What Flarm really needs...

[[email protected]]

Flarm needs a box that is similar to that used by A&Ps to do transponder checks. Something portable that would allow you to test the send and receive range of your glider on the ground. Idally you would do sy 4 tests. Off the nose, behind, and left and right.

Range analysis tool is ok, but it's really pretty useless if you're trying to diagnose a problem.

If there were 10 of these boxes available in the US, I'd happily put down a significant deposit on the box and a reasonable rental to be able to check not just my glider, but all the gliders at my airport before returning the box to get my deposit back.

[[email protected]]

I must heartily second this suggestion.
One of the continuing problems with FLARM is antenna placement and function.. There are many gliders in my area that have significant blind spots due to antenna placement and glider construction. For a safety device this is totally unacceptable to me. A safety device must be predictable and consistent across the entire installation population.

A thought is that SSA might be a good organization to find a way to investigate and standardize the installation of FLARM in virtually every glider flying so that there is a predictable way to install the devices and have acceptable function. Finding someone with the skills and time like Dick Johnson used to do with flight tests is one possible way. The SSA should take the lead on this type of research, especially since they require FLARM devices in competitions.

My two cents.

[[email protected]]

On Monday, June 8, 2015 at 12:04:50 PM UTC-4, wrote:
> I must heartily second this suggestion.
> One of the continuing problems with FLARM is antenna placement and function. There are many gliders in my area that have significant blind spots due to antenna placement and glider construction. For a safety device this is totally unacceptable to me. A safety device must be predictable and consistent across the entire installation population.
>
> A thought is that SSA might be a good organization to find a way to investigate and standardize the installation of FLARM in virtually every glider flying so that there is a predictable way to install the devices and have acceptable function. Finding someone with the skills and time like Dick Johnson used to do with flight tests is one possible way. The SSA should take the lead on this type of research, especially since they require FLARM devices in competitions.
>
> My two cents.

I'm sure SSA would be pleased to know of a real expert that it could recommend to people for advice and expertise.
This forum has provided a lot of good information on the topic.
"They" (SSA) does not require Flarm in competition. The SSA contest board is on record as strongly encouraging contest pilots to use Flarm but has not made it mandatory.
UH

[Steve Koerner]

OK, here's a method that you could use to perform a PowerFlarm ground range test on the cheap...

Get a portable PowerFlarm unit (hopefully this can be borrowed from someone that owns one). Prepare a battery setup to power it. Connect a 40 dB RF attenuator between the portable unit and its antenna. The Attenuator will have the effect of simulating a 100:1 range reduction. Put your glider in an open field with the tail propped up to flying angle. Now walk out on various radials from your glider to determine the point of drop out -- multiply the drop out distance by 100 to get the approximate flying range.

At the portable setup, attach the attenuator on the PF unit with maybe 6 ft of coax hanging off to the PowerFlarm antenna. The antenna should be mounted on a stick and held vertical in the air to get it away from your body. Getting an RF attenuator configured with the right connectors might require help from a professional EE or tech or maybe an advanced HAM kind of guy.

This of course only gives you a zero azimuth range measure, but that's the most important for Flarm operation anyway. Ground reflection and any extraneous objects in the environs will introduce some error. There are many other caveats that make this an imperfect method for sure but it will get you reasonably close. Your attention should be focused on closely spaced radials in the forward angles from your glider as this is the direction which places the most demand on anti-collision range.

[[email protected]]

Nice suggestions.
I take issue with the zero azimuth as being good enough.
I worry about gliders under my belly and behind and above in my blind spots.
Pull-ups and diving for airspeed are part of soaring.

All the gliders with carbon cockpits and having the antennas under of on the glareshield means that there is a blindspot below the zero azimuth.

[Steve Koerner]

I should add that the professional or Ham guy should probably be part of the antenna on the stick design as well. There can be issues with respect to the type of antenna and the lead-in arrangement. I'd be inclined to use a PowerFlarm dipole antenna and set it up so that the lead in cable is orthogonal to the antenna for at least 6 inches or so.

[Steve Koerner]

On Monday, June 8, 2015 at 10:21:31 AM UTC-7, wrote:
> Nice suggestions.
> I take issue with the zero azimuth as being good enough.
> I worry about gliders under my belly and behind and above in my blind spots.
> Pull-ups and diving for airspeed are part of soaring.
>
> All the gliders with carbon cockpits and having the antennas under of on the glareshield means that there is a blindspot below the zero azimuth.

Yes, under the belly is important. This is not really an important consideration for testing however. The reason is that it would be essentially impossible to create an installation that would so strongly attenuate in the under the belly direction compared to the zero azimuth directions such that acceptable range is found at zero azimuth and yet is not sufficient for good anti-collision operation in the very very close range that matter for under the belly, etc.

[John Carlyle]

Steve, good idea for a first approximation. If under the belly and behind is really a worry that you'd go to some lengths, you could do what the radar boys do - put the glider on a pedestal. I still remember the F-18 I saw on a post 50 feet above the ground...

-John

On Monday, June 8, 2015 at 1:33:40 PM UTC-4, Steve Koerner wrote:
> Yes, under the belly is important. This is not really an important consideration for testing however. The reason is that it would be essentially impossible to create an installation that would so strongly attenuate in the under the belly direction compared to the zero azimuth directions such that acceptable range is found at zero azimuth and yet is not sufficient for good anti-collision operation in the very very close range that matter for under the belly, etc.

[Steve Koerner]

On Monday, June 8, 2015 at 11:45:29 AM UTC-7, John Carlyle wrote:
> Steve, good idea for a first approximation. If under the belly and behind is really a worry that you'd go to some lengths, you could do what the radar boys do - put the glider on a pedestal. I still remember the F-18 I saw on a post 50 feet above the ground...
>
> -John

Again, I strongly believe that worrying about elevation angles is not worthwhile. Having said that, there's an easier way than building a pedestal into the sky. Take the wings off and pivot the fuse at various roll angles if you really must see what happens to range above and below your glider.

[Dan Marotta]

Awwww... Way too logical. I favor standing the glider on its nose and
walking around it to take up/down measurements! :-D

<snip>

> Take the wings off and pivot the fuse at various roll angles if you really must see what happens to range above and below your glider.
>

--
Dan Marotta

[son_of_flubber]

On Tuesday, June 9, 2015 at 11:27:28 AM UTC-4, Dan Marotta wrote:
> Awwww...* Way too logical.* I favor standing the glider on its nose
> and walking around it to take up/down measurements!* :-D

Or you could more easily hoist YOUR fuselage vertical by the nose hook.

[jfitch]

On Monday, June 8, 2015 at 4:54:11 AM UTC-7, wrote:
> Flarm needs a box that is similar to that used by A&Ps to do transponder checks. Something portable that would allow you to test the send and receive range of your glider on the ground. Idally you would do sy 4 tests. Off the nose, behind, and left and right.
>
> Range analysis tool is ok, but it's really pretty useless if you're trying to diagnose a problem.
>
> If there were 10 of these boxes available in the US, I'd happily put down a significant deposit on the box and a reasonable rental to be able to check not just my glider, but all the gliders at my airport before returning the box to get my deposit back.

Doesn't Flarm broadcast in the blind all the time? There is plenty of test equipment available to test the field strengths of transmission. Not as cheap as the Portable recommendation, but probably more accurate. Look around your area for a lab that does EMI testing.

[son_of_flubber]

On Tuesday, June 9, 2015 at 12:32:51 PM UTC-4, jfitch wrote:

> Doesn't Flarm broadcast in the blind all the time? There is plenty of test equipment available to test the field strengths of transmission.


Flarm/Powerflarm use the ISM/SRD band. Wi-fi uses the same band (though maybe not the same exact frequencies?).

If the frequecies are common, maybe you could use something like http://www.ekahau.com/wifidesign/ekahau-heatmapper to map Flarm signal strength around the glider.

[SF]

Why not use the Flarm range Analyzer?
https://flarm.com/support/tools-software/flarm-range-analyzer/

SF

[[email protected]]

Because if you are trouble shooting a problem, you'd have to go fly with a bunch of other gliders and then come back and see if anything changed.

What's needed is a box that could tell you on he ground that "yes, your flarm is transmitting at an acceptable power level, or no, you have a problem." Similarly, it would be just as important to determine that your Flarm is receiving a signal that duplicates a glider at say a 3km range"

[Dave Leonard]

On Wednesday, June 10, 2015 at 4:39:22 PM UTC-6, wrote:
> Because if you are trouble shooting a problem, you'd have to go fly with a bunch of other gliders and then come back and see if anything changed.
>
> What's needed is a box that could tell you on he ground that "yes, your flarm is transmitting at an acceptable power level, or no, you have a problem." Similarly, it would be just as important to determine that your Flarm is receiving a signal that duplicates a glider at say a 3km range"

Links to example cheap chinese ebay parts for the setup Steve brought up earlier in the thread, $23 + $3 shipping. Its simple screw together connectors. This plus a trusty portable power flarm gives the functionality you are looking for. Stand back 100 ft and rotate the glider to demo a ~ 2 mile range. Check receive in your cockpit and transmit at the test flarm. Its a simple "can you hear me now" test, but quick and comparable to what you get from the flarm range analysis tool and as effective as the portable transponder checker.

http://www.ebay.com/itm/1pce-Adapter-RP-SMA-male-jack-to-SMA-female-connector-straight-gold-plating-/271847027517?pt=LH_DefaultDomain_0&hash=item3f4b58733d

http://www.ebay.com/itm/1pce-Adapter-RP-SMA-female-plug-to-SMA-male-connector-straight-gold-plating-/271672415310?pt=LH_DefaultDomain_0&hash=item3f40f0144e

http://www.ebay.com/itm/40dB-SMA-RF-Coaxial-Fixed-Attenuator-DC-4GHz-Omni-Spectra-20510-40-/390932728408?pt=LH_DefaultDomain_0&hash=item5b05680a58

[Steve Koerner]

Dave is an RF Engineer, so his affirmation is significant. I agree with Dave that rotating the glider gets the same result as walking out on radials while probably being a little quicker and it's likely to be easier to find a good place to do the test that way.

[[email protected]]

Parts are one order. I'll report back on how it goes.

Thinking I might start next to the glider and then walk away until I lose signal first.

[Steve Leonard[_2_]]

On Wednesday, June 10, 2015 at 8:48:40 PM UTC-5, Dave Leonard wrote:

> ... Stand back 100 ft and rotate the glider to demo a ~ 2 mile range. Check receive in your cockpit and transmit at the test flarm. Its a simple "can you hear me now" test, but quick and comparable to what you get from the flarm range analysis tool and as effective as the portable transponder checker.

And with wing and tail dollies on, the "rotate" part is really easy. You can get a small bit on elevation, too, by putting the wing away from the portable on the ground, or placing the glider on a higher spot than the portable, as I hear not all places are as flat as where I typically fly.

And, since you are running two Flarms to do the test, you should be able to run it through the range analysis tool, too. Or, does one of them have to be moving to create a log file?

Steve Leonard

[Andy Blackburn[_3_]]

On Thursday, June 11, 2015 at 6:51:58 AM UTC-7, Steve Leonard wrote:
> On Wednesday, June 10, 2015 at 8:48:40 PM UTC-5, Dave Leonard wrote:
>
> > ... Stand back 100 ft and rotate the glider to demo a ~ 2 mile range. Check receive in your cockpit and transmit at the test flarm. Its a simple "can you hear me now" test, but quick and comparable to what you get from the flarm range analysis tool and as effective as the portable transponder checker.
>
> And with wing and tail dollies on, the "rotate" part is really easy. You can get a small bit on elevation, too, by putting the wing away from the portable on the ground, or placing the glider on a higher spot than the portable, as I hear not all places are as flat as where I typically fly.
>
> And, since you are running two Flarms to do the test, you should be able to run it through the range analysis tool, too. Or, does one of them have to be moving to create a log file?
>
> Steve Leonard

You could mount a Flarm on a helicopter drone, which could help if you really want to do a thorough and precise job. It would also allow you to test positive elevation angles. You can program many drones to fly a pre-programmed set of circular paths around a point. The FAA frowns on flying drones at airports so maybe you'd need to assemble at a local parking lot or park to do this.

As I understand the range tool you need a minimum number of points from at least 5 other Flarms for the tool to give a result. I doubt that it rejects non-moving targets since my Flarm display shows other gliders on the ground when I'm on the ground, but it would be hard to test since the tool only uses first/last contact to estimate maximum range, so motion is required to the extent that you need to move into/out of range to have the tool pick a max range point.

9B

[NG[_2_]]

Standing a glider on its nose is certainly possible, see http://noss.ws/ssc/LS4_OnNose.jpg . (OK, this was actually XZ helping HR with a difficult retrieve, but it can be done....)

[Steve Leonard[_2_]]

Many glider repair shops have "rings" they can mount a fuselage in to turn it over and work on the side, bottom, or whatever. And they often have the parts needed to connect any fuselage to the "ring". So, this could be a side business for a sailplane repair shop. Ask Paul Gaines about his "ring".. If it could be borrowed, you could place your fuselage in the ring, turn in 90 degrees onto its side, and get a straight down pattern, turn it 45 degrees and get a thermal bank pattern.

Steve Leonard

[[email protected]]

If the attenuator is not on the portable, but is on the brick would it still work though? Is the brick also RF leaky?

[Dan Marotta]

Well, since my last professional experience with RF was in 1970, I'll
defer detailed comments to others more up to date like Dave (ZL). All I
can say about the below statement is: Shoddy engineering! How many
harmonics are bouncing around behind your panel?

Now I begin to understand why the FAA is so hard over on TSO equipment
for such things as ADS-B...

On 6/19/2015 11:17 PM, Steve Koerner wrote:
> The real world throws curve balls sometimes (actually, almost all the time)...
>
> Britton Bluedorn has conducted some tests using his brick and portable PowerFlarm. He and I have been in email interchange through his testing. What we've found is that the portable unit is RF leaky. That is, a lot of energy gets in and out of the box without going through the antenna connector. This isn't a flaw really, it's just the way it is. There's not a compelling reason that the PowerFlarm RF section needs to be well shielded.
>
> The upshot is that the 40 dB attenuator scheme isn't workable. There is an alternative. Instead of 40 dB, use a 20 dB coaxial RF attenuator. That makes the range factor 10X instead of 100X. That means, of course, that the test site has to be bigger -- an airstrip would work.
>
> In addition to the attenuator change, one should shield the portable box by wrapping it up in aluminum foil. The battery should be inside the shielded system and the foil should wrap tightly all around the unit and be taped in place. The foil shield should be pressed against the connector junction between the attenuator and the antenna or antenna cable with tight tape wrapping there for best effectiveness.

--
Dan Marotta

[[email protected]]

In all transparency while I am an engineer I'm not an EE or RF professional. That stated I would *not* use my one data point as gospel. Looking forward to someone else performing the experiment again with Steves instructions and reporting back.

Britton

[[email protected]]

On May 5th weather cooperated and I flew. Flarm Range tool applied to that flight log showed all points outside 2km and several at 4km range.

June 6/7 flights show almost zero range and inflight I only picked the one known FLARM equipped glider that weekend when I got within about 300 yards. I'm pretty sure I've got some sort of issue, so that's where this thread started.

I bought a 40db attenuator and the adapters and put that inline with the FLARM A antenna for my core unit and borrowed a portable this morning.

I was able to maintain communication between the units to a distance of about 150' which I thought from the earlier posts was a good sign. However, when I removed the attenuator and tried again I lost contact with the portable at around 300-500 yards, not a good sign.

When I removed the antenna from the attenuator I happened to notice that I didn't lose contact with the portable unit. The portable was sitting on my wing about 1/2 way out, but it was curious that the units were still making contact. Perhaps the Core is leaky as well and the test with the attenuator is flawed? Wrapping everything up in tin foil seemed like a pain so I didn't take the time to mess with that.

Unfortunately, almost the entire season has been rained out here in Houston and we won't fly tomorrow either so I'll have to wait until maybe next weekend to hope for another flight to see what happens in the air.

Back to my original idea, it sure would be nice to have a rentable box that would definitively diagnose an issue while on the ground.....