In my limited experience the “true” C.P. antenna is of Helical design, are there others configurations? From: John Shutt Sent: Wednesday, April 27, 2011 7:50 PM To: opendtv@xxxxxxxxxxxxx Subject: [opendtv] Re: Circular, elliptical antenna polarization improves mobile DTV reception reliability "True" CP with a true CP receive antenna has an advantage over a horizontally polarized signal when in high multipath environments. When a CW CP signal bounces off of a hard reflector (such as a building) it becomes CCW polarized, and is rejected by the CW polarized receive antenna. The direct path maintains its CW polarization and is accepted by the CW polarized receive antenna. The advantage of CP, dual polarization, elliptical polarization, or however you wish to categorize it, in a mobile environment is simply that the receive antenna is rarely horizontally oriented. Therefore, if there is a vertical component to the broadcast signal, there is more signal for a vertically oriented antenna to receive. John ----- Original Message ----- From: Mark Aitken To: opendtv@xxxxxxxxxxxxx Sent: Wednesday, April 27, 2011 8:47 PM Subject: [opendtv] Re: Circular, elliptical antenna polarization improves mobile DTV reception reliability Dale, correct to both of your points. As to "advantage" of CW or CCW true circular...only needed to provide isolation or discrimination from opposing rotational emissions...used in space activities for example for DTTH satellite. Regards, Mark