Antennae

[John McCullagh]

I have a new glider on order and naturally I want to build-in all the
things it will need over the next ten years at least, rather than adding
things later piecemeal. In the non-carbon part of the fin I plan to have a
radio aerial, a transponder aerial and a Flarm aerial. However it seems
that ADS-B (In & Out) is the coming thing and so presumably another
built-in aerial would be a good idea, rather than something above the
instrument panel. Have anyone fitted four aerials in the fin and do they
co-exist happily with each other? I don't know if differences between
European standards and US standards would make a difference to the type of
aerial fitted.

[kinsell]

European and U.S. radios only differ in channel spacing, so they would
use the same type of aerial. I would prefer to put the transponder
antenna down low near the main gear, since it's very high power and
could interfere with receivers. ADS-B out is usually the same output as
the the transponder, so no need for separate antenna. ADS-B in is a
small antenna, receiving very high power signals, so placement is not
critical.

PowerFlarm uses very small cables with high loss, don't think they
belong in the tail. Do the best you can with them near the glare
shield. Maybe you run a Flarm B cable all the way to the tail, but I'm
dubious of the benefit. Definitely wouldn't put a Flarm antenna
anywhere close to transponder output.

Dave

[moshe....@gmail.com]

On Friday, July 19, 2019 at 1:21:32 PM UTC-4, kinsell wrote:
>
> PowerFlarm uses very small cables with high loss, don't think they
> belong in the tail. Do the best you can with them near the glare
> shield. Maybe you run a Flarm B cable all the way to the tail, but I'm
> dubious of the benefit. Definitely wouldn't put a Flarm antenna
> anywhere close to transponder output.
>
> Dave

I'm trying to fit two FLARM antennas and a goTenna, plus GPS reception by cellphone for IGCdroid (besides the GPS reception within the FLARM) into my cockpit, and that's enough to give me a headache. Existing glider, with VHF radio antenna in the tail, but probably won't add anything to the tail. Would like to keep the goTenna far away from the FLARM antennas, since it's relatively high power (1 watt - nothing like a transponder) on a very similar frequency. Also would like to mount the FLARM antennas one forward of the pilot and one aft, to maximize the coverage by minimizing the impact of the pilot's body blocking the signals. And of course want to keep the antennas away from metal objects such as control cables and electrical wires. It's a puzzle. At least my glider is all glass, no carbon.

[Martin Gregorie]

Depending on what there is to attach the FLARM antennae to, they should
be fine on either side of the fuselage somewhat in front of the panel and
instruments, which would mean the Gotenna antenna should be OK behind the
cockpit.

I fly a 2021 Libelle with a standard FLARM, i.e. not PF. Its antenna is
mounted centrally on the front of the instrument tray at an adjustable
potition:

https://www.gregorie.org/gliding/libelle/FLARM_install.jpg


This puts the antenna just below the top of the fuselage and about half-
way between the instruments and the rudder pedals. The position is quite
critical, I think this is due to RF reflections off pedals and
instruments, but when placed in the right fore/aft poisition it shows
good range forward and to the sides and acceptable range behind.



--
Martin | martin at
Gregorie | gregorie dot org

[stu8...@gmail.com]

While they are building it, it would be neat if they could put some non-carbon antenna windows in the belly and top for these?

[George Haeh]

Assuming a carbon fiber fuselage, I'd put the transponder and PowerFLARM A antennae in the fin. The COM antenna is in the rear of the fin. There should be one foot separation among the antennae.

You will need something like LMR-300 cable to the Flarm, and perhaps transponder, antenna in the fin to limit loss to acceptable values. Get a Flarm Antenna with a short lead.

Consider an access port in the fin.

It would be really nice if glider manufacturers included a conduit to accommodate future cables between the instrument panel and the fin.

The PowerFLARM ADS-B antenna will do just fine ahead of the instrument panel. Transponder signals are considerably stronger than Flarm signals.

It won't hurt to have a Flarm B antenna ahead of the instrument panel. The Core 1.1 can transmit on both antennae if you purchase the RFB option.

If installing ADS-B Out, you may be facing extra requirements for the GPS antenna. Plus the vario and Flarm have their own GPS antennae. A splitter may help.

[moshe....@gmail.com]

On Friday, July 19, 2019 at 4:19:15 PM UTC-4, stu8...@gmail.com wrote:
> While they are building it, it would be neat if they could put some non-carbon antenna windows in the belly and top for these?

While we are talking about building it right in the first place: There are many issues with long air tubes connecting a TE probe (typically back in the tail) and the vario(s). How come I havn't seen a vario design that puts the pressure sensor near the probe, and connects that to the panel part of the vario via electrical wires instead of air tubes? You'd want to build that with a way to access the pressure sensing unit for future maintenance or replacement. The sensor does not need to be immediately adjacent to the probe, could be down near the tailwheel, or somewhat more forward in the tailcone, wherever access can be arranged.

[Dan Daly]

On Friday, July 19, 2019 at 6:19:07 PM UTC-4, George Haeh wrote:

> It won't hurt to have a Flarm B antenna ahead of the instrument panel. The Core 1.1 can transmit on both antennae if you purchase the RFB option.

Hi George. I believe the dual-transmit is not yet for us in North America; from the release notes for firmware 6.40:

"PowerFLARM: Fully symmetric antenna diversity, dynamic receive and transmit on both antennas (except USA and Canada)"

I'd love to be wrong on this one. I have read (somewhere) that it's an FCC/ISEDC (Industry, Science, Economic Development Canada - replaced IC) approval problem. I have re-read the release notes up to the current fw 6.67 and North American approval isn't mentioned.

Dan

[Dave Nadler]

On Friday, July 19, 2019 at 6:19:07 PM UTC-4, George Haeh wrote:

> Assuming a carbon fiber fuselage, I'd put the transponder and
> PowerFLARM A antennae in the fin. The COM antenna is in the rear of the fin.
> There should be one foot separation among the antennae.

Except, it's impossible to achieve required spacing for all 3 in the fin,
(COM, transponder/ADS-b, FLARM) even very large gliders.
If you put the FLARM antenna in the fin, you'll need to put the
transponder antenna on the fuselage in the vicinity of the gear.
If you put the transponder antenna near the FLARM antenna (as in
both in the fin), you will fry the FLARM receiver.
Details of required spacing are in the FLARM manual.

Also, if you put the FLARM antenna in the fin, you will need to
specify the country it where will be used, as the different frequencies
required by different countries will require different antennas.

Some manufacturers have been happy to put all the antennas in the
fin when requested by the customer. The customer may not have been
too happy with the outcome.

Hope that helps,
Best Regards, Dave

[Martin Gregorie]

I don't think that's relevant with modern pressure sensing varios though
it was with the older flow sensors. This is because a pressure change can
propagate along a relatively small tube a lot faster than air can flow
through the same tube.

[George Haeh]

Hi Dan,

I do get different range patterns for the Flarm A&B antennae, which I have mounted on both sides of my canopy.

What I don't know is whether my Flarm is seeing a glider that's not seeing me.

But at least one of us knows about the other.

[Dan Daly]

Interesting! I will have to install a second antenna (I'm grandfathered) and have a go...

[moshe....@gmail.com]

It's worth having the two antennas even if the "B" antenna only receives. That fills in gaps in your reception pattern. And as far as the FLARM range report, that is ONLY using reception data - it has no way to know who can receive your transmissions, since the protocol is a blind broadcast with no acknowledgment.

[Dan Daly]

You can see some of that with the Open Glider Network (OGN). The KTrax range analysis shows receipt by OGN stations (if you have any nearby). Here is an example (ASW24): https://ktrax.kisstech.ch/cgi-bin/flarm-txrange.cgi?command=plot&flarmid=C05FDB from last week. You can see the glider got about 15 km from one station, and another 33 km distant picked up the glider from 33-38 km.

Here's another glider (PIK20) which flew from one OGN station to the other. At 40 km, still 5 dB.

The OGN network is also handy for troubleshooting cabling, antennae, etc since you can get a signal strength reading directly (swap a cable or antenna to see if they're bad - might save a trip for $$ troubleshooting). It also has SAR features.

[Tim Newport-Peace]

At 13:07 20 July 2019, moshe....@gmail.com wrote:
>On Saturday, July 20, 2019 at 6:44:25 AM UTC-4, Dan Daly wrote:
>> On Friday, July 19, 2019 at 10:30:50 PM UTC-4, George Haeh wrote:
>> > Hi Dan,

>> >=20

>> > I do get different range patterns for the Flarm A&B antennae, which I

>h=
>ave mounted on both sides of my canopy.=20
>> >=20

>> > What I don't know is whether my Flarm is seeing a glider that's not

>see=
>ing me.=20
>> >=20

>> > But at least one of us knows about the other.

>>=20

>> Interesting! I will have to install a second antenna (I'm
grandfathered)

>=

>and have a go...
>
>It's worth having the two antennas even if the "B" antenna only receives.

>=

>That fills in gaps in your reception pattern. And as far as the FLARM

>rang=

>e report, that is ONLY using reception data - it has no way to know who

>can=

> receive your transmissions, since the protocol is a blind broadcast with

>n=
>o acknowledgment.
>
Not quite true. If you are in an area where the OGN network is active and
has tracked you, you can see how others see you.

URL is https://ktrax.kisstech.ch/flarm-liverange/

[Dan Marotta]

That's very interesting!

Having both A and B antennae on top of the glare shield in my Stemme, I
get poor results with gliders directly below me (carbon fuselage).  I'll
try this again afterI move the antennae to the canopy rail and see what
improvement I get.

--
Dan, 5J

[moshe....@gmail.com]

On Saturday, July 20, 2019 at 10:00:07 AM UTC-4, Tim Newport-Peace wrote:
> >
> Not quite true. If you are in an area where the OGN network is active and
> has tracked you, you can see how others see you.
>
> URL is https://ktrax.kisstech.ch/flarm-liverange/

I meant the range report the FLARM website offers, via analyzing your flight logs. Those capabilities of OGN are cool, but I didn't think about OGN since I am in the USA, where OGN is very sparse.

[moshe....@gmail.com]

On Saturday, July 20, 2019 at 10:36:32 AM UTC-4, Dan Marotta wrote:
> That's very interesting!
>
> Having both A and B antennae on top of the glare shield in my Stemme, I
> get poor results with gliders directly below me (carbon fuselage).  I'll
> try this again afterI move the antennae to the canopy rail and see what
> improvement I get.

Dan, the benefit of using two antennas is maximized if you separate them as much as possible. That's why I'd like to install the "B" antenna behind the pilot seat, to help reception from the rear. Of course in a carbon fuselage that may not be a viable option. Unless you have a glass-fiber turtledeck, which I gather some gliders do, although the top part of the tailcone would still be in the way.

[Dan Marotta]

The turtle deck on the Stemme is fiberglass but I already have two
antennae on top of the glare shield.  I'd like to put one on the bottom
of the aircraft.  An ideal location would be on the propeller dome, but
the transponder antenna is mounted on the bottom of that in the middle
fore and aft.  What's the minimum spacing required between a transponder
antenna and a flarm antenna?

Another possibility would be to install an antenna in the engine bay
right at the bottom.  I think the lower cowl is fiberglass, but I'd have
to check.

Since I trimmed the antenna cables to length when I installed them on
top of the glare shield, I'll have problems that may require buying new
antennae.  Bummer...

--
Dan, 5J

[moshe....@gmail.com]

On Saturday, July 20, 2019 at 9:37:25 PM UTC-4, Dan Marotta wrote:
> The turtle deck on the Stemme is fiberglass but I already have two
> antennae on top of the glare shield.  I'd like to put one on the bottom
> of the aircraft.  An ideal location would be on the propeller dome, but
> the transponder antenna is mounted on the bottom of that in the middle
> fore and aft.  What's the minimum spacing required between a transponder
> antenna and a flarm antenna?
>
> Another possibility would be to install an antenna in the engine bay
> right at the bottom.  I think the lower cowl is fiberglass, but I'd have
> to check.
>
> Since I trimmed the antenna cables to length when I installed them on
> top of the glare shield, I'll have problems that may require buying new
> antennae.  Bummer...

I'd keep all other antennas as far as possible from the transponder antenna, since it transmits (in short bursts) at about 200 watts.

Extra FLARM antennas are cheap here:
https://www.mouser.com/Passive-Components/Antennas/_/N-8w0fa?P=1yy3dsh&Keyword=ANT+916+MHW&FS=True

[kinsell]

Here's a note that says don't use small diameter coax like RG174 for
long runs, use something like RG58 or RG400 (pg 16)

https://flarm.com/wp-content/uploads/man/FTD-041-Application-Note-FLARM-Antenna-Installation.pdf

Wonder how many glider mfgs are doing quality installations when the
customer asks for multiple antennas in the tail? Probably not many.

[tow...@gmail.com]

Since it's apparently ok to install a transponder antenna under a carbon glider, which requires drilling a hole, why not drill a small hole and feed a cable through to an external flarm antenna?

[Dan Marotta]

I'm considering that, though access to the bottom can be a problem.

On 7/22/2019 7:48 AM, tow...@gmail.com wrote:
> Since it's apparently ok to install a transponder antenna under a carbon glider, which requires drilling a hole, why not drill a small hole and feed a cable through to an external flarm antenna?

--
Dan, 5J

[kinsell]

On 7/22/19 7:48 AM, tow...@gmail.com wrote:
> Since it's apparently ok to install a transponder antenna under a carbon glider, which requires drilling a hole, why not drill a small hole and feed a cable through to an external flarm antenna?
>

That's a fine solution, particularly for a B antenna on the belly. But
I think people are trying to be super cool and eliminate external
antennas on carbon ships by putting them all in a fiberglass tail.

[George Haeh]

Another possibility is putting the Trig remote box and PowerFLARM Core in the fin with possibly a LiFePO4 battery. Perhaps less coax to run, but the transponder harness would have a long way to run.

As for distance between Flarm and transponder antennae, you can check with Flarm and Trig.

[Dave Nadler]

> As for distance between Flarm and transponder antennae,
> you can check with Flarm and Trig.

Apparently I was not clear enough above.
Do NOT put both transponder antenna and a FLARM antenna in the vertical fin.

[George Haeh]

"Apparently I was not clear enough above.
Do NOT put both transponder antenna and a FLARM antenna in the vertical fin."

Could you share the reasons and data supporting this statement?

[uncl...@ix.netcom.com]

I'll give you 3 reasons not to put the PowerFLARM antenna in the vertical fin.
1- It is a very low power device and antenna losses matter.
2- The elevator push rod will do no good things for performance.
3- There is no reason to do so. There are many well functioning systems with the A antenna up front as suggested. The higher the better.
Reason for not putting the transponder antenna in the fin? The suppliers of the devices say best performance is on the bottom of the aircraft.

FWIW
UH

[Richard Pfiffner]

How about it won't work.

Richard

[moshe....@gmail.com]

All good points. But I think Dave emphasized the word "both". As in: you can put either one of those antennas in the fin, but not both. As he wrote in his first posting in this thread: "If you put the transponder antenna near the FLARM antenna (as in both in the fin), you will fry the FLARM receiver." The transponder transmits at about 200 watts!

FLARM A antenna in front is good, but where to put the B antenna, that's what I'm pondering. If the A antenna is in front of the pilot, I suspect there will be a gap in reception from the direction behind (and somewhat below) the pilot. It's not too hard in my case, given no carbon (and no transponder) in the glider, so even if the B antenna is mounted high (under the turtledeck) it should have a "view" of that direction. Aluminum control rods nearby won't help, but perhaps won't hurt too much.

Anybody know where I can get adhesive pads with small non-metallic rings attached? That would help with experimenting with antenna locations. There is one such in my glider holding some electrical cables tidy, but when searching for such on Amazon I got the strangest irrelevant search results.

[JS]

Today's analysis from 2 OGN receivers of my PowerFLARM with a single antenna, Craggy part number 500107, mounted to the glare shield.
Looks like about 270 degrees of 20km range better than 10dB.
Jim

https://www.dropbox.com/sh/nidqq8s4scwsadu/AADHDTyYsl1yy58HKIQg2dCta?dl=0

[k...@cni.net]

Actually, putting the Flarm antenna in the vertical stabilizer works well. Of course, how well I "see" another glider depends on their Flarm installation. For example, I "see" K4 and DZ consistently at 8-10 miles. DL and 4AF at not more than one mile. 5E and L6 at 4-5 miles.

The SZD 55-1 has a battery box at the base of the vertical stabilizer. I took the battery out, and put the Flarm in the battery box. The Flarm and ADS-B antenna are mounted in the gap between the rudder and the vertical fin. The Flarm antenna is located as high as possible but below the metal components of the horizontal stabilizer. The ADS-B antenna is located as low as possible, but above the mass balance weight. This gives a very short distance between the Flarm and the antennas. The trick was running the data cable forward to the Butterfly display.

The comm antenna is located in the vertical fin, the transponder antenna is bonded to the inside of the fuselage aft of the main gear.

P9

[stu8...@gmail.com]

> The trick was running the data cable forward to the Butterfly display.
>

I guess you're not going to tell us your trick?

[John McCullagh]

It is interesting how a thread diverges from the original question. I
posted this new thread because I had been talking to a former world
champion who has just taken delivery of a Ventus 3M. Schempp-Hirth put
three aerials in the fin: radio, transponder and PowerFlarm apparently
without problems, and they should know. Many of the replies in this thread
have been why this wouldn't work. I originally asked whether it was also
possible to put in an ADS-B aerial. I will be asking Schempps but I thought
I would ask around first.

At 06:38 23 July 2019, k...@cni.net wrote:
>Actually, putting the Flarm antenna in the vertical stabilizer works
well.

>=

> Of course, how well I "see" another glider depends on their Flarm

>installa=

>tion. For example, I "see" K4 and DZ consistently at 8-10 miles. DL and

>4A=
>F at not more than one mile. 5E and L6 at 4-5 miles.=20

>
>The SZD 55-1 has a battery box at the base of the vertical stabilizer. I

>t=

>ook the battery out, and put the Flarm in the battery box. The Flarm and

>A=

>DS-B antenna are mounted in the gap between the rudder and the vertical

>fin=
>.. The Flarm antenna is located as high as possible but below the metal
>com=

>ponents of the horizontal stabilizer. The ADS-B antenna is located as
low

>=

>as possible, but above the mass balance weight. This gives a very short

>di=

>stance between the Flarm and the antennas. The trick was running the
data

>=
>cable forward to the Butterfly display. =20

>
>The comm antenna is located in the vertical fin, the transponder antenna

>is=
> bonded to the inside of the fuselage aft of the main gear. =20
>
>P9
>

[jpg...@gmail.com]

On Tuesday, July 23, 2019 at 5:15:07 PM UTC+1, John McCullagh wrote:
> It is interesting how a thread diverges from the original question. I
> posted this new thread because I had been talking to a former world
> champion who has just taken delivery of a Ventus 3M. Schempp-Hirth put
> three aerials in the fin: radio, transponder and PowerFlarm apparently
> without problems, and they should know. Many of the replies in this thread
> have been why this wouldn't work. I originally asked whether it was also
> possible to put in an ADS-B aerial. I will be asking Schempps but I thought
> I would ask around first.
>

I have a V3M due soon with a transponder and 9070 + PF/ADSB/Dual antenna options. The primary Flarm BD12, transponder, and radio antennae are going in the fin . As John M says, SH report that the various fin antennae work OK together.

John Galloway