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Picking a frequency for transmitter


scubado

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I've got a question that might be stupid, but might provoke some interesting feedback. I haven't seen anything about picking a frequency. Do you find a frequency first that won't interfere with local stations and then try to match an antenna? Or are there some other considerations to think about also? This might be pretty straight forward once you have a transmitter, but I'm in the same boat as others wanting to get one this year, so I thought I'd ask the dumb question.

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The link above is a very good place to start.

In some areas, you have other considerations as well. If you are close to a border, it may not reflect the crazy station in Mexico that stomps on an otherwise attractive looking frequency.

But, it is a good starting place. For optimal distance, look for not just minimal signal on the frequency in question, but also minimal signal on adjacent frequencies. If you are staying legal, you don't have to worry so much about interfering with anyone, so much as getting adequate range through all the clutter. But if you are running a hot rig, you really do want to pay attention..

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Like klb says, NOT running a "hot rig", and staying legal, is your best bet..;)

Listen for several days on your selected freq, both morning, dusk, and at night.

One thing to consider is, if you do broadcast on a local channel (you'd think it would be something someone just would not do, but I'm sure its happened..), you're more likely to get a complaint from a neighbor (to the station and possibly the FCC..), than you are the FM station whose operating freq you are on. They likely won't notice you...one of their devoted listeners will.

Imagine the phone conversation as this person calls the station and asks why they are suddenly paying Christmas music in August...:D

I won't even get into the debate of how imprecise you'll likely be trying to match antenna to exact operating freq...:D

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You really do not need to worry about matching the antenna to an exact frequency. Given the low output power of these transistors, you risk damage to them as much/more from a static discharge than you do reflected power from a standing wave.

The easiest thing to do is to cut you antenna for exact midband - 98Mhz, which will more than cover 88 - 108 without issue.

That way if you need to change frequencies later, as many of us have had to do when newly licensed stations come on board, you will not have to make any changes to your transmission system.

Again, we are dealing with flea power outputs from transistors, the vast majority of which can be driven much harder than the kit designs allow to keep it within part 15.

Greg

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What I did last year for my first year was to use that website, then get some ideas where the free frequencies would be. Then I got in the car and tuned to them. I finally found a couple.

I would tune to them over a period of a week to each frequency to see which ones were still clear. I found that at night some come through that you do not hear during the day, so you should do a good check, just as Don mentioned. Also weather affects the channels a bit and we get a lot of rain around here.

I finally nailed it down, then transmitted our station for a week test, and driving around and that seemed to be the one. Once you drove a few miles out of town, you could hear a very distant station, but it was extremely far and very faint. But it was clear and clean in town.

One other thing I have learned from the forums here, is don't count on that frequency next year. Sometimes they change, so make sure you think about that for the following year.

I bought one of the coro signs that is pre drilled with holes for lights, so I can change it if the frequency has to change next year. I hope not, but just in case.

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paulanator wrote:

One other thing I have learned from the forums here, is don't count on that frequency next year. Sometimes they change, so make sure you think about that for the following year.

I bought one of the coro signs that is pre drilled with holes for lights, so I can change it if the frequency has to change next year. I hope not, but just in case.


Excellent point! It would appear that you learn very quickly!:(

I purchased an aluminum sign for my listen to sign a number of years back. So far I have been lucky (the fact that I live remote from cities greatly helps), but I am cognizant it may require a change at some point.

A sign allowing frequency updates/changes is a much better idea! :cool:

Greg
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