Linking part 15 transmitters by phone line

Try to find out what type of circuit you can get from the phone company. Ideally, you want a solid copper pair running from the studio to the transmitter. Often, the phone company will put loading coils on the line, which will affect the frequency response of the line.

If you can get a radio control circuit, that's what you should try to get. It's designed to pass audio and DC to control a two-way base station radio.

The telcos have so much fiber now. It's getting harder to find copper pairs.

There will probably be some frequency beats where the two transmitter's patterns overlap. It's something we just have to live with.

Frank
www.easthillradio.com

Depending on the type of station you have, AM or FM, audio phasing problems can be significant for multiple transmiters with over lapping coverage areas. Not only will the RF signal produce a beat frequency, but so will the difference in the audio phase. It usually shows up as attenuated high frequency audio (AM). However, over a phone line, it will be hard to tell without doing an audio frequency sweep and measuring the high fequency attuation at the second transmitter site over the raw phone line. When licensed broadcast stations used to use phone lines (broadcast loops) for sending audio to remote transmitter sites, the phone company set up equalizer units at both ends of the circuit. The inductive reactance in a couple miles of copper wire is sufficient to knock out most of the audio above 5 KHz.

My suggestion would be to set the remote transmitter to a different frequency from the first and deliver the audio by streaming the programming over the internet. Then, if you wanted to, you could locate remote transmitters wherever you wanted, and as many as you wanted. Just promo the different frequencies for different neighborhoods or communities.

And finally, If you want to get entirely trick. Try a company called Trango Communications for 2.4 GHz (Eagle system) or 5.8 GHz (Falcon System) Part 15 microwave systems. They are not cheap, but they work like gang busters. That's how I plan to deliver my program audio to the remote transmitters.

http://www.trangobroadband.com/products/ntsc_pal_video_products.shtml

I hope this helps a little bit.

Marshall Johnson, Sr.
Rhema Radio - The Word In Worship
http://www.rhemaradio.org

Marshall gives good advice. I would add that many moons ago I engineered and managed a 24/7 life support computer system where I needed to move analog data over phone lines. I leased what were known as 3004 direct metallic conductor lines which were really intended for alarm circuits with COAM terminal equipment (phone co. jargon for customer owned and maintained...my jargon "It's not our problem if it doesn't work"). There are restrictions governing their use including bandwidth limits and you can get disconnected if you put audio frequencies through these lines. It was difficult to get the phone company techs to cooperate when the lines went down even though they were "red capped" meaning critical circuits.

Avoid this if you can. I worked at a carrier current station on a major college campus. We had leased broadcast quality phone lines to our transmitter sites which cost $100 / month in 1960's. They were terrible! Very poor bandwidth, long outages without response, and the volume levels would change from hour to hour.

Marshall's suggestion about microwave links is worth a close look. The high initial costs may well be offset over the time that you use them compared to leased lines. Plus, you are in complete control of the situation. Try calling for phone co. service at 3 AM as I have and you will learn the lesson.

Neil