STL Repeater?

[TheSigma]

HI, I assist an engineer in a small religious station (FM). we are going to be moving our studios to a new location and we are concerned about losing line of sight for the stl. it is 900Mhz I believe or is it 950. anyway, we have considered satellite, but would rather not go that route. What we are considering, if the city will not let us put up our own tower on our site, is to use the roof of a taller building nearby (about 2,000 feet or so). Of course this depends on working out an arrangement with the building owner. The question that remains for us is how to go from our location to this rooftop 2000 feet away? I thought about a laser at first, but what if we have a flock of birds fly through the beam? is there some sort of repeater we can use? please forgive my ignorance but my Real world RF experience is mostly with Cable Television systems. The chief engineer was going to do some more research on it but I thought I would ask here, since you all are so nice.

\Thanks,
NS

[techboywi]

Now...I'll preface this by saying I'm not a engineer.. But, I have learned several things from reading things on here, and listening to TWiRT. Another option is to use IP Audio. You can run a T-1 line from the studio to the transmitter site, put the audio on that, and your in business. The braintrust here can provide you more details on how all that works, as I don't really know how it does...it just does

[RGORJANCE]

There is another option. Purchase a pair of TIELINES, get a local straight pots line set between the studio and the transmitter site. The pots line is then dialed and you have a mono path set and ready to go. It is reliable, high quality and may be cheaper in the long run than paying roof top rent on the other building.

Contact Kevin at TIELINE for specifics.

The other possibility is to try for a "billiard shot" path attempt if you lose the signal.

A short story - back in the 50's a new TV station was going on on the air in Tulsa, OK. They built their studios in a solidly built building on the NW side of downtown. As they were getting ready to put in the waveguide they found the floors to be solid concrete with no path to the roof. The solution was to connect the xmttr to an antenna and point it out the window and using two 10 ft square aluminum panels, one outside the window and one by the top floor, outside and did a billiard shot signal to the TV xmttr site about 15 miles out of town. Worked perfectly for several years.

Fossil

[RGORJANCE]

Oooopppsss! Sorry, I failed to notice you're FM and probably running stereo. Still possible, talk to Kevin.

Fossil

[NECRAT]

In Boston, a station group is using a Moseley 5.8 GHZ Spread Spectrum STL to link from the studios to their AM tower, as they can't hit the Newton tower directly from the studio and need to from the AM array, which is about 3000 feet away.

[TheSigma]

The other possibility is to try for a "billiard shot" path attempt if you lose the signal.

A short story - back in the 50's a new TV station was going on on the air in Tulsa, OK. They built their studios in a solidly built building on the NW side of downtown. As they were getting ready to put in the waveguide they found the floors to be solid concrete with no path to the roof. The solution was to connect the xmttr to an antenna and point it out the window and using two 10 ft square aluminum panels, one outside the window and one by the top floor, outside and did a billiard shot signal to the TV xmttr site about 15 miles out of town. Worked perfectly for several years.

Fossil

OK, am I understanding this correctly? They bounced the signal off of the two aluminum plates? Will that work at 950MHz? I just confirmed that is definitely our STL frequency.

AT others, thanks for the suggestions, we were avoiding POTS/T1 due to expense but if the roof lease would be more costly then it is an option. We are stereo but as I understand it we are sending discrete mono channels to the TX where it is made stereo. If the new building deal goes through we will be able to dosome tests probably first of the year. Thanks for the suggestions.

[RGORJANCE]

Here's what they did. A large square aluminum plate was mounted outside the window with the stl xmit dish inside the window. The plate was angled so that the signal was directed straight up. The upper plate was mounted on the outside of the building near roof level and angled in order to direct the signal horizontally, with a slight lean to the North-Northwest to reach the xmttr site.

As to the physical size you would use, I would guess you could keep it reasonably small if you don't have the physical beef to support it. I would bet that you could even use a light metal screen to achieve the same effect. How long is your path?? Do you have lots of snow/ice in the winter?

Deep Thought is much more qualified to suggest size on the reflectors than I am.

Hope this helps. By the way, once you dial up the pots line, you only get charged for one call unless you are crossing into long distance service - but there is a way around that too.

Fossil

[NECRAT]

In Boston, a station group is using a Moseley 5.8 GHZ Spread Spectrum STL to link from the studios to their AM tower, as they can't hit the Newton tower directly from the studio and need to from the AM array, which is about 3000 feet away.

What about what I said??

[boiseengineer]

Don't think the FCC allows passive reflectors @ 950 MHz.

[Dale H. Cook]

is there some sort of repeater we can use?

One possible option is a passive repeater. If you can put the transmitting STL antenna on the roof of your new studios, put two antennas on the roof of the taller building - one pointed at the studios and the other at the transmitter site, connected by a jumper. You will need to do path studies for both legs to see if you can get enough power into the repeater to make the haul to the transmitter site. You would also need to go through frequency coordination and re-licensing.

[TheSigma]

In Boston, a station group is using a Moseley 5.8 GHZ Spread Spectrum STL to link from the studios to their AM tower, as they can't hit the Newton tower directly from the studio and need to from the AM array, which is about 3000 feet away.

What about what I said??

That would work, I'll have to look into what it cost's. We are exploring all options at the moment, though I think the boss prefers a radio link rather than being dependant on the phone or internet companies. at least if the radio link goes down we know who to blame and can get right on to fixing it. I think he would rather do a sattelite hop than pots/T1/IP.

@RGORJANCE: WE had a whole heck of a lot of snow and Ice last winter, not the most I've ever seen in our area, but probably the most in ten years. It's usually not that bad but we almost always get some accumulations. We are in N. VA just outside the actual DC/Metro Area to the southwest (more west than south)

[KPJL FM]

FCC no longer allows passive reflectors for transmit on anything, and frowns on them for receive sites. Too much scatter. Used to see them on CATV inter-city relay towers many moons ago way up north.

why not use Barix Instreamer and Extreamer IP boxes, only $600 or so for the pair. www.barix.com

[w4cl]

If the RF level is high enough, why not use a directed reflector. Take a dish, aimed at the studio, take a second dish back to back and point it to the transmitter. The only thing between the two dishes is a chunk of RF cable. Maybe the FCC has outlawed those too.

[Deep Thought]

§ 74.532 Licensing requirements.

(d) Licensees of aural broadcast STL and intercity relay stations may be authorized to operate one or more aural broadcast microwave booster stations for the purpose of relaying signals over a path that cannot be covered with a single station.

(e) Each aural broadcast auxiliary station will be licensed at a specified transmitter location to communicate with a specified receiving location, and the direction of the main radiation lobe of the transmitting antenna will be a term of the station authorization.

§ 74.535 Emission and bandwidth.

(e) The following limitations apply to the operation of aural broadcast microwave booster stations:

(1) The booster station must receive and amplify the signals of the originating station and retransmit them on the same frequency without significantly altering them in any way. The characteristics of the booster transmitter output signal shall meet the requirements applicable to the signal of the originating station.

There is no mention of antennas except for the beamwidth requirements. Whether the rocket scientists who administer Form 601 would approve a passive repeater is unknown, but except for the "amplify" part of the description above two antennas properly licensed as a receive and a transmit would comply with the antenna part, and you could easily calculate the EIRP for the "transmit" side.

[dataman19]

Moderator - I know this is an older post - but I feel my comments are still relevant..
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Yes - Passive reflectors are banned- why? because they only redirect about 60-80% of the signal. the rest is sent into outer space (and beyond). This used to wreack havoc with orbiting satellite systems in the 60's and 70's (when satellites became the electronics rage in communications).
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The passive reflectors at the top of towers was a late 1950's / early 1960's solution to expensive waveguide runs up expensive towers. Cheaper towers, and less waveguide meant less money spent on a radio shot. Less money, meant more profits. But passive reflectors radically changed the Microwave Path profile models. Since they had really loud side lobes (and often many side lobes) they limited the number of links that could be accommodated on any given land plot map. Where the old waveguide to dish configuration allowed re-use of frequencies that had large azmith (directional) orientations. The reflectors did not have that advantage - because they resulted in an near omni directional side lobe cluster.
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Tying two parabolic antennas is not against the rules... Why? Because they are not diffractive, nor are they reflective - they are directional. Putting a panel up on a post, the roof of a building - or even the top of a mountain does not allow you to control side lobes. Nor will it allow you to funnel the signal - just scatter it in a general direction. In fact , I can remember using a sky scraper as a reflector in the early seventies outside Washington DC (we were Presidential Comm - no body questioned us - and we never shared anything) it acted just like any rock-solid Microwave path. One of my predecessors eMailed me about six years ago and told me the path died when the old building was demolished. The link died the day the demolished the building. In all the years, no one re-verified or questioned the link. In fact only a light mention was made that the shot had a "non-standard path profile" when the installed the digital microwave replacement was installed in the 1990s. Since my signature was on the upgrade - no one even though to challenge it (This is a testament to how the politicians are afraid of the ear bending term "Presidential Communications"). I was both delighted, and surprised that it had survived - but it survived because it worked so well.
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But even two parabolics with say 6db gain connected with spriral or waveguide interconnection will have at least a 1-2db through signal loss (-3db to -7db is the norm). You cannot add power at each end or one end - without risking violating your power restrictions for the Radio Link. If your radio link is licensed - and then: then you cannot move one end without re-applying for a new license. But you can use a bigger parabolic for the receive dish, and a smaller one for the transmit (if you are talking about a one-way STL link). The larger parabolic on the receive would have a better RF Coupling/capture rating, and result in less path loss. But you are talking about a Parabolic at least double or triple the required parabolic - the feed horn would have to be tuned to the operating frequency, naturally. This arrangement could be placed on the side of a building, and the feedline ran around the building to the transmit parabolic aimed at the distant receiver.
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But - you can use two parabolics hooked together with a feed line to essentially turn your new link (or bend the signal say 60 degrees). But to be legal you will have to do the engineering study and plot field strength and signal paths for "both" and indicate the passive directional repeater in the middle (along with all the same engineering performance data as if it were an active repeater. You still have to comply with mitigating any interence to "other" licensed carriers, etc in the frequency band. Yes - the FCC does look down on these "passive repeaters" - but on the other hand - "They Do license them". Just like they license on-frequency boosters (which virtually eliminate the problems of changing frequencies when using repeaters, and are virtually transparent to the radio consumer driving around in their car) - but no one seems to apply for those licenses either. I wonder why? Oh yea, - because "they don't understand them".
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