I will be second to agree with what Mighty just said... Artisan has hit the nail on the head by saying (in Post#74) "That's why I suggested to define 'neighbourhood' very carefully, the smaller it can be the greater liklihood of success."
Why didn't I or anyone else think of that? We've been stuck on this nebulous term "community" all this time.
I would define a Part 15 neighborhood as "The Immediate Neighborhood," and for me that has defined itself now that I think of several experiences.
A couple years ago a woman who lived down the block and around the corner hand-delivered red paper messages to certain people she knew. I saw every few mailboxes with the red paper half-in and half-out so it was visible from the outside.
The message said "A burglary ring has been hitting homes in the area."
Except for her red-newspapers I otherwise didn't hear about the burglary ring.
Two other times I got such news from neighbors living within a block and a half.
With a slight boost in power and well-designed antenna systems the "Imediate Neighborhood" is a reachable distance for Part 15.
Because it's such a contained area, I would even suggest publishing a newspaper to stick on people's doors with news and station promotion!
I would call anything beyond 750 feet to be "out of range".
EDIT ADDED: I just thought of another name for it...
"The Gossip Zone".
1mV/m (city grade signal) @ 1 mile contour is a good neigborhood definition.
In Reply 62, Thelegacy wrote: How much is that NEC software and where do you get it?
Here are a couple of sources:
Some NEC2 programs are free to download and use in trial form, but have limitations compared to the more accurate NEC4 engine -- the software and license for which is not free.
Just to note that in order to produce their most accurate results, ALL versions of this software require the user to have a good background and understanding of antenna engineering theory and practice, and a good understanding of the use of that software.
Otherwise those results truly can be cases of "GIGO."
The way I feel is that even if you have one listener, you are responsible for his safety. It doesn't matter if your transmitter covers 100 Ft, 200 Ft, 1 mile you are responsible for that listener. If you don't have an EAS system and you got severe weather coming in, you need to get on that mic immediately and tell your listener to immediately tune in a local commercial station TV, AM, or FM (insert in your local station) for their safety.
I can tell you this, 1 Watt will cover 3 miles no issue in most cases. With 18 watts even though NEC maps suggest otherwise your signal can be heard 20 miles +- 5 miles here and there depending on receiver, terrain and atmospheric conditions. I've worked for a 10 watt station that could o 20 miles on a good day.
I've been saying a mile or two for about a year now.
To follow up on kc8gpd's post, the FCC calculator says that to get a 1 mV/m signal (which is actually an urban grade signal, rather than a city grade signal) at 1 mile, you'd need the equivalent of 10 watts at 50 feet above average terrain. To get the same strength signal at 1.5 miles out, your 10 watts ERP would have to be 200 feet above average terrain. I post this information just for reference purposes.
marosborne posted in Reply 81 ... the FCC calculator says that to get a 1 mV/m signal (which is actually an urban grade signal, rather than a city grade signal) at 1 mile, you'd need the equivalent of 10 watts at 50 feet above average terrain. ...
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Just curious, what "FCC calculator" did you use?
AFAIK, the FCC online calculator for FM field intensities where the radiation center of the transmit antenna was less than 30m HAAT is re-set to 30m HAAT -- which would not provide the correct field for that ERP from an HAAT of less than 30m.
If you go for too much range, then you risk having both the FCC and the NAB rejecting your proposal out of hand, without reading any further. I like Carl's definition of a few blocks better, but even that is rather nebulous.
Just to put some tangible numbers to this, I live in an area called Osprey Village, which is in the south end of Pitt Meadows, BC, Canada. It consists of a small 'downtown' core of shops, surrounded immediately by townhouses and then detached houses. It is about 500 metersx500 meters in size, bounded by the main feeder roads to the north and east, a river to the south and parkland/farms to the west. Both physically and socially it can certainly be classified as a neighbourhood, distinct from other areas in Pitt Meadows.
I've taken a quick look at other neighbourhoods within Pitt Meadows, and most, from what I can tell, range from a little smaller than mine, to about 1kmx1km at most (not always square). Each has its own distinct character and demographics. I don't think that Pitt Meadows is all that different from most other places, except perhaps downtown cores, and that is a different ball of wax entirely.
It would seem to me that going for a clear signal to a decent portable receiver somewhere around 500 meters would likely cover the majority of neighbourhoods ( even though you're not always going to be located in the centre).
I don't know what that means in terms of required power for that scenario. But remember that coverage to more sensitive radios, particularly car receivers or those with outside antennas, would be far greater (probably that mile or two referenced earlier in this thread).
Anyway, just some food for thought. Remember that you're not going to be a general purposes radio station - at least, I don't believe that that should be the goal, as it will likely never get off the ground.
Keep in mind that 310 mW will go 1.1 miles on a 5 Ft piece of vertical wire. This is without a counter poise. To go 2.1 miles you would run 600 mW. And to go 3.1 miles you'd need 900 mW into a 5 Ft piece of wire on the first floor of a house next to a window. That said that 3.1 mile coverage to a Digital car Radio or sensitive Digital receiver could mean quick response during an emergency situation. Remember a licensed station can't move if it gets knocked down for several reasons I'll get to. First due to the licensing laws the station would have to be re certified as far as I know just to move 300 Ft. During a natural disaster time equals lives. That little transmitter connected to a 5 Ft piece of wire at 1 Watt going 1 mile to a cheap piece of crap dollar store Radio at least could save a life. This goes back to what I said about the fact that it does not matter how far your transmitter goes, if it can save a life you are responsible to do what you can to relay that information. A FCC authorized factory modified to meet the new service could do this at a very cheap price. It could be clean since the FCC certified it and to boot since your a valuable service how can that be detrimental to FM? In actuality its an asset to the FM band at best. The difference is that its owned and operated by an individual (or group of) instead of a large corporation. Again we're talking about individual Hobby Radio broadcasting. But must because its a hobby does not mean it can't meet a immediate need. So that little 1 mile range to a crap Radio and 2-3 to a high end Radio is an asset. It still falls way under LPFM and even the abolished 10 Watt LPFM service. Multiple transmitters in an array could be erected relaying the same message at intervals to where the message could go 12 miles or more. This is good for a localized area but slightly larger than a neighborhood. At first I thought neighborhood and I'm still thinking small, but just a slight bigger than that. It should be smaller than the first licensed service. Its something to bring up in two weeks at the next meeting. Alan Weiner is a good source too since he wants a similar service. So now is the time to unite and get it done. If it was such a fantasy he would not be proposing it for 6.9 Mhz.
You can simply accomplish your goals by using an AM transmitter under existing Part 15 rules. I get a 1.5 mile radius, that's a 3 mile diameter from my antenna. You may do less in a city setting of course. Why all this effort to accomplish the same thing, except on FM?
You don' t need EAS to send severe weather. I've been doing it for three years with a $30 weather radio that has a relay output that closes when there's a watch or warning that affects my area (the radios are programmable for what areas to cover and which types of alerts to react to) This relay in the radio trips a relay I built that switches my air audio from regular programing to the wx radio, then back after the alert plays.
You don't have to convince your listeners to buy a relaly good FM radio or receiver, or put up an antenna to hear you. I see so much talk about FM "to a good receiver" you might get 1/4 mile, or 1/2 mile, etc. You get more than that to a typical AM radio on AM.
This seems like a lot of work just because some formats might sound better on FM.
Everyone who owns an FM radio also owns an AM radio.
TIB
Tim raises a great point,
Only real objection I see is the lack of reliable nighttime coverage on AM and the listening habits of today favoring the FM band. (Though in rural areas this is a non issue)
when you live in apartments and have no real mounting options and a high qrm level, AM doesn't do so fantastic.
this is where expanded fm can fit the bill.
even 100V/m @ 30m same as canada BETS-1 would be a huge improvement over what we have now. i think canada has a 1mW ERP class as well. both very feasible options here in the USA.
Edit: under RSS-123 (licensed auxilliary) you can run 1 Watt on FM
link: https://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf01323.html
Arguing that there should be a higher powered unlicensed use of the FM band is silly when there won’t be room. The FM band is crowded. It is going to get more crowded. (That was my point starting this thread). The class B and A AM’s get a 250mile FM translator window. Then the class D and C AM’s get a new FM translator application window. Then the class B and A’s get a new application window. At some point in all of that the FCC may relax the requirement for the 60 dBu contour to be within 2mv/m contour and 25 mile radius; if the translator just needs to be within one of those we may see an increase in translator HAAT and/or ERP and less directional antennas. Once the AM’s get their translators built and they have been on the air for 4 years, there will be a free for all seeing what will make the most money feeding the 250 mile relocated higher powered translators. Then there may be a trend where former AM translators will move slightly (minor modifications that do not require a filing window), and/or increase their ERP/HAAT to better “fill in” for HD 2/3/4 channels on FM’s. The FCC, while they not may do the best things, is not stupid and knows what could happen to the FM band in the next 5 years; it will be packed.
Arguing that 87.7 and 87.9 should be given to part 15 operators seems moot. If the FCC thought there was money in an expanded FM band they would have done it in 2009, or they would have planned it in the current TV auction frame work. Realistically the FCC knows AT&T and Verizon have deeper pockets than the AM/FM broadcast industry. While VHF low only offers 5 channels, if the FCC can get stations from UHF to 2,3,4,5,6 they may think it will help more people than if 76-88 MHz went to an expanded FM band. There is more turn over in cell phones than radios, so devices that can use LTE in the 600MHz block will be in people hands quickly. On the other hand radios that could tune 76-108 MHz may never make it to everyone; most radio listening is done in the car and people are keeping their cars longer and longer. The lack of radio turnover is part of what has hurt HD radio.
I have said it before, but the “best” chance to get more unlicensed range on FM is an extremely smart device that is almost tamper proof. It would have a GPS to check where it is. It would have a receive SDR with a receiving antenna to check what is actually on channels. It would require an internet connection to check the FCC database for FM white space. It would have a variable power transmitter and a known gain antenna. The device would choose the best channel for the location using the GPS, the receive antenna, and internet connection. It would use as much power as was permitted to not interfere with licensed stations. If someone contacted the FCC with an interference complaint, the FCC could mark the location of the complaint in a database and devices near that location would scale back their power. I would bet the FCC would make the rule changes to enable such a device if a reputable manufacturer or consortium put the idea forward, but I doubt there would be enough demand for anyone to build it profitably at a price a hobbyist would be willing to pay.
we need to curb and roll back this abuse of translator rules. if there is room for another translator on first adjacents to a full power fm there is no reason why a low power station that will actually service the local community can't be put there.
Yes there is a reason: NAB