> Any suggestions or recommendations for transmitting data 5km to 10km ?

Audio modulation into a PRS CB would probably work.
A relatively low gain additional aerial would be needed for this range.
From my reading of the spec this would probably be legal in NZ as long as
the specified EIRP was not exceeded.
(A recent response expressly noted that 802.11B was legal at up to 4 watts
EIRP - ie you can use a card with about 30 mW out and a 26 dB odd parabolic
dish to achieve this.
In the case of the CB a simple Yagi would suffice. The web is mildly awash
with designs for these (or see me).
DSE has a small PRS unit for $100 ish that would do the job.
An FX604 modem IC would do the job (see me for cct) or almost anything else
at all.

> The transmitting unit has these requirements -
>
>  - No bigger than 100mm x 100mm x 20mm (100 x 50 x 20 prefered)
> - Battery-powered for up to 2 years (if possible, solar an option)
> - Data transmission probably a dozen bytes every 5 minutes

Say 50 mA est (could be WAY less than this) tx for say 2 seconds.
50 mA x 2s/300s duty cycle =~ 0.3 mA mean
0.3 x 8765 hrs =~ 3000 mAH/year.
Alkaline C cells would do this.

> - Aerial acceptable only if short, stubby, robust etc

Ah - maybe more info needed - if a Yagi at far end OK then can still work.

> - Receive capability not needed

Yo're not going to receive the daya you send ? :-)


> Apart from the tx, everything else is pretty much sorted. A couple of
> days ago someone mentioned the 340 as a better choice for a very
> low-power sleeping micro. Is that true it's better than the PIC ?

Yes. Can be very very very low - PIC seems almost impossible to get into
single digit microamp range unless essentiall;y dead in the water. For the
yltimate in low power, turn it off and wake it up with an RTC chip with
under 1 uA drain (1000 years on Alkaline C cells :-) ) (ignoring shelf life)



        RM

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