Odd tower config.

[SFM-Ptgal]

I was told that these 2 towers broadcast the same frequency, for the same station. What I ask is if can it be true? I find odd the use of 2 towers for the same purpose...

http://i215.photobucket.com/albums/cc118/SFM-PTGAL/8f93.jpg

Pedro

 

[rfry]

Appears to be two towers each supporting a multibay FM transmit antenna, in which case the frequencies would be different. Using the second tower might have been necessary if the first tower could not support the weight/windload of the second antenna.

Let's hope they have some good r-f filtering in place to control r-f intermodulation.
//

 

[SFM-Ptgal]

Appears to be two towers each supporting a multibay FM transmit antenna, in which case the frequencies would be different. Using the second tower might have been necessary if the first tower could not support the weight/windload of the second antenna.

Let's hope they have some good r-f filtering in place to control r-f intermodulation.
//

They use the same frequency, I was told...

Another question, a few (many) years ago a local station tilted their V.Pol. dipoles towards de village wich was located down there at the sea level, not with the tower in sight. Is there an advantage tilting dipoles for nullfill?

 

[rfry]

If those FM antenna arrays are on the same frequency, and fed with a stable r-f phase relationship then the net radiation pattern (plus the tower effects) would have numerous lobes and nulls in both the elevation and azimuth planes. I doubt that it would give usable performance.

As for tilting vertical dipoles, the link below leads to a NEC plot of the surface pattern for an array of four "vertical" dipoles tilted by rotating them so the top and bottom of each dipole is offset 12" from the vertical plane. The top and bottom dipoles can be seen in the plot, the middle two are obscured by the pattern.

The resulting pattern might have helped, if the village was in the right place for the path geometry to radiate that large lobe pointed toward the ground in the right direction.

http://i62.photobucket.com/albums/h85/rfry-100/4BaysofDipolestipped.gif

//

 

[DTV-Chief]

Appears to be two towers each supporting a multibay FM transmit antenna, in which case the frequencies would be different. Using the second tower might have been necessary if the first tower could not support the weight/windload of the second antenna.

Let's hope they have some good r-f filtering in place to control r-f intermodulation.
//

They use the same frequency, I was told...

Another question, a few (many) years ago a local station tilted their V.Pol. dipoles towards de village wich was located down there at the sea level, not with the tower in sight. Is there an advantage tilting dipoles for nullfill?

I wonder if one is the main and one is a backup? When they told you they used the same frequency, did they mention whether or not simultaneously?

 

[bilco]

my Guess would be main and standby if on the same frequency. Maybe Analog FM on one, HD FM IBOC for the same channel on the other? Several years back, if memory serves me right, there was a station in Vail Colorado that had two seperate Collins 25 KW transmitters fed with a single exciter, then feeding seperate coaxes and Antennas on the same tower. I remember it didn't really work that well the way it had been predicted. Several very good engineers lost hair trying to make that work. There may be some on here who know more than I as I only visited the site twice. As Richard said, it may not really have that much advantage.

Bill C. the Chief E.

 

[stace]

Apologies if this is not on topic.

Our capital city Wellington is a very difficult market to broadcast in due to terrain, and most stations require two frequencies, one at 50kW and one usually 2kW. However one station uses a method I'm told called synchronous, which allows both transmitters to broadcast on the same frequency obviously from different locations, but in situations where ocassionally signals from both transmitters can be recieved.

How does this work?

Regards
Stace

 

[littlejohn]

>how does this work?

Better than if they aren't synchronized

Usually, each transmitter uses a high stability freauency standard, and the modulation should be matched to the extent possible. In areas where both are line - of - sight, the power levels between the two should be fairly large to precklude complete nulls of the signal. Works better in rugged terrain - which is where you usually see the setup. Currently, a common method of keeping both together is locking the reference frequency to a GPS signal.