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LRN.FM - The Liberty Radio Network => Free Radio Forum => Topic started by: sillyperson on December 29, 2008, 07:53:33 PM

Title: Step-by-step for the clueless (Part 15)
Post by: sillyperson on December 29, 2008, 07:53:33 PM
I may well set up a transmitter or two if I had a nice, simple, step-by-step cookbook to follow.
To that end, I request a set of instructions.

Assume I have about zero time, but do have some extra money to invest in this. Give me a list of specific things to buy -- preferably with direct links to where I can buy them. Make it as no-hassle, "plug-and-play" as possible.

Assume I have no intention of paying a fine or going to jail over this -- I want a strictly legal "Part 15" thingy.

If you can provide a few alternate cookbooks, for different amounts of capital outlay, that would be ideal. Presumably doing it "on the cheap" involves more time investment & fiddling around, which may be appealing to lots of people looking to pick up a hobby. As for me -- my barrier to entry is time. Lower that barrier and I am more likely to jump in.

Thanks!

Title: Re: Step-by-step for the clueless
Post by: FTL_Ian on December 30, 2008, 09:24:16 AM
For Part 15 AM, you can go the hobby route, or you can go with the Rangemaster:

http://www.am1000rangemaster.com/

The testimonials are pretty amazing.  The good news is it looks like they've lowered their price.  These used to be $1,000.  Either way, it's a lot of money for 1/10 of a watt. 

More info on getting started:
http://www.am1000rangemaster.com/intro.html


Don't even bother with Part 15 FM.
Title: Re: Step-by-step for the clueless (Part 15)
Post by: FTL_Ian on December 30, 2008, 09:27:04 AM
Kdus may have more suggestions on how to set up the antenna, but for AM, you need some height and a ground:
http://www.am1000rangemaster.com/hints.html
Title: Re: Step-by-step for the clueless (Part 15)
Post by: sillyperson on December 30, 2008, 12:41:56 PM
Indeed, AM makes the most sense. I'm vaguely toying with the idea of putting one up in a spot I'd have permission to put the antenna -- it'd be on the flat roof of a 2-story building, that just might have coverage out to a main road in Manchester. Actually I just checked Google Maps and it's 2700 feet from I-293, and about the same distance from Queen City Avenue.

Is 2,700-3,000 feet a reasonably likely range?

The idea is that I could then put up a sign on each road saying "TUNE TO 1590 AM" (or whatever). A lot of people would come across it.

Hmmm... $795 for the antenna. That's outside of what I was hoping for in terms of price range. I was hoping for like half that price.

Says it has an audio input. That's cool. What I really want is a setup than will broadcast the FTL stream (that replays the most recent show). I have (several) old, underpowered PCs with internet access that can suck down the stream... presumably it would be easy to set one up and plug the PC audio output into the RangeMaster audio input. Analog quality, but who cares on short-range AM.

Hmmm.... I suppose another possibility would be to put up a chip-in. I'd toss in the first few hundred bucks and invite FTL fans and Porcs to contribute what they could.

I'm just noodling with the idea at this point.

Comments?
Title: Re: Step-by-step for the clueless (Part 15)
Post by: FTL_Ian on December 30, 2008, 01:13:24 PM
I have no idea what you can expect in your terrain.  Check their testimonials to see what others have gotten.

There are cheaper AM transmitters - that's just one with a fair amount of "buzz" in the Part15 world.  I haven't really been watching the message boards, so maybe there is a new competitor around.

-googles-

Yep.  This is why Rangemasters are no longer $1,000.  Competition in the form of another FCC certified part 15 transmitter, the Procaster, which apparently has internal audio processing:
http://www.chezradio.com/

detailed review
http://www.hobbybroadcaster.net/reviews/Procaster_05_2008_P01.html
Title: Re: Step-by-step for the clueless (Part 15)
Post by: FTL_Ian on December 30, 2008, 01:30:42 PM
Rangemaster review from the same site:
http://www.hobbybroadcaster.net/reviews/Rangemaster_10_17_2008_P01.html
Title: Re: Step-by-step for the clueless (Part 15)
Post by: NHArticleTen on January 08, 2009, 11:42:08 AM

I was thinking along the lines of constructing micro-transmitters that could be utilized in a multitude of ways...

my rock bottom, lowest cost device would use a disposable battery, one of those micro-sound-recorder/repeaters, the transmitter, and antenna...

it would only repeat a very short message and would continue until the battery went dead or it was otherwise incapacitated...

say something like "Free Talk Live Dot Com"...


still...you'd have to drive it hard enough to be able to over-power the local station within your chosen broadcast area(since that would be the frequency where you'd get the most people listening)...


probably do better standing on a corner with a good sign...


at any rate...


enjoy!

Title: Re: Step-by-step for the clueless (Part 15)
Post by: KDus on January 10, 2009, 08:01:28 PM
I think we're moving toward some of those little Ramsey transmitters fed by $89 dollar internet "radios" that I saw on e-bay.
Title: Re: Step-by-step for the clueless (Part 15)
Post by: KDus on January 10, 2009, 09:00:34 PM
The rangemaster includes features most of us won't need.
If AM stations want to use the internet streams for programming, it will be even more important to put the audio processing at the originating end to keep things simple and get the loudness needed to make AM effective.

AM requires a very long antenna and a serious ground system to get the most distance out of your transmitter. Many of those radio towers you see ARE the antenna. The height of the tower is a fraction of the wave legnth: 1/4, 1/2, 5/8, 3/4. A full wave is unlikely because it would be virtually impossible to feed; impedance wise. The 102" whip that is suggested by Rangemaster is about 1/100 of the wave legnth and they probably expect to waste lots of power into the antenna.
Title: Re: Step-by-step for the clueless (Part 15)
Post by: sillyperson on January 10, 2009, 09:13:26 PM
Interesting posts, KDus.

Assuming I am, as stated in the top post, entirely (a) clueless and (b) short on time, what would you suggest?

Also, I have a location on a roof 2 stories high, just shy of 3,000 feet from main roads in NH's biggest city. It makes no sense for me to put up a transmitter and get 2,000 feet of coverage; it's be a kickass win to get 3,000 feet (and 3,500-4,000 is exponentially better)

So far I don't even see an order-of-magnitude guesstimate as to what I could expect with a given setup.
Title: Re: Step-by-step for the clueless (Part 15)
Post by: NuroSlam on January 11, 2009, 12:09:26 AM
Interesting posts, KDus.

Assuming I am, as stated in the top post, entirely (a) clueless and (b) short on time, what would you suggest?

Also, I have a location on a roof 2 stories high, just shy of 3,000 feet from main roads in NH's biggest city. It makes no sense for me to put up a transmitter and get 2,000 feet of coverage; it's be a kickass win to get 3,000 feet (and 3,500-4,000 is exponentially better)

So far I don't even see an order-of-magnitude guesstimate as to what I could expect with a given setup.

I guess the question for me is, are you in the center of town or on the outskirts?
Title: Re: Step-by-step for the clueless (Part 15)
Post by: sinceredagreat on January 11, 2009, 09:01:35 AM
All that shit is SO not necessary to get good range on an AM frequency, when you know about skip distances, dead zones that you don't care about, how to properly get your signal concentrated in certain directions. This is what I used to do before I was intel. 2841 and 2844 in the Marines. All I did was fuck with ground radios, and sometimes microwave systems, but if you want a really good setup for an antenna, PM me, and I will tell you some real high-tech shit.
Title: Re: Step-by-step for the clueless (Part 15)
Post by: NuroSlam on January 11, 2009, 10:21:18 AM
note the title of the post "For the clueless"

Title: Re: Step-by-step for the clueless (Part 15)
Post by: sinceredagreat on January 11, 2009, 10:25:59 AM
note the title of the post "For the clueless"



I know. I can give some good clues for the "clueless"
Title: Re: Step-by-step for the clueless (Part 15)
Post by: NuroSlam on January 11, 2009, 11:20:17 AM
you must consider the size of antenna's at these freqs

1/2 dipole   = 283ft. 7 - 21/32in.
1/4 vertical = 141ft. 9 - 27/32in.

Title: Re: Step-by-step for the clueless (Part 15)
Post by: KDus on January 11, 2009, 06:20:18 PM
Here's the reality of Part 15 AM. I don't want to burst bubbles, but we're talking about LEGAL levels here.  The 100mW limit is only part of the legal barrier. You can use up to 100mW to achieve a field strength of about 20microV per meter at 30 meters (98 feet) from the antenna.  (24000[/f(kHz)] uV/m @ 30 meters) The antenna can't be longer than 3 meters.

If you have a good signal past 200 feet, you probably aren't Part 15 compliant. The only way to be sure is to get your hands on a field strength meter that reads that low.
Title: Re: Step-by-step for the clueless (Part 15)
Post by: sillyperson on January 15, 2009, 01:49:59 AM
If you have a good signal past 200 feet, you probably aren't Part 15 compliant.
Holy. Crap.

So... it's pretty much impossible to remain legal, and broadcast to the High School just 1,500 feet from my rooftop?
Title: Re: Step-by-step for the clueless (Part 15)
Post by: KDus on January 15, 2009, 08:09:34 PM
Get a transmitter from a company that claims to be legal and then you can blame them.
Title: Re: Step-by-step for the clueless (Part 15)
Post by: vonu on January 15, 2009, 08:15:43 PM
If you want part 15 coverage, you'd get it cheaper by putting up a sign in your yard.
Title: Re: Step-by-step for the clueless (Part 15)
Post by: KDus on January 15, 2009, 08:24:34 PM
For AM, yes, get a magaphone.
For FM, height will get you close to the high school.
Title: Re: Step-by-step for the clueless
Post by: vonu on January 15, 2009, 08:40:14 PM


Don't even bother with Part 15 FM.

Agreed, just make sure not to interfere with anything within 2 channels on either side, and there will be no reason to track you down.
Title: Re: Step-by-step for the clueless (Part 15)
Post by: marknh on July 08, 2009, 02:16:10 AM
like someone else mentioned part15 fm is good for about 200 feet max.
and part 15am if i recall is about 200mv at 200 feet going on memory here.
and toss in the ant length and high above ground.

you might as well bootleg a few watts on fm.
Title: Re: Step-by-step for the clueless (Part 15)
Post by: KDus on August 01, 2010, 04:40:52 PM
Here's the reality of Part 15 AM. I don't want to burst bubbles, but we're talking about LEGAL levels here.  The 100mW limit is only part of the legal barrier. You can use up to 100mW to achieve a field strength of about 20microV per meter at 30 meters (98 feet) from the antenna.  (24000[/f(kHz)] uV/m @ 30 meters) The antenna can't be longer than 3 meters.

If you have a good signal past 200 feet, you probably aren't Part 15 compliant. The only way to be sure is to get your hands on a field strength meter that reads that low.

I have been very remiss in making a point about part 15. This is because I support running LRN, which is a full time broadcast.
There is another option within Part 15, for periodic broadcasts. You can run 500microVolts at 3meters, which is twice the full time limit. So, you could transmit a scanner or porc411 when something happens. The  problem is that broadcast receivers don't mute when the signal isn't present.
Title: Re: Step-by-step for the clueless (Part 15)
Post by: RFBurns on September 04, 2010, 10:49:27 AM
Here's the reality of Part 15 AM. I don't want to burst bubbles, but we're talking about LEGAL levels here.  The 100mW limit is only part of the legal barrier. You can use up to 100mW to achieve a field strength of about 20microV per meter at 30 meters (98 feet) from the antenna.  (24000[/f(kHz)] uV/m @ 30 meters) The antenna can't be longer than 3 meters.

If you have a good signal past 200 feet, you probably aren't Part 15 compliant. The only way to be sure is to get your hands on a field strength meter that reads that low.

Indeed. Pretty simple math and techniques to check field strength.

And on another thread...someone mentions about an operator claiming 8 miles coverage. Ya...with multiple 100mw transmitters scattered everywhere.....but just one single unit....well let the math explain it.

RFB
Title: Re: Step-by-step for the clueless (Part 15)
Post by: RFBurns on October 21, 2010, 12:47:33 PM
If you have a good signal past 200 feet, you probably aren't Part 15 compliant.

For FM this is most of the time true, however if conditions are right, a Part 15 FCC certified FM transmitter can send its signal well beyond 200 feet.

For AM, well this is a hit and miss best guess because of the variables such as ground conductivity, the grounding system utilized and the coupling/tuning efficiency to the 3 meter antenna. Ive seen 70mW in a very well designed Part 15 2.19 system send a signal out to 3/4 mile no problem. Daytime of course. Night..well at that point 200 feet or so is about as much to expect for a clear signal, after that...it ends up buried in the skywave noise.


The only way to be sure is to get your hands on a field strength meter that reads that low.

According to the rules, a quasi-detector with no AGC is the industry standard for measuring AM transmission field strengths. These are easy to build and can be made just as sensitive and accurate as the infamous Potmac FS unit the FCC engineers use. I know...I built one and use it monthly to verify my CC station's emission limits. I calibrate it to a fellow engineer's Potmac FS and every time, it indicates the same readings as the expensive Potmac.

A good communications service monitor can also serve as a fairly accurate FS meter for close to nth decimal point measurements, at least within the ball park.

After playing around with the "carrot on a stick" method for a number of years and always being let down by the poor range even at 3/4 mile on a good day with moist ground, carrier current is the way to go with AM. Though many state the lower band is best for carrier current, I found it to be opposite and that the upper portion works best for my installation. My TCU-30 couples to the neutral and grid ground lead in's right off the drop. Fortunately that ground drop is isolated and with the addition of 4 ground rods at 15 foot intervals, 5 watts was all that was needed to get my signal down the line and into listener's homes and without all that nasty hum.

If your really wanting to reach more listeners and expand the range of your station LEGALLY, then carrier current is the way to go.

Although LPB is not manufacturing new CC units, Radio Systems does, however their unit is limited to 10 watts carrier power while one can find an LPB unit on ebay that can pump out 3 to 5 times that power level.

And its great to see a 1982 design work so well with a 2000 era C-QUAM exciter. Chris never expected to see one of his transmitters mounted into an LPB TX as an exciter. I bought 3 more of his units as spares plus one that was un-assembled to have individual parts on hand if needed.

And if you cannot find an LPB or cannot afford a Radio Systems unit, there are plenty of schematics and plans out here on the web for building a transmitter and coupling circuit.

2 watts coupled through a 10mH inductor and a .1mf 3kv ceramic cap onto the neutral line will work with fantastic results! However to maximize the RF induction, use an antenna tuner such as an MFJ 900 and add 6 more turns to the upper portion of the inductor coil and add two 500 pf caps across each of the variable caps and with the above 10mH inductor and .1mf cap, you got yourself a very effective coupler that works just as well as the infamous LPB TCU-30 and TC-8 couplers.

Happy building and broadcasting!  :D



RFB
Title: Re: Step-by-step for the clueless (Part 15)
Post by: RFBurns on October 21, 2010, 01:19:41 PM
like someone else mentioned part15 fm is good for about 200 feet max.

Yep...but even a fully certified FM unit can send a signal beyond 200 feet with good conditions such as hight of the unit so its antenna is above obstructions and in line of sight.

..and part 15am if i recall is about 200mv at 200 feet going on memory here.
and toss in the ant length and high above ground.

Actually its 15mV/30m (45.715/f for metric , 157000/f for feet). It amazes me how many mix up the differences between the FM field strength limits and the AM field strength limits. They are not the same 200 foot range limit syndrome.

you might as well bootleg a few watts on fm.

The biggest mistake most make by bootlegging a few watts on the FM band is that they do not take the time to ensure their signal is clean and not filling the spectrum with spurious. Also most forget that the IF frequency of FM receivers is 10Mhz. So if your pumping a signal on 90.1 Mhz, and someone down the street is trying to tune in a station on 100.1 Mhz, guess what happens....your signal will ride along with the other station's signal via the IF and the listener of the 100.1 Mhz station hears two stations! Next day a letter or email is sent off to the FCC in the form of a complaint. Shortly thereafter...the interfering bootlegger receives a NOUO..or worse a NAL.

I would be outright lying if I said I never threw up an FM with a few hundred watts. I have...all home built equipment pumping out a stereo signal on 107.7 at 400W into a 2 bay dipole antenna system constructed of 1/2 inch copper tubing and PVC fittings mounted at 40 feet on a tv receiving mast. Yep it was fun, for a 3 full years....till a "friend" who I thought was a good guy decided to contact the FCC and a few weeks later, both the FCC and the Sheriff's department showed up to partake in the party..cept their plans were not to enjoy a beer and pizza.

At least the FCC guy let me announce the station was going off the air. He even commented on how clean the signal was compared to licensed stations in the area. I told the field agent.."that is due to well designed home built equipment using good engineering practices and building the thing to conform to the spirit of the rules for spectral purity". The agent actually looked surprised after saying that to him. I think I even caught a grin from the agent's expressions.

The key words in the rules is "harmful interference". It is the harmful interference that lands an operation in trouble....though not the only thing that can land an operation into problems. Things like indecent programing and foul mouthed fools will no doubt bring unwanted visits. It is this kind of operations that even I would hunt down and turn in myself. These types of operations ruins it for the rest of us who take the time to properly set up a station in the spirit of the technical parameters that licensed stations adhere to.

Just slapping up a signal and ohh ahh'ing over "Im on the air!" is not good enough...be it Part 15 or Part Bootleg. If your going to risk throwing out some watts, then do it RIGHT and at least impress the field agents when they come to bust your butt. The least that will happen is they smile while they take your beautiful home made transmitter! (UGGGHHHH!!!) Just dont tell them what I said as they walked out the door with my home made transmitter and antenna system..."You can take that equipment but you cant take whats in my head"...meaning the schematics to the unit they were taking as well as many other ideas were not on paper, but in my mind! Ha Ha!  :P



RFB