Re: [uracoli-devel] Question regarding LQI and ED values [Update]

[Eric Jennings]

On Aug 29, 2012, at 6:23 AM, Joerg Wunsch wrote:

> As Eric Jennings wrote:
> 
>> Really interesting antenna design.  Did you try to see what your
>> maximum working distance was between two boards (despite the fact
>> that the design goal only needs them to be a few meters away from
>> each other?)
> 
> No, I didn't.  I only made radiation measurements in comparison with
> other boards and antennas, using an older spectrum analyzer as test
> receiver.  As I've got a few spare PCBs, I could run a test series
> with different lengths of the antenna traces.

This would be interesting to see, if you happen upon a rainy afternoon on a 
weekend!


> As a special feature with the Atmel transceivers, they've got a
> symmetric RF port with nominal 100 Ω impedance requirement.  A plain
> open dipole has about 120 Ω, and thus fits almost optimal to the
> transceiver.  That's what I've been using on the Tic-Tac-Toe board.
> You don't need the balun, and get a good antenna for cheap.  (However,
> it's really advisable to still spend the Pi-type output filter in both
> RF branches, RFP and RFN, to improve the spurious emission
> supression.)

On page 496 of the rfa1 datasheet, the comment column of the balun record 
states that the filter is included within the balun.  Is that indeed the case 
for all baluns, or just the ones noted in the datasheet? 


> So far the most efficient (and still cheap!) antenna I've seen is the
> one described in Atmel's appnote AVR2006.  Of course, it's a
> directional antenna, antenna gain can only be achieved by bundling the
> radiation in a certain direction.  (In contrast, you can get antenna
> losses even without the antenna being required to be omnidirectional,
> or to radiate any of the energy at all. ;-)  According to my
> measurements, the main directional radiation of that antenna is as
> good (or even more) as the one of much longer lambda/2-style whip
> antennas.  If I compare it to the plain dipole of the Tic-Tac-Toe
> (with an assumed gain of 2 dBi), the 6.5 dBi claimed in AVR2006
> appear to be realistic.

This antenna looks interesting.  It's a bit large for my application, but I'll 
definitely keep it in mind for future work. 

Seems like this could be a really great and inexpensive antenna design for a 
router/amplifier node. 


> Just for fun, I once soldered a "quick hack" Yagi antenna for 2.4 GHz,
> by taking antenna design data from amateur radio literature, and
> resizing them for 2.4 GHz.  You can find the picture (and some
> explanation in German) here:
> 
> http://www.mikrocontroller.net/topic/247618#2543650

Wow, awesome!  Looks like hot glue and cardboard did pretty well though!


> ...also shows that you have to spend quite some material to get *real* 
> antenna gains.

This is something I'm coming to realize in delving further into this 
discussion!  

As always, your knowledge-sharing is appreciated.

-Eric