FM transmitter wanted with more power

[Kristian Hermansen]

I am looking to buy/modify/build an FM transmitter that will work on normal USA radio frequency range of 88-108 MHz. I have purchased an in-store product that limits the distance of effective trasmission to ~15 feet -- most likely due to FCC requirements for car FM transmitting devices. However, I have a somewhat larger vehicle and would like to transmit a more powerful signal so that interference is not a problem. To my knowledge, the FCC restrictions apply to consumer products, and not to educational experimentation/projects. This would be powered by the car's cigarette lighter, so I am sure that it can provide for more power -- given that the transmitter's circuitry would allow it. I currently am using two different devices, neither of which have worked well. The product that worked best was the iRiver AFT-100. I would like to either modify this device (or send it to you for modification if it requires more knowledge/tools than I have), have someone point me in the direction of the knowledge to do it myself, or buy one from someone on this list. I have Googled around, but the quality of online web searches can only be verified by people who have experience with these thi
ngs -- for instance -- you!

I am not a total dummy, and even took some courses in Electrical Engineering before majoring in Computer Science. Any help would be appreciated though. If I decide to have one of you build it for me at a fair price, there is also a future project I am working on that would require a more powerful FM transmitter -- about a mile or so of directed transmission. Thanks, and hope to hear from you soon! You can email me off list if you like as well -- just remove the "NOSPAM" portion of my address...

Kristian Hermansen


--------------= Posted using GrabIt =----------------
------= Binary Usenet downloading made easy =---------
-= Get GrabIt for free from http://www.shemes.com/ =-

 

[Larry Brasfield]

"Kristian Hermansen" <kristian.hermansen@NOSPAM.gmail.com> wrote
in message news:rY2se.8361$V31.2593@fe42.usenetserver.com...

I am looking to buy/modify/build an FM transmitter that will work on
normal USA radio frequency range of 88-108 MHz. I have purchased
an in-store product that limits the distance of effective trasmission to
~15 feet -- most likely due to FCC requirements for car FM transmitting
devices. However, I have a somewhat larger vehicle and would like to
transmit a more powerful signal so that interference is not a problem.
To my knowledge, the FCC restrictions apply to consumer products,
and not to educational experimentation/projects.

You might be surprised to learn that ignorance of the law
is not considered a defense against charges of violating it,
at least not in court. You might get some sympathy from
such a defense, but you will get no break from a judge.

You should also be aware that the emission limits set by
the FCC for unlicensed stations are not dependent on
how the equipment was procurred.

I am not a total dummy, and even took some courses in Electrical
Engineering before majoring in Computer Science. Any help would be
appreciated though. If I decide to have one of you build it for me at a
fair price, there is also a future project I am working on that would
require a more powerful FM transmitter -- about a mile or so of
directed transmission.

Good luck finding somebody equally willing to break
the law. By the way, this post may well serve to make
even the weak "I was ignorant" defense untenable.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

 

[John - KD5YI]

Kristian Hermansen wrote:

I am looking to buy/modify/build an FM transmitter that will work on normal USA radio frequency range of 88-108 MHz. I have purchased an in-store product that limits the distance of effective trasmission to ~15 feet -- most likely due to FCC requirements for car FM transmitting devices. However, I have a somewhat larger vehicle and would like to transmit a more powerful signal so that interference is not a problem. To my knowledge, the FCC restrictions apply to consumer products, and not to educational experimentation/projects. This would be powered by the car's cigarette lighter, so I am sure that it can provide for more power -- given that the transmitter's circuitry would allow it. I currently am using two different devices, neither of which have worked well. The product that worked best was the iRiver AFT-100. I would like to either modify this device (or send it to you for modification if it requires more knowledge/tools than I have), have someone point me in t
he direction of the knowledge to do it myself, or buy one from someone on this list. I have Googled around, but the quality of online web searches can only be verified by people who have experience with these things -- for instance -- you!

I am not a total dummy, and even took some courses in Electrical Engineering before majoring in Computer Science. Any help would be appreciated though. If I decide to have one of you build it for me at a fair price, there is also a future project I am working on that would require a more powerful FM transmitter -- about a mile or so of directed transmission. Thanks, and hope to hear from you soon! You can email me off list if you like as well -- just remove the "NOSPAM" portion of my address...

Kristian Hermansen


--------------= Posted using GrabIt =----------------
------= Binary Usenet downloading made easy =---------
-= Get GrabIt for free from http://www.shemes.com/ =-

You would do well to heed Mr. Brasfield's comments.

Here is a link to the FCC's rules so you can verify it for yourself. Find
and read about modifications to approved equipment. What you want to do is
strictly illegal.

http://www.access.gpo.gov/nara/cfr/waisidx_04/47cfr15_04.html

Cheers,
John

 

[Mac]

On Wed, 15 Jun 2005 23:38:24 -0400, Kristian Hermansen wrote:

I am looking to buy/modify/build an FM transmitter that will work on normal USA radio frequency range of 88-108 MHz. I have purchased an in-store product that limits the distance of effective trasmission to ~15 feet -- most likely due to FCC requirements for car FM transmitting devices. However, I have a somewhat larger vehicle and would like to transmit a more powerful signal so that interference is not a problem. To my knowledge, the FCC restrictions apply to consumer products, and not to educational experimentation/projects. This would be powered by the car's cigarette lighter, so I am sure that it can provide for more power -- given that the transmitter's circuitry would allow it. I currently am using two different devices, neither of which have worked well. The product that worked best was the iRiver AFT-100. I would like to either modify this device (or send it to you for modification if it requires more knowledge/tools than I have), have someone point me in the direction of the knowledge to do it myself, or buy one from someone on this list. I have Googled around, but the quality of online web searches can only be verified by people who have experience with these t
hings -- for instance -- you!

I am not a total dummy, and even took some courses in Electrical Engineering before majoring in Computer Science. Any help would be appreciated though. If I decide to have one of you build it for me at a fair price, there is also a future project I am working on that would require a more powerful FM transmitter -- about a mile or so of directed transmission. Thanks, and hope to hear from you soon! You can email me off list if you like as well -- just remove the "NOSPAM" portion of my address...

Kristian Hermansen


--------------= Posted using GrabIt =----------------
------= Binary Usenet downloading made easy =---------
-= Get GrabIt for free from http://www.shemes.com/ =-

What kind of antenna does your transmitter use? Is there any provision for
connecting an external antenna?

--Mac

 

[JustMe]

"Kristian Hermansen" <kristian.hermansen@NOSPAM.gmail.com> wrote in message
news:rY2se.8361$V31.2593@fe42.usenetserver.com...

I am looking to buy/modify/build an FM transmitter that will work on normal
USA radio frequency range of 88-108 MHz. I have purchased an in-store
product that limits the distance of effective trasmission to ~15 feet --
most likely due to FCC requirements for car FM transmitting devices.
However, I have a somewhat larger vehicle and would like to transmit a more
powerful signal so that interference is not a problem. To my knowledge,
the FCC restrictions apply to consumer products, and not to educational
experimentation/projects. This would be powered by the car's cigarette
lighter, so I am sure that it can provide for more power -- given that the
transmitter's circuitry would allow it. I currently am using two different
devices, neither of which have worked well. The product that worked best
was the iRiver AFT-100. I would like to either modify this device (or send
it to you for modification if it requires more knowledge/tools than I
have), have someone point me in the direction of the knowledge to do it
myself, or buy one from someone on this list. I have Googled around, but
the quality of online web searches can only be verified by people who have
experience with these things -- for instance -- you!

I am not a total dummy, and even took some courses in Electrical
Engineering before majoring in Computer Science. Any help would be
appreciated though. If I decide to have one of you build it for me at a
fair price, there is also a future project I am working on that would
require a more powerful FM transmitter -- about a mile or so of directed
transmission. Thanks, and hope to hear from you soon! You can email me
off list if you like as well -- just remove the "NOSPAM" portion of my
address...

Kristian Hermansen


Perhaps you can use the existing transmitting device by directing the output

into a "leaky feeder" placed where you require reception. This should not
put you outside the law. Google came back with 4100 hits. There should be
some help there.

 

[Mebart]

You should be able to get much more than 15 feet range and still be
within the law.

Ramsey used to make a very high quality part 15 transmitter, but it is
pricey.

With 100 milliwatts and a 3 meter antenna, you should be able to do
300 to 500 feet with a decent receiver.

I'm assuming you want a real FM transmitter, capable of doing stereo
with good frequency stability (quartz based frequency).

If you just want someting to make noise with, there are many
schematics and products you can buy and operate legally. But, you will
have to chase the signal up and down the FM band unless you get one
that uses a quartz crystal to determine it's transmit frequency.

GL.

On Wed, 15 Jun 2005 23:38:24 -0400, "Kristian Hermansen"
<kristian.hermansen@NOSPAM.gmail.com> wrote:

I am looking to buy/modify/build an FM transmitter that will work on normal USA radio frequency range of 88-108 MHz. I have purchased an in-store product that limits the distance of effective trasmission to ~15 feet -- most likely due to FCC requirements for car FM transmitting devices. However, I have a somewhat larger vehicle and would like to transmit a more powerful signal so that interference is not a problem. To my knowledge, the FCC restrictions apply to consumer products, and not to educational experimentation/projects. This would be powered by the car's cigarette lighter, so I am sure that it can provide for more power -- given that the transmitter's circuitry would allow it. I currently am using two different devices, neither of which have worked well. The product that worked best was the iRiver AFT-100. I would like to either modify this device (or send it to you for modification if it requires more knowledge/tools than I have), have someone point me in the
direction of the knowledge to do it myself, or buy one from someone on this list. I have Googled around, but the quality of online web searches can only be verified by people who have experience with these things -- for instance -- you!

I am not a total dummy, and even took some courses in Electrical Engineering before majoring in Computer Science. Any help would be appreciated though. If I decide to have one of you build it for me at a fair price, there is also a future project I am working on that would require a more powerful FM transmitter -- about a mile or so of directed transmission. Thanks, and hope to hear from you soon! You can email me off list if you like as well -- just remove the "NOSPAM" portion of my address...

Kristian Hermansen


--------------= Posted using GrabIt =----------------
------= Binary Usenet downloading made easy =---------
-= Get GrabIt for free from http://www.shemes.com/ =-

 

[John - KD5YI]

Mebart wrote:

You should be able to get much more than 15 feet range and still be
within the law.

Ramsey used to make a very high quality part 15 transmitter, but it is
pricey.

With 100 milliwatts and a 3 meter antenna, you should be able to do
300 to 500 feet with a decent receiver.

I'm assuming you want a real FM transmitter, capable of doing stereo
with good frequency stability (quartz based frequency).

If you just want someting to make noise with, there are many
schematics and products you can buy and operate legally. But, you will
have to chase the signal up and down the FM band unless you get one
that uses a quartz crystal to determine it's transmit frequency.

GL.

Actually, the rules permit 100 mW and a 3 meter antenna (combined with
ground and feeder) on the AM broadcast band (525 - 1705 kHz), but not in the
FM broadcast band (88 - 108 MHz). For the latter, the rules state:

[Code of Federal Regulations]
[Title 47, Volume 1]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR15.239]

[Page 816-817]

TITLE 47--TELECOMMUNICATION

CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION

PART 15_RADIO FREQUENCY DEVICES--Table of Contents

Subpart C_Intentional Radiators

Sec. 15.239 Operation in the band 88-108 MHz.

(a) Emissions from the intentional radiator shall be confined within
a band 200 kHz wide centered on the operating frequency. The 200 kHz
band shall lie wholly within the frequency range of 88-108 MHz.
(b) The field strength of any emissions within the permitted 200 kHz
band shall not exceed 250 microvolts/meter at 3 meters. The emission
limit in this paragraph is based on measurement instrumentation
employing an average detector. The provisions in Sec. 15.35 for
limiting peak emissions apply.


It is paragraph (b) above that is the stickler. It takes only about 20
nanowatts into an efficient antenna (say, a quarter or half wave) to get
that 250 microvolts/meter at 3 meters. Of course, you could use a kilowatt
into a really bad antenna so long as you don't produce a field greater than
250 microvolts/meter at 3 meters.

Sorry to be the bearer of bad news.

John

 

[Kristian Hermansen]

"JustMe" <á@á> wrote:

Perhaps you can use the existing transmitting device by directing the output
into a "leaky feeder" placed where you require reception. This should not
put you outside the law. Google came back with 4100 hits. There should be
some help there.

OK, that sounds like a good start. Can anyone else point me in the direction of a more powerful solution? I really want my other project to have about a one to three mile radius of transmission. I will be using this more powerful transmitter on a Camp Ground where the people are more spread out and it is difficult to get messages out to people who are not close to the base. Walkie takies are out of the question, because we need normal radios to pick up the signals. We also don't want them to have to buy a special device.

FM radios are cheap and almost everyone has one. Campers will have their radios on a certain frequency to get updates over the weekend of festivities. I would plan on using this via a 120V AC input in a wall socket. Does anyone have some suggestions? Is there a good hobby magazine dedicated to FM radio building? Or can I purchase the device as described above cheaply from somewhere? Your recommendations so far have been very helpful, thanks guys...

Kristian Hermansen


--------------= Posted using GrabIt =----------------
------= Binary Usenet downloading made easy =---------
-= Get GrabIt for free from http://www.shemes.com/ =-

 

[Mac]

On Fri, 17 Jun 2005 13:37:05 -0400, Kristian Hermansen wrote:

"JustMe" <á@á> wrote:
Perhaps you can use the existing transmitting device by directing the
output into a "leaky feeder" placed where you require reception. This
should not put you outside the law. Google came back with 4100 hits.
There should be some help there.

OK, that sounds like a good start. Can anyone else point me in the
direction of a more powerful solution? I really want my other project
to have about a one to three mile radius of transmission. I will be
using this more powerful transmitter on a Camp Ground where the people
are more spread out and it is difficult to get messages out to people
who are not close to the base. Walkie takies are out of the question,
because we need normal radios to pick up the signals. We also don't
want them to have to buy a special device.

FM radios are cheap and almost everyone has one. Campers will have
their radios on a certain frequency to get updates over the weekend of
festivities. I would plan on using this via a 120V AC input in a wall
socket. Does anyone have some suggestions? Is there a good hobby
magazine dedicated to FM radio building? Or can I purchase the device
as described above cheaply from somewhere? Your recommendations so far
have been very helpful, thanks guys...

Kristian Hermansen


--------------= Posted using GrabIt =---------------- ------= Binary
Usenet downloading made easy =--------- -= Get GrabIt for free from
http://www.shemes.com/ =-

I re-formatted your text because each paragraph was on one long line.
Annoying!

What you are talking about sounds illegal to me (in the USA). If that
doesn't bother you, maybe you should search for information on the
Internet about pirate radio and so-on.

You really should reconsider this, though, because any type of illegal kit
may cause interference on other bands which could cause genuine problems
for other people. This would be very inconsiderate, or possibly even
dangerous.

Maybe there is a way you can get permission at the campsite to broadcast
at low power using approved equipment.

--Mac

 

[Mac]

On Fri, 17 Jun 2005 04:42:01 +0000, John - KD5YI wrote:

Mebart wrote:
You should be able to get much more than 15 feet range and still be
within the law.

Ramsey used to make a very high quality part 15 transmitter, but it is
pricey.

With 100 milliwatts and a 3 meter antenna, you should be able to do
300 to 500 feet with a decent receiver.

I'm assuming you want a real FM transmitter, capable of doing stereo
with good frequency stability (quartz based frequency).

If you just want someting to make noise with, there are many
schematics and products you can buy and operate legally. But, you will
have to chase the signal up and down the FM band unless you get one
that uses a quartz crystal to determine it's transmit frequency.

GL.


Actually, the rules permit 100 mW and a 3 meter antenna (combined with
ground and feeder) on the AM broadcast band (525 - 1705 kHz), but not in the
FM broadcast band (88 - 108 MHz). For the latter, the rules state:

[Code of Federal Regulations]
[Title 47, Volume 1]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR15.239]

[Page 816-817]

TITLE 47--TELECOMMUNICATION

CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION

PART 15_RADIO FREQUENCY DEVICES--Table of Contents

Subpart C_Intentional Radiators

Sec. 15.239 Operation in the band 88-108 MHz.

(a) Emissions from the intentional radiator shall be confined within
a band 200 kHz wide centered on the operating frequency. The 200 kHz
band shall lie wholly within the frequency range of 88-108 MHz.
(b) The field strength of any emissions within the permitted 200 kHz
band shall not exceed 250 microvolts/meter at 3 meters. The emission
limit in this paragraph is based on measurement instrumentation
employing an average detector. The provisions in Sec. 15.35 for
limiting peak emissions apply.


It is paragraph (b) above that is the stickler. It takes only about 20
nanowatts into an efficient antenna (say, a quarter or half wave) to get
that 250 microvolts/meter at 3 meters. Of course, you could use a kilowatt
into a really bad antenna so long as you don't produce a field greater than
250 microvolts/meter at 3 meters.

Sorry to be the bearer of bad news.

John

In the AM case, wouldn't it be pretty hard to push those 3mW into a 3
meter antenna at those frequencies? I'm not saying it couldn't be done,
mind you.

--Mac

 

[John - KD5YI]

Mac wrote:

On Fri, 17 Jun 2005 04:42:01 +0000, John - KD5YI wrote:


Mebart wrote:

You should be able to get much more than 15 feet range and still be
within the law.

Ramsey used to make a very high quality part 15 transmitter, but it is
pricey.

With 100 milliwatts and a 3 meter antenna, you should be able to do
300 to 500 feet with a decent receiver.

I'm assuming you want a real FM transmitter, capable of doing stereo
with good frequency stability (quartz based frequency).

If you just want someting to make noise with, there are many
schematics and products you can buy and operate legally. But, you will
have to chase the signal up and down the FM band unless you get one
that uses a quartz crystal to determine it's transmit frequency.

GL.


Actually, the rules permit 100 mW and a 3 meter antenna (combined with
ground and feeder) on the AM broadcast band (525 - 1705 kHz), but not in the
FM broadcast band (88 - 108 MHz). For the latter, the rules state:

[Code of Federal Regulations]
[Title 47, Volume 1]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR15.239]

[Page 816-817]

TITLE 47--TELECOMMUNICATION

CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION

PART 15_RADIO FREQUENCY DEVICES--Table of Contents

Subpart C_Intentional Radiators

Sec. 15.239 Operation in the band 88-108 MHz.

(a) Emissions from the intentional radiator shall be confined within
a band 200 kHz wide centered on the operating frequency. The 200 kHz
band shall lie wholly within the frequency range of 88-108 MHz.
(b) The field strength of any emissions within the permitted 200 kHz
band shall not exceed 250 microvolts/meter at 3 meters. The emission
limit in this paragraph is based on measurement instrumentation
employing an average detector. The provisions in Sec. 15.35 for
limiting peak emissions apply.


It is paragraph (b) above that is the stickler. It takes only about 20
nanowatts into an efficient antenna (say, a quarter or half wave) to get
that 250 microvolts/meter at 3 meters. Of course, you could use a kilowatt
into a really bad antenna so long as you don't produce a field greater than
250 microvolts/meter at 3 meters.

Sorry to be the bearer of bad news.

John


In the AM case, wouldn't it be pretty hard to push those 3mW into a 3
meter antenna at those frequencies? I'm not saying it couldn't be done,
mind you.

--Mac

Hi, Mac -

Did you mean 100 mW? Yes. It's very difficult when the FCC limits your
entire antenna installation (ground, feeder, and antenna) to 3 meters:


"Sec. 15.219 Operation in the band 510-1705 kHz.

(a) The total input power to the final radio frequency stage
(exclusive of filament or heater power) shall not exceed 100 milliwatts.
(b) The total length of the transmission line, antenna and ground
lead (if used) shall not exceed 3 meters."


This makes the radiating system very low in efficiency. The whole idea (as
far as the FCC is concerned) is to limit the field strength thus limiting
the ability to interfere with licensed stations. It makes sense to me.

Nevertheless, I've heard that the range achievable on the AM band far
exceeds the range achievable on the FM band when both meet the FCC rules.

Cheers,
John

 

[JustMe]

"Kristian Hermansen" <kristian.hermansen@NOSPAM.gmail.com> wrote in message
news:GkAse.601$gC3.388@fe31.usenetserver.com...

"JustMe" <á@á> wrote:
Perhaps you can use the existing transmitting device by directing the
output
into a "leaky feeder" placed where you require reception. This should not
put you outside the law. Google came back with 4100 hits. There should be
some help there.

OK, that sounds like a good start. Can anyone else point me in the
direction of a more powerful solution? I really want my other project to
have about a one to three mile radius of transmission. I will be using
this more powerful transmitter on a Camp Ground where the people are more
spread out and it is difficult to get messages out to people who are not
close to the base. Walkie takies are out of the question, because we need
normal radios to pick up the signals. We also don't want them to have to
buy a special device.

FM radios are cheap and almost everyone has one. Campers will have their
radios on a certain frequency to get updates over the weekend of
festivities. I would plan on using this via a 120V AC input in a wall
socket. Does anyone have some suggestions? Is there a good hobby
magazine dedicated to FM radio building? Or can I purchase the device as
described above cheaply from somewhere? Your recommendations so far have
been very helpful, thanks guys...

Kristian Hermansen

For the larger project, there is no obvious way you can do this with direct
radio without risking a well earned visit to the slammer.

Perhaps you should be saying "Mobile phones are cheap and almost everyone
has one." A little thought on instant messaging may provide you with a very
economical, and legal, answer.

I suspect that deep down you may be thinking of the sort of "Butlin's
Radio" that was endemic in British holiday camps in the 50's. That, in my
opinion, would merit an "Albert Pierpoint" response : <(

 

[Mac]

On Sat, 18 Jun 2005 01:09:12 +0000, John - KD5YI wrote:

Mac wrote:
On Fri, 17 Jun 2005 04:42:01 +0000, John - KD5YI wrote:
Actually, the rules permit 100 mW and a 3 meter antenna (combined with
ground and feeder) on the AM broadcast band (525 - 1705 kHz), but not in the
FM broadcast band (88 - 108 MHz). For the latter, the rules state:

[Code of Federal Regulations]
[Title 47, Volume 1]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR15.239]

[Page 816-817]

TITLE 47--TELECOMMUNICATION

CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION

PART 15_RADIO FREQUENCY DEVICES--Table of Contents

Subpart C_Intentional Radiators

Sec. 15.239 Operation in the band 88-108 MHz.

(a) Emissions from the intentional radiator shall be confined within
a band 200 kHz wide centered on the operating frequency. The 200 kHz
band shall lie wholly within the frequency range of 88-108 MHz.
(b) The field strength of any emissions within the permitted 200 kHz
band shall not exceed 250 microvolts/meter at 3 meters. The emission
limit in this paragraph is based on measurement instrumentation
employing an average detector. The provisions in Sec. 15.35 for
limiting peak emissions apply.


It is paragraph (b) above that is the stickler. It takes only about 20
nanowatts into an efficient antenna (say, a quarter or half wave) to get
that 250 microvolts/meter at 3 meters. Of course, you could use a kilowatt
into a really bad antenna so long as you don't produce a field greater than
250 microvolts/meter at 3 meters.

Sorry to be the bearer of bad news.

John


In the AM case, wouldn't it be pretty hard to push those 3mW into a 3
meter antenna at those frequencies? I'm not saying it couldn't be done,
mind you.

--Mac


Hi, Mac -

Did you mean 100 mW?

Yes. But it would probably be difficult either way. ;-)

Yes. It's very difficult when the FCC limits your
entire antenna installation (ground, feeder, and antenna) to 3 meters:


"Sec. 15.219 Operation in the band 510-1705 kHz.

(a) The total input power to the final radio frequency stage
(exclusive of filament or heater power) shall not exceed 100 milliwatts.
(b) The total length of the transmission line, antenna and ground
lead (if used) shall not exceed 3 meters."


This makes the radiating system very low in efficiency. The whole idea (as
far as the FCC is concerned) is to limit the field strength thus limiting
the ability to interfere with licensed stations. It makes sense to me.

Limiting interference is one of the main mandates of the FCC. So I'm not
complaining about that. It's just that it would be a lot easier to radiate
100 mW if you could build a larger antenna! Maybe you can buy antennas
designed for this application. I guess some kind of resonant matching
network would help quite a bit. I'm not really an antenna expert. Or maybe
a magnetic dipole.

Nevertheless, I've heard that the range achievable on the AM band far
exceeds the range achievable on the FM band when both meet the FCC rules.

Cheers,
John

Makes sense. An awful lot more power, if you can just get the little
antenna to radiate!

--Mac

 

[John - KD5YI]

Mac wrote:

Limiting interference is one of the main mandates of the FCC. So I'm not
complaining about that. It's just that it would be a lot easier to radiate
100 mW if you could build a larger antenna! Maybe you can buy antennas
designed for this application. I guess some kind of resonant matching
network would help quite a bit. I'm not really an antenna expert. Or maybe
a magnetic dipole.

Hi, Mac -

A good place to start is Low Band DXing by ON4UN. Although the book
addresses the frequencies below the AM band (160 to 190 kHz, I think), the
inherent problems of short antennas are discussed, I am told. On that band,
an input power of one Watt and an antenna length (including ground and
transmission line) of 15 meters is allowed. Even so, if I recall correctly,
radiated power is in the low milliwatts due to low antenna and network
efficiencies.

It is a challenge.

Cheers,
John