Synchronized Translators

[David Sharp]

I've recently had to compile some FM lists for a major publication. And I've found that in many markets, i.e. San Francisco and New York (amongst others), stations are putting synchronized translators to work. I realize, to do so in TB would probably mean a major shake-up on some frequencies. But...wouldn't it be a better use of spectrum, than having, for example, a dozen translators (on as many frequencies) rebroadcasting Joy FM or some other station? Maybe someone on the technical end of the business can explain why sync translators aren't being used in TB?

 

[rfrus]

Synchronous translators cant be used to extend a stations coverage. They are used to just fill in coverage blocked by mountains or buildings within their existing coverage. Regular translators on other frequencies can be used to extend station coverage.

 

[badjef]

How would you be able to "fill in the gaps caused by the geography of political boundries of county lines?

Synchronized transmitters have always seemed to me to be an under-used answer to signal and coverage problems.

Jeff in Sa-ra-so-ta!

 

[fybush]

How would you be able to "fill in the gaps caused by the geography of political boundries of county lines?

Synchronized transmitters have always seemed to me to be an under-used answer to signal and coverage problems.

They simply don't work over very flat terrain like Florida.

Here's the way the rule works: an on-channel FM booster can't extend your coverage beyond your predicted 60 dBu contour. In Florida, there's nothing to keep your real-world signal from matching your predicted contour. No hills, no really tall buildings a la midtown Manhattan or Chicago. So all that an on-channel booster would do is create interference between the booster signal and the main signal.

Where boosters work well is out west, where you can have areas that are close enough to the transmitter to be within the predicted 60 dBu contour, but in reality are on the other side of a mountain range and not hearing the main signal at all. Pop in a booster and you're in business. In NYC, they're used to improve the in-city Manhattan signals of stations like WFUV and WFMU that have their main transmitters outside Manhattan, suffering signal blockage from the "terrain" of those skyscrapers.

 

[badjef]

Still sounds as though the problem is not so much technical as it is political.

In Florida, A problem is protection to the north from stations operating in the "upper 47" as I call it. Pasco and Hernando Counties are part of the Tampa ADI but signals are nulled.

In NJ, Z-100 and CBS-FM have a problem because of co-channel. Seems to me that lower powered synchronized would be the answer to that problem.

Philly was looked at as that small town. If a house was able to pick up both markets, the antenna was invariably aimed toward NYC. This was mostly due to the "New York 7". All the "important stations" were on VHF.

Jeff in Sa-ra-so-ta!

 

[fybush]

Still sounds as though the problem is not so much technical as it is political.

Not so. If the signal's not reaching Pasco and Hernando counties now, then it's probably outside the 60 and you can't put a booster there anyway.

I guess you could call that "political," but only in the sense that any limits on a station's power are ultimately set as much by politics as by engineering.

And again, here's the thing - analog FM radio simply falls apart when the radio is hearing two signals on the same frequency coming from two different locations, even if they're "synchronized." On-channel boosters only work in areas that get essentially no signal from the main transmitter, either because they're behind a mountain or because they're behind tall buildings. They don't work well at all when there's a decent-but-not-great signal coming in over flat terrain from the main transmitter.

That's not political. It's technical.

 

[HadYourPhil]

Scott is correct.

 

[badjef]

Still sounds as though the problem is not so much technical as it is political.

Not so. If the signal's not reaching Pasco and Hernando counties now, then it's probably outside the 60 and you can't put a booster there anyway.

I guess you could call that "political," but only in the sense that any limits on a station's power are ultimately set as much by politics as by engineering.

And again, here's the thing - analog FM radio simply falls apart when the radio is hearing two signals on the same frequency coming from two different locations, even if they're "synchronized." On-channel boosters only work in areas that get essentially no signal from the main transmitter, either because they're behind a mountain or because they're behind tall buildings. They don't work well at all when there's a decent-but-not-great signal coming in over flat terrain from the main transmitter.

That's not political. It's technical.

The tri-cast of Y-107 would support that. No matter where I was around the City, I would still hear the picket fencing of the co-channel.
Although I never knew if it was "synchronized" or just simulled.

But, what about WWV and WWVH? are they synced?

Jeff in Sa-ra-so-ta!

 

[fybush]

But, what about WWV and WWVH? are they synced?

Kinda sorta. They're certainly both precisely on frequency, and the time pips are (obviously) synchronized. The audio is separate on each transmitter, and scheduled so that Mr. WWV and Ms. WWVH are never talking at the same time.

But AM is a different beast. Since there's no capture effect like on FM, you don't get the same kind of destructive interference from picking up two signals at once. In Europe, it's common to have national networks of "synchro" transmitters all carrying the same programming on the same frequency. They work pretty well, although in some cases they use two frequencies (like BBC Radio 5's 693 and 909 kHz in the UK) to allow for more high-powered transmitters and less interference.

You can do that here, too - except that the FCC doesn't allow synchro AM except on an experimental basis, and there are only a handful of them.

 

[badjef]

But, what about WWV and WWVH? are they synced?

Kinda sorta. They're certainly both precisely on frequency, and the time pips are (obviously) synchronized. The audio is separate on each transmitter, and scheduled so that Mr. WWV and Ms. WWVH are never talking at the same time.

But AM is a different beast. Since there's no capture effect like on FM, you don't get the same kind of destructive interference from picking up two signals at once. In Europe, it's common to have national networks of "synchro" transmitters all carrying the same programming on the same frequency. They work pretty well, although in some cases they use two frequencies (like BBC Radio 5's 693 and 909 kHz in the UK) to allow for more high-powered transmitters and less interference.

You can do that here, too - except that the FCC doesn't allow synchro AM except on an experimental basis, and there are only a handful of them.

Sounds like politics to me.. nevertheless, the TIS's would be more efficient if they could just target the Interstate. Construction zones would be paid closer attention to, and emergency services would be able to make better use of unused frequencies for their purposes, especially since local stations are almost non-existent when needed.

Jeff in Sa-ra-so-ta!

 

[fybush]

Sounds like politics to me.. nevertheless, the TIS's would be more efficient if they could just target the Interstate. Construction zones would be paid closer attention to, and emergency services would be able to make better use of unused frequencies for their purposes, especially since local stations are almost non-existent when needed.

TISes are another kettle of fish entirely. They're governed by different rules (and indeed by a completely different branch of the FCC), and they can indeed be operated synchronously. We have a bunch of them on 1610 strung along the NY Thruway up here, for instance.

There are some good engineering reasons for not allowing synchro operation on a regular basis on AM in the US. We have a much more crowded spectrum than Europe does, by several orders of magnitude. Adding dozens or even hundreds of synchro transmitters at night would create even more skywave chatter and even more noise on the band for other stations.

 

[badjef]

I seem to recall there was an antenna system designed to reduce nightly skywave propagation effects. Whatever happened to it?

Jeff in Sa-ra-so-ta!