PowerFLARM Core secondary FLARM antenna

... didn't seem to help nearly as much as getting the 'A' antenna up high and away from the instruments and other metal/carbon clutter.


Does "carbon clutter" include the pilot?

On Tuesday, September 30, 2014 7:21:18 PM UTC-7, wrote:
... didn't seem to help nearly as much as getting the 'A' antenna up high and away from the instruments and other metal/carbon clutter.


Does "carbon clutter" include the pilot?

On too many days, yes.

9B

On Tuesday, September 30, 2014 8:28:46 PM UTC+1, wrote:
Having done extensive testing with both 'A' and 'B' antennas of various types in various locations and combinations I have come to the conclusion that the 'B' antenna is mostly for extending range at the limit. Very few gliders have blind spots that are so directional that a 'B' antenna will add materially to collision avoidance functionality. To the extent that they do have very specific blinds spots it is likely due to poor placement of the 'A' antenna and/or RFI in the cockpit which can be remedied without a 'B' antenna.

Can't argue with practical testing, but I can't reach the same conclusion. If there are attenuating items in the aircraft, a single antenna must have diminished performance in their direction, just as individuals lit by a single candle in the middle of a room must throw a shadow. Moving the antenna away from the attenuating items may reduce the areas affected, but there will still be specific areas of reduced performance. A second antenna should bring the coverage closer to the ideal.

As for the significance of attenuated areas / blind spots: I think I recall FLARM using the example of the steady-state collision course scenario where both aircraft maintain constant heading, speed and climb rate. In this situation there is effectively no movement of the conflicting aircraft against the background, so it's difficult to spot the conflicting traffic visually. Since the relative bearing to the conflicting aircraft will be nearly constant in this scenario, even a narrow area of attenuation can be potentially significant if it happens to lie in the right (wrong?) direction.

I conclude the 'B' antenna is mostly for pilots who want the absolute maximum range limit for better tactical situational awareness in contests or buddy flying.

I don't see how the configuration suggested in the manual would provide extra range, and I haven't seen high-gain directional antennas being marketed by FLARM or its suppliers. I have to conclude the B antenna function is intended to cover blind spots, as the documentation suggests.

As to pricing models - it's a software world where much, most, or even all of the value of products is attributable to the intellectual property that goes into a product (embodied in software), rather than means of delivering that intellectual property - including the hardware. You should expect that pricing will increasingly be based on customer value, rather than COGS (Cost of Goods Sold). Deleting ADS-B, PCAS, the 'B' antenna and other features are what allowed Flarm to dramatically reduce the price to reach new customers who don't value the full-featured version to the tune of $1500. Price elasticity of demand and market segmentation, pure and simple.

I understand the rationale behind making various features on the Core Plus chargeable, and I have no objection to the other features which have only secondary relevance to electronic conspicuity. I still find it difficult to understand why the capability of increased antenna coverage has apparently been categorised as an additional, chargeable 'feature', discouraging users from fitting a second antenna.

On Tuesday, September 30, 2014 5:20:33 PM UTC-7, wrote:
On Tuesday, September 30, 2014 4:43:29 PM UTC-7, jfitch wrote:

On Tuesday, September 30, 2014 4:23:43 PM UTC-7, Ramy wrote:



I think it is like the ENL - they give you a code, you put it in the config file, and it is supposed to be good for the duration. Code is hashed to the unit ID so only works on that one.



That's correct - I've done it. The higher-price variants have more features enabled then the newer, lower-price variants like PF Core Pure. Pay more, get more capability.



Have you noticed any difference since you installed it? I really want greater leeching range....



No. For more than a year I've run multiple antenna types beyond the standard quarter-wave dipole and at multiple locations and a second antenna didn't seem to help nearly as much as getting the 'A' antenna up high and away from the instruments and other metal/carbon clutter.



Maybe it would help in the situation where you have a strongly asymmetric radiation pattern AND a place to mount a second antenna to specifically fill the gap. I suppose mounting in the tail could help seeing behind you - but I don't know many pilots who worry a lot about range on overtaking scenarios. Also, keep in mind that Flarm recommends keeping multiple Flarm antennae well separated.



Load some log files into the Flarm range analysis tool to find out where your coverage gaps a http://www.flarm.com/support/analyze/index_en.html



I'd be curious to know if others have tried two antennae - where they mounted them and to what effect.



9B

"but I don't know many pilots who worry a lot about range on overtaking scenarios"

I was in just such a scenario this last summer. Flying a local friendly contest run as a Grand Prix handicap type of task (parallel start and handicap applied at far turn point, first glider back wins) I was comfortably entrenched in 2nd place with no hope of catching the leader and two gliders trailing some distance behind on final glide. I flew a 60 mile final glide at a leisurely 80 knots, arriving about 4,000 ft above pattern and took second place. That evening looking at the log files, I noted that the two gliders behind were flying the final glide at 120 knots and had closed within a couple of miles by their minimum altitude finish. I was watching Flarm and had not seen them, as they were well below and behind, the worst direction for my Flarm pattern. Normally fine, since overtaking speeds are low and not generally a collision concern. Had I seen them on Flarm, I would certainly have sped up a bit to make sure they didn't pass!!

On Monday, September 29, 2014 10:41:45 AM UTC-7, wrote:
I was really surprised to see this in the PowerFLARM Core manual:



'CORE has two separate FLARM radio transceivers FLARM A and FLARM B. FLARM A is used to receive and transmit and must always be connected to an antenna. FLARM B is only used to receive, an optional antenna may be used for better reception performance. Usage of FLARM B requires purchase of the respective feature licence.'



Feature licence? Turns out it's a 44EUR charge http://www.air-avionics.com/support/...rflarm_lic.pdf to enable this feature. My understanding is that this fee is just a software activation; the hardware (antenna and cables) seems to be extra.



Later in the manual:



'The primary antenna (FLARM A) should have good view into the direction of flight. FLARM B (if used) should be placed to complement the field of view of FLARM A.'



.. So, if you're following the recommended install, the secondary FLARM B antenna should be configured solely to reduce your radio reception blind spot.



From the description, it looks like this functionality is entirely safety related; assuming you follow the recommended install, it won't provide any real advantage for the more frivolous functions of FLARM (ie being able to track traffic way ahead of you)



Hopefully I've completely misunderstood the situation, because this seems like a really odd decision by FLARM. What's a feature charge going to do except actively discourage users from fitting the ideal antenna configuration for their aircraft?

For all interested I have a variety of Powerflarm antennas.

http://www.craggyaero.com/cables_&_antennas.htm

Richard
www.craggyaero.com

Some people use a directional yagi antenna on the canopy and a omnidirectional one behind the main gear. This combination seems to work very well with otherwise problematic carbon fuselages.

On Wednesday, October 1, 2014 6:05:28 AM UTC-7, wrote:

I understand the rationale behind making various features on the Core Plus chargeable, and I have no objection to the other features which have only secondary relevance to electronic conspicuity. I still find it difficult to understand why the capability of increased antenna coverage has apparently been categorised as an additional, chargeable 'feature', discouraging users from fitting a second antenna.

I like your use of 'conspicuity'.

While it is theoretically possible to have really good coverage in one direction and basically none in another direction, my experience with a number of different gliders is once you get the 'A' antenna right with a good view out the front to cover converging traffic you generally have more than enough coverage out the back (or along the wings, or wherever the "dead spots" are). The speeds for overtaking traffic are such that you are more than fine if you can get half a mile to a mile. That's why I say that the "B" antenna seems most useful to extend the blind spot range from "fine for collision avoidance" to "good for full tactical coverage" (for cases like jfitch mentioned - the leeches were never collision threats, just competitive ones).. You just don't get situations where you have good coverage everywhere except a narrow corridor that is basically zero range and therefore a collision threat. The physics of radiated energy declining with R-squared just doesn't allow it and gliders are too thin and delicate to block a signal that completely.

At US$54, it is hardly a bank-breaker for anyone who owns a glider. I think forcing everyone to pay $54 extra for a feature that less than 10 percent might use seems like the wrong call.

9B

Wasn't the original "brick" which is now called "core" supposed to include the use of both FLARM antennas and the logger?
Aren't only the less expensive ones limited in functionality, requiring paid permissions?
Jim

wrote, On 10/1/2014 1:13 PM:
At US$54, it is hardly a bank-breaker for anyone who owns a glider. I
think forcing everyone to pay $54 extra for a feature that less than
10 percent might use seems like the wrong call.

If they made the other 90% pay for it, they'd only have to charge
everyone $5.40 to make the same amount of money. And, no irritated
customers, either. They are probably smart enough to know that, so
perhaps there are other factors, or a higher percentage taking it.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
http://tinyurl.com/yb3xywl

On Wednesday, October 1, 2014 1:43:06 PM UTC-6, wrote:
Some people use a directional yagi antenna on the canopy and a omnidirectional one behind the main gear. This combination seems to work very well with otherwise problematic carbon fuselages.

How is the secondary antenna placed? The one I received is flat but is supposed to be in a vertical attitude. I can't find a place that works in my mostly carbon Ventus. I think the blind spot issue is significant. My main dipole is mounted on the glare shield and I get good performance when the line of sight doesn't go through the carbon fuselage. It is easily noticed while thermalling when an alert disappears and reappears depending on the obstruction.