On Jun 12, 5:14*am, Dan wrote:
On Jun 12, 3:55*am, Bert TW wrote:









On Jun 11, 9:13*pm, Kimmo Hytoenen wrote:

At 13:44 10 June 2012, Bert TW wrote:

On Jun 10, 1:16=A0am, Chris Nicholas *wrote:
I think that if Flarm were installed with 2 antennae, one high
in the
cockpit or on top of the fuselage, and the other below, there
would be
no Flarm blind spot and it would be as near perfect as
possible. We
don=92t do that because it is too much trouble and/or too
expensive. It
is hard enough to persuade many pilots to have Flarm even
in its most
basic available form.

Chris N.

That's what I decided on last winter., because the Flarm range
analysis on my carbon fuselage Flarm installation (Ventius cM)
showed
that there were some blind spot (ranges 2km). I installed an
antenna
splitter, the original Flarm antenna outside the fuselage near
the
gear doors, and a stripe antenna behind my head inside the
canopy.
"Blind spot" now means a range of 4 km ( a bit more than 2
nautical
miles for the colonials).
Investment was $200. My ass is worth more than that.

Bert,

This kind of information is exactly what I would like to hear.
FLARM is an excellent idea, and I hope everyone installs one in
their ship. Also I hope that everyone make sure that his/her
FLARM system operates well. My problem is, that I have no idea
how to improve FLARM operation. I have changed the position of
antennas, and got mixed results, according to the range
analysis.

I believe that system of two antennas would be good. Can you
Bert please share with us your knowledge of antenna splitters
and antennas used, so that we can make similar installations.
Possibly we could add necessary components intowww.soartronic.comasDIYkits, so that everyone can have one
on minimum cost.

Kimmo,

I am not a specialist at all. By chance I discoveredwww.dolba.de
where you can see the antenna mounted as strips into the canopy. I
talked to the guy (Bernd Dolba, I'm pretty sure that he speaks English
as well), and he talked me into installing two antennas. He obviously
sold be the stuff he makes for that :-) but I'm happy with it. The
splitter is a small passive box which receives the input of the two
antenna, and feeds them into the antenna input of the Flarm. I did
measure the required cable lengths first, and he send me the antenna,
the splitter and the three cables (the lower antenna outside the
fuselage is the original Flarm antenna, he just provided me the
socket).
Improvement was great - I had tried various positions/antennas in the
previous year, but the combination of a carbon fuselage, a relatively
solid instrument panel (it's GRP, but behind its crammed with metal
boxes...) and my requirement that I don't want any antenna blocking
any of my view is more or less hopeless for not having blind spots.
With the present configuration, I cover the whole space around me.

I see those antennae are optimized for 868 Mhz, not 915 for north
america; there will be some loss as a result. Nice to see the market
come up with solutions like this, though.

FWIW, there are a lot of aftermarket antennas available for 915 MHz.
Google "915MHz antenna". EDN has some interesting PCB antenna designs
which could be modified for thin-film stick-on antennas.