Powerflarm transmit antenna defect

A big Thanks to Rex Mayes at Williams Soaring Center for a replacement Plarm A antenna. I installed the new one and TG reports now seeing me at 6nm! instead of less than 1nm.

The original antenna delivered with the unit actually had a short, unknown to me as others reported actually being able to see me at short distances despite this flaw(found at the crimp of the SMC connector). If others have transmit range issues, then consider ohming out your antenna and check for a short.

Darren

On Thursday, May 19, 2016 at 1:34:45 AM UTC-4, wrote:
If others have transmit range issues, then consider ohming out your antenna and check for a short.


What should the ohm readings be for healthy Flarm antennas?

On Thursday, May 19, 2016 at 7:06:35 PM UTC-7, son_of_flubber wrote:
On Thursday, May 19, 2016 at 1:34:45 AM UTC-4, wrote:
If others have transmit range issues, then consider ohming out your antenna and check for a short.


What should the ohm readings be for healthy Flarm antennas?

Measuring from the coax connector center pin to the outer housing, should read open or infinite ohms.

To check the antenna without an RF type SWR meter, you would need to either remove the vinyl caps on the radials (if it's a dipole antenna) and measure those. One should read a short to either the coax center pin or outer housing, and the other radial should be a short to the other part of the coax fitting. It's a simple antenna with no loading coils or baluns etc.

If working on avionics a lot, there are testers like this available: http://www.mfjenterprises.com/

bumper
MKIV & QV

I suspect this may be a common problem with the stock antennas. In my case it was a bad ADS-B antenna.. I heard of others with antenna issues.
I recommend folks who have poor range issue with antennas that are installed properly to simply try with another antenna.

Ramy

Yep, simply check for open. This coax has no characteristic impedance unlike other coax types used for video, for example.

Also for the PF designers if they are reading, would be good to sense this case as is done on the Becker Transponder and issue an error. I imagine there a number of ways to do it, like a self test during boot.

On Friday, May 20, 2016 at 12:52:11 PM UTC-7, wrote:
Yep, simply check for open.

scratch that comment about the coax impedance. Darryl rightfully pointed out it will have a characteristic impedance. But we are interested in whether the core and shield have been bridged here.

On 5/20/2016 3:52 PM, wrote:
Also for the PF designers if they are reading, would be good to
sense this case as is done on the Becker Transponder and issue an
error. I imagine there a number of ways to do it, like a self test
during boot.

Unfortunately an automated antenna self-test would not be as simple as
simply checking the antenna for a DC short, because some antennas are
purposely designed to incorporate a DC short. It's possible to check a
transmit antenna by sensing the reflected power using a bridge
arrangement, but that requires extra components and (therefore) extra
expense. Building a circuit to automatically check a receive antenna
would be even more difficult.

I have very poor forward performance from my powerflarm, who could I send photos of the install and range analysis image to get some suggestions?

In the mean time I should test the flarm antenna if i can figure out the correct procedure.

Chris

On Friday, May 20, 2016 at 5:55:11 PM UTC-4, wrote:
I have very poor forward performance from my powerflarm, who could I send photos of the install and range analysis image to get some suggestions?

In the mean time I should test the flarm antenna if i can figure out the correct procedure.

Chris

1. Is the firmware the most recent (6.06)?
2. Are your antennas vertical when in flight?
3. Did you follow the antenna separation criteria in the manual?
4. Is the PowerFLARM GPS antenna at least 12" from the other GPS antennas in your system?
5. Are the connectors correct (RPSMA to FLARM A, SMA to ADS-B)?
6. Are the connectors tight?
7. Have you swapped your antennas from a known good installation set to see if the problem is with them? Do your antennas work in a known good installation?
8. Are your antennas on the glareshield or elsewhere? See PowerFLARM application note rf antennas on cumulus soaring website.
9. When you do the RF analysis, how many flarm/flarm interactions are you seeing? Are their installations good (i.e., do they have good RF analysis charts)?
10. Is your glider carbon fibre, glass, metal, wood?
11. Have you shortened your cables to the antenna or GPS? Are the antenna wires near any wires which carry large current?
12. Is there any metal object forward of your FLARM A antenna (eg., compass)?
13. If you are grandfathered, have you installed a FLARM B antenna? What were the results?

On Saturday, May 21, 2016 at 8:00:38 AM UTC-4, Dan Daly wrote:
On Friday, May 20, 2016 at 5:55:11 PM UTC-4, wrote:
snip

Answer some of the questions below and I posted lots of photos and other information to this link, please take a look and share any thoughts.

https://docs.google.com/presentation...it?usp=sharing

1. Is the firmware the most recent (6.06)? Yes
2. Are your antennas vertical when in flight? Yes
3. Did you follow the antenna separation criteria in the manual? I read it and tried to, though there are so many variables it is hard to know what trade offs are more important than others. With so many rules it is almost impossible to obey every rule simultaneously. There are metal parts: the instruments, canopy support brackets, wires, lead weights for nose ballast, nose tow release, and other antennas, etc.
4. Is the PowerFLARM GPS antenna at least 12" from the other GPS antennas in your system? No, they are about 4inch 96mm apart atop the vario and ASI, I never would have guessed that this would be a related to a reception issue for the Flarm communications. Best I can tell both antennas seem to get along fine and get good reception, they are both for new instruments so I hope that the newer gps antennae interfere with each other less than older generations. Maybe this close placement is something I should test.
5. Are the connectors correct (RPSMA to FLARM A, SMA to ADS-B)? Yes, factory supplied
6. Are the connectors tight? Yes, finger tight, no wrench used
7. Have you swapped your antennas from a known good installation set to see if the problem is with them? No, not many other flarm equipped gliders around, and doubt others would appreciate me removing theirs.
Do your antennas work in a known good installation? No, have not thought of testing, but with few other flarm targets around except in a large contest that is hard to study.
8. Are your antennas on the glareshield or elsewhere? Yes, see pictures, temporary location on top of glareshield.
See PowerFLARM application note rf antennas on cumulus soaring website. I have referred to this but as I mentioned above it is hard to obey all the rules simultaneously so I need advice on what other things to try, other placements and other ideas.
9. When you do the RF analysis, how many flarm/flarm interactions are you seeing? Yes, see page 1
Are their installations good (i.e., do they have good RF analysis charts)? There were lots of others, i don’t know how well their installs are done, but at Perry it is a pretty good example of average or the target normal audience that I would fly with.
10. Is your glider carbon fibre, glass, metal, wood? Fiberglass, with metal bits in various places like other gliders.
11. Have you shortened your cables to the antenna or GPS? No, they are stock.
Are the antenna wires near any wires which carry large current? Near other instrument power feed lines with 12v, not sure i would call any of that “large current� in this context, but that is a relative term. Nothing draws a lot of amps like an electric motor glider might.
12. Is there any metal object forward of your FLARM A antenna (eg., compass)? Yes, see other pages
13. If you are grandfathered, have you installed a FLARM B antenna? What does Grandfathered mean? What were the results? See page 1


thanks
Chris