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Range
I am interested in starting a Part 15 AM station. I have applied for full power AM licenses, but the applications will be tied up for some time and I’m anxious to get something on the air.
I’m sure that the question of range will have a lot of “that depends” type of answers, but I’m wondering if I could get a general idea.
I’m in a small town on the west coast (about 30,000) and have an office in the center of town. I have access to the roof which is about 30′ above the ground and from there have a line of site for a couple of miles in all directions.
I am considering using the Hamilton unit. Also, I’ve heard I could use two transmitters at the same location and increase the range by 25%.
I have heard all kinds of stories about range and how good the sound is, from half a block to two miles or more.
Just wanted to know what I might be able to expect if I set this up properly, and don’t cut any corners (while keeping it legal of course).
A one mile radius would probably cover about 70% of the town, a 1.5 mile radius would cover about 85%.
Lastly, I wanted to know if there is anybody who is actually making money with a Part 15 station.
Total posts : 45366Hmm…By what I hear you would get 1/2 to a 1 mile coverage (With some static.)
Hey, on a side note, does anyone know about a Rangemaster’s Nighttime coverage?
Total posts : 45366Broadcastman,
I have a Part-15 AM and was on the air part time until I took early retirement from a commercial station in July.
It is not making a lot of money, but it is making some. You can visit
my website at http://www,expage.com/wjjd to visit my site. Near the
bottom, you’ll see a link that says “our advertisers are here” and you’ll
see the list of everything that is on the air.I use a Cunningham transmitter with a listenable 1.5 miles. I’m moving
within the next year to a small rural area (population 430) and this station
will pretty much cover the town. I operate as a daytimer, so don’t know
how the night coverage would be. I’d imagine it would get drowned out
pretty quickly. 🙂
Total posts : 45366Sorry…typo on the URL above!
http://www.expage.com/wjjd
Sponsors direct link: http://www.expage.com/wjjdsponsors
Total posts : 45366Here’s my $0.02:
1. Having a good antenna ground (actually a counterpoise on an elevated installation) makes a lot of difference in range. Rangemaster has a drawing of a good ground plane system on this page:
http://www.am1000rangemaster.com/groundxmit.html
The transmitter should be located in or near the center of the ground plane, so the “To Trans” lead shown in the diagram is as short as possible. The FCC considers the ground LEAD from the transmitter to the ground SYSTEM (or PLANE) to be part of the 3-meter limit.
The Rangemaster drawing indicates 64 or more radials of #12 or larger wire. However, if your situation demands thinner wire or fewer radials, then go with as much as you can put up. The better your ground, the more use you can make out of your site (which is pretty good from your description). With a good antenna and ground, you should get at least 1 mile range, 1.5 is definitely possible.
Given the antenna restrictions, your frequency will also affect range. A 3-meter antenna is massively short anywhere in the AM broadcast band, but it will be much less so toward the high end. Prevailing wisdom is to be at least above 1500 kHz, and preferably above 1600, which is in the less-populated “extended” band.
Receiving setup also affects range. Encourage your listeners to get a good receiver (the GE SupeRadio III is one of the best for performance and value) or a manufactured passive loop antenna such as:
* The Select-A-Tenna (get one that goes to 1700, some older ones don’t)
* The Terk AM-1000 Advantage
* The Radio Shack 15-1853 (discontinued, available used but seen less than the others)
The GE SupeRadio III has a large internal ferrite rod loop antenna. The loops mentioned above may not really improve the GE’s performance, but will help on many other radios.
2. The idea behind multiple transmitters is to have them at different locations. I don’t think two at the same place will really help you. If you are going to run multiple transmitters on the same frequency, they must be synchronized in phase and frequency to avoid interference. If you are interested in this, Manteca Community Radio is using a 2-transmitter setup, I think with a wireless link between them. Their Web page is at:
http://www.am1700.org OR http://www.mantecaradio.com
The owner / manager / chief cook / dishwasher is our member MLR.
Total posts : 45366About MCR: we’re going to be moving to 5 air tx’s and 3 or 4 CC tx’s very soon. We found a low cost source for STL systems (WAY cheaper than the original) – about 85.00 (includes shipping) – plus you need antennas for the links.. and let me tell you.. they know they have a monopoly, so they are pricey (24-35 for the recieve, and 129 for the tx).
About Ganging TX’s: Experience shows that putting multiple tx’s in one spot wont get you anywhere. I didn’t see any difference at all in having 4 tx’s in one spot or one.
Linking: This is great (*if* you are lucky and live in a place that wants you there 😉 ). It’s apparent that some areas shun part 15.. I still dont understand that, and hope I never do. As soon as I get more info on the new STL system – I’ll post it here or on the tech lib or somewhere handy.
General: I am very lucky. My town really likes the station. I also get involved in the community (I hand flags out to be placed all over town, I help the scouts on thier car washes, I help local businesses get thier stores setup – actually ripping out carpet, puttying the floors down – that sort of thing) .. the real key to a successful community radio station is to be in touch with your community 🙂 It’s taken a year for me to get there..
Total posts : 45366I would love to get info about STL equipment.
The stuff I have found is priced at about $600 for the transmitter plus the cost of receivers. (I believe it works for video as well).
Are there cheaper set-ups?
Total posts : 45366I’m setting up my low power AM tomorrow with the help of a radio engineer. Will be usinging the Hamilton transmitter on 1700 for now. I will update as to range we’re getting etc. after set-up and testing.
Total posts : 45366Another major factor in determining AM range is ground conductivity. In the US, it varies from 0.5 millimhos to 30 millimhos. (Seawater is 5000!)
My area is somewhere from 15 to 30. I’m near the Gulf Coast. The California Pacific Coast’s doesn’t look as good as mine on the FCC’s map.
http://www.fcc.gov/mb/audio/m3/index.html
Mountainous and rocky terrain have poor ground (soil) conductivity. I wish you well.
* * *
For those who have not seen it yet, my station’s design is at:http://members.aol.com/K5BY/MP_Radio/MP_Radio0.htm
I have instructions and a drawing as how I plan to use my (still in the box) SSTRAN AMT3000 with a full length CB whip antenna from Radio Shack just as the Hamilton Rangemaster AM1000 uses.
The last link on my main page is to a page with updates. The latest is how to install the SSTRAN in its case for mounting the transmitter in a weatherproof enclosure.
Best wishes,
Bill in SE Texas
Total posts : 45366just curious – how do you plan to tune this antenna?
Total posts : 45366MLR: << just curious – how do you plan to tune this antenna? >>
With the SSTRAN’s internal tuning network, just as one would do to tune to the wire that comes with it. The lengths of the wire and the whip are similar.
That’s why I have to fasten the circuit board in the cover section with the long ends, so I can access the tuning network inside. The cover screws go through the section with the short ends.
Bill in SE Texas
Total posts : 45366i didnt realize there was a tuning coil inside the sstran 🙂
Total posts : 45366MLR: << i didnt realize there was a tuning coil inside the sstran >>
There are, in fact, four coils in series. Which one(s) to be used is determined by the frequency of operation and each is selected or shorted by a DIP switch array. It is a separate DIP switch array from that used for selecting the PPL’s operating frequency. Tables are provided for the switches.
The coils are a part of a pi network tuning in a low pass configuration (good for harmonic suppression). A fixed capacitor to ground is on the input end of the coils and a variable capacitor, for fine tuning, is on the output (antenna) end.
Bill in SE Texas
Total posts : 45366I had a radio engineer help me install my transmitter yesterday. We got done late in the day and didn’t have a whole lot of time to tune it.
So far I seem to be getting only about 1/4 mile range. I can hear the station fairl well one mile away if I turn off my engine when listening to my car radio. I must be getting some interference from it, but it does not have that effect on stronger stations.
I’m hoping to do some more tuning when weather permits.
Today, I put in a second 8′ ground rod. It seemed to help a little. Anyone know if it will make much difference if I put in several more–and how far they should be spaced? Also, could it help to run a second ground wire? Would it help to run it down the same path as the first one, or what if the second one were attached to some of the metal pipes on the roof?
I’m told I should be getting a 1.5 mile range. Would that be with a strong signal, or would that be barely audible at 1.5 miles?
Total posts : 45366Howdy BC Man…
Because your ground conductivity may be poor out there in CA, judging by the FCC map, a 1/2 mile range seems quite good for your area.
Adding a second ground wire will halve your inductance, making the ground looking twice as close. But it generally will have the opposite effect except to put more power into the antenna.
Shotgunning your ground wires will distort your radiation pattern. What you should do, after peaking up the tuning, is to drive around and determine your contour. The range in some directions may be better or worse than what you’ve already found. Too, there may be hot spots well beyond the contour.
It’s best to use a radio other than a car radio. Car radios are more sensitive than the usual radio a listener would use.
I recall you have a Rangemaster. What do you have it mounted on? I would ground to the support and then ground the support to the ground rod. That would make it more legal-seeming, too. If there are any unbolted joints in the support, they should be jumped with a wire.
You might look at the Transmitter/Antenna Installation info at my Web site;
http://members.aol.com/K5BY/Index.htm
My SSTRAN will be configured similar to that of a Rangemaster.
One other thing… Ungrounded metal absorbs transmitted energy. But, grounded, it will then act as a reflector or a director and thus affect the radiation pattern.
Best wishes,
Bill in SE Texas
Bacliff Radio (still UC)
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