Prometheus Background

Organizing Your Station

Creating a community-based low-power radio station takes more than engineering expertise, it takes grassroots and political organizing. Prometheus Alumni Amanda Huron gives some helpful tips on organizing your station, and getting community support for your effort.

Some Ideas About Equipment and Facilities

Pete Tri Dish, from Radio Mutiny and Prometheus Radio Project

[Things to look for in a transmitter][Other stuff you will need]

The Low-Down on Low Power Transmitter Shopping

It is funny, because everyone wants to know right now about transmitter shopping, even though it makes no sense to buy one until you have received your license - which is at least six months from the day that this is being written. But I will humor everyone with a quick guide, which can help you start nosing around and budgeting for the most exciting part of your station, the transmitter.

Things to Look for in a Transmitter

All-in-one versus a bunch of little boxes: It is important to realize that what you need is a set of functions, as opposed to a set of boxes with names on them. Some transmitters (which are generally more expensive) have more of these functions built in. Cheaper transmitters may have less functions built in, and so you may have to buy separate little boxes that do these jobs. Some fancy transmitters may have features or high quality specifications that you will never need, so it makes more sense to have separate boxes. If things are in a series of boxes, they will need connectors and wires, which are often a key point of failure. On the other hand, it is often easier to troubleshoot a discrete part of the chain than to go into the main transmitter and figure out what is going on in there. For example, it may be cheaper to buy a new SWR meter to put in line than to get the one built into the transmitter serviced by the factory.

Approximate Cost

100 watt transmitters of this nature can go for from $3000 to $5000, depending on features. Certified 10 watt transmitters can run from $700-$1500.

Type certification

A type certified transmitter is required for a LPFM license - absolutely no homebrew kits will be tolerated. Type certified kits are made at a factory and tested on a spectrum analyzer before they go out the door. Be careful - some transmitters may claim to "meet FCC requirements" but they have not been through the type-acceptance process at the FCC. When they are certified, it means that not only does the manufacturer claim that the equipment meets the FCC specs, but certification means that the FCC engineers have looked over the design, and agree that it is good enough to meet their standards. It further means that the producer of the transmitter is responsible for guaranteeing that it will not emit spurious signals (that interference that the NAB and FCC kept on complaining about from pirate stations).

Consider donating your old pirate rig to a group in the third world where there are less stringent technical standards because the radio dial is not so populated. Prometheus is collecting a list of groups overseas that can use your old gear - get in touch with us to meet your sister station! Or keep it in the closet for the next Y2K style apocalypse scare....

Frequency selection

Some transmitters set frequency using a little screen and buttons, sort of like setting a watch. Some just have thumb switches. Some transmitters, you may have to open up the box and fiddle with some switches - it is doubtful that these are type-certified.

Power selection

The transmitter should be capable of putting out the power that you intend to broadcast at. Note that this is not necessarily 10 or 100 watts exactly. As a result of your antenna height and other factors, your actual transmitter power may need to be substantially more or less than the ten or hundred watt class of service. Thus it is very useful to be able to vary your output power without a lot of fuss - inquire specifically how the power level is adjusted.

Built in meters

Some transmitters have a variety of meters built in to them. It is up to you whether it is more useful to have a separate frequency counter, power meter, SWR meter, modulation monitor, etcetera. They can be useful in troubleshooting other rigs if they are not built in, but they can lead to a tangle of wires and general chaos if they are not inside the same box with the transmitter.

Signal processing

Some transmitters have their signal processing built in. In others, their signal processing takes place in the mixer, or between the mixer and the transmitter. Some will have a built in limiter, which will prevent your audio levels from going so high that you cause interference to other radio stations.

Maximum SWR

This tells you how badly screwed up your antenna can be without the transmitter burning itself up. Another feature that a good transmitter may have is that it will shut itself off if it senses that the SWR is too high. This is sometimes called VSWR foldback.

Solid state vs. tube driven

Most new things you find today (for a hundred watts or less) will be solid state, meaning they use power transistors rather than tubes. Some old transmitters that you may run across may be hard to find tubes for. Be sure that the key components are readily available on the market, and are produced by companies that are not likely to disappear or go into a different business three years from now. A good place to look for replacement parts is a company called RF Parts www.rfparts.com.

Filters

See if the transmitter has all the filtering that it needs internally, or if it needs more to meet FCC specs.

Guarantee

Like everything else you buy, you should compare the terms of the guarantees that the transmitter companies provide.

Service

A good company will provide over the phone or email assistance - some may even offer it toll free or twenty four hours a day. You can also inquire how long it takes them to make repairs if it is necessary, what they bill for those services, etc.

Other Stuff You Will Need

An Emergency Alert System Receiver. These are not currently on the market. What is on the market is an encoder/ receiver, which costs between $1000 and $1500. It is likely that some manufacturer will seize the opportunity to manufacture an EAS receiver only unit, and the cost has been projected to be between $600 and $1000.

For the studio, there are no requirements. I have put on radio stations that had no audio source besides a walkman in my day. Hopefully you will have more than that. You can use consumer audio equipment that you buy at yard sales and have a perfectly respectable set-up for a few hundred dollars. Keep in mind that that stuff will break and your long term planning should allow you to get professional gear - more expensive, but better sounding and built for constant use.

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