revisiting the 434 MHz band

Ron K. Jeffries rjeffries at gmail.com
Tue Jul 20 19:49:31 EDT 2010


*I am not an expert.*

My reading indicates that the rules for both
868 and 915 MHz are complex and impose multiple limits.

I question whether is if feasible (legal) to ship
a commercially available kit where the user selects between 868 and
915 MHz. We need solid info.

the 2.4 GHz band has lots to recommend including
it's legal everywhere.

There are lots of interesting 2.4 GHz options including Zigbee and
derivatives. Unlike the 868 and 915 MHz bands, it offers high
bandwidth, and the hardware is very low cost.

If a future Nanonote were to support a wifi stack,
Nanonotes could be used with the internet at tech conferences, airport
terminals, cafes, even on about 1/3 of the flights in the US (for
example).

---
Ron K. Jeffries









On Tue, Jul 20, 2010 at 16:14, Werner Almesberger <werner at openmoko.org> wrote:
> When reading about the 434 MHz band, I often saw remarks suggesting
> that it was regionally limited, much like the 868 MHz and 915 MHz
> bands are. Yet, the Wikipedia article on ISM bands [1] doesn't
> mention any constraints.
>
> As it turns out, the 434 MHz band may be even more troublesome than
> the 868 and 915 MHz bands. First of all, the German Wikipedia
> article [2] indicates that the 434 MHz band is regionally
> constrained. The article on short-range devices [3] adds more
> constraints, like a maximum transmit power of only 10 mW. For
> comparison, FCC 47.15.247 allows up to 1 W in the 2.4 GHz band [4,
> 5]. The article also claims that the 434 MHz band is full of
> interferences and will face more restrictions in the future.
>
> Furthermore, the 434 MHz band is notably absent in FCC 47.18.301
> [6]. (The same text confusingly states on the next page that ISM
> equipment is free to put as much energy in the air as it desires
> [7], seemingly directly contradicting 47.15.257.)
>
> [1] http://en.wikipedia.org/wiki/ISM_band
> [2] http://de.wikipedia.org/wiki/ISM-Band
> [3] http://de.wikipedia.org/wiki/Short_Range_Devices
> [4] http://www.wi-fiplanet.com/tutorials/article.php/1428941/EIRP-Limitations-for-80211-WLANs.htm
> [5] http://edocket.access.gpo.gov/cfr_2005/octqtr/pdf/47cfr15.247.pdf
> [6] http://edocket.access.gpo.gov/cfr_2007/octqtr/pdf/47cfr18.301.pdf
> [7] http://edocket.access.gpo.gov/cfr_2007/octqtr/pdf/47cfr18.305.pdf
>
> This leaves two choices: 1) either live with a design that operates
> in different bands, depending on location, or go to what appears to
> be the only globally safe place, the 2.4 GHz band.
>
> Regarding 1), it should be possible to meet regulatory requirements
> for 868 MHz and 915 MHz with the same hardware, i.e., without the
> need for regionally different hardware. Users would still have to
> know whatever band(s) is/are available in their region, and
> configure their system accordingly. Well, if you add a GPS
> receiver, even this could be automated ;-)
>
> - Werner
>
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