• Get involved.
    We want your input!
    Apply for Membership and join the conversations about everything related to broadcasting.

    After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
    If you use a disposable or false email address, your registration will be rejected.

    After your membership is approved, please take a minute to tell us a little bit about yourself.
    https://www.radiodiscussions.com/forums/introduce-yourself.1088/

    Thanks in advance and have fun!
    RadioDiscussions Administrators

circular vs. horizontal polarization

B

Bob E. Nelson

Since there's not a ``Nashville TV'' board and several threads about DTV has set a precedent...

...what are the pros and cons for the two major types of polarization (discounting elliptical for simplicity)? WTVF (RF-5) is at 22 kw with CP at 1394' and WSMV (RF-10) is 42.4 with HP at 1361'.

In short, would WTVF be better off with horizontal polarization given the characteristics of the Nashville DMA?
 
The vertical component tends to cause more phase cancellations in the analog world. Bonneville did a lot of research on this back in the 70’s that proved there was more ghosting with CP. I don’t know if there is a study as to how this may impact DTV transmission but I’ll bet there is somewhere in the IEEE journals. One could reason it might be a problem as a result of the deep phase cancellations and resulting non-linearity inherent with circular polarized signals. You don’t see a lot of them being ordered though, so that may be a clue. As far as I can tell, Ch-5 OTA DTV has BIG problems in many places.
Time will tell....
 
Watt Hairston said:
The vertical component tends to cause more phase cancellations in the analog world. Bonneville did a lot of research on this back in the 70’s that proved there was more ghosting with CP. I don’t know if there is a study as to how this may impact DTV transmission but I’ll bet there is somewhere in the IEEE journals. One could reason it might be a problem as a result of the deep phase cancellations and resulting non-linearity inherent with circular polarized signals. You don’t see a lot of them being ordered though, so that may be a clue. As far as I can tell, Ch-5 OTA DTV has BIG problems in many places.
Time will tell....
Click to expand...

Interesting, I'd not heard of that part.

Circular polarization is nearly universal among FM stations. (WFSK 88.1 may be horizontal - if it is, to my recollection it would be the only non-circular FM in the Nashville market) It is very rare among TV stations.

Channels 4 and 5 had circular analog signals. (I guess channel 4 still does for another week!) A simply empirical (sp?) test - comparing channels 4/5 vs. chs. 2/8 with indoor antennas at a West Nashville apartment -- suggested circular works very well. Especially by comparison to the horizontal-only channel 3 station I worked for before moving down here. Large reduction of multipath (ghosts) and noise on indoor antennas. But that's only one site.

Circular polarization requires double the power to obtain the same ERP in the horizontal plane. I'm sure that's why there are few UHF circular stations and would bet it's a contributing factor to CP's rarity on VHF.

I strongly suspect WTVF-DT is circular only because they're using their old analog antenna. (there is a possibility that WTVF may be the only circularly-polarized DTV station?)
 
Status
This thread has been closed due to inactivity. You can create a new thread to discuss this topic.


Back
Top Bottom