. A decent-sized multi-turn loop (say a foot to a meter in diameter) that is tuned to resonance at the frequency of interest (using an air variable cap or remotely controlled varactor tuning) can be quite efficient, as well as providing a high degree of front-end filtering for your receiver – very useful if trying to receive a weak remote station in the presence of a nearby stronger signal. These loops need a coupler to drive the receiver; in my experience, the best coupler is an EMI test current probe; it is much more efficient than the coupling loops traditionally used for this purpose. Ken Javor Phone: (256) 650-5261 ________________________________ From: Richard Stone <richard.st...@dialogic.com> List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org Date: Tue, 5 May 2009 09:24:01 -0400 To: "Pettit, Ghery" <ghery.pet...@intel.com>, Kim Boll Jensen <k...@bolls.dk>, EMC PSTC <emc-p...@ieee.org> Conversation: AM antennas Subject: AM antennas Hello group Is there a preferred AM antenna (Loop or Vertical Type) to connect locally to receiver for best reception thru out New England area incl. NY. Thanks Richard, From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Pettit, Ghery Sent: Friday, May 01, 2009 11:01 AM To: Kim Boll Jensen; EMC PSTC Subject: RE: EN 55022 A1 and CISPR 22 Kim, This is not correct. We purchased EN 55022:2006 through BSI and got the same as you did. When it was pointed out to them they quickly withdrew the standard and re-issued it without the limits above 1 GHz. It should be pointed out that Amendment 2 to CISPR 22:2005 adopted the European common modifications that are contained in EN 55022:2006, so if you take CISPR 22 Edition 5 and add Amendment 2 you basically have EN 55022:2006. Ghery S. Pettit, NCE From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Kim Boll Jensen Sent: Friday, May 01, 2009 4:58 AM To: EMC PSTC Subject: EN 55022 A1 and CISPR 22 Hi all I think we got into a special problem. When we bought EN 55022 (before A1 was harmonized) we got CISPR 22 ed. 5.2 as the main standard attached. This version contains A1 and A2 of CISPR 22. The problem is that the EN 55022: 2006 is based on CISPR 22 ed. 5.0 without A1 and A2 and therefore without requirements for emission over 1 GHz. The Danish Standard from where we bought the standard have informed us that it is CENELEC that have decided to include the ed. 5.2 and not ed. 5.0 and therefore this must be a EU problem since all EN 55022: 2006 then should contain the ed. 5.2. Is this correct? And if it is correct how can we know, if we got the right standards and not future requirements ? We have over the last year claimed to costumers that there was requirements for emission over 1 GHz from 1/10 2009 and now we can see that this requirements is first from 1/10 2010 (dow of EN 55022 A1). I see this as a very big problem since A1 could have been stopped or just not implemented and we would then have been testing for wrong requirements. Do you know if there are other standards which contains wrong versions of basic standards ? And lastly; what is the wording of CISPR 22 A2, because we will also need to remove this text from our ed. 5.2. Best regards, Mr. Kim Boll Jensen Bolls Rådgivning Ved Gadekæret 11F DK-3660 Stenløse Phone: +45 48 18 35 66 k...@bolls.dk www.bolls.dk - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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