Marti STL-20M Question

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coastbroadcaster80
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Marti STL-20M Question

Post by coastbroadcaster80 » Sun Oct 28, 2018 4:57 pm

I currently have a Marti 20M transmitter at my studio location going to the tower site where an R-10 receiver is.

At the present we are running a talk format so mono was fine, however we are upgrading to a music format with our new FM translator in place and need to be in stereo.

Is it as simple as just upgrading to a new stereo Marti transmitter? If so can this utilize the current dishes in place or does it require and upgrade on everything?

TPT
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Re: Marti STL-20M Question

Post by TPT » Sun Oct 28, 2018 6:03 pm

You need to buy a stereo (i.e.--composite stereo) transmitter and receiver pair. I would recommend an Armstrong X-Link rather than the Marti composite STL systems--have two of the later at one site, and have had periodic problems with the power supplies.

If you have a good signal with the present system (near full scale on the receive end) you should not have signal problems, and can use the present antenna system.

You will need to go through the frequency coordination process since the stereo system occupies more bandwidth. I would normally use Terrestrial RF--but they are an I-heart subdivision and I see they have stopped work. Comsearch maybe? You can search the FCC's ULS licensing to see if there is someone on an adjacent channel that might be a problem: http://wireless.fcc.gov/uls/index.htm?job=home

TPT
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Re: Marti STL-20M Question

Post by TPT » Mon Oct 29, 2018 2:11 pm

Another option is to buy another mono Marti transmitter receiver pair. Another Marti STL 20M system is slightly cheaper than a composite system. You can also find refurbished STL-10/R-10 combos on line for around $2500. You would then need a combiner (sometimes called a "circulator") which will allow you to connect both translators to the same antenna. The device provides an isolation network so the transmitters don't try to burn the other transmitter's output transistors. Marti made one, but these are hard to find on the used market. Suggest calling SCMS, Inc., BSW, or Broadcaster's General Store & see what they might have available.

You don't need anything more than a "T" connector at the receive end. However, with this set-up, you do need to move your audio processing out to the transmitter site.

If you haven't built the translator yet, you may want to check into either Nautel or Gates Air, since both sell an add-on Orban processor card that goes right into their transmitter. Then you would need to have a system that brings left and right audio to your translator site, instead of using a single stereo (composite or multiplex audio) system.

Lee_Wheeler
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Re: Marti STL-20M Question

Post by Lee_Wheeler » Mon Oct 29, 2018 5:03 pm

If the translator is at the AM tower site you will need either a composite system or, as was suggested, a second mono system. With the composite system your FM processor will be at the studio but with the two channel mono system the FM processor will be at the transmitter site.

The nice thing about the Marti STL-20C is that there are both composite and mono outputs and the mono output is de-emphasized. You wind up with processed FM composite for the translator and also processed and de-emphasized audio for the AM system. When I install the 20C in that configuration I back the AM processor off a good bit and let the newer FM processor do the heavy lifting. In most cases the AM processor at most sites is fairly long in the tooth and the AM sounds a good bit better with the FM processor doing the bulk of the work.

...Lee

RodeoJack
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Re: Marti STL-20M Question

Post by RodeoJack » Mon Nov 05, 2018 8:16 am

I've only had 3 dual-mono systems under my care over the years. The concept was preferred by the engineer I followed at those stations. He (and George Marti) didn't have much use for composite at the time, though admittedly, it was early in those years and control of overshoots wasn't fully understood. In my teens or early 20's, I talked to both of them about it and was quickly shot down.

That said, the one dual-mono system I still have sounds very good. When we started having problems with it (an older Marti) system, the station elected to have the units, including an AM link, refurbished. With the use of some loaner gear, I sent them all out to Bohn Broadcast, who replaced the power supplies and a raft of capacitors, obsolete transistors, a couple of rotary selectors and the incandescent meter lamps. They came back working rock-solid. Where I needed a few watts to get from one end to the other, now less than 1. The combiner runs much cooler, as a result.

Use of a dual-mono analog system requires the processing be at the transmitter, but that's not really much of an issue... especially if you have online access to the site and a processor you can get into.

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