"JIMMIE" wrote in message
...
On Oct 5, 2:34 pm, Jim Lux wrote:
david boyd wrote:
Are there any websites that give the polarization for TV signals?
For the US, the FCC database tells the polarization (elliptical is
pretty common.. mostly horizontal, with some vertical component)
For instance, here's the stuff for KCBS-TV in the Los Angeles
area:http://fjallfoss.fcc.gov/cgi-bin/ws....cc/prod/eng_tv....
Horizontal pol
But channel 11,
KTTVhttp://fjallfoss.fcc.gov/cgi-bin/ws.exe/prod/cdbs/pubacc/prod/eng_tv....
has Elliptical..
The search page is
hehttp://fjallfoss.fcc.gov/prod/cdbs/p...d/sta_sear.htm
Concerning a TV station using elliptical polarization is there a
purposeful phase difference between the horizontal and vertical fields
or is it simply just dividing power between horizontal and verical
radiators with no concern as to phase relationship
Jimmie
Probably the latter, as is done around the world nowadays for VHF FM radio,
although I confidently predict someone will contradict me with stuff about
odd-order reflections changing the sense of rotation and stuff like that.
Unless the receiving antennas are circularly polarised that won't count for
much. There's a potential benefit when mobile receivers are in use, in some
cases portable receivers as well..
In the UK the term 'mixed' polarisation is used in Band II and the
broadcasters (mainly via Arqiva) don't pay extra for a specified phase
relationship, but antenna manufacturers like Alan Dick
(
http://www.alandick.com/broadcast_an...roduct_004.htm) produce
mixed-polarisation and circularly-polarised versions to suit different
markets, as they would. UK terrestrial television in Bands IV/V is all
plane polarised (H from 50 main stations and V from most of the rest) at the
moment. DVB-H trials in L-Band may have used mixed (i.e. slant or
elliptical) polarisation.
Way back up the 'phone bill I posted in a thread titled 'Circular versus
linear polarisation' a link to:
http://downloads.bbc.co.uk/rd/pubs/reports/1970-35.pdf which you may find
interesting.
Chris