@Dan
Do you expect to lose (lot of) range going from external aerial to internal ?
The range that your FLARM unit is capable of is very difficult to gauge as it is also dependent on the ( usually ) unknown antenna status of the target aircraft.
Having used the Air Avionics AT-1 in two aircraft ( indication on Garmin map display) fitted with top & bottom external antennas 5 nm seems to be the minimum range that reliable contact can be maintained with much greater intermittent range.
As FLARM is primarily fitted to detect gliders it needs to be understood that most gliders are using FLARM antennas that are fitted internally in the cockpit area and it is my feeling that if I encountered a powered aircraft with external FLARM antennas fitted the reliable detection range would be greater.
The bottom line is 5nm is a far better glider detection range than my eyes are capable of so the safety enhancement from FLARM is clear.
When we get time we will download the data from the AT-1’s under our control ( as Airborne Again has done ) and build up a database that undoubtedly will be much more reliable than my perception gained while flying with the device.
@PetitCessnaVoyageur
Mounting the Flarm antenna(s) internally shouldn’t reduce the range by much, if at all. What it is reducing is coverage, as in sky visibility.
A_and_C wrote:
The range that your FLARM unit is capable of is very difficult to gauge as it is also dependent on the ( usually ) unknown antenna status of the target aircraft.
It is actually not difficult at all, as long as you flown with a reasonable about of targets. The PowerFLARM range analysis function simply remembers the distance and direction for every target it sees. As FLARM provides the GPS position of the targets, this is easy.
Dan wrote:
Mounting the Flarm antenna(s) internally shouldn’t reduce the range by much, if at all.
I did some tests with a portable FLARM unit – obviously with internal antennas – in “spamcan” aircraft and the results were very poor. It was clear that the fuselage shielded the antennas as targets would come and go as you banked the aircraft.
Airborne Again.
You are measuring the range that you are detecting targets, not the range that you are detected by others.
The data collected is dependent on the performance of other aircraft, if these aircraft have a poor antenna system then the range that they’re detectable by your aircraft will be lower than an aircraft with a well fitted external antenna.
If you are located in the frozen north and know all the local aircraft you might have a point but in the south of England I have no idea of the quality of installation of the vast majority of my targets or the range they detect my aircraft.
I have been experimenting with FLARM range a bit lately. A few thoughts:
- Judging reception range using normal other traffic is difficult as you do not know how their installation performs and you can fly for a long time without finding a suitable target. But at least in Germany there are quite some FLARM installed on wind farms. Those FLARM seems to make up consistent and safe “training targets”. Looking at this map you can see their locations: https://glidertracker.de
- Some FLARM devices seem to be delivered from the factory with bad antenna designs. I got one PowerMouse with an antenna with integrated 1.5m RG174 cable. That already seems to about 1.5dB loss right from the factory. Also my AT1 was delivered with about 1.1m similar cable. So keep the cables short and/or use better cable.
- I have a Stratux which displays more diagnostic data. It shows that it is very easy to pick up a huge amount of signal noise. It makes a big difference to move the antenna away from all other electronic equipment. My unproven theory is that the advantage of those external antennas is probably more about distance to other stuff than about actually being external. This also suggest that maybe portable designs with antnnas attached directly to any kind of device might be a bad idea alltogether.
- I did some experiements with this additional amplifier. I can not yet comment on the exact performance but in all configurations I did test it seemed to boost reception range significantly. Unfortunately that thing is a big pricy and I wonder if there are cheaper alternatives (I am not related to those guys in any way): https://shop.jetvision.de/FLARM-BOOSTER
Bottom line is that in one case I had to really struggle to get 0.9NM range on the ground with line of sight and then on Friday I received 4 frames at about 18.5NM from one of those wind farms in flight when everything aligned just right…
portable FLARM unit…
Peter and Airborne_Again report bad results using the portable FLARM…
I used one in (actually 2 of them…) in different wooden aircraft, Jodel D11 Special Uetz, but mainly my Falco #2, flown for 650+ hrs prior to being sold.
I can only report good to very good coverage (detection) using the (over priced…) portable in those wooden aircraft. Not scientifically backed up, but day to day observation.
Or was I just being dazzled by the new tech? 
Dan wrote:
I can only report good to very good coverage (detection) using the (over priced…) portable in those wooden aircraft. Not scientifically backed up, but day to day observation.Or was I just being dazzled by the new tech?
I tried it in metal aircraft, you did in a wooden aircraft. I would think that makes all the difference. Just like most gliders have internal antennas and that works just fine.
