Multiple Transmitters

Careful Planning for Maximum Coverage

Here in Sioux Falls, SD you can say we are your proving grounds for various multiple transmitter set-ups. There are several points to make for deciding your overall plan as well as the RF (radio frequency patterns) considerations to the desired coverage area.

Most of your plan will be limited to the real estate available for the antenna and audio source equipment. If most people knew the importance of your project it would be easy to get volunteers for mounting points. But with one station already on air others may be inspired to lend a hand!!

Areas to cover - varies according to size of town.

Basic Multiple Transmitter Strategies

For larger towns 150,000 populations or more I like the 2nd strategy. Starting with a planned concentration of an specific area will not only cover that area as desired but if the units are placed properly the overall daytime signal will bleed out further making future expansion more desirable.

The entire strategy is based on the size of the city and the resources you have to get the word out once you are on air. There is no reason to blanket isolated areas across town unless you have the means, signs or help to get the word out about your transmission.

The 4th option in the list above works well as long as your stations don't overlap in strong areas. If transmitter #1 has a 1.5 mile daytime radius then the next transmitter should not be any closer than 3 miles away and further if the 2nd location has a height or ground advantage. Otherwise you will get a zone of phase flutter. Synchronizing the audio is easy with the Barix units feeding the transmitters.

I am currently putting together a synchronized system of hardwired transmitters (3) which will later be fed with a 4th transmitter on a apartment rooftop just over a mile away via microwave. That microwave location (also with a AM transmitter) will point towards an area where there are no obstructions for future systems further away. That location will also right away feed a closer in 3rd location about 5 degrees to the west totaling 5 transmitters in the area. Thus the apartment mounted AM transmitter also has the Microwave transmitter which feeds my three transmitter array on the shopping mall via a microwave receiver and also one to the west near the busiest intersection in town. This total array also serves a mejor apartment (dozens of complexes) and retail area with TWO shopping malls and dozens of service shops who all leave radios on all day. It's quite a plan!

5 transmitters connected together in one spot (50 feet apart minimum) has the effect of doubling the signal service area. My above plan will have two transmitters 1 mile away so should even more effective.

Multiple transmitters can cover the area you need if one transmitter won't do the job. The most common method people are using to cover a larger area with multiple transmitters is place RangeMaster transmitters around town and link them by Internet using a IP/MP3 decoder by BARIX, see this link.
When using this method there are some important things to know. First you need to keep your audio in sync, even a few tenths of a second delay of audio between the transmitter s will cause a noticeable echo as a person drives between transmitter zones. Second, the RF carrier is not in phase sync using this method, the transmitters will not heterodyne (you must use the crystal controlled model) but the PHASES of the carriers will not be synced. Normally you will have a short zone of "flutter" as you drive between zones, not too noticeable, like driving under a power line. However if you don't do a good job of planning transmitter locations and get the transmitters to close together then the flutter will become worse. Do not try to use other (PLL) type transmitters with this method, you can get into all kinds of heterodyne problems.

More on the phase linking with our hardware

An alternative is to have one system pick up the audio, then connect near and/or far your other transmitters via microwave (also part 15). This system also works with our transmitters for seamless coverage. This particular unit we are testing is analog so there are no delay latency problems.
Only Microwave, GPS and direct wiring will allow for perfect phase coordination. The quality of the Rangemaster I must say works well for those who can only depend on the crystal control to zero-beat other non synchronized transmitters. At least with the Barix you can easily adjust the delay.

Additional ways to link and/or synchronize your studio or main transmitter to 2nd and third transmitters:
Dedicated Phone Line
ISDN and Comrex over telco
SCA Transmitted signal (FM sideband) service from local FM station
Local wireless internet service to provide IP/MP3 at distant location. This is also a good back-up system ie - no wires to cut from DSL service.. Can operate 100% on battery and solar. (one must purchase their proprietary wireless modem which uses privately licensed frequencies to guarantee no interference.)

 

 

 

 

MENU

Main Transmitter Page Sales Page Radio Station Page Inquiry Form