Safe distance between PowerFLARM and Mode-C antenna

[Marton K.Sz.]

Hi Soaring,

Our club glider (a Grob G-102) is about to get a new PowerFLARM portable unit, which we're planning to install on the top of the instrument panel because of the good visibility of the display.
I've noticed that the Mode-C transponder antenna is also on the top of the instrument panel. There's probably enough space for the PowerFLARM unit, but my concern is that the Mode-C transponder transmits with high power pulses (up to 400 watts), which could instantly destroy the sensitive and delicate RF input stages of the PowerFLARM.

Is there an established safe distance that should be maintained between the Mode-C antenna and the PowerFLARM unit or antennas? Are there any guideleines or experience on this? I haven't found anything in the manual.

Thanks,
Marton

[kinsell]

Start with this app note, although it may not directly answer the question:

https://flarm.com/wp-content/uploads/man/FTD-041-Application-Note-FLARM-Antenna-Installation.pdf


If possible, use a Core instead of a Portable, people get significantly
better performance with a Core.

Your concerns are quite valid, although degrading performance of the
unit is more likely than actually destroying the electronics. Move the
transponder antenna to bottom of the ship behind the gear if at all
possible.

-Dave



On 08/14/2017 12:29 PM, Marton K.Sz. wrote:
> Hi Soaring,
>
> Our club glider (a Grob G-102) is about to get a new PowerFLARM portable unit, which we're planning to install on the top of the instrument panel because of the good visibility of the display.
> I've noticed that the Mode-C transponder antenna is also on the top of the instrument panel. There's probably enough space for the PowerFLARM unit, but my concern is that the Mode-C transponder transmits with high power pulses (up to 400 watts), which could instantly destroy the sensitive and delicate RF input stages of the PowerFLARM.
>
> Is there an established safe distance that should be maintained between the Mode-C antenna and the PowerFLARM unit or antennas? Are there any guideleines or experience on this? I haven't found anything in the manual.
>
> Thanks,
> Marton
>

[Dave Nadler]

On Monday, August 14, 2017 at 1:29:06 PM UTC-5, Marton K.Sz. wrote:
> ...the Mode-C transponder transmits with high power pulses (up to 400 watts),
> which could instantly destroy the sensitive and delicate RF input stages
> of the PowerFLARM.
>
> Is there an established safe distance that should be maintained between the
> Mode-C antenna and the PowerFLARM unit or antennas? Are there any guideleines
> or experience on this? I haven't found anything in the manual.

Yes you can destroy your PowerFLARM by placing FLARM antenna too close to
your transponder antenna.

Well hidden in the FLARM manual:
Antennas should be spaced **at least 30cm apart**, including other antennas
like COM/NAV, XPDR, etc.

Hope that helps,
Best Regards, Dave

[Paul Agnew]

My transponder installation manual says the antenna must be at least 3 ft from the pilot's body. I've seen them installed in the nose just inches from the pedals, but mine is going in the tail just to be safe. That will automatically prevent the Flarm interference issue when I get one.

Paul A.
ASW-19