Hi all,
I've got my hands on two 1.5 xrf's and am keen to start testing their LOS range.
I work in electronics everyday but have to admit my rf knowledge is limited, didn't pay particular attention during those lectures.

Anyway, I have an application where I would love to get as large an omnidirectional LOS range as possible using 10mW TX power.
I've read the thread about the 3.4Km which is incredible and if repeatable then that’s the sort of range I am interested in.

Can anyone give me any pointers on the best type of antenna to use?
I read somewhere about a colinear omnidirectional antenna but based on my (rough) guestimates, running at about 900 Mhz would produce an antenna length of about 66 cm (λ/4 + 3λ/4 + 3λ/4). I would love to have as small an antenna as possible. (I guess there must be a tradeoff!)

Anyway, any advice would be very welcome.

3.4Km was at the very lowest baud rate (just 150 chars/sec), we have had to detune on the 1.5 to make work with the newer hardware the has reduced the range. To achieve this sort of range "reliably" you will need either amplification CC1190 we are testing (0.5w) or higher gain antennas.

Make sure you run at the frequency appropriate for your location, here in the UK 900 is not an ISM band.

Thanks for your quick reply.

woops, yes I’m in Ireland so presumably would need to go down to the 433.5 MHz?

A very low baud rate isn't the worst in the world as I only need to send a few characters infrequently.

0.5W sounds promising buy does that not start to infringe with OFCOM? (There are too many regulations for me to understand)

Anyway, getting back to the main question, higher gain antennas seem to be line I should be looking down, any advice on suitable ones? Is there such a thing as an active antenna?

Europe is 433 or 868

The current XRF is tuned for max performance at 868-915 (range is less lower down). We are just testing a 433 version now, it'll be SMA only as we cant imagine anyone will want a 6 inch whip.

The 9dB yagi from LPRS is good, we hope to stock them soon, they are £29

0.5w is the max, you can bring down further, ETSI rules are slightly less than full power. The rules are based around many things, duty cycle, specific frequency and radiated power (whats "seen" rather than how much power goes in)

The XRF has a repeater mode so you can put a "man in the middle", you can string as many as you like it just adds a few ms to each "hop"

Thanks for your reply and patience!

The yagi sounds good gain wise but I require something omnidirectional and a bit smaller. I just don’t know if what I’m looking for exists!

Also the repeater mode is a great function but unfortunately isn’t feasible for my application.

Thanks again for your help.

Miles wrote:


Just did a bit of research into the CC1190, have you any plans to release the CC1190 as an amplification extension board for the XRF?

We are testing a CC1190 design, I have no dates or prices yet

"I have no dates or prices yet "

www.goodnessdirect.co.uk/cgi-local/frameset/detail/152752_Goodness_Dried_Pitted_Dates_500g.html?utm_source=google&utm_medium=shop&utm_campaign=feed

This site has both!

I thought orignally that the link was spam, but now I see it's "dates"

As did I!

I got playing with the XRF's over the weekend and I am suitably impressed with their performance! It's a pretty slick setup in that once they are passing serial data, they just work without a fault continuously! I'll keep my eyes open on a CC1190 desgn, not trying to put any pressure on you.

Another quick question which I don't think is worth starting a new thread for.
RE. the XBBO board. It works fine and I have used the MPWR pin on the right angled pin to supply 5v to my micro.
Is is possible to use the same pin to supply power to the XRF, does it go through the regulator?

Cheers.

Yey, sounding great.

There is in the articles section a doc on the XBBO, I hope it mentions this, if what I think you mean - can I use an XBBO active to "take" power from that pin and power the XRF then yes, the doc should say which jumper setting.