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low-cost RF transeivers?

Started by Doug Metzler November 19, 2005
At 11/21/2005 09:39 AM, you wrote:
>Interesting - so you're saying that devices in the 433/434 MHz range are
>infringing on amateur radio space? Do you think there's an exception for
>devices that are under a specific power rating?

I tried looking through FCC Part 15 for some answers & got nothing that's
explicit. However, the 433.5-434.5 MHz sub band is apparently intended for
RFID tags. Under those provisions, the maximum permissible field strength
is 11,000 microvolts at 3 meters. However, operation is prohibited within
40 km of 5 U.S. Air Force bases/stations. See
<http://ftp.fcc.gov/oet/info/rules/part15/part15-91905.pdf> for more
detailed info.

> Because the other
>transmitters/receivers I've gotten have been from www.rentron.com
><http://www.rentron.com/> and they are also in the same frequency range
>(plus 315 MHz), so I just assumed it was legal use. I can't imagine that
>multiple vendors would be selling products that were not FCC legal?

I think the key question is whether the individual products are FCC Part 15
certified. From the Rentron webpage:

"Note: Please download the Linx RXM-433-LC-S datasheet above, and review
the legal considerations section for operation of RF equipment prior to
use. These modules are sold in unfinished form, and require external
components to function. The purchaser understands that approval may be
required prior to the sale or operation of the device, and agrees to use
the component in accordance will all laws governing its operation in the
country of operation."

If they're not FCC certified, they're illegal to use in the U.S. If in
doubt, ask the manufacturer.

Bob NO6B



>Anyone found a good source for low cost RF transceivers?

Doug, have you tried Radio Shack? I'm using a pair of Motorola T4900
FRS Radios that I bought there for $30 on sale. You can legally use them
to send a short text message, but with restrictions. In short; the request
must be manually initiated, and digital transmissions must be shorter than
one second. You can not make any internal modifications, nor modify the
antenna (among other restrictions.)

I took the speaker wire and connected it to a PicAxe and can uniquely
identify one of the Call Tones in code; which I will use to manually
initiate a text message request. The CPU will trigger the Push-to-Talk
(PTT) and jam a 1 second DTMF signal in to the external microphone
connection. On the other end I will have a DTMF Decoder that will convert
it to Serial Data and passes it to a Laptop.

It's still a work in progress, but check out
http://www.geocities.com/almost_there_weather_balloon/ Good Luck!
Ken_S.

--
http://www.access.gpo.gov/nara/cfr/cfr-table-search.html#page1
[Code of Federal Regulations]
[Title 47, Volume 5]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR95.193]

[Page 532-533]

TITLE 47--TELECOMMUNICATION

CHAPTER I--FEDERAL COMMUNICATIONS
COMMISSION (CONTINUED)

PART 95_PERSONAL RADIO SERVICES--Table of Contents

Subpart B_Family Radio Service (FRS)

Sec. 95.193 (FRS Rule 3) Types of communications.

(a) You may use an FRS unit to conduct two-way voice communications
with another person. You may use an FRS unit to transmit one-way voice
or non-voice communications only to establish communications with
another person, send an emergency message,

[[Page 533]]

provide traveler assistance, provide location information, transmit a
brief text message, make a voice page, or to conduct a brief test.
(b) Non-voice communications. (1) The FRS unit may transmit tones to
make contact or to continue communications with a particular FRS unit.
If the tone is audible (more than 300 Hertz), it must be transmitted
continuously no longer than 15 seconds at one time. If the tone is
subaudible (300 Hertz or less), it may be transmitted continuously only
while you are talking.
(2) The FRS unit may transmit digital data containing location
information, or requesting location information from one or more other
FRS units, or containing a brief text message to another specific FRS
unit. Digital data transmissions must be initiated by a manual action or
command of a user, except that an FRS unit receiving an interrogation
request may automatically respond with its location. Digital data
transmissions shall not exceed one second, and shall be limited to no
more than one digital transmission within a thirty-second period, except
that an FRS unit may automatically respond to more than one
interrogation request received within a thirty-second period.
(c) You must not use an FRS unit in connection with any activity
which is against federal, state or local law.
(d) You must, at all times and on all channels, give priority to
emergency communication messages concerning the immediate safety of life
or the immediate protection of property.
(e) No FRS unit may be interconnected to the public switched
network.

[61 FR 28768, June 6, 1996, as amended at 68 FR 9901, Mar. 3, 2003]

--
[Code of Federal Regulations]
[Title 47, Volume 5]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR95.194]

[Page 533]

TITLE 47--TELECOMMUNICATION

CHAPTER I--FEDERAL COMMUNICATIONS
COMMISSION (CONTINUED)

PART 95_PERSONAL RADIO SERVICES--Table of Contents

Subpart B_Family Radio Service (FRS)

Sec. 95.194 (FRS Rule 4) FRS units.

(a) You may only use an FCC certified FRS unit. (You can identify an
FCC certified FRS unit by the label placed on it by the manufacturer.)
(b) You must not make, or have made, any internal modification to an
FRS unit. Any internal modification cancels the FCC certification and
voids your authority to operate the unit in the FRS.
(c) You may not attach any antenna, power amplifier, or other
apparatus to an FRS unit that has not been FCC certified as part of that
FRS unit. There are no exceptions to this rule and attaching any such
apparatus to a FRS unit cancels the FCC certification and voids
everyone's authority to operate the unit in the FRS.
(d) FRS units are prohibited from transmitting data in store-and-
forward packet operation mode.

[61 FR 28768, June 6, 1996, as amended at 68 FR 9901, Mar. 3, 2003]

At 08:38 PM 11/19/2005, you wrote:
>Anyone found a good source for low cost RF transceivers? I'm able to find
>good discrete transmitters and receivers, but as soon as I look for a
>transceiver the price jumps to $100. >
>Thanks, >
>DougM >Yahoo! Groups Links >
>




I have to say, that is a rather brilliant hack. What kind of accuracy and
throughput do you expect to see?
Thanks,
DougM _____

From: basicx@basi... [mailto:basicx@basi...] On Behalf Of
Robotics_Job_Search
Sent: Monday, November 21, 2005 5:57 PM
To: BasicX@Basi...
Subject: Re: [BasicX] low-cost RF transeivers?

>Anyone found a good source for low cost RF transceivers?

Doug, have you tried Radio Shack? I'm using a pair of Motorola T4900
FRS Radios that I bought there for $30 on sale. You can legally use them
to send a short text message, but with restrictions. In short; the request
must be manually initiated, and digital transmissions must be shorter than
one second. You can not make any internal modifications, nor modify the
antenna (among other restrictions.)

I took the speaker wire and connected it to a PicAxe and can uniquely
identify one of the Call Tones in code; which I will use to manually
initiate a text message request. The CPU will trigger the Push-to-Talk
(PTT) and jam a 1 second DTMF signal in to the external microphone
connection. On the other end I will have a DTMF Decoder that will convert
it to Serial Data and passes it to a Laptop.

It's still a work in progress, but check out
http://www.geocities.com/almost_there_weather_balloon/ Good Luck!
Ken_S.

--
http://www.access.gpo.gov/nara/cfr/cfr-table-search.html#page1
[Code of Federal Regulations]
[Title 47, Volume 5]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR95.193]

[Page 532-533]

TITLE 47--TELECOMMUNICATION

CHAPTER I--FEDERAL COMMUNICATIONS
COMMISSION (CONTINUED)

PART 95_PERSONAL RADIO SERVICES--Table of Contents

Subpart B_Family Radio Service (FRS)

Sec. 95.193 (FRS Rule 3) Types of communications.

(a) You may use an FRS unit to conduct two-way voice communications
with another person. You may use an FRS unit to transmit one-way voice
or non-voice communications only to establish communications with
another person, send an emergency message,

[[Page 533]]

provide traveler assistance, provide location information, transmit a
brief text message, make a voice page, or to conduct a brief test.
(b) Non-voice communications. (1) The FRS unit may transmit tones to
make contact or to continue communications with a particular FRS unit.
If the tone is audible (more than 300 Hertz), it must be transmitted
continuously no longer than 15 seconds at one time. If the tone is
subaudible (300 Hertz or less), it may be transmitted continuously only
while you are talking.
(2) The FRS unit may transmit digital data containing location
information, or requesting location information from one or more other
FRS units, or containing a brief text message to another specific FRS
unit. Digital data transmissions must be initiated by a manual action or
command of a user, except that an FRS unit receiving an interrogation
request may automatically respond with its location. Digital data
transmissions shall not exceed one second, and shall be limited to no
more than one digital transmission within a thirty-second period, except
that an FRS unit may automatically respond to more than one
interrogation request received within a thirty-second period.
(c) You must not use an FRS unit in connection with any activity
which is against federal, state or local law.
(d) You must, at all times and on all channels, give priority to
emergency communication messages concerning the immediate safety of life
or the immediate protection of property.
(e) No FRS unit may be interconnected to the public switched
network.

[61 FR 28768, June 6, 1996, as amended at 68 FR 9901, Mar. 3, 2003]

--
[Code of Federal Regulations]
[Title 47, Volume 5]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR95.194]

[Page 533]

TITLE 47--TELECOMMUNICATION

CHAPTER I--FEDERAL COMMUNICATIONS
COMMISSION (CONTINUED)

PART 95_PERSONAL RADIO SERVICES--Table of Contents

Subpart B_Family Radio Service (FRS)

Sec. 95.194 (FRS Rule 4) FRS units.

(a) You may only use an FCC certified FRS unit. (You can identify an
FCC certified FRS unit by the label placed on it by the manufacturer.)
(b) You must not make, or have made, any internal modification to an
FRS unit. Any internal modification cancels the FCC certification and
voids your authority to operate the unit in the FRS.
(c) You may not attach any antenna, power amplifier, or other
apparatus to an FRS unit that has not been FCC certified as part of that
FRS unit. There are no exceptions to this rule and attaching any such
apparatus to a FRS unit cancels the FCC certification and voids
everyone's authority to operate the unit in the FRS.
(d) FRS units are prohibited from transmitting data in store-and-
forward packet operation mode.

[61 FR 28768, June 6, 1996, as amended at 68 FR 9901, Mar. 3, 2003]

At 08:38 PM 11/19/2005, you wrote:
>Anyone found a good source for low cost RF transceivers? I'm able to find
>good discrete transmitters and receivers, but as soon as I look for a
>transceiver the price jumps to $100. >
>Thanks, >
>DougM >> Terms of Service.
_____


HELLO FELLOWS,

THE FCC RULES ALLOW 433 MHZ OPERATION OF INCONSEQUENTIAL TRANSMISSIONS
IN THE USA ON A NIB (NON INTERFERENCE BASIS). THIS MEANS YOU MAY NOT
CAUSE INTERFERENCE TO LICENSED OPERATIONS AND MUST ACCEPT "ALL"
INTERFERENCE FROM LICENSED OPERATIONS.

73
SPENCE
K4KEP EX W9QNI
HAM SINCE 1951



Thank you Spence, that clears it up. My transmissions (between the
controller and the tank) are definitely inconsequential :-)
DougM
_____

From: basicx@basi... [mailto:basicx@basi...] On Behalf Of
BOYD S.(SPENCE) MINER
Sent: Tuesday, November 22, 2005 8:21 AM
To: basicx@basi...
Subject: [BasicX] Re: low-cost RF transeivers?
HELLO FELLOWS,

THE FCC RULES ALLOW 433 MHZ OPERATION OF INCONSEQUENTIAL TRANSMISSIONS
IN THE USA ON A NIB (NON INTERFERENCE BASIS). THIS MEANS YOU MAY NOT
CAUSE INTERFERENCE TO LICENSED OPERATIONS AND MUST ACCEPT "ALL"
INTERFERENCE FROM LICENSED OPERATIONS.

73
SPENCE
K4KEP EX W9QNI
HAM SINCE 1951
SPONSORED LINKS Microprocessor
<http://groups.yahoo.com/gads?t=ms&k=Microprocessor&w1=Microprocessor&w2=Mic
rocontrollers&w3sicx&w4=Pic+microcontrollers&w551+microprocessor&c=5&s
5&.sig=_YKW_KvdWM7nsvZLWwMhnw>

Microcontrollers
<http://groups.yahoo.com/gads?t=ms&k=Microcontrollers&w1=Microprocessor&w2=M
icrocontrollers&w3sicx&w4=Pic+microcontrollers&w551+microprocessor&c=5
&s5&.sig=UfvbdAF0r5o48CkzYmXRww>

Basicx
<http://groups.yahoo.com/gads?t=ms&ksicx&w1=Microprocessor&w2=Microcontro
llers&w3sicx&w4=Pic+microcontrollers&w551+microprocessor&c=5&s5&.si
g=Nggd_ZUrVU6qzPviDXpKSw Pic
<http://groups.yahoo.com/gads?t=ms&k=Pic+microcontrollers&w1=Microprocessor&
w2=Microcontrollers&w3sicx&w4=Pic+microcontrollers&w551+microprocessor
&c=5&s5&.sig=dhYy34C8Xq6aeJfBsd7maw> microcontrollers

8051
<http://groups.yahoo.com/gads?t=ms&k51+microprocessor&w1=Microprocessor&w
2=Microcontrollers&w3sicx&w4=Pic+microcontrollers&w551+microprocessor&
c=5&s5&.sig=iJA-sY2QEUOfoaMmW8c17g> microprocessor _____

> Terms of Service.
_____


http://www.aircable.net/serial.html

$69 EACH (+ $5 FOR WALL WART UNLESS YOU CAN SUPPLY THE 5-15 VOLTS ON PIN
9. READ THE MANUAL ON LINE.)

I AM USING AT 85' BETWEEN CAMPER AND GREENHOUSE WITH MODULES AT 5' ON
ONE END AND 4.5' ON THE OTHER.

WARNING MINIMUM BAUD IS 4800.

73
SPENCE
K4KEP


Based on your comments I have had second thoughts about the bluetooth approach and will now be exploring the WiPort from Lantronix.

http://www.lantronix.com/device-networking/embedded-device-servers/wiport.html

The cost is much higher unfortunately (120$) but we already have the WiFi infastructure in place so perhaps gives us a better platform.
This device has 2 serial ports so you could always say its 60$ per port !

We have ordered the development kit and another unit so I will let you know how it goes.

Probably my unit will have parents and good hearing but will be speaking a language no one else understands!!

Comments as always would be aprreciated.

Art

[]



>I have to say, that is a rather brilliant hack.

Thanks!!! >What kind of accuracy and throughput do you expect to see?

I suspect it will be very accurate, right up until the fringe of
reception. Through-put... a blinding 4 to 5 characters per second (since
it implies that you can only legally, manually request one message every 30
seconds, it amounts to about 5 characters per 35 seconds or so by the time
you send the request and get the response.) Good enough for what I'm
doing, I only have to send (a minimum of) 8 Hex Characters (the two numbers
between 0 and 65536 - ie. 0x0000 and 0xFFFF.) Good Luck!
Ken_S.

At 01:28 AM 11/22/2005, you wrote:
>I have to say, that is a rather brilliant hack. What kind of accuracy and
>throughput do you expect to see? >
>Thanks,
>DougM




Why so slow? I would have expected maybe double that?

-T




It depends on what "standard" you read. One (so-called) standard says
40mS tone and 40mS of seperation (quiet) between tones; other places I read
200mS tone and 50mS between tones AND if it's going to be on a noisy radio
link then you should extend the 200mS even longer to improve reliability.

Actually, now that I'm looking at it I suspect that one is the
absolute minimum that will work under optimum conditions, and the other may
be suggested real world values. I'll play with it, but I'll probably start
at 50mS each and see how it goes; that would net me 10 Hex Characters in
950mS, or about 40 bits/second. Good Luck!
Ken_S.

At 12:29 PM 11/27/2005, you wrote:
>Why so slow? I would have expected maybe double that?
>
>-T >
>
>Yahoo! Groups Links >
>





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