Strange range problem.

[John Verschoor]

Yesterday i flew with my t-beam for the first time. On the ground, the reception was good, i saw other gliders a few miles away. Once in the air, the reception got worse, only seeing gliders within a mile. After landing the range was better again...

 In a side by side compare to my original classic flarm, the t-beam is actually better:

Screenshots from spot the gliders, KTrax

This is however transmission strength, not receive. The classic flarm shows poor reception in the flarm range tool on their website.

Both were flown with the same antenna. I use a "superfant" antenna, the Y shaped dipol.

Its mounted in front of the panel, away from metal and electonics as far as possible.

But the weirdest thing is the difference in receiving range between flying and on the ground, i would expect a better range in the air. Anyone seen something like this before?

Regards,

John

[Moshe Braner]

John: what type of aircraft is it?  If it has an engine that is running at the time, maybe it is creating radio noise?  Or maybe some other device in the aircraft, that you turned on after testing just the T-Beam on the ground?  E.g., a transponder, or canopy flasher?  The fact that your FLARM gets even worse reception indicates there is some other problem that affects both devices?

[John Verschoor]

Hi Moshe, it is a pure glider, type Glasflugel Kestrel 17. No canopy flasher, but i do have a transponder (pretty much mandatory in the netherlands) Perhaps the transponder is less active on the ground, but it was on before and after the flight. Next flight i will shut everything down except the t-beam and the kobo.

I dont have any powerbanks or 5v adapters (known for their problems)

Thanks for all your help!

John

Op maandag 11 augustus 2025 om 15:36:53 UTC+2 schreef Moshe Braner:

[Mik Garwood]

Hi

I'm assuming that yours is the only glider with this problem, else it could be local interference from something? 

When I had a transponder in my glider (in the UK) it didn't start working until about 1500ft as it wasn't being seen by the radar until then. I didn't notice any difference between ground and airborne range but wasn't really looking for it either - I used the Flarm range tool for transmission range and a log of received contacts for reception range.

Not sure what the radiation pattern of the superfant antenna is, if it's like a groundplane antenna then aircraft below you would be seen less easily. I presume the transponder antenna is well away from the flarm antenna and underneath the glider? Could the glider battery/supply being pulled down when the transponder is on? Not so easy to measure as it only transmits for a very short period of time.

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[John Verschoor]

Hi Mik, the superfant is a dipole type, and doesn't need a groundplate. It's mounted in my glider as advised: www.gliderdesignparts.de (no commercial interest:))

with a short cable to the t-beam. The transponder is a trig 21, with a control unit in the panel and the power part mounted behind the pilot, antenna inside behind the wheel. 

It's a glass glider, no carbon or metal. except for the nose hook and the rudder pedal parts.

My current setup: T-beam on its own battery, via wifi to a kobo, also on its own battery.

XCVario, currently stand alone (wifi and bluetooth off)

Trig 21 transponder.

Krt1 8.33khz radio.

no powerbanks or other "noisy" electronics. 

I hope to do a another test flight soon and will switch of as much electrics as possible, just the t-beam and the kobo.

Regards, John