Whirled One
01-18-2006, 07:59 PM
While flipping through some old copies of Electronic Servicing (a service industry trade magazine that was published by SAMS), I noticed a cover story in the November 1975 issue describing the initial results of some TV transmitter tests using circularly polarized transmitter antennas rather than the usual horizontally polarized variety. The FCC was allowing these tests on an experimental basis at the time in order to evaluate whether or not to approve CP (circular polarization) transmission on a permanent basis.
It seems the upside to CP on the receiving end (when used with a circular polarized receiving antenna) would have been to substantially reduce ghosting and improve fringe reception (even with small indoor antennas), while apparently not negatively impacting reception for those with existing horizontally-polarized antennas.
In general, the article gives a glowing report on the improvments that would be realized with CP transmitting, and suggests a high level of industry interest (despite the added costs for the transmitting stations if they decided to switch to CP). ...But, since we're still using horizontally-polarized TV antennas, I assume the FCC decided not to approve the use of CP. So what happened? Was some issue discovered later that caused it not to be approved, or was the industry support just not as high as the magazine article author would have liked to believe..? Just curious...
It seems the upside to CP on the receiving end (when used with a circular polarized receiving antenna) would have been to substantially reduce ghosting and improve fringe reception (even with small indoor antennas), while apparently not negatively impacting reception for those with existing horizontally-polarized antennas.
In general, the article gives a glowing report on the improvments that would be realized with CP transmitting, and suggests a high level of industry interest (despite the added costs for the transmitting stations if they decided to switch to CP). ...But, since we're still using horizontally-polarized TV antennas, I assume the FCC decided not to approve the use of CP. So what happened? Was some issue discovered later that caused it not to be approved, or was the industry support just not as high as the magazine article author would have liked to believe..? Just curious...