Hi, Ma: No, I think it is different. |S11| = - 3 dB means |S11| is about 0.707 or |S11*S11| = 0.5 or 50% of the power is reflected. If there is little metallic, dielectric and radiation losses (normally the case unless for antennas), the |S21| should be 0.707 or |S21*S21| = 0.5 or 50% of the power is transmitted. Regards. ---------------------------------------------------------------------------- Jian X. Zheng, Ph.D., Zeland Software, Inc. 48834 Kato Road, 103A, Fremont, CA 94538, U.S.A. Tel: 510-623-7162, Fax: 510-623-7135 ---------------------------------------------------------------------------- > -----Original Message----- > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] > On Behalf Of ma mu > Sent: Wednesday, January 25, 2006 2:17 PM > To: si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] -3dB at S21 graph > > Hi all, > > In my insertion loss, S21 graph, I got -3dB loss at 1.5 Ghz. My question > is : > transmission at 1.5 Ghz is 50% or 70% ? I thnik 50% . please give > me feedback. > > Ma > > > > --------------------------------- > Bring words and photos together (easily) with > PhotoMail - it's free and works with Yahoo! Mail. > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > List FAQ wiki page is located at: > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > List technical documents are available at: > http://www.si-list.org > > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu