Type of Modulation Used in Walkie Talkie

[rcl...@frontier.com]

Does anyone know what the transmitted waveform of a current production
walkie talkie looks like. Would it be suitable for continuous data
transmission?

Originally, I think they used FM. Are they all digital now?

What type of modulation is used?

Thanks

Richard Clarke

[Clifford Heath]

On 10/02/14 12:22, rcl...@frontier.com wrote:
> Does anyone know what the transmitted waveform of a current production
> walkie talkie looks like.

Probably still NBFM.

> Would it be suitable for continuous data transmission?

Maybe, but that's unlikely to be legal. Check local regulations
for the band of interest... or just buy a data transceiver.
They're plentiful, cheap and legal.
See for example <http://rf-data.com>

[rcl...@frontier.com]

>See for example <http://rf-data.com>\
>

Some of the newer ones are UHF digitali, I believe. Not sure how
common they are yet.

I am likewise uncertain about the llegality of continuous
transmission, but one factor is a built-in time limiter once you press
the talk button. I have seen retriggering circuits to circumvent this.

I wonder if anything in the unit would overheat. I do have a portable
refrigerator.

Richard Clarke

[Jasen Betts]

On 2014-02-10, rcl...@frontier.com <rcl...@frontier.com> wrote:
>
> Does anyone know what the transmitted waveform of a current production
> walkie talkie looks like. Would it be suitable for continuous data
> transmission?

Look into radio control as used by model enthusiasts, that's
continuous data, but not full time.

> Originally, I think they used FM. Are they all digital now?

the 27MHz HF ones were mostly AM, with some doing SSB also, I have not looked closely
at the UHF ones, but as TVs could receive the signals I assume it was
FM.

--
Neither the pheasant plucker, nor the pheasant plucker's son.


--- news://freenews.netfront.net/ - complaints: ne...@netfront.net ---

[artie]

(Note this assumes you're a U.S. resident. Outside the U.S., the rules
are different)

Cheepie FRS handhelds are NBFM -- remember, cost is king. FCC type
acceptance requires an essentially sealed package and a fixed antenna.
Piggybacked data? Garmin had to go through many interesting times to
get FCC approval for their Rino handhelds that piggyback GPS location
data with voice on FRS channels.

Some commercial stuff is digital, but those are expensive. Ham radio is
starting to work more with digitally encoded voice, but FCC regs still
make that work difficult.

And speaking of ham radio, if you are interested in experimenting with
data transmission, the Technician Class ham radio license consists of
35 multiple-choice questions. You can pass this test after a one-day
cram class, using short-term memory and common sense. 12 and 14 year
olds regularly pass this test. (Discussions of this study methodology
are best left for other forums).

Get your tech class license and you can explore these areas in the 50
MHz and above ham bands. Type acceptance? In the ham bands, not as much
of an issue, particularly for experimental uses (yes, I know, much fine
print applies).

And if you're looking to do specific kinds of telemetry, such as
location and data from a balloon, hams have developed solutions to
those problems, such as APRS, the automatic packet reporting system,
which can be used to track and monitor weather, balloons, cars, and
much other stuff.

APRS is based on packet radio. Low-speed packet radio still makes uses
of voice-grade ham transceivers (usually in the 144 MHz band) and an
external packet modem. More specialized data radios evolved that
achieve higher data rates by designing for data, rather than voice.

Packet radio lets you send data from place to place. Protocols range
from the very simple to AX.25, derived from X.25, and providing the
data link layer as a building block (AX.25 is supported under Linux).

Have fun--


In article <15agf9h044ido70i4...@4ax.com>,

[mhend...@unitrans.com]

On Mon, 10 Feb 2014 12:22:28 +1100, rcl...@frontier.com wrote:

>Does anyone know what the transmitted waveform of a current production
>walkie talkie looks like. Would it be suitable for continuous data
>transmission?
>

This looks like an interesting option. Designed for continuous
operation and rated at 7W. Price is right.

http://www.ebay.com.au/itm/121270618857?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Mark Henderson

[Paul Hovnanian P.E.]

rcl...@frontier.com wrote:

>
> Does anyone know what the transmitted waveform of a current production
> walkie talkie looks like.

Probably this:

http://en.wikipedia.org/wiki/Family_Radio_Service

> Would it be suitable for continuous data transmission?

Not really. And it might not be permitted by FCC rules against modding FRS
radios in certain ways (can't change antennas, etc.)

How far and at what rate do you need to t/r data? There are some ready made
solutions you could adapt to your app. that may work.

--
Paul Hovnanian mailto:Pa...@Hovnanian.com
------------------------------------------------------------------
On a clear desk, you can sleep forever.

[Phil Allison]

<rcl...@frontier.com>

> Does anyone know what the transmitted waveform of a current production
> walkie talkie looks like. Would it be suitable for continuous data
> transmission?

** Only if you don't give a hoot about the data getting through.

Or a hoot about the relevant law.



.... Phil

[miso]

Oh, I don't think that is legal in the US, at least unlicensed. But good for
a pirate FM station, even in Japan. I worry about cheap FM transmitters
drifting into the nearby aviation band, but this one is PLL based.

If I were to do a data link, I'd do it in the 900MHZ ISM with a hopper. Many
of the users are hopping and directional, so the shared band isn't as bad as
one would think. There are ethernet backhaul systems in this band.