Doesn't it boil down to reflection coefficient and then return loss and mismatch loss? So the reflection coefficient will be 0.2 or about -14dB of S11. The S21 or mismatch loss or extra attenuation at the load will be 0.2dB. Best Regards Charles Grasso Compliance Engineer Echostar Communications (w) 303-706-5467 (c) 303-204-2974 (t) 3032042974@xxxxxxxxx (e) charles.grasso@xxxxxxxxxxxx (e2) chasgrasso@xxxxxxxxx -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of steve weir Sent: Thursday, June 07, 2012 4:05 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Discussion: What is the extra attenuation if a 50ohm source interfacing a 75ohm cable which terminated with 75ohm? No, assuming ideal components PointA acts like a simple divider: 0.6V/V = -4.44dB versus a zero impedance voltage source directly driving the cable. Were the cable lossless that wavefront would travel a cable of arbitrary length. The terminator at Point B if perfectly matched, makes the cable look like it goes on forever: In the ideal case there is no attenuation and no reflection at PointB. Steve. On 6/7/2012 1:41 AM, Zhenwei Wang (zhenwwan) wrote: > Hi experts, > Today I have a dicussion with my colleague. The topic is What is > the extra attenuation if a 50ohm source interfacing a 75ohm cable which > terminated with 75ohm resistor? Just like that when using a 75ohm cable > connected to a 50ohm output instrument. > The scenario is: > Source(50ohm resistor)===>PointA===75ohm cable===>PointB > > || > > ||(75ohme resistor) > GND > > My opinion: Based neglecting the multi-refection, there will be > refection factor at pointA, which is 0.2. So 80% energy was launched > into 75ohm cable. Then the voltage at pointB is Vin*0.8/2=Vin*0.4. But > it should be 0.5*Vin at pointB. So the extra attenuation is > 0.5-0.4=0.1==>-20db. > Am I right? > > > BR > Zhenwei(Jason) Wang > Cisco Systems (Shanghai) Video Technology Co., Ltd. > ------------------------------------------------------------------ > 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 forum is accessible at: > http://tech.groups.yahoo.com/group/si-list > > List archives are viewable at: > //www.freelists.org/archives/si-list > > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > > > -- Steve Weir IPBLOX, LLC 150 N. Center St. #211 Reno, NV 89501 www.ipblox.com (775) 299-4236 Business (866) 675-4630 Toll-free (707) 780-1951 Fax All contents Copyright (c)2012 IPBLOX, LLC. All Rights Reserved. This e-mail may contain confidential material. If you are not the intended recipient, please destroy all records and notify the sender. ------------------------------------------------------------------ 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 forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list 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 forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu