Artisan you make a good point about an OCF dipole. Making some assumptions here: A standard halfwave dipole antenna would be approximatly 275 feet @ 1700 kHz. That being said, I wonder what the FS would be if mounted on a 266 foor mast with the other 8.5 feet being the antenna/ counterpoise?
ArtisanRadio Said in post #14
With a rooftop mounted vertical, I was able to achieve range of several miles to a good car receiver. With FM, the antenna (mounted up high) is everything.
MrBruce Said:
The tests we performed were done with the antenna authorized to be used on the transmitter, a built in telescopic rod.
You mentioned an outdoor antenna. I believe this setup had a length of coax between the transmitter and antenna. If I am wrong then please correct me.
I am glad to hear that you have done your own tests, because I believe you have that right to either conclude they are right about the negativity about part 15, or, they are wrong about part 15.
I welcome all comments and even if you prove me wrong, I'd still appreciate your input. I am willing to learn from you. But, before I'll lay down and agree to an old standard many years out of date, I'd like the right to see if times really have changed and perhaps the FCC rules need a revamp on both AM and FM.
Now, please do not get me wrong, I think AM has very good potential if two things were to change.
One, AM stereo DOES have a positive potential, if radio manufacturers were to start manufacturering AM radios with a stereo decoder.
But do you really think they are going to listen to us part 15 radio stations who have taken over the abandoned AM broadcast band? Are they listening to the current NAB supported part 73 licensed AM broadcasters NOW? Of course not!!! AM is a dying breed and IBOC is not saving it.
I have a Chris Cuff AM C-Quam stereo transmitter, besides the fact the RF section is VERY LIMITED, I wish there was more people who had an AM stereo system like I do. I have a Realistic TM-152 AM stereo tuner with signal LED meter that allows me to listen to AM stereo broadcast stations.
Second, All future AM radios should be AM stereo capable right from the factory.
How do we push the stereo manufacturers and cell phone makers to include AM stereo?
If it were possible, I'd be 100% pro AM and say the Hell with FM altogether.
Bruce.
Artisan Radio I agree with what you said about AM and 100 mW to a good long ground lead or even a good antenna. Now for some other issues I want to discuss:
Mr. Bruce said “The weakest licensed FM station in my area is 50 watts, it carries only a few miles line of sight, it is also known as a God-caster translator station”
I say: If you have a 50 Watt transmitter and only get out 2-3 miles there is something terribly wrong. They could be using horrible coax where most of the signal is radiating inside the studio or transmitter site (This can cause RF interference to their audio equipment and to neighbors due to a blanket effect). I know that 10 watts can travel well over 20 miles with a nice full quieting Stereo signal and if a listener has a outside antenna or sensitive FM receive with good adjacent channel rejection your signal would carry 40 miles with that sort of power. The antenna should be at least a 3db gain antenna making that a 100 watt ERP signal.
Can 1 Watt get out far? Yes if you have an outside dipole with at least 3db gain the ERP is multiplied by a factor of 2. So your looking at 2 Watts ERP (If there is little line loss going up to the outside antenna). With 1 Watt in NZ there is not every Tom, Dick, Harry running a Hobby Broadcasting station. Plus if it becomes legal here I don't expect to see them in Wal Mart or even Best Buy as its a novelty item or specialty item. Maybe site to store at best, but I don't expect to see the extended part 15 transmitters running wild on store shelves. It may be something that these jealous stations may try and squawk about, but again in areas where this is already legal you don't see it and in America it seems to take 10 years before new technology catches on (Look at Video Laser disc which after 10 years started to catch on and quickly was replaced by the DvD). If FM does become super crowded in every city I think then more folks will flock to AM and hopefully more manufacturers will develop carrier current standard plug in boxes for those who live in apartment complexes. The Talking House AM Transmitter could have made a Carrier Current device that plugs into or screws into the 75 ohm output. This would allow in some areas 4+ miles of legal operation. If FM becomes unusable to me I'll try and get carrier current more easily available to AM Hobby Broadcasters. But again something should be done to at least allow more FM signal for rural Hobby Broadcasters even if you had to sign for a permit of some sort and still be FREE.
The big advantage we have in New Zealand I think is not the 1 watt power (though it does help a little), its that we have our own bands to use. 87.6 to 88.3 & 106.7 to 107.7. The big boys have the band in the middle so we cant interfere with them. Spectrum Management dont care if we interfere with each other, its our problem to sort out. It does get harder in the big citys, but in the smaller towns its not a problem.
Thelegacy Said:
I say: If you have a 50 Watt transmitter and only get out 2-3 miles there is something terribly wrong. They could be using horrible coax where most of the signal is radiating inside the studio or transmitter site.
MrBruce clarifys by saying:
When a 50 watt RF transmitter is transmitting into a CIRCUMPOLAR antenna, 50% of the POWER IS VERTICAL, 50% is HORIZONTAL.
This god-caster uses a single circumpolar antenna attached to a large water tower in Preston Connecticut. When you think vertical or horizontal antenna, yes, 100% of the signal is at that polarity. But circumpolar antennas work differently, because the signal is both Vertical and horizontal at the same time.
50 Watts is not at the horizontal or vertical polarity with this type of antenna, it is SPLIT in HALF and some line loss brings the result down even more than that, perhaps 20 watts vertical, 20 watts horizontal. Therefore, the transmitter and antenna system is working like it should.
Also factor in the terrain between the antenna and my house, my area of Connecicut has many many many hills and valleys.
I am sorry I did NOT offer more information on the station in question. If need be, ask me and I'll give you the translator call letters and you take it from there at the FCC database for more information.
If you are broadcasting with a vertical broadcast antenna, your signal is 100% vertically poloarized, you may be great for car stereo reception, but home stereos use horizontal antennas, thus why broadcast stations use circumpolar antennas.
Bruce.
Something to think about however as if it were not for the hills even 20 watts should get you well over 15 miles with flat terrain without many trees to block the signal. Still remembering my experience at WOCR where as the teacher could not believe a 10 Watt signal would go more than 3-5 miles.
Johny C Said:
The big advantage we have in New Zealand I think is not the 1 watt power (though it does help a little), its that we have our own bands to use. 87.6 to 88.3 & 106.7 to 107.7. The big boys have the band in the middle so we cant interfere with them. Spectrum Management dont care if we interfere with each other, its our problem to sort out. It does get harder in the big citys, but in the smaller towns its not a problem.
MrBruce Said:
Johny C thanks for your input!!! You proved my point.
I said put part 15 FM on 87.9MHz!! To Hell with 87.7 already! That is the television channel 6 audio frequency and mentioning it over and over again is only going to get a BIG FAT NO!!!
Try, if anything, for 87.9MHz or forget it! We know we are NOT getting anything past 108.0 MHz, so don't bother including that either. If 87.9MHz is a no go, then I guess we could lobby for AM stereo and give that a try. But mentioning 87.7MHz is NOT going to work out period!
AM as it is now is NOT saving AM, AM stereo may have failed due to the lack of available receivers that can decode the stereo portion of the carrier.
Johny C has brought forth a good point, but I'll be damned if we can do research here in the USA without the trolls getting mad because we went over the legal power allotment a tad bit or tried a different channel such as 87.9MHz. Some of us are simply trying to get out of the broadcaster's way, but God forbid if you try doing tests on 87.9MHz while conducting research, finding a better way for part 15 and part 73 to co-exist.
As long as people want to be forced into believing what other's have said and not being allowed to find out for our selves what would work best, we are always going to be stuck believing in myths, not facts. I can only believe in what I, myself have seen, not what others have tried to tell me, because not everyone is right.
Bruce.
Bruce is Right, 1 watt isn't squat and typically doesn't even require antenna tuning on the FM band. 5 watts is where things can start getting nasty on dirtier TXs, 7 watts seems to be about the limit before consumer grade electronics near the antenna start having fits.
500mW on AM will get about 1 - 2 miles with a half-assed outdoor setup in a ruralish area. (Atleast where ground conductivity is decent)
As far as AM on cellphones, as much as I'd like this it would never work. The phones are too small and too crammed with electronic noise. You should see the spectrum's noise floor at a cell tower site, YUK!
Thelegacy posted (in part): ... I know that 10 watts can travel well over 20 miles with a nice full quieting Stereo signal and if a listener has a outside antenna or sensitive FM receive with good adjacent channel rejection your signal would carry 40 miles with that sort of power. ...
Just to note that the FCC defines the ~reliable coverage radius (a field of 1,000 µV/m, or 60 dBµV/m) for listeners in the general public of a licensed LPFM station radiating 100 watts in __both__ horizontal and vertical polarizations from a transmit antenna elevated 100 feet above level terrain to be about 3.5 miles.
I remember reading reports where that 7 Watt SainSonic transmitter overheated when someone tried to use the telescoping whip antenna that came with it. But at 1 Watt it was not an issue. There was a CZH-01A that folks reported to have gone 3 miles on the telescoping whip antenna next to a window. 3 miles here would almost cover my whole town here. 500 mW on AM was something I wondered about as far as how far it would have gone on the wire antenna such as the one that came with the Talking House. 2 miles would be well served in a rural town like this one. This is why we should have at least city permits for 1 watt or lower in rural areas where the issues with interfering with a high power licensed station is smaller. This along with offering frequencies within the FM band to the higher power hobby broadcaster. Maybe it should go by your location. I can't see translators taking over the smaller cities, but I could be wrong for FM. We'll have to keep a sharp eye on these applications for AM stations to set up FM translators.
Thelegacy Said:
Something to think about however as if it were not for the hills even 20 watts should get you well over 15 miles with flat terrain without many trees to block the signal. Still remembering my experience at WOCR where as the teacher could not believe a 10 Watt signal would go more than 3-5 miles.
MrBruce Said:
Thelegacy, the only problem with your assessment is, in a PERFECT world yes, you are correct.
In the real world, we would have to start talking about RF power levels way past any acceptable power level in the USA for part 15 radio devices.
This is a part 15 radio related web site, not a site for licensed part 73 stations. We can discuss power levels of 100 watts to 300,000 watts ERP, but then that goes beyond the scope of part15.us.
So, that being said, our discussing power outputs over 1 watt is not productive for our cause.
Trust me please, without going into non-related points, that FM is not fool proof, you can't use every example across the USA as being possible in every situation.
I want to talk about 1 watt maximum on FM nothing more! And based on crazy tests we have conducted without going into it deeply, it does not work like you think, let's leave it at that and move on. Sticking to part 15 not part 73.
Of course, we all know FM is line of sight, after you lose sight of the transmission antenna, things start to go down hill, you get co-channel, you get reflected signals, when your signal arrives at the antenna from different angles or at different times, with a slight delay.
Analog television sets had what was called GHOSTING in the video signal, multible images on the screen, multi-path is a big headache for FM audio, I've heard it and it's not pleasant to listen to to tell you the truth.
Okay here is the FCC database for WCSE radio NOT the one I spoke about earlier, but similar. Look at the vertical and horizontal power ratings and if you can, check their 60dBu contour.
I can not find info on the Preston Connecticut translator, perhaps it is now off the database, because it really had a limited signal and that total area is now being demolished. It once was the State Mental Hospital which closed in the early 1980's. That water tower may have been finally dismantled, it served as a fire water tank for the hospital fire dept. That translator had their antenna on that water tower. In case anyone is interested, the hospital was called the Norwich State Hospital which was ran by the state of Connecticut.
Bruce.
I think the New Zealand model with the reserved part of the band for hobby radio is the best system. It seems to work for both sides and should be considered here.
But I wonder how enforcement works with transmitter power, not field strength the rule? The signal strength will vary depending on transmitter location and type of antenna.
If someone is breaking the rule and using a 5 watt transmitter how do they detect this and enforce the 1 watt rule?.....JohnyC?
Mark
The LPFM I operate for our city is licensed for 18 watts ERP.
The antenna is a single bay Shively cirularly polarized antenna mounted 138 feet above ground level. The height above average terrain is a little higher as the tower is on a bit of a rise.
The total output power of the transmitter is 52 watts. Losses on the coax deliver about 40 watts to the antenna. The antenna has a gain of .46 as the power applied splits between horizontal and vertical planes. That ends up being 18 watts radiated.
The FCC projected countour is shown as approximately a 3 miles radius. But, to a car radio the usable range is more like 15 to 20 miles. Of course when you get out that far the signal will "picket fence" as terrain and foliage conditions change.
A good, solid signal though can be had at 10 miles out. That being the case, the FCC's standard for a usable signal requirement is very generous.
Thanks Bob for your report on WCFI. Not too bad for 18 watts circumpolar and 20 miles would be what I'd expect from a sensitive car Radio. A youtube video showed 20 miles with a 7 Watt transmitter. The dude was surprised it got out that far. I was too on a telescoping antenna. Now with a vertical ground plane maybe if you were high enough and there was little foliage. Its fun learning about FM transmitters and what they can put out to different antenna designs and the height as well. That is why I miss working at a collage Radio station like WOCR. I remember having Dad drive out from WOCR and showing how far it went out. When they were working on their station at the time I wanted to transmit at 100 mW for a short time while they were down just to see how far it would go while they were adding more music and working on their studio. I thought at the time it would be part 15 because it was less than a watt and even if not they had a license for 10 Watts so 100 mW as an experiment should not break the law. But anyway I don't think the FC would allow them to run short 100 mW transmissions even as an experiment to show how far it would go. I think it should be legal to once a month show at lessor power how far it would go so that we could learn from that. I still want to take my Whole House 3 up on a high place say a 20 story building and transmit and see how far it would go. This would help when we ask for power off the top of our head. We can say “with a circumpolar antenna it goes X and with a dipole it goes Y with a rubber Duck it goes 1 mile or whatever it would. Seeing what 100 mW would do on a 150 Ft tower is interesting.
Mr Bruce Said: ...So, based on my personal survey, I can not see every Tom, Dick and Harry suddenly putting a transmitter on the FM band... ..I just do not see what has been said above happening, not everyone gives a toot about being an on air DJ, if they did, everyone would have gone to broadcast school to become a disc jockey...
I understand where your coming from Bruce, but having a desire to be on the air wouldn't neccessarily be the reason they would do it. More likely, they would just want to put a playlist on of the music they want hear, much the same as people in a bar will constantly be returning to the jukebox pumping dollar after dollar in to hear what they want to hear.
No, most every tom dick harry jane have no interest whatsoever of going through setting up a transmitter now, it's too time consuming and difficult to get it set up just right under current regulations, not to mention expense involved in the higher end equipment need to squeeze out every little ounce of range possible to reach out usually less than a half mile away... why bother, it seems silly and pointless to most people, so instead they just play their cd, or mp3 or whatever.
But if the rules were relaxed allowing a few watts of legal unlicenced power, then it's very likely a totally different situation would arise, because that would make the setup quick and simple.. buy a cheap transmitter, plug in an mp3 player or pc, and bang!, in 5 minutes you got your own playlist airing for miles around.