very small low power simple transmitter (ideally single chip)?

[Rich Grise]

See how that screws up the natural flow of the threae? Sheesh!

I guess that makes my 500 milliwatt, 560,000 Gigahertz transmitter
illegal!!!

(LED flashlight)

Only if they can receive it on their FSM! ;-)

Cheers!
Rich

 

[John - KD5YI]

And even less, if your antenna has gain, right? Because it still has to
be < 200 uV/m at 3 meters, looking right up the throat of the antenna,
right?

You are correct about antenna gain. The FCC spells out many of the test
conditions.

So, what's the deal with those RF modems with thousands of meters' range?
Are they, like, pre-licensed or something?

I cannot answer your question about RF modems without much more study of the
regulations. Most likely they are manufactured to meet some other part of
the regulations and have probably been submitted to the FCC for approval. In
some of these cases, it is illegal for the end user to tamper with any part
of the device, including attaching an external antenna.

And will a signal that weak reach an RC airplane that's, say, 300m away?

Presumably you mean 13 nW. I estimate that the signal strength would be
about -115 dBm at the receiver (isotropic source in free space) at 300
meters. I wouldn't try it.

<google...>
Anyway, here's some frequencies:
http://www.modelaircraft.org/Comp/frequency.htm

That band is regulated in other parts of the rules. I do not remember the
appropriate section. I am certain that higher power is permitted for those
specific frequencies.

Cheers!
Rich

See (a) above. There are exceptions listed elsewhere in part 15. For
example, they allow 100 mW input power to the final stage in a transmitter
on the AM broadcast band (with not more than 3 meters of antenna, lead-in,
and ground combined). In the 88-108 MHz (commercial FM) band, 250 uV/m at 3
meters is allowed. The OP asked about the 144-146 MHz band which is alloted
to licensed amateur use (covered by Part 97 rules). Unlicensed operation in
that band is limited to 150 uV/m at 3 meters per the above table.

It is important to wade through all applicable regulations to discover what
is permitted.

Cheers to you, too.
John

 

[John - KD5YI]

And will a signal that weak reach an RC airplane that's, say, 300m away?
<google...>
Anyway, here's some frequencies:
http://www.modelaircraft.org/Comp/frequency.htm

Part 95 ( http://www.access.gpo.gov/nara/cfr/waisidx_05/47cfr95_05.html)
covers the 72 MHz R/C frequencies. As you can see, power output can be up to
0.75 watts (95.210). That's high power!

See 95.201 through 95.225 (R/C Rules).

Note that an R/C transmitter must be FCC certified. You may make no
modifications to the transmitter.

Cheers,
John

 

[John - KD5YI]

I guess that makes my 500 milliwatt, 560,000 Gigahertz transmitter
illegal!!!

(LED flashlight)

Luhan

Read Title 47 and decide for yourself. In the meantime, I will ask them if
there is a reward for reporting lawbreakers such as yourself.

John

 

[John - KD5YI]

If it's under 100mW, is that not legal?

Mark

Hi, Mark -

AFAICT, only on the commercial AM broadcast band.

I have a feeling that the belief that 100 mW is legal came from the FCC's
rule that you may transmit using 100 mW on the AM broadcast band (510-1705
kHz) which is very popular with the hobbyist home broadcasting group and it
got erroneously applied to all frequencies.

By the way, the FCC says

"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."

Note the reference to filaments indicating it is a rather old rule. In
addition, note that it is *input* power to the final stage. With less than
100% efficiency in the final, it will be less at the antenna (which, at 3
meters for antenna, lead-in, and ground) will give very low radiated power.

AFAIK, this is the only reference to 100 mW in the FCC regulations. However,
I have not been through them all and I may someday be corrected.

Cheers,
John

 

[Tim Auton]

No. For Part 15 rules (unlicensed operation), see
http://www.access.gpo.gov/nara/cfr/waisidx_05/47cfr15_05.html

which says, in part....

Subpart C_Intentional Radiators

Sec. 15.209 Radiated emission limits; general requirements.

(a) Except as provided elsewhere in this subpart, the emissions from

an intentional radiator shall not exceed the field strength levels

specified in the following table: [snip table]
According to the above, you are allowed 200 uV/m at 3 meters.

This is equivalent to 13 nanowatts of isotropically radiated power.

And even less, if your antenna has gain, right? Because it still has to
be < 200 uV/m at 3 meters, looking right up the throat of the antenna,
right?

So, what's the deal with those RF modems with thousands of meters' range?
Are they, like, pre-licensed or something?

I think the only important bit of that quote from the FCC is this bit:
"Except as provided elsewhere in this subpart". Elsewhere in the subpart
you'll find the limits for the ISM bands, RC frequencies etc. and they
are of course much higher.


Tim

 

[Michael A. Terrell]

Read Title 47 and decide for yourself. In the meantime, I will ask them if
there is a reward for reporting lawbreakers such as yourself.

[email protected] is the address to report suspected illegal use of RF
equipment to the FCC. I contacted them to ask where to report the
people spamming cell phone jammers and [email protected] is where I was
told to make reports.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[John - KD5YI]

[email protected] is the address to report suspected illegal use of RF
equipment to the FCC. I contacted them to ask where to report the
people spamming cell phone jammers and [email protected] is where I was
told to make reports.

My comment was in the same vein as Luhan's. I should learn how to put in
smiley faces, I guess.

If I were to report Luhan, I would also have to report all those other
lawbreakers who drive around with their headlights on.

 

[Michael A. Terrell]

My comment was in the same vein as Luhan's. I should learn how to put in
smiley faces, I guess.

If I were to report Luhan, I would also have to report all those other
lawbreakers who drive around with their headlights on.

I wasn't suggesting you report him. Like I said, it is the link if
there is a real need to report anything to the FCC.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Rich Grise]

My comment was in the same vein as Luhan's. I should learn how to put in
smiley faces, I guess.

If I were to report Luhan, I would also have to report all those other
lawbreakers who drive around with their headlights on.

In what state is it illegal to turn your headlights on?

Thanks,
Rich

 

[Ancient_Hacker]

Yes exactly thanks!

Yep, that's a good transmitter circuit. If you need longer batery
life, you can add a 74HC14 and set it up as a short pulse oscillator,
say 10 seconds on, a minute or two off.

 

[RST Engineering \(jw\)]

The state of insobriety?

Jim

 

[megoodsen]

...and I'm sure you have the ham radio license required for transmission in
this band? And if you do, why are you asking the question in the first
place?

Jim

In fact, yes I do have the appropriate licence for operation on 144MHz
(and all others) amatuer bands.

I doubt the cat has though, and he will be the one 'transmitting'...

I suspect at the RF output levels the cat will be transmitting, he
won't need one. Here.

I asked originally for a simple circuit, knowing this sort of thing
would have been done already, why re-invent the wheel...

And just a comment following the er, expansion of the thread.

As far as I know the FCC is only the American radio regulatory body.

There IS life outside the US of A you know!!

 

[Alan]

In fact, yes I do have the appropriate licence for operation on 144MHz
(and all others) amatuer bands.

I doubt the cat has though, and he will be the one 'transmitting'...

I suspect at the RF output levels the cat will be transmitting, he
won't need one. Here.

I asked originally for a simple circuit, knowing this sort of thing
would have been done already, why re-invent the wheel...

And just a comment following the er, expansion of the thread.

As far as I know the FCC is only the American radio regulatory body.

There IS life outside the US of A you know!!

Have a search for animal tracking collars/transmitters. Usually a
simple one or two transistor crystal controlled oscillator circuit
normally used at about 152MHz so easily modified for 2m.

Alan

 

[Rich Grise]

In fact, yes I do have the appropriate licence for operation on 144MHz
(and all others) amatuer bands.

I doubt the cat has though, and he will be the one 'transmitting'...

I suspect at the RF output levels the cat will be transmitting, he
won't need one. Here.

I asked originally for a simple circuit, knowing this sort of thing
would have been done already, why re-invent the wheel...

And just a comment following the er, expansion of the thread.

As far as I know the FCC is only the American radio regulatory body.

There IS life outside the US of A you know!!

Well, I suggested looking into key fob transmitters, that you could
hack into and bypass the button with a little CMOS pulser, but you
seem to have ignored my suggestion.

RS has a transmitter/receiver set (the receiver is like a coffee timer,
but without the knob) for about $15.00. Or they did when I went there
a few years ago.

Good Luck!
Rich