Most mixers are a poor match to 50 Ohms, and the manufacturer's instructions will generally advise insertion of 10 dB between mixer and cable for that reason. Of course, their noise figure or noise floor specification is based on 0 dB attenuation. Connecting the mixer directly to the antenna output places two potentially poor matches to 50 Ohms in immediate proximity, and the short distance between them will minimize vswr-induced inaccuracy. Then the rest of the connection all the way back to the receiver should be well-matched 50 Ohm sections. Ken Javor
Phone: (256) 650-5261 > From: John Woodgate <j...@jmwa.demon.co.uk> > Date: Wed, 31 Aug 2011 18:51:32 +0100 > To: <EMC-PSTC@LISTSERV.IEEE.ORG> > Subject: Re: EMI Receiver - Recommendations? > > In message <ca83d601.bf043%ken.ja...@emccompliance.com>, dated Wed, 31 > Aug 2011, Ken Javor <ken.ja...@emccompliance.com> writes: > >> Cable is usually 50 Ohms. > > Well, people do sometimes tread on it or even stand heavy equipment on > it, but in general I agree that, if treated with care, good quality > cable has an impedance more stable and better-behaved than many antennas > and even receivers. > -- > OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk > John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK > When I point to a star, please look at the star, not my finger. The star will > be more interesting. > > - > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. To post a message to the list, send your e-mail to > <emc-p...@ieee.org> > > All emc-pstc postings are archived and searchable on the web at: > http://product-compliance.oc.ieee.org/ > Graphics (in well-used formats), large files, etc. can be posted to that URL. > > Website: http://www.ieee-pses.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...@radiusnorth.net> > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher: <j.bac...@ieee.org> > David Heald: <dhe...@gmail.com> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
