--- In basicx@basi..., Robotics_Job_Search
<Robotics_Job_Search@C...> wrote:
>
>
> 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.
Oh, I see. I was thinking more like a radio modem, where the baud
rate is limited by the quality of the connection. In principle, a
digital transmission could be respectably fast.
But with that "standard", utilizing off the shelf radios, I can see
that 50mS on and 50mS off would be a reasonable limit.
I agree, trying various signal timings would be useful to see what
the limit.
I am also very disappointed by the range of the FRS radios. THey
advertise several miles, but even in close to optimal conditions, I
am lucky to get 1/2 mile.
Are you going to launch one of this type of device?
-Tony
low-cost RF transeivers?
Started by ●November 19, 2005
Reply by ●November 29, 20052005-11-29
Reply by ●November 29, 20052005-11-29
Tony;
>where the baud rate is limited by the quality of the connection.
This is one way communication; the modems can not negotiate an
acceptable baud rate, or request resending a lost/corrupted packet. It
sends it out and you hope for the best. >I am also very disappointed by the range of the FRS radios.
Humm... I heard someplace that most people get better than advertised
range for the cheaper units (so they can justify higher prices of ones that
just go a little bit further.) At this page
(http://www.eoss.org/ansrecap/ar_060/ans47.htm) they talk of having several
hundred mile range with only 350mW when the antenna gets high
enough. Antenna height is THAT important. >Are you going to launch one of this type of device?
That is the plan. Good Luck!
Ken_S.
At 08:42 AM 11/29/2005, you wrote:
>--- In basicx@basi..., Robotics_Job_Search
><Robotics_Job_Search@C...> wrote:
> >
> >
> > 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.
>
>Oh, I see. I was thinking more like a radio modem, where the baud
>rate is limited by the quality of the connection. In principle, a
>digital transmission could be respectably fast.
>
>But with that "standard", utilizing off the shelf radios, I can see
>that 50mS on and 50mS off would be a reasonable limit.
>
>I agree, trying various signal timings would be useful to see what
>the limit.
>
>I am also very disappointed by the range of the FRS radios. THey
>advertise several miles, but even in close to optimal conditions, I
>am lucky to get 1/2 mile.
>
>Are you going to launch one of this type of device?
>
>-Tony >
>Yahoo! Groups Links >
>
Reply by ●November 29, 20052005-11-29
I would have to say several hundred miles with the antennas certified for
FRS/GMRS radios is a bit of bull. It would be one hell of a stretch with a
parabolic antenna but surely not with a whip of that lenght with no ground
plane. The FRS radios are not supposed to have great range. Part of the
consessions you make with unlicensed bands is poor range. Even the long
range FRS radios are running as GMRS which require a license but the FCC is
all but powerless to enforce the issue.
[]
FRS/GMRS radios is a bit of bull. It would be one hell of a stretch with a
parabolic antenna but surely not with a whip of that lenght with no ground
plane. The FRS radios are not supposed to have great range. Part of the
consessions you make with unlicensed bands is poor range. Even the long
range FRS radios are running as GMRS which require a license but the FCC is
all but powerless to enforce the issue.
[]
Reply by ●November 30, 20052005-11-30
At 11/29/2005 17:47, you wrote:
>Tony;
>
> >where the baud rate is limited by the quality of the connection.
>
> This is one way communication; the modems can not negotiate an
>acceptable baud rate, or request resending a lost/corrupted packet. It
>sends it out and you hope for the best. > >I am also very disappointed by the range of the FRS radios.
>
> Humm... I heard someplace that most people get better than advertised
>range for the cheaper units (so they can justify higher prices of ones that
>just go a little bit further.) At this page
>(http://www.eoss.org/ansrecap/ar_060/ans47.htm) they talk of having several
>hundred mile range with only 350mW when the antenna gets high
>enough. Antenna height is THAT important.
So is lower frequency, better antenna & clear channels.
Bob NO6B
>Tony;
>
> >where the baud rate is limited by the quality of the connection.
>
> This is one way communication; the modems can not negotiate an
>acceptable baud rate, or request resending a lost/corrupted packet. It
>sends it out and you hope for the best. > >I am also very disappointed by the range of the FRS radios.
>
> Humm... I heard someplace that most people get better than advertised
>range for the cheaper units (so they can justify higher prices of ones that
>just go a little bit further.) At this page
>(http://www.eoss.org/ansrecap/ar_060/ans47.htm) they talk of having several
>hundred mile range with only 350mW when the antenna gets high
>enough. Antenna height is THAT important.
So is lower frequency, better antenna & clear channels.
Bob NO6B
Reply by ●November 30, 20052005-11-30
I have the GMRS type. The range is only slightly better. Less than
1/2 mile. Flat terrain, a few trees, essentially line of sight. But I
was in my car, but my son was outside the house. And this was using
the GMRS bands. Motorola brand units. I forget the model number.
These units I have advertise 3 (actually I think it is 5) mile range.
-Tony
1/2 mile. Flat terrain, a few trees, essentially line of sight. But I
was in my car, but my son was outside the house. And this was using
the GMRS bands. Motorola brand units. I forget the model number.
These units I have advertise 3 (actually I think it is 5) mile range.
-Tony
Reply by ●November 30, 20052005-11-30
As a ham radio operator for over 40 years I have developed a
"feel"
for what works on VHF and UHF. FRS/GMRS radios could reach out
beyond 100 miles given line of sight conditions and best alignment of
antennas. Good FRS radios run about watt (effective radiated
power) and GMRS is allowed up to 5 watts (for most small station
users). GMRS radios are allowed to be attached to external antennas
which would improve the range dramatically, but are not specifically
permitted to be used to send data.
There appears to be a documented story of FRS communications breaking
100 miles:
"REACT honors young FRSers for rescue: REACT has honored brothers
Fletcher and Parker Wold of McMinnville, Oregon, for their role in
the rescue of two hikers stranded on Mt Hood. The brothers
intercepted the hikers' rescue calls via FRS radio at a distance of
more than 100 miles. REACT International CEO Frank Jennings presented
awards to the boys along with Salem REACT and the Yamili County
Search and Rescue Team. The youngsters also got caps from Yamili
County Sheriff Norm Hand. Fletcher, 8, and Parker, 5, picked up the
hikers' distress signal while they were playing at home. They alerted
their parents, who called the authorities, and the hikers were found.-
-Paula Glovick/Pacific Northwest REACT Council "
That said, the legality of connecting anything to a FRS radio beyond
what the manufacturer certifies, is definitely a gray area. Unless
you are working with a commercial project, a ham license will give
you access to endless flexibility for radios, power and data modes.
Good Luck,
Dennis
for what works on VHF and UHF. FRS/GMRS radios could reach out
beyond 100 miles given line of sight conditions and best alignment of
antennas. Good FRS radios run about watt (effective radiated
power) and GMRS is allowed up to 5 watts (for most small station
users). GMRS radios are allowed to be attached to external antennas
which would improve the range dramatically, but are not specifically
permitted to be used to send data.
There appears to be a documented story of FRS communications breaking
100 miles:
"REACT honors young FRSers for rescue: REACT has honored brothers
Fletcher and Parker Wold of McMinnville, Oregon, for their role in
the rescue of two hikers stranded on Mt Hood. The brothers
intercepted the hikers' rescue calls via FRS radio at a distance of
more than 100 miles. REACT International CEO Frank Jennings presented
awards to the boys along with Salem REACT and the Yamili County
Search and Rescue Team. The youngsters also got caps from Yamili
County Sheriff Norm Hand. Fletcher, 8, and Parker, 5, picked up the
hikers' distress signal while they were playing at home. They alerted
their parents, who called the authorities, and the hikers were found.-
-Paula Glovick/Pacific Northwest REACT Council "
That said, the legality of connecting anything to a FRS radio beyond
what the manufacturer certifies, is definitely a gray area. Unless
you are working with a commercial project, a ham license will give
you access to endless flexibility for radios, power and data modes.
Good Luck,
Dennis
Reply by ●November 30, 20052005-11-30
A transmitter at 460 Mhz with 350 mw output will produce 1 microvolt at a
receiver at
200 miles distance with unity gain antenna.
receiver at
200 miles distance with unity gain antenna.
Reply by ●November 30, 20052005-11-30
Reply by ●November 30, 20052005-11-30
> ... 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. Tom
Cite your source or the math, please. Tom
Reply by ●November 30, 20052005-11-30
At 11/30/2005 10:28 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.
By "unity gain" you mean with respect to a dipole, otherwise the numbers
don't add up.
The built-in antenna on a FRS radio will be considerably less than 0
dBd. Probably more like -3 to -5 dBd. Split the difference, & you get ~77
miles for 1 microvolt.
Bob NO6B
>A transmitter at 460 Mhz with 350 mw output will produce 1 microvolt at a
>receiver at
>200 miles distance with unity gain antenna.
By "unity gain" you mean with respect to a dipole, otherwise the numbers
don't add up.
The built-in antenna on a FRS radio will be considerably less than 0
dBd. Probably more like -3 to -5 dBd. Split the difference, & you get ~77
miles for 1 microvolt.
Bob NO6B
