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2 STL's on Same Frequency

B

BobOnTheJob

I once tried running 2 STL transmitters on the same frequency with opposite polarity and aimed in substantially different directions. It didn't go well. Curious to know if anyone has also attempted this?
 
We have two STL shots...two different stations in the same market...on the same frequency...we send a signal in their direction and they send one, basically, past where our xmtr is (towards us).

It was never really an issue when we were both running composite analog....until THEY went digital and we noticed noise in our baseband signal feeding the xmtr.

When we eventually went digital, the problem disappeared.
 
I had a problem sharing a cross polarized STL with another station going in completely opposite directions. I was getting into their audio. I was able to resolve it by putting in a 10dB pad and still had plenty of signal at my receiver.
 
Bob, was your transmit dishes on the same tower or something? I have had luck doing this, as long as the transmit dishes are not too close together.
 
The dishes were about 15' apart with 1 aimed east & 1 aimed southwest. One analog & one digital. One H and one V. The digital showed a higher than usual error rate, but worked. The analog one had some noise in the background. In this case (the boonies), finding another freq was no problem. The owner was just wanting to avoid the cost of re-crystalling the STL's.
 
Bob, I've seen it operated the way you describe for a day/night AM STL relay site and it worked fairly well. We used the same model transmitter on both paths, both analog with digital encoders in to the composite input. Old Mosley PCL series stuff i think.
 
I've seen a power splitter on one transmitter feeding two different antennas & sites. They were using a 4-channel DSP6000 so each had it's own program feed. It was in a location where the 950 band was full.

We've had bad luck when trying to get other stations digital to co-exsist with our our analog path. Even when spaced +- 250 KHz. However, many cross-pol 250 KHz spaced analogs at this site get along just fine.
 
I have two Starlink transmitters on the same frequency shooting in nearly opposite directions
from the same studio site. One v-pol, one h-pol. About thirty feet of horizontal separation
between the antennas. No problem.
 
Fifteen years ago I worked for a frugal (that's being kind) owner doing on air and production. The prior engineer had placed the STL transmitter and processing under a desk. During a Saturday shift I walked into the control room and heard oldies instead of classic country on a noisy signal. I called the transmitter and the remote control indicated 100 percent power. Other radios had the same thing, oldies on our frequency. The signal ID was from a station in an adjoining market about thirty-five miles away. I called the contract engineer and general manager and they were stumped as I was.

After about an hour of going crazy trying to figure out what the hell was going on, the GM fixed the problem. It turns out I had kicked the power button on the STL transmitter located under the desk and shut down the unit. The STL receive antenna was high enough in elevation and aimed in the same direction as the distance signal and our studio. Their STL was licensed, our wasn't. The previous engineer was given an STL by the frugal owner and neither bothered with paperwork, they just put it on the air.

Soon after the processing and STL were placed in the rack so that would never happen again. I think they eventually licensed the STL.
 
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