Short-Spacing, Part Deux - TV Signals

[eacalhoun]

FM Short Spacing is being discussed in another thread...turning to TV, I've often thought about the proximity of WWAY(Wilmington) and WBTV. Now, I know just enough about radio engineering to be DANGEROUS! But, it seems I've heard that analog TV signals transmit on a positive or negative side of their frequency(or SOMETHING like that) and apparently one way is more favorable than the other. This vague description is the reason--I've been told--that these two channel 3s can be so close.

Also, are there any cable systems aroound Rockingham or Lumberton that carry both WBTV and WWAY? Is there enough overlap--for rooftop antenna users in these areas--to cause interference?

 

[mike704]

> FM Short Spacing is being discussed in another
> thread...turning to TV, I've often thought about the
> proximity of WWAY(Wilmington) and WBTV. Now, I know just
> enough about radio engineering to be DANGEROUS! But, it
> seems I've heard that analog TV signals transmit on a
> positive or negative side of their frequency(or SOMETHING
> like that) and apparently one way is more favorable than the
> other. This vague description is the reason--I've been
> told--that these two channel 3s can be so close.
>

I know we are on the radio board talking about TV but does anyone know why WBTV's signal sucks so bad? I am in east Charlotte and the move from Spencer Mt to the tall tower was a very minor improvement in signal strength here. WBTV-DT does much better.

MikeM

 

[wncmacs]

Without knowing better, I think there's a null in channel 3's signal to the east due to WWAY. That's why 3 is more popular in the western parts of the Charlotte ADI because their signal is much stronger than channel 9's (whose tower is located physically closer to Charlotte).

Eric, there is a +/- shift in TV transmissions, and it is to help with protection of coverage, but I can't tell you much about the engineering behind it, and I don't know which side WBTV and WWAY fall in terms of this.

I'd bet that WBTV-DT is on a different channel than WWAY and the null has disappeared. It will be interesting to see if that helps channel 3 with their ratings in Charlotte, since east-skewed books have always helped the competition.

wncmacs

 

[RickRose]

>
> Eric, there is a +/- shift in TV transmissions, and it is to
> help with protection of coverage, but I can't tell you much
> about the engineering behind it, and I don't know which side
> WBTV and WWAY fall in terms of this.

WBTV has a zero offset while WWAY has a minus offset

>
> I'd bet that WBTV-DT is on a different channel than WWAY and
> the null has disappeared. It will be interesting to see if
> that helps channel 3 with their ratings in Charlotte, since
> east-skewed books have always helped the competition.
>
they are on different DT channel numbers WBTV (23) WWAY (46)



WBTV is non-directional while WWAY is directional

It looks like WWAY is pulled in most towards WTKR Norfolk but the signal map I see is pretty circular.


The separation is 191 miles.

The WSOC and WNCT separation is only 199 miles

 

[mike704]

WBTV signal

If you have rabbit ears on my side of Charlotte (east) WBTV barely comes in. If it does it looks like an out of market signal.

An engineer frind of mine says there are similar stories from stations on Channel 3,(I think he said they have similar problems with Channel 3 in Cleveland) leading him to believe there is just something odd (pun intended) about that frequency.

WBTV-DT and WCNC-DT come in great but even better is WNSC-DT Rock Hill which seems to come in well no matter where I point the antenna. The others can be rather picky even the ones close to me like WSOC, WCCB, WUNG.

MikeM

 

[ncradioeng]

Re: WBTV signal

Cochannel stations are assigned offsets of 0, +10khz or -10kHz to reduce interference from the "beat effect" of two signals very close in frequency. You will see this during band openings as two pictures on the TV - one behind the other with the black verticle bar (horizontal blanking pulse) moving across the screen. If one station is offset from the other by 10 kHz, then the interference is see as thin horizontal lines in the picture which is usually less objectionable the flickering caused by no offset.

 

[Keith_Lake]

Re: WBTV signal

Do WNCT-TV 9 in Greenville and WSOC-TV 9 in Charlotte have similar offset arrangements? What about WCTI-TV 12 in New Bern, WXII-TV 12 in Winston-Salem and
WWBT-TV 12 in Virginia?

Of course the impending digital switchover will make all these points moot, but I was kind of wondering...

KL <P ID="signature">______________
<a href="http://home.nc.rr.com/gttyson/lastradio.html">The Last Radio Station<a></P>

 

[ncradioeng]

Re: WBTV signal

Go to www.recnet.com and enter the call sign of the station. It gives all you need to know about power, offset, etc.

 

[moedog1]

Re: WBTV signal

Its funny---lower band Tv channels (2-6)used to be considered to have the advantage---with UHF thought to be at a great disadvantage. Now, with increased electrical interferrence, it seems the opposite is true. WBTV and WWAY are not short spaced and neither is directional towards the other. But it is true that WBTV has serious reception problems in Charlotte and all points east. I think WWAY's tower site very close to the Atlantic plays a role in this. I lived in Cheraw SC for years and subscribed to Adelphia Cable which always carried WBTV. Reception of WBTV was always poor, but whenever there was a cloud cover over the Atlantic in the Wilmington area, you could just about forget any reception of WBTV OTA or on cable. Often you would get WWAY instead, even though Adelphia had a gigantic antenna for WBTV high up on their 400 ft tower. For the last year or so, I have noticed on trips back that reception of WBTV on Adelphia is much improved, with no electrical or weather interferrence---I believe they are now recieving WBTV via Dish or Direct--the picture has the characterisitic pixelization/fuzziness seen on DBS locals. Regarding Rockingham/Wadesboro cable, Time Warner has been recieving WBTV (and all Charlotte stations) there via fiber for years.