"Hamilton Keith" <A...@Hampcb.com> wrote in message
"unkbeel" <rams...@bushnell.net> wrote in message
"Hamilton Keith" <A...@Hampcb.com> wrote in message
The only way to get out of your own house with the part 15 limitations, are to
use carrier current and live out in the country where you don't have a big
transformer on your powerline poles every 2 or 3 houses like you do in populated
If it were possible to broadcast for miles using legal part 15 power, then the
dial would be crowded with thousands of these radio stations.
Take a look at the back of your computer monitor. IT complies with part 15
rules so that it will NOT radiate outside of your house. If you are getting 2
- 3 miles, and not using carrier current out in farm country, then you are NOT
complying with legal part 15 rules.
> Take a look at the back of your computer monitor. IT complies with part 15
> rules so that it will NOT radiate outside of your house. If you are getting
> - 3 miles, and not using carrier current out in farm country, then you are NOT
> complying with legal part 15 rules.
The part 15 rules for radiating from an antenna on the AM band
specify: transmitter input power <= 100 milliwatts; antenna and
ground lead (if used) together no more than 3 meters long. This
does tend to limit one's range. However experiments are being
done with a technique called clustering, where several transmitters
that comply with these limits are phase-locked and spaced in a way
that allegedly causes their RF fields to combine, kinda like
the towers in a real AM station's directional antenna array.
An expensive and IMHO not well-documented technique.
The fields may combine in some directions but they cancel
in others. There is no possible way of phasing the
different transmitters to do otherwise (unless they all
feed the same antenna which violates the FCC rules).
Putting several transmitters and antennas very close to
each other may approach omnidirectional radiation patterns,
but the close proximity will cause a reduction in the even
low radiation resistance of each antenna - and it violates
FCC rules to boot.
The problem with most Part-15 transmitters like the
Vectronics and its kin is the poor approach they use in an
attempt to impedance match the antenna. A 3 meter antenna,
even at the highest AM-band frequency, still presents
a high capacitive reactance in series with an exceptionally
low resistance. It is the radiation resistance that does
the real work. With better design of the transmitter
impednace matching, an excellent ground, and a large
conductor for the antenna, an effective range of a few
thousand feet is possible.
The original article referred to a while back about using
Part-15 transmitters to cover several miles actually used
several transmitters on different frequencies fed by a
common audio source. The use of a "leaky coaxial cable"
(Radio Shack "high quality" garbage comes to mind here) is
a better approach.
Or just buy a Ramsey and run it at the 1-watt which their pdf files shows
how and run it around teh 530 khz frequecny. FCC ignores AM - they are
spending all thier time busting FM pirates. 1-watt at end of aM band would
not even get noticed IMO ;-).
An unjust king asked a devotee what kind of worship is best? He replied:
'For thee the best is to sleep one half of the day so as not to injure the
people for a while.'
I saw a tyrant sleeping half the day.
I said: 'This confusion, if sleep removes it, so much the better;
But he whose sleep is better than his wakefulness
Is better dead than leading such a bad life.'
> Or just buy a Ramsey and run it at the 1-watt which their pdf files
> how and run it around teh 530 khz frequecny. FCC ignores AM - they are
> spending all thier time busting FM pirates. 1-watt at end of aM band
> not even get noticed IMO ;-).
This is an even sillier idea. The Ramsey garbage rigs have some of the
poorest antenna impedance matching of any transmitters out there. And
transmitting on the low end of the band makes the antenna problem far
worse. The antenna radiation resistance is about a third of what it is on
the high end of the and losses in the matching circuits will be about an
order of magnitude higher.
Your result will be even less range than a good 100 milliwatt transmitter
on 1600 kHz.
And actually the FCC does monitor these frequencies. Whenever they travel
through a given area for any reason, they tend to monitor the Traveler
Information System transmitters at the ends of the bands. A few nice fines
have been given levied on state Departments of Transportation, airports and
cities for violations.
But the real issue really is - for listening to old radio broadcasts on
authentic receivers, why do you need much range? Fidelity and stability
are far more important. Not very many of us own mansions longer than 1000
[Remove NO SPAM to reply directly, Barry]
yes I know low end is less range.
> The antenna radiation resistance is about a third of what it is on
> the high end of the and losses in the matching circuits will be about an
> order of magnitude higher.
> Your result will be even less range than a good 100 milliwatt transmitter
> on 1600 kHz.
Are you serious?! I'm asking becuase I assumed the difference would be
around 50-percent less. I'm not an expert.
> And actually the FCC does monitor these frequencies. Whenever they travel
> through a given area for any reason, they tend to monitor the Traveler
> Information System transmitters at the ends of the bands. A few nice
> have been given levied on state Departments of Transportation, airports
> cities for violations.
TIS - never thought of this........something to consider for an aspiring
LPAM station operator. Good point.
> But the real issue really is - for listening to old radio broadcasts on
> authentic receivers, why do you need much range?
Becuase listening to this stuff on an old radio (which I have) or from the
computer (which I choose to listen through) isnot the point for some.
For some it is offering this programing to the neighborhood, so other may
hear how good radio used to be before ClearChannel and ilk ruined
it..................Basicaly an alternative to all that hate-rant-drivel
which corporate radio forces down our throats.
Even if only for a few square blocks of town.....at least a few will not be
stuck with Rush and all the other hate-talkers. Or souless automated
playlists of the BeeGees/ad nauseum.
> Fidelity and stability
> are far more important. Not very many of us own mansions longer than 1000
Let me check my numbers again to be sure...
Let's assume the antenna is a 3 meter wire, 2 millimeters
in diameter, perfectly conducting working against an ideal
ground. This is rather ideal but the data can be
calculated easier this way. A real antenna over real earth
will not do nearly as well.
At 1600 kHz, Z = 0.0947 - j 4130
or 0.0947 ohms in series with 24.09 pF capacitance
At 530 kHz, Z = 0.0105 - j 12500
or 0.0105 ohms in series with 24.02 pF capacitance
So the radiation resistance of the antenna at the lower
frequency is about a ninth of that at the higher
frequency. My "back of the envelope" guess originally was
based on direct scaling of the resistance to frequency, but
I checked and it scales as the square of the frequency. This
agrees with the figures shown above.
To get the antenna to accept power, you have to tune out
the reactance with a series loading coil. Again let us
assume a high quality coil with a Q-factor of 100 is used
to do this. This is about the best you can expect to do in
To tune at 1600 kHz you need an inductance of about 411
microhenries. The coil will have a series resistance of
about 4.13 ohms. If you feed 100 milliwatts to the series
combination of the loading coil and antenna you will
develop a voltage of about 0.65 volts RMS at the input of
the coil. But the antenna only sees about 0.0146 volts.
Only about 2.2 milliwatts actually makes it to the antenna.
At 530 kHz, the inductance will be 3.754 millihenries and
its series resistance will be 125 ohms. Feeding 100
milliwatts to the loading coil develops 3.535 V RMS at the
input of the coil. The antenna only sees about 0.296
millivolts. In this case only about 8.4 microwatts is
If you accept the FCC's recommendation that 1000 microvolts
per meter field strength is a good, clean signal, then at
1600 kHz, you will reach this point around 630 meters from
the antenna. But at 530 kHz, the same field strength will
be reached between 60 and 70 meters.
So in the ideal case, at 1600 kHz, you might reliably cover
up to a 2000 foot radius, while at 530 kHz the radius would
be around 200 feet. Increasing the transmitter power
to one watt at 530 kHz would not be near enough to achieve
the greater range as it would only get you about 360 feet.
This result is even shorter than I expected. It shows that
for greatest range, use the high end of the band. It also
shows that most of the transmitter power is lost in the
loading coil. In actuality additional power is lost in the
impedance matching network in the transmitter. Because the
loading coil and the impedance matching network are usually
combined in real transmitters, my earlier comments about
impedance matching are especially true.
73, Dr. Barry L. Ornitz orni...@SPAMusa.net
[Copyright 2002 B. L. Ornitz - don't repost this to the weenies on the
pirate radio groups without permission]
Wow 1600 it is then......whenever that may be. thanks!
Who are these "top enforcement officials" at the FCC you are
I think he is the top enforcement official or close to it.