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I Wanna Start My Own Part 15 Station Someday BUT....

JeeperOne

Banned
Hi everyone:

.....I live in a high rise apartment building (Though at present I'm near the top) and (at present at least) there's NO way to put an antenna outside (I say "At Present" because I'll soon be relocated by management to a new apartment as they are preparing to gut this one and remodel it).

My question is AM I DOOMED or just severely limited as to what I can do?

I can't climb towers, so that's not an option. I can probably put the transmitter here inside the apartment somewhere (Depending on how big it is).

My plans are to run my current Comedy/Talk/OTR/Music format that's on Jeeper One Radio now. It'll also be simulcast on Live365 as that's where the biggest OTR Broadcasting community is (That translates to LISTENERS :) ).

But seriously though....How realistic is this? Also, which would be best to use - AM or FM?

Thoughts & Comments anyone?

Cheers :D
 
Tough call, Pat...

Hate to say it, but you're in quite the pickle here... significant disadvantages for either option, given your situation. FM stations' range is defined by line of sight -- I know pirates, i.e. way above Part 15 levels, who would KILL to live in a high-rise -- BUT at the power levels allowed by Part 15 FM, a great line of sight is pretty much useless from the perspective of a 2-D coverage map, as your signal will fade into inaudibility well before it ever hits the ground. Another explanation for why this happens is the definition of FM Part 15 itself. The legal maximum for FM isn't based directly on the power generated by your transmitter or radiated by your antenna, but by the field strength of the signal once it gets out into the world. In other words, the rule itself limits your maximum effective range. You're only allowed to have 48 dBu (about the signal strength that will reliably "seek" in most cars) ten feet from the antenna. This means you'll be down to 28 dBu (1/10 of the arithmetic signal strength, and around the threshold of even the fuzziest detectability in most cars) within 32 feet (i.e. 10 feet times root-10). And even the hardiest of DX geeks with multi-element Yagis who can somehow pull in another 1/10 of THAT signal strength will only get you for 100 feet.

My own experiments, even with modulators that seem to somewhat exceed these Part 15 limitations, have proven this point with abject clarity. Once, in a fit of great boredom, I duct-taped my little GE modulator to the outside window of my third-floor apartment, thinking this would get me out at least *barely detectably in my car* to the next city block. (This street is 500' distant and bridged over my own road, putting the bridge at pretty much eye-level to my window.) Despite its combination audio cord/antenna being aligned in a completely vertical position, I faded into total inaudibility at what I later calculated to be 176 feet from the base of my building, i.e. along a two-dimensional straight line. Later that day, I tested the modulator just sitting in a random position on the floor of my room -- no line of sight, and five feet lower than it was on the window -- and was able to "seek" the signal at a rough distance of 70 feet in my parked car, *on a 3-D straight line taking building height into account.* With 2.5 being a bit less than root-10 (which would allow for the fact that real-world conditions never match the theoretical lab), my car seek at 70 feet would end up giving substantially the same result for absolute fade-out distance from 48 to 28 dBu (i.e., 70 * 2.5 = 175, while even taking 28' height into account on 176' flat-ground distance barely gives you 180' according to Pythagoras). And this is despite the fact that my second test had no unobstructed line of sight!

(Note to any REAL engineers, as opposed to wanna-be geeks like myself, who are browsing this board: The first paragraph's theoretical distance calculations seem a little "off", compared to what I've observed in the real world with even the cheapest battery-powered modulators. Either my modulators haven't really been Part 15 compliant, or I did some math wrong, or my theoretical approximations for usable signal strength are hosed. Please let me know if I misapplied the inverse-square law somehow, or used the wrong dB-to-arithmetic-multiplication scale... I seem to remember there being two different ones...)

On the AM side, the FCC defines AM Part 15 limits by *power level* -- in this case, 1/10 of a watt. Though there are some limitations on which antennas are legally permissible, at least you're not stuck with a statutorily limited range -- so clever engineers have been able to squeeze 1 mile (almost always), 2 miles (from time to time), and occasionally up to FOUR MILES of usable signal out of their AM Part 15s! However, effective antennas here are much more complicated to design (as far as impedance matching, their angle of radiation, etc.); there are more physical factors coming into play (such as the electrical conductivity of the ground in your area); and these antennas almost always require some kind of ground connection in order to behave most effectively. Getting to the ground directly is obviously going to be a pain in the tuchis in your situation, but there might be some experts on this board who could tell you how to ground to something *in your building.* (Note -- I'm not saying to go ahead and do this, because my own knowledge is extremely limited, especially with respect to any potential consequences for your neighbors of having even 100 milliwatts of RF injected into metallic or electrical systems in the building...)

Personally, if I were in your situation, I'd go with something like a quarter-watt Ramsey FM kit. If memory serves, they offer 250-mW units that, while not technically Part 15 compliant, offer stereo sound and PLL (so you don't "drift" off frequency) and are exceedingly unlikely to get you busted at this power, especially if you stay on a really open frequency. (Even an RF-"dirty" output -- i.e. a signal with harmonics or spurious outputs on other frequencies -- is going to have unwanted frequencies a couple orders of magnitude... 20 or 30 dB... below the actual signal. On 250 milliwatts, this isn't too big a deal, but by the time you hit a watt or two, these kinds of spurs become more significant just because the *baseline* signal to which they're compared is that much stronger.)

In addition to being fairly interference-safe, a quarter-watt should get you out a pretty decent distance as well -- theoretical calculations aside, my admittedly unscientific experiments have made it apparent that there's some kind of critical power level below which transmissions just die after a certain distance, possibly because a small level of RF resistance in the atmosphere (again, the real world's not a lab vacuum) becomes much more mathematically significant at such low power levels. When I was 15, I had a Ramsey FM-4 (250 mW but unfortunately NOT PLL) that I was able to pull in on a car stereo for 1.3 miles after attaching it to a random agglomeration of copper wire, a volleyball pole, and (I'm not kidding) CURTAIN RODS pointing out an attic window... so I think 250 mW should put you well above the point where the signal will keep on truckin' as far as the radio horizon (i.e. line of sight) allows, or at least far enough that you get significant distance coverage before path loss kicks in.

Hope this helps. ;D
 
Re: Tough call, Pat...

Grrrradio said:
FM stations' range is defined by line of sight -- I know pirates, i.e. way above Part 15 levels, who would KILL to live in a high-rise -- BUT at the power levels allowed by Part 15 FM, a great line of sight is pretty much useless from the perspective of a 2-D coverage map, as your signal will fade into inaudibility well before it ever hits the ground. .... Note to any REAL engineers, as opposed to wanna-be geeks like myself, who are browsing this board: The first paragraph's theoretical distance calculations seem a little "off", compared to what I've observed in the real world with even the cheapest battery-powered modulators. Either my modulators haven't really been Part 15 compliant, or I did some math wrong, or my theoretical approximations for usable signal strength are hosed. Please let me know if I misapplied the inverse-square law somehow, or used the wrong dB-to-arithmetic-multiplication scale...

Received power changes by the inverse distance squared, but received voltage (that is, field strength) is a function of the inverse distance, only. So if the radiated field is 250 µV/m 3 meters away from the transmit antenna, it will be 125 µV/m at 6 meters, and so on.

The fields at various distances produced by several powers radiated by a 1/2-wave dipole are shown in the plots here http://i62.photobucket.com/albums/h85/rfry-100/6417f684.gif

Radiated field strength does not reduce at any faster rate with distance for very low radiated power than for very high values.

FWIW: The FCC has taken action against unlicensed stations/operators whose measured fields at a given distance were less than those shown for the higher powers in my plots. All of the powers used in the plots are less than the 250 mW suggested earlier in this thread.

RF http://rfry.org
 
Hi everyone:

From my current building, I've received 900 Mhz. cordless phone signals with my handset in the field from its base here in the apartment quite reliably for about five blocks and 49 Mhz cordless phone signals (Again with my handset in the field from its base here in the apartment) almost as reliably. Both of these can't have more power output than a Part 15 transmitter does (In fact, dare I say, but I believe they put out even less power if I'm not mistaken).

Part 15 AM would probably be next to impossible to do I would think, which is why from a logistics standpoint, Part 15 FM would be more feasible I would think.

And let's not forget one very important thing. Not even the FCC can control how far an RF signal truly reaches, no matter what band or service you're on. RF is going to travel if conditions are right no matter what. It's just the nature of RF.

I don't think I'm totally doomed. But I do believe I'm more challenged than most Part 15 stations are.

Just my $.02 worth from a licensed Ham Radio Operator (Callsign KB0OXD) :D

Cheers :D
 
EEK! I didn't realize you were a licensed Ham, Pat... Sorry if I sounded condescending in my original post by attempting to explain radio basics that you already knew. :) On the cordless-phone thing, I'd be willing to believe that 49 MHz units run FM broadcast Part 15 power levels, since path loss is lower and line of sight less important as transmit frequency decreases. For those same reasons, I'm a bit more skeptical that 900 MHz performs as well as it does on a power that low. (Though the improved performance could owe to the greater ease of putting an electrically matched antenna, or even one of multiple-lambda length, onto that shorter wavelength...) In any event, I'm pretty sure Part 15 defines acceptable unlicensed radiation separately for dang near every band on the spectrum, so higher power levels could be legally "Part 15" for phones.

R.Fry -- Thanks very much for the clarification on field strength. Using 48 dBu as the approximate equivalent to 250 mV/m, would the math then predict the 28 dBu signal (rather than the 8 dBu signal) to go 100 feet? This would certainly square much more closely with what I've observed. However, this still leaves me curious as to why practice squares so much more closely with theory in this case than it does with full-power broadcast signals. (In other words, why is it that the 28 dBu signal of a Part 15 appears actually to go ten times as far as the 48 dBu, yet the 100 KW stations in my market which are 70 dBu at 30 miles are certainly not 50 dBu at 300 miles?)
 
Grrrradio said:
R.Fry -- Thanks very much for the clarification on field strength. Using 48 dBu as the approximate equivalent to 250 mV/m, would the math then predict the 28 dBu signal (rather than the 8 dBu signal) to go 100 feet?

A field strength of 48 dBµV/m is 250 µV/m (microvolts/meter), not 250 mV/m (millivolts/meter).  Probably just a typo, but maybe not everyone would recognize that.  A 28 dBµV/m field is about 25 µV/m.  So if the field 3 meters away from a Part 15 FM transmit antenna is 48 dBµv/m, then by the inverse distance rule it will be 1/10 of that value 10X further along the same (clear) propagation path, as you suspect.

This is the value plotted in my graphic at my earlier link for a compliant Part 15 FM at 100 feet (the red trace), but it is difficult to read it accurately on the logarithmic plot.  Note that I plotted the values in units of mV/m, not µV/m.  The red trace starts out at 3 meters at 0.25 on the vertical axis (0.25 mV/m is the same as 250 µV/m).

... why is it that the 28 dBu signal of a Part 15 appears actually to go ten times as far as the 48 dBu, yet the 100 KW stations in my market which are 70 dBu at 30 miles are certainly not 50 dBu at 300 miles?

Mainly because of earth curvature and other terrain obstacles (hill/mountains).  The inverse distance attenuation factor applies equally well for high-power FM broadcast stations over short, line-of-sight paths.

But the longer the propagation path, the more that path obstruction losses accumulate, to reduce the radiated field beyond the inverse distance loss.  Once the signal is beyond the radio horizon, those losses become severe.  The radio horizon over smooth earth from the top of a 1,000 foot tower is about 44.7 miles away.

//
 
As a practical matter, being in an apartment building could still work for AM. There is always the Slinky antenna, and creative connections to water piping as ground or even as the antenna (same difference here) might work well, yet not get into everyone's telephone.
There is also the big balloon with 300 feet of magnet wire! So easy to dispose of.....
It is unlikely in any case to get anything other than a decidedly cardioid (big lobe one way) pattern, unless you use the balloon.
So many variables come into play that a helper with a cell-phone or walkie-talkie will be necessary during adjustments.
The ability to actually hear, from a remote, while you are tuning your antenna, would be the ideal situation.
If you are going to drop a (ahem) part 15 AM with any "extra" power, be sure you can keep your freq "spot on".
No one enjoys moans and whistles, which the FCC can find faster than a dog finds food in your pockets, if they want to.
 
I live in a townhome so I share many of the problems you do about antenna placement and usage.

I've been intrigued by this design:

http://www.qsl.net/g3pto/roofant.html

Although this hidden, roofspace antenna is designed for the higher bands, I'm thinking that it could be adapted for Part-15 AM use, especially if paired with one of Carl Van Orden's coils:

http://antenna18431.tripod.com/antenna.htm

If you do a Google search for "hidden" or "stealth" antennas, you'll find a bunch of ideas for broadcasting from your apartment.

db
 
Google "crossed field antenna" and you will find some very interesting designs for MW.
 
Tom Wells said:
Google "crossed field antenna" and you will find some very interesting designs for MW.

The designs are interesting, but unfortunately they have not been found to deliver what they promise.

The link below leads to a short summary of a very complete engineering analysis of the CFA, including field strength measurements from an operating CFA. The conclusion of the study in the complete report included these statements, "The CFA appears to be a little worse than the reference monopole in gain and bandwidth. ... Improved performance of a roof-mounted CFA can be explained by the effective increase in the antenna length due to the ground connection system. ... Given the greater complexity of the CFA there does not appear to be any benefit in pursuing this approach."

Here is the link:
http://www.fi.uba.ar/materias/6654/download/CFATCheck.pdf

And here is a link to another analysis:
http://w8ji.com/e-h_antenna.htm

//
 
I did read them in April ths yr, and it sounded to me as if the antenna becomes, in effect something much like a small motor field, "taking" a load,
running synchrounously, "behaving" yet not really >coupled< into any load.

The resultant radiation off the feedline then seems to be confused for radiation off the antenna.
Does it or doesn't it?
At MW, individual situations limited ability to put in good grounds may make these work better than others, but probably only accidentally.
It is easy enough looking... I haven't wound one up yet..far too many other things hogging my time.

I mentioned it just to show at there are choices, but bottom line is effectiveness.
Just ask someone who has chased ground loops and hum.
Sometimes, to cure it, you must do exactly the opposite of the standard good shielding termination.
Why? " You could spend a week finding out why. Fortunately we cured your hum in only a 5-hour visit. make sure
nobody changes CD decks around by themselves, etc.
That's just how it is. Have a nice day. Please sign the form here."
Same way with radiation. wrong thing in the right place can work, perversely.
 
Thanx for the Mention DB....SSTRAN antenna information for 2006

Hi DB, and everyone.
First time for me on the new RADIO INFO Board, and with a computer no less (no more ugly webtv artifacts).

First off, my name is spelt wrong; it took so many months to get onto this new board that when I finally did............yep, spelt my name wrong.

I thank DB for mentioning my website, which features coils and antennas for certain part 15 operations/transmitters. I have a lot to say about this subject since I've been off the board for nearly the entire year.

The part 15am antenna biz was wonderful and somewhat overwelming last year as I built 73 antennas/projects for nearly as many customers. I also stupidly erased most of their comments about my product so they do not appear on the most recent edition of the site (mentioned on DB's post).
This year however yielded just three orders, and I believe that may be to either the fact that I didn't talk about the antenna on "here" this year, OR, the decline of AM part 15 interest/market used up.

The original letter from the poster stated he had problems putting up a part 15 am because of his apartment location.

Even though I had established a wide range of products last year (and discontinued most of them this year in the interest of building a 'standard product' I can not recall too many customers who desired a "regular" installation and thus had several different requests for customization...........in short that is what made my business so "busy"...because I was always trying to concoct ways in which people who wished to put a part 15am on the air could do so in their particular circumstances.

We have had several instances of success using the "sstran am antenna" and the tx inside of a house or an apartment. It can be done, but most people, especially those with very limited knowledge of radio or the AM band believe that with 1/10th of a watt in an incorrectly (read technically incorrect) antenna installation situation feel they should be blanketing their area in RF. And there is where the problem laid.

And, to do this, certain "give ups" have to be made by the person wishing to put on such an AM installation.
While it is true that copper in a building can be used as a ground, most buildings these days utilize pvc. And most grounds in electrical outlets these days are not really true grounds or are leaky............so generally these items can be ruled out.
And apartment buildings tend to frown on running copper cable down to a busted in rod in their land..............it's a tricky biz.

So, in instances like these, we set our sights very low, and work our way up.

A couple examples of in-apartment/house installations I've built are....
1. One man purchased the complete antenna system including the ground system from me; he took my advice and spread the ground system out on his (livingroom?) floor, and covered it with a rather thick rug. Because his building was mostly lumber, the system worked, shooting signal out of windows. He liked the installation, but we were probably talking about 1/2 mile of solid signal and again, most people expect miles and miles of signal out of something that was never meant to produce that type of signal.

2. I'd had several requests for antennas that could be put in an attic. So, what I simply did was break the antenna down into a size that could be installed in the highest part of the attic roof. Again, we spread the ground system over the floor where it could be done, and either connected into a ground rod (for extra grounding) OR went into an electrical juncture/soldered to copper water pipe. The downside to this is generally the signal became a directional one..........because the antenna ended up with several foot made into a top hat, which tended to concentrate signal into one or as much as three areas while nulling the last area. Of course something like this can be pointed and an antenna like this works better the less insulation and other material is concentrated into the attic area.

3. There were several requests by customers that had concluded they could indeed hang the antenna outside their window onto the building, courtesy of the landlord. A simple purchase (and a little changing of them) of antenna hangers ususally used for TV aeriels made this possible. I probably built 5 of these units, no problem.

Of course my biggest problems last year were because of people who could not read, or follow basic instructions, and took matters into their own hands. This is ok for people with a radio background (who kind of knows what to expect) but for beginners, this is a deadly path, even with 100mW.

To finish, I appreciate DB's mention of my name (correctly spelled!) and mention of my website.
I didn't do much advertising this year simply because the work became to be too much, but also, this year I had so many requests for antennas............and I spent a lot of time answering questions that I felt that either most people were not interested in the expense of buying one, OR, they decided to build their own...........and it was the people who ultimately decided to build their own that I heard the most from in 2006 (like I'm INTERESTED in their problems!!.....ie; I'm not).

I have no problem hearing from customers who buy from me who have questions, but I have a real problem with people who take on the job, and write me complaining that they can't get it right..........like it is my fault. Those same people, after spending a lot of money on a project they couldn't build, I think, just gave up...........but for sure I heard from them! And here is the funny part (I learned this when I tested the products I built before I attempted to sell them)......THEY DIDN'T BUILD THEM RIGHT...........winding a coil is not very easy, and the material is expensive. The only reason I could afford to sell one for less than $100, is because I got a lot of orders and bought 20 pound spools of magnetic wire.............which made them affordable. If you buy just enough to build a coil that operates in the 1610-1710kHz band, and mess up the job, it is a large amount of money wasted............for some, enough to give up the project.

The subject of being on the air in the standard band came up. I built about 4 very long coils designed by an engineer which did indeed extend just past 1400am...........and that is because there are truly a few areas in the country where the expanded band (or high standard band) is crowded. So we looked at what I would need to do to build one that would operate from 1250kHz on up.................and came up with one which ended up to be thinner than my standard coil but about 3 feet long with a lot of taps...........it was quite a project to build and it was priced high.

I still have some supplies left to build antennas, ground systems and coils for the sstran and Ramsey TX's (those that are kits that can be adapted to accept a copper/coil based antenna. You are welcome to write me at this address: [email protected] if you are interested in the current prices. Remember, copper has gone WAY up in price and so I base prices on those prices now; and, I no longer provide the long pipe (I leave that up to the customer to purchase since it is cheaper to buy locally than to ship!).
If there is a demand, I'll continue to build them, but this year had very little demand and I used up my prebuilt supplies in sales last year and this year.

I would like to stay in the coil winding/ground system business and leave the simplest parts of the antenna (and the heaviest to ship) to the customer in the future.

So, if you have a request for either product or for something you think you can't build, please feel free to email me at this address, and include as much information as you can; I'll be glad to write you back.
Carl Van Orden
Antenna Guy
 
As a follow-up to this discussion, you might want to read about the efforts of Hams For Action which is seeking government protection from HOA bans on Ham antennas.

If anything comes of this, it could, as a residual effect, give Part-15 operators the right to erect antennas in condos and townhomes without regulation from HOAs.

http://www.rwonline.com/pages/s.0044/t.464.html

db
 
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