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by Jonathan Smick
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It takes about 8-10mW T.P.O (Transmitter Power Output) into a 0dBi antenna (like a 1/4 wave groundplane) to get in the ballpark of 250 uV/m at 3 meters (one wavelength at FM Broadcast Frequencies)…

by Jonathan Smick
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It takes about 8-10mW T.P.O (Transmitter Power Output) into a 0dBi antenna (like a 1/4 wave groundplane) to get in the ballpark of 250 uV/m at 3 meters (one wavelength at FM Broadcast Frequencies)…

The higher the gain above 0dBi the less transmitter power required to reach legal limit. ERP, EIRP,and TPO are not the same thing.

EIRP (Equivalent Isotropically Radiated Power) is the amount of energy, which when integrated over a sphere radius of R(assumed isotropic or point source)equals the total energy density radiated by a gain antenna in its favored direction.

EIRP when integrated over a sphere (assuming true isotropic)at Part 15 Legal FM power level is in the nanowatts(can’t recall the exact figure, but suffice it to say, minuscule).

ERP (Effective Radiated Power) is the total energy density (degree of concentration of radiation, or collimation) radiated by any antenna in it’s favored direction (if it has gain) verus a true (theoretical) isotropic or point source.

Thus 0dBi means a perfectly (or close enough to it)spherical radiation pattern, energy radiated equally in all directions. Think “lightbulb”.

Actually, a good analogy, since light is simply very high frequency EM waves, essentially “radio we can see.”

Another example: An antenna has 6dBi gain. This means in it’s favored direction, it radiates 4 times as much power as an isotropic radiator (0dBi) would AT THE SAME TPO.

Put another way, the isotropic source’s TPO would have to be increased by a factor of four to equal the energy density of the gain antenna in the gain antenna’s direction of maximum radiation.

UHF TV stations have ERP’s in the multi-megawatt range, but their TPO is only 10’s or at most a couple of 100’s of KW. TPO is simply the actualpower output at the antenna terminals of the transmitter, in watts (or fractions thereof).

Jon
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Thanks to our contributor for bringing one of Jon’s articles back from the past. Jon operates an awesome Part 15 station list site at The Master List of Part 15 Radio Stations of North America

Many Part 15 operators want to play music the audience is familiar with, and it is certainly easier to get folks to tune in when the program material is tried and true.

But that might not be the only way to go…

Many Part 15 operators want to play music the audience is familiar with, and it is certainly easier to get folks to tune in when the program material is tried and true.

But that might not be the only way to go…

Back in the 1950s broadcasters in cities like Chicago, Detroit and Philadelphia faced a similar problem. The radio dial seemed saturated with the dominant music of the time, and visionary broadcasters were looking for a way to capture a new audience.

For probably the last time in broadcast history, program directors took a chance on a new, untried style of music, and tried to reach an audience few considered accessible or important.

When those new records started spinning, a little thing called Rock & Roll was born.

Today, Part 15 broadcasters have the same awesome opportunity. There is so much new music, so many new bands, and so much opportunity for innovation today, in all genres and styles.

Part 15 broadcasters who want to take the time to give these new sounds a listen will find awesome variety and ease of accessibility never available before.

Your station could be on the forefront of a new revolution in broadcast variety and excitement, providing your audience with a unique and appealing product far superior to the standard fare.

Best of all, it’s as free as the wind. No pesky fees to pay, no contracts to sign.

Here’s a short list of a few new music web sites. The next necessary band is there right now, just waiting for you to discover them!

www.iuma.com – New music from everywhere

www.unsigned-bands.com – Pretty straight forward

www.unsignedbandweb.com – The name says it all

www.overplay.co.uk – New Music from accross the pond

www.bardscrier.com – Music Promotion

dmoz.org – Unsigned Band Resources

www.alternativeaddiction.com – the Unknown and Unsigned

dir.webring.com – Unsigned Bands webring

www.extraplay.com – new music, free stuff

www.therecordindustry.com – mp3 site listing

www.archive.org – Internet Archive Audio Department

If you can’t find something you like, I’ll give you double you money back 🙂

The Antenna Guy writes Dear Readers,

This year has been rough on part 15ers. There had been a period of time this past winter that made it look like part 15 kits were not legal…

The Antenna Guy writes Dear Readers,

This year has been rough on part 15ers. There had been a period of time this past winter that made it look like part 15 kits were not legal…

Not true!

But it took a great deal of work and a great letter from the FCC to allow this to happen. Part 15 kits are LEGAL to use!

I kind of took a chance: I know that a ton of part 15 transmitters are sold to service a household, or a yard. Most of us are broadcasters, so I decided to build part 15 antennas for those that wanted to be on the air, and service more than a quarter acre.

Part15.us has been more than generous; actually posting some of my antenna pictures, and if the instructions get you on the air, that is all I hope to accomplish.

At this time, I don’t feel as though part 15 am broadcasting is in jeopardy; in fact, I feel strongly that our future is strong. I’m amazed at the number of emails I get (not only wanting to order an antenna!) from people interested in getting on the air.

This is directly proportional to the amount of stations that are on the air, but do not serve their populations. The People writing me want to be on air, and to serve with excellent programming ideas.

To hear from them, I am excited about the future of the AM dial! It is unreal the ideas these folks have to invigorate the AM dial as we know it.

My thinking, over the past couple years has been to make it simple for people to go on the air, legally, and make a difference in their communities. Or at least SERVE them with something they can NOT get at all on AM or FM.

Doing it on AM is easier, simpler, and you can get a very decent signal out.

(BTW: enough of the “I want to get out 8 miles” emails; they are funny. If you want to get out 8 miles, buy a radio station or build a linear!)

All we are attepting to do is to provide a very easy, very very affordable way for people to put an AM signal on the air. And for those that think I am making major money helping people get on the air, think again; I build a very simple, and effective antenna; it costs 30 or 40 bucks to ship, and I spend a lot of time building them, to the point where it is becoming impossible to even cover my costs to equip someone with a broadcast antenna.

Building antennas is not a business to consider. I’ve considered giving it up; it costs too much in time emailing back customers, and in packaging and shipping, and building units. If I cut the costs, I do it for free. BUT, if I can cover my costs, I feel an obligation to help anyone who wants to get on the air!

Everyone wants me to wind coils. Let me tell you something about this: I wound (at a cost of nearly $200!) 5 or 6 coils at first, all of which were junk. These are not easy to do. But I learned from doing them, and now I can wind a great one in less time than the three days it originally took me! My coils are state of the art now. So, I realized that what most people wishing to go on the air would build their own antenna, which I get a ton of emails about.

I really can’t solve issues involved when someone builds their own antenna, but that what they wanted was coils built. So, that is what I do. I wind, wind, wind, daily.

The result? I’m selling lots of coils.

And the end result? Lots of people are getting on the air. AND THAT IS A GOOD THING. Every single kit manufacturer has written me saying they want to feature my antennas on their website. I think this is a great idea, I also think I am looking at working myself to death.

One day, we will come up with a map, which showcases all the part 15 stations and their contours. When this is done, we will see exactly where our part 15 am’s are, and where they broadcast, and we will also see where we can utilize room for improvement.

Carl Van Orden
[email protected]
Maker of part 15 antennas/coils

Thank you for emailing WCRV/”THE ANTENNA GUY” I welcome your questions about our antenna!

Most information can be found on our website http://antenna18431.tripod.com/antenna.htm

Special orders welcome; Churches and Schools welcome to apply for discounts.

[email protected] – New products for part 15’ers added as soon as they are available!

We now accept PayPal!

Our part 15 am radio station website: http://wcrv1540am.tripod.com/wcrv.html

It seems folks are always trying to figure out how to make a short antenna…

It seems folks are always trying to figure out how to make a short antenna…

Ever since a fellow named Wheeler wrote a 1947 article called “Fundamental Limits of Small Antennas,” we’ve been trying to do more with less.

Recently, some developments at the University of Rhode Island have been attracting some attention.

You can read more in the latest edition of EETimes, at
http://www.eet.com/showArticle.jhtml?articleID=21600147

A google meta search is Here

An altavista meta search is Here

and a Yahoo meta search is Here

Contributor tregonsee adds “On Friday, May 06 On 31 March 2005, the US Navy tested several versions of the antenna mentioned in the article, apparently with good results. See the University of Rhode Island news release at:

http://www.uri.edu/news/releases/?id=3126

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…and from our February 23 blog post…
Can you construct a small antenna with PVC plumbing tube and discarded fruit cans? Can such an antenna really work? Well, that depends on who you ask… The best answers are probably found by reading rather than wiring. As Don Lancaster always says, an hour of reading equals a month in the lab!

Here are a few sources to get you started:

http://www.rexresearch.com/harteh/harteh.htm

http://www.eh-antenna.com/library/EH_ANTENNA_FOR_HAMS.pdf

http://www.eham.net/articles/3586

http://www.w8ji.com/e-h_antenna.htm

http://www.rexresearch.com/xfldant/xfldant.htm

Hi everyone,

I wanted to know your opinion on having a
part 15 newsletter…

Hi everyone,

I wanted to know your opinion on having a
part 15 newsletter…

My idea is simple; we have quite a few websites out there, and I thought a bi-monthly newsletter; delivered via email would be a good
idea.

What could we put in the news letter? Well, just a ton of info! From new stations, to new products, to new websites, to new information, the list goes on and on.

Of course, I’d need some input to put it together, articles, pictures, opinions.

Let me know if you are interested in contributing to the newsletter and/or receiving it.

For those of you interested in getting a few stations on soon (and several of you are), I’m running a special sale on coils. Looks like most of you don’t mind building the antenna, but dislike building the coil.

It is true; the coil is kind of cumbersome, so for the next week, I’m sellling it for $20 bucks off….that is $65.00 shipping included while
the special supply of wire lasts. Just
thought I’d mention it, cause I have some extra time this week, and after this week, I won’t.
I several more to do this week and can only fit a couple more in.

Let me know if you are interested in such a newsletter (I’m looking for opinions!), and if you would like to contribute to it.

Keep in touch,

Carl

Thank you for emailing WCRV/”THE ANTENNA GUY”
I welcome your questions about our antenna!
Most information can be found on our website:
http://antenna18431.tripod.com/antenna.htm

Special orders welcome; Churches and Schools welcome to apply for
discounts. [email protected]
New products for part 15’ers added as soon as they are available!

We
now accept PayPal!

Our part 15 am radio station website:

http://wcrv1540am.tripod.com/wcrv.html

Oldbuckeye writes:
First of all I feel that 1 to 5 watts would be fine for legal unlicensed AM broadcasting…

Oldbuckeye writes:
First of all I feel that 1 to 5 watts would be fine for legal unlicensed AM broadcasting…

What I’m concerned about are the advocates for LPAM situation involving becoming FCC Licensed.

Then the government steps in and requires
this that and the other thing and usually it’s costly and out of the reach of the average person.

If we could just get from 1 to 5 watts that
would be fine to cover a suburb or small town or village which has no
radio service. The other thing I wanted to share with you is that I
operate a part 15 low power station and use the Talking House Transmitter
with an ATU in which a 10 foot antenna is attached.

The ATU is actually
a variable tuning coil which matches the antenna to the transmitter
frequency. The tunning box also has a ground which I connected to about
65 horrizontal copper radials buried about three to 4 inches under the
earth.

My antenna is perched on a 60 foot pole.
I get out during the day about one and a half miles strong and another
1/2 mile weak.
I get out about 1/2 mile good at night. Take care and God Bless!