At 11/30/2005 11:04 AM, you wrote:
> > ... A transmitter at 460 Mhz with 350 mw
output will produce 1
> microvolt at a receiver at 200 miles distance with unity gain antenna.
>
>Cite your source or the math, please.
If you plug in 2.12 dBi (=0 dBd) into the Friis transmission formula, the
numbers add up. However, as I pointed out in a previous post, I believe 0
dBd is overly optimistic for a FRS radio. This is based on my experience
comparing side-by-side an Alinco DJ-S41T (FRS-style ham transceiver,
probably marketed under a different brand name & firmware as FRS) & a
G5T
set to 250 mW with standard BNC rubber duck ant. The G5T consistently
delivered much more signal than the S41T, which makes sense given the
electrically short antenna on the latter.
Bob NO6B
low-cost RF transeivers?
Started by ●November 19, 2005
Reply by ●November 30, 20052005-11-30
Reply by ●November 30, 20052005-11-30
In a message dated 11/30/2005 2:52:21 P.M. Eastern Standard Time,
no6b@no6b... writes: The 200 mile pathloss at 460 mhz is 132 db
350 mw is 25.5 dbmw
Got calc from RF Manual
Reply by ●November 30, 20052005-11-30
Dennis;
>That said, the legality of connecting anything to a FRS radio beyond
>what the manufacturer certifies, is definitely a gray area.
Thanks for your response. My take of Title 47 Section 95.193 & 194 is
that I can send non-voice communications consisting of a short text message
- with restrictions.
1) Digital transmissions must be manually initiated.
2) Digital transmissions must be shorter than one second.
3) No more than once every 30 seconds.
4) I can not modify the FCC Certified Antenna.
I'd appreciate your opinion. Thank you. (See 95.193 and 95.194 at
http://www.access.gpo.gov/nara/cfr/waisidx_04/47cfr95_04.html) >Unless you are working with a commercial project, a ham license will give
>you access to endless flexibility for radios, power and data modes.
I plan on finishing this project (since I'm so far along on it,) and
then getting my Ham License (which I should-a done 30 years ago anyway!) Good Luck!
Ken_S.
[]
>That said, the legality of connecting anything to a FRS radio beyond
>what the manufacturer certifies, is definitely a gray area.
Thanks for your response. My take of Title 47 Section 95.193 & 194 is
that I can send non-voice communications consisting of a short text message
- with restrictions.
1) Digital transmissions must be manually initiated.
2) Digital transmissions must be shorter than one second.
3) No more than once every 30 seconds.
4) I can not modify the FCC Certified Antenna.
I'd appreciate your opinion. Thank you. (See 95.193 and 95.194 at
http://www.access.gpo.gov/nara/cfr/waisidx_04/47cfr95_04.html) >Unless you are working with a commercial project, a ham license will give
>you access to endless flexibility for radios, power and data modes.
I plan on finishing this project (since I'm so far along on it,) and
then getting my Ham License (which I should-a done 30 years ago anyway!) Good Luck!
Ken_S.
[]
Reply by ●December 1, 20052005-12-01
Ken,
The key phrase, I believe is found here:
"(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."
"or other apparatus" may be the defining prohibition. I can't claim
to be an expert on these rules, but if the data sending capability
isn't built in (and certified by the manufacturer), then it seems
that you can't add it. Certainly, soldering to the internals is
out. One might claim there is wiggle room in using an externally
connected earphone and microphone if there is a connector, but the
word "attach" seems to cover that together with the prohibition of
anything the manufacturer didn't certify. Just my best guess how the
FCC would look at it if you put it in their face and asked for an
opinion.
I don't like to rain on anyone's parade, but that's just how the rule
seems to be written. Yes, a FRS radio can send data within the
narrow confines of the rules, but it seems that capability is for the
manufacturer to build in. I believe it was Trimble that went to bat
for this change to the rules so they could market the Rino with GPS
built in that would map other similar radio's locations on the
screen. The original rules prohibited any data transmission.
Hope you find a satisfactory out in your project.
Dennis
The key phrase, I believe is found here:
"(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."
"or other apparatus" may be the defining prohibition. I can't claim
to be an expert on these rules, but if the data sending capability
isn't built in (and certified by the manufacturer), then it seems
that you can't add it. Certainly, soldering to the internals is
out. One might claim there is wiggle room in using an externally
connected earphone and microphone if there is a connector, but the
word "attach" seems to cover that together with the prohibition of
anything the manufacturer didn't certify. Just my best guess how the
FCC would look at it if you put it in their face and asked for an
opinion.
I don't like to rain on anyone's parade, but that's just how the rule
seems to be written. Yes, a FRS radio can send data within the
narrow confines of the rules, but it seems that capability is for the
manufacturer to build in. I believe it was Trimble that went to bat
for this change to the rules so they could market the Rino with GPS
built in that would map other similar radio's locations on the
screen. The original rules prohibited any data transmission.
Hope you find a satisfactory out in your project.
Dennis
Reply by ●December 1, 20052005-12-01
Reply by ●December 1, 20052005-12-01
Reply by ●December 1, 20052005-12-01
Another take on UHF data radio:
http://www.radiotelemetry.co.uk/pdf%20files/Ap121%20A%20Practical%20Guide.pdf
Nothing like 200 miles for practical links at 500mW on 433MHz, even
with elevated gain antennas. Why? Tom
http://www.radiotelemetry.co.uk/pdf%20files/Ap121%20A%20Practical%20Guide.pdf
Nothing like 200 miles for practical links at 500mW on 433MHz, even
with elevated gain antennas. Why? Tom
Reply by ●December 1, 20052005-12-01
At 11:30 AM 12/1/2005 -0500, you wrote:
Nothing like 200 miles for practical links at 500mW on 433MHz, even with
elevated gain antennas. Why?
<---I don't believe it. The math doesn't work out.
Ken
------
President and CTO - Arcom Communications
Makers of state-of-the-art repeater controllers and accessories.
http://www.ah6le.net/arcom/index.html
We offer complete Kenwood TKR repeater packages!
We are now an authorized Telewave Dealer!
AH6LE/R - IRLP Node 3000
http://www.irlp.net
Nothing like 200 miles for practical links at 500mW on 433MHz, even with
elevated gain antennas. Why?
<---I don't believe it. The math doesn't work out.
Ken
------
President and CTO - Arcom Communications
Makers of state-of-the-art repeater controllers and accessories.
http://www.ah6le.net/arcom/index.html
We offer complete Kenwood TKR repeater packages!
We are now an authorized Telewave Dealer!
AH6LE/R - IRLP Node 3000
http://www.irlp.net
Reply by ●December 1, 20052005-12-01
This thread has been a little confusing to my ears - is there some
confusion
between 200 meters and 200 miles?
Keith
International Perspective
Although a common UHF band is used national authorities have defined
different
specifications for licence exempt radio data transmissions.
They differ in the number of allocated RF channels, their bandwidth,
spurious emissions
and maximum RF power that can be transmitted. In the UK, the ETSI 300-220
specification for operating on the 433.92MHz channel, allows one channel at
10mW RF
power.
The radio range is limited to a few hundreds of metres. But the power
consumption is low
as is the unit cost of the transmitters and receivers. Radios conforming to
this
specification are widely used in portable battery equipment or communicating
with
moving machinery. -----Original Message-----
From: basicx@basi... [mailto:basicx@basi...]On Behalf Of Tom
Becker
Sent: Thursday, December 01, 2005 6:30 PM
To: basicx@basi...
Subject: Re: [BasicX] Re: low-cost RF transeivers? Another take on UHF data radio:
http://www.radiotelemetry.co.uk/pdf%20files/Ap121%20A%20Practical%20Guide.pd
f
Nothing like 200 miles for practical links at 500mW on 433MHz, even with
elevated gain antennas. Why? Tom
Yahoo! Groups Links
between 200 meters and 200 miles?
Keith
International Perspective
Although a common UHF band is used national authorities have defined
different
specifications for licence exempt radio data transmissions.
They differ in the number of allocated RF channels, their bandwidth,
spurious emissions
and maximum RF power that can be transmitted. In the UK, the ETSI 300-220
specification for operating on the 433.92MHz channel, allows one channel at
10mW RF
power.
The radio range is limited to a few hundreds of metres. But the power
consumption is low
as is the unit cost of the transmitters and receivers. Radios conforming to
this
specification are widely used in portable battery equipment or communicating
with
moving machinery. -----Original Message-----
From: basicx@basi... [mailto:basicx@basi...]On Behalf Of Tom
Becker
Sent: Thursday, December 01, 2005 6:30 PM
To: basicx@basi...
Subject: Re: [BasicX] Re: low-cost RF transeivers? Another take on UHF data radio:
http://www.radiotelemetry.co.uk/pdf%20files/Ap121%20A%20Practical%20Guide.pd
f
Nothing like 200 miles for practical links at 500mW on 433MHz, even with
elevated gain antennas. Why? Tom
Yahoo! Groups Links
Reply by ●December 1, 20052005-12-01
Dennis;
>Hope you find a satisfactory out in your project.
Throw the @#$%&* thing in a box and forget about it. :)
Well then again, maybe I could do it in the middle of the night and
not tell anyone. :) >(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.
I hate to say it, but you're probably right. That is exactly why I
wanted to get someone else's point of view. Thank you. <sarcasm>(Can I
put batteries in the unit that the manufacturer didn't certify? Can I
"attach" a Happy Face Sticker?)</sarcasm>
Okay, it looks like the next thing on the agenda is to start studying
for the Ham Test! Good Luck!
Ken_S.
At 11:25 PM 11/30/2005, you wrote:
>Ken,
>
>The key phrase, I believe is found here:
>
>"(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."
>
>"or other apparatus" may be the defining prohibition. I can't claim
>to be an expert on these rules, but if the data sending capability
>isn't built in (and certified by the manufacturer), then it seems
>that you can't add it. Certainly, soldering to the internals is
>out. One might claim there is wiggle room in using an externally
>connected earphone and microphone if there is a connector, but the
>word "attach" seems to cover that together with the prohibition of
>anything the manufacturer didn't certify. Just my best guess how the
>FCC would look at it if you put it in their face and asked for an
>opinion.
>
>I don't like to rain on anyone's parade, but that's just how the rule
>seems to be written. Yes, a FRS radio can send data within the
>narrow confines of the rules, but it seems that capability is for the
>manufacturer to build in. I believe it was Trimble that went to bat
>for this change to the rules so they could market the Rino with GPS
>built in that would map other similar radio's locations on the
>screen. The original rules prohibited any data transmission.
>
>Hope you find a satisfactory out in your project.
>
>Dennis
