FM Tropo Ducting - Is There a Solution to This Problem?

[Kmagrill]

Boosters do work great on AM, space them right and sync the carriers it works well. FM (because of the nature of the modulation, cant have carrier sync *I think*)

It is possible to sync FM boosters, but it's not trivial or cheap. Among other things, it requires an audio delay with microsecond precision. An aux transmitter located in the heart of the population that employs a high powered transmitter, driving an antenna with as few bays as possible, is a cheaper and more practical solution for severe ducting.

 

[Studio1]

FM (because of the nature of the modulation, cant have carrier sync *I think*)

Synchronous modulation on FM is certainly possible, but not cheap. It's being done a lot here to enable re-use of frequencies on networked stations. There is some very fancy controlling electronics.
It seems to work reasonably well, although there is usually a patch of 'crap' where the two signals overlap, but this only lasts for a few moments then it's gone.
It would be a solution to your ducting issue though.

 

[kenglish]

I was thinking about my previous post last night, after a couple of days off playing with antennas (yeah..I know! : )....

Has anyone ever done a comprehensive study (FCC, NAB, colleges, etc.) of tropo ducting, and how it affects broadcasting?
Anything ever been tested on how high the ducts are, how tall or short they are, etc?

I was thinking about what it would take to put some RF beacons (maybe on Channel 6, narrow band CW Identifiers, very low power, slightly different frequencies for each 100 feet above ground) that could be monitored by anyone with a communications receiver or scanner, on some of the tall towers, and see how these things work.

It would be a little bit like the HF Beacon network that Hams use, but the ID's would not need to be precisely timed.

 

[local oscillator]

Just in case anyone here is not familiar with the Hepburn tropo ducting site, here's the url: http://www.dxinfocentre.com/tropo.html. It doesn't solve the problem, but at least it tells you with quite high accuracy when you're about to be nailed!

 

[mikl73]

and you should also bookmark http://aprs.mountainlake.k12.mn.us/

This uses the Automatic Packet Reporting System that is used by many of us Amateur Operators on 144.390mhz.

 

[TomZ]

Thanks Michael for this link.

 

[OKCRadioGuy]

The mountainlake APRS site has proven to be very accurate near-realtime for ducting issues for our stations. I'd "go to the bank" with what you see there....

 

[kenglish]

I've found both sites to be very accurate, even with the limited amount of tropo here (Utah).
It would be nice to evaluate the heights of the ducts, too, in real time.