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Riggers
04-10-14, 13:55 PM
On the Trig TT21 thread, I mentioned mounting the transponder antenna on a 6" X 6" ground plane, halfway down the fuselage, on the underside, or just inside it:

11733

I've been advised this might not be the best idea, rendering the occupants vulnerable to toasting by the sideways trons, a la microwave. Better by far, my respected chum says, would be mount it under one of the seats, sticking down into the airflow, with a ~6" X 8" alloy ground plane to afford some protection. I can't be the first to mount such a device on a Nynja - where does everyone else stick it? (No rude answers, PLEASE!)

The one caveat I have is that my inspector will give me another sound thrashing, if I contravene BMAA doctrine, (HADS/TILS, etc), so I'd like just to get an idea of where I should be looking, (any pics of installations would be much appreciated).

There's no rush - any time before 14:00 today will do....

Phil (@ 13:55 today)

Paul Dewhurst
04-10-14, 17:57 PM
On the Trig TT21 thread, I mentioned mounting the transponder antenna on a 6" X 6" ground plane, halfway down the fuselage, on the underside, or just inside it:

11733

I've been advised this might not be the best idea, rendering the occupants vulnerable to toasting by the sideways trons, a la microwave. Better by far, my respected chum says, would be mount it under one of the seats, sticking down into the airflow, with a ~6" X 8" alloy ground plane to afford some protection. I can't be the first to mount such a device on a Nynja - where does everyone else stick it? (No rude answers, PLEASE!)

The one caveat I have is that my inspector will give me another sound thrashing, if I contravene BMAA doctrine, (HADS/TILS, etc), so I'd like just to get an idea of where I should be looking, (any pics of installations would be much appreciated).

There's no rush - any time before 14:00 today will do....

Phil (@ 13:55 today)

talkimg of which - I presume you are working with this http://www.bmaa.org/files/smm_104_4__transponders.pdf as part of your installation process? ( and the other SMM forms for radio etc)

meeting 4.8 might be tough with aerial under seat?

Paul

Riggers
04-10-14, 18:53 PM
talkimg of which - I presume you are working with this http://www.bmaa.org/files/smm_104_4__transponders.pdf as part of your installation process? ( and the other SMM forms for radio etc)

meeting 4.8 might be tough with aerial under seat?

Paul

Well, er, obviously. <nervous, involuntary cough>

Looks like it's 'fry, or don't fly', then.... :-)

Rick Moss
04-10-14, 21:29 PM
Yes, but Phil has a Trig, and manufacturers spec overrules.... and section 5.11 of the installation manual states:

 Where practical, plan the antenna location to keep the cable lengths as short as possible and avoid sharp bends in the cable to minimise the VSWR.

Paul Dewhurst
04-10-14, 22:22 PM
Yes, but Phil has a Trig, and manufacturers spec overrules.... and section 5.11 of the installation manual states:

 Where practical, plan the antenna location to keep the cable lengths as short as possible and avoid sharp bends in the cable to minimise the VSWR.

Thanks Rick, its useful to know that's the case with the Trig.

4.8 does state unless the manufacturer allows. - so its a case of reading all the documentation and the forms Phil!

for your inspector ( me in this instance!) when you present for final inspection he will need to tick it off against the requirements to submit the SMM forms with the build, so the builder should have done that themselves with any applicable notes, to show the inspector, so it all goes smoothly and there are no 'oh ****' bits that fail the inspection and have to be redone.

the SMM form also has a link to some additional information on radiation hazards - which also might influence your personal decision where the antenna would be best placed.....!

Paul

Riggers
04-10-14, 22:52 PM
Phew, thank goodness that's all cleared up, then.....

Think I found the Archbishop of Canterbury's explanation, of 'Salic Law', (the reason why the king of England might claim the French throne), in Laurence Olivier's 1944 wonderful film of Henry V, a little easier to follow!

Paul: I understand your caution, (much appreciated, on my gonads' behalf!), and will see if some compromise might be possible. To what does the BMAA '1 metre' rule apply? the Trig header unit, on the panel, or its remote processor box, on mine located on the floor, under the stick?


Any restriction on the size of the ground plane? If not, how about a sheet of aloominum foil, or speed tape, covering a major part of the forward fuselage skin?

Thanks to all for the dialogue.

Phil

Rick Moss
04-10-14, 22:57 PM
In the case of the Trig, the 1m rule doesn't apply as above. For clarity, the transponder is the gold coloured remote box; the small unit on the panel is purely a remote control for the transponder (although also includes the altitude encoder I believe). The microwave transmission from the antenna will not penetrate the ground plane, and given the modest length of the antenna, a surprisingly small ground plane will put the occupants in its shadow.

Riggers
05-10-14, 07:05 AM
Thanks, Rick.

Sorry if I'm not the sharpest pencil in box, when it comes to matters avionic...

Riggers
05-10-14, 10:32 AM
In case it's of interest, I've come across these photos of a transponder installation on a SkyRanger Classic or Swift: I'm not sure where I got them, since I've been accumulating intel to support my build for some time, but acknowledgements & thanks to whoever's responsible....
11737 11738 11735 11736

The installed position appears to be just aft of the undercarriage beam, abeam the two seats, so perhaps it's a Trig-based system, with its concessed installation. The ground plane appears riveted to an 'L' section, which shows two attachment points: I'll look at my u/c beam to see if there are correlating existing bolts to pick up. Paul: I'll obviously discuss with you, before I do anything surgical!

Another (dumb?) question: located beneath the seats will put the antenna between the undercarriage legs and wheels. Won't that upset propagation? Simplistically, if I'm 90 degrees to the monitoring station, will I still be visible?

Thanks, chaps, [not gender-specific!]

Phil

Rick Moss
05-10-14, 11:26 AM
Hi Phil; to my mind that ground plane looks a little over-engineered, as the reality is that from an rf perspective, tinfoil is an adequate material. Durability and ease of mounting means that I have always used .6 or .8mm aluminium. Given the fibreglass underside of your aircraft, I'd suggest the simply drilling a hole where you wish the antenna to be, and then assembling it with the ground plane between the fibreglass and the backnut of the antenna will be a perfectly adequate solution, possibly with a small spot of silicone on each corner to eliminate any possible vibration resonance from a single central mounting.

The pictures you show would not be my chosen location, only because there is a direct line from the antenna to the occupants without a ground plane in between.

The UC legs have never proven to cause reception problems for me (Skyranger classic, antenna beneath passenger seat), although in theory they possible could. The location shown above could potentially have the exact same issue, just at a different angle to the interrogating station. Short of mounting it on an undercarriage leg, I think this is unavoidable, but also unnoticeable.

Happy to be corrected on all the above.... Based ok experience.

Riggers
05-10-14, 17:24 PM
.... to my mind that ground plane looks a little over-engineered....


Rick,

Yes, it DOES have a satisfying 'Brunel' air about it, I suppose.

The thinnest material I have is 2mm aluminium, so I'll buy some thinner at B&Q tomorrow, (at ~25 per square micron, no doubt). I'll use it as you suggest, as both ground plane AND reinforcement for the fibreglass, with a splurge of sillycon, for acoustic attenuation. If mounted beneath the pax seat, as was your Classic's, the cable from the transponder should only be about 2' long:

11739

The ground plane sheet will come larger than the 6" X 8" we spoke of. Any functional problem, if I make it larger?

I'll run all the documentation past my inspector before fitting it, to make sure he's happy - better a stern talking to before the event, rather than a sound beating afterwards!

goldrush
05-10-14, 17:25 PM
Not disagreeing at all that tin foil is adequate, but I have found that cheapo "builders roofing moss stopper copper foil" is much easier to ensure a good connection to... i.e solder!... same for radio ground plane

Such as: (although 50mm is wider than the minimum required)

http://www.ebay.co.uk/itm/Copper-strip-per-metre-x50mm-roofing-moss-killer-fix-to-ridge-to-stop-moss-/120915487273?pt=LH_DefaultDomain_3&hash=item1c271fea29

Rick Moss
05-10-14, 18:30 PM
No problem at all with the ground plane being larger. The 6x8 size was decided upon as being the smallest size that would maximise performance. Larger will not offer any benefit beyond RF protection for anything it shields.

Riggers
05-10-14, 19:59 PM
....Larger will not offer any benefit beyond RF protection for anything it shields.

Thanks, Rick

That's all I'm looking for...

Terry Viner
05-10-14, 20:12 PM
Ive got my groundplane under my seat, just a small 6" piece cut to shape and sits between the poles held in by rubber mounted P clips.

Riggers
06-10-14, 05:32 AM
I've got my ground plane under my seat....

Hi Terry,

What's cooking? :D

But seriously, thanks for the feedback!

Phil

Terry Viner
06-10-14, 09:22 AM
Well known for my bacon butties.

Riggers
06-10-14, 09:53 AM
Well known for my bacon butties.

I heard that was 'bacon buttocks'....

:lettersrofl:

Riggers
10-10-14, 06:45 AM
I know that the distance between the Trig transponder and Trig radio boxes and their respective antennas should be minimised, to reduce losses, but what's the upper limit? - how much is too much? I'm currently trying to separate the antennas and their cable runs from each other's influence, and also from extraneous influences, like control cable runs. I've also got to prevent the crew from frying, and I understand the transponder antenna imposes a 500mm-diameter vertical 'no-go' column, above it. I'm somewhere around 3 m for each cable at the moment. :-(

What's a safe maximum length? Is there a rule of thumb, such as 'double the distance & quadruple the losses', or somesuch?

I could locate each unit near the antenna in the fuselage, but there might be CofG implications, among other issues, and in any case, I'd like to keep them warm n' safe with me, in the cabin.

bryannortje
10-10-14, 11:41 AM
Riggers - this is what i bought from LX Aviation and fitted on my Nynja in the centre of my lower Fuzz between nose wheel and main undercarriage (basically almost right below control stick). Easy to fit - just drill a hole, stick it down and fit the antenna - Job done

To be fair i did plan ahead and did this before fitting the fuselage bottom

Ground Plane - self adhesive copperhttp://www.microlightforum.com/images/mesh-anntena-s.jpg (javascript:OpenCentreWindow('mesh-antenna.htm');)With a diameter of 160mm this self adhesive copper sheet is pre drilled to take the blade antenna and is popular with the home installer for its ease of installation.
Price 22.50 excl VAT: 27.00 incl VAT Buy now! (http://ww10.aitsafe.com/cf/add.cfm?userid=C2231174&product=F1010 Ground Plane&price=27.00&return=www.lxavionics.co.uk/avionics-accessories.htm)
Order Code: F1010 - add 4.00 for UK delivery by post
Remember: Transponder antennas will not work properly without a ground plane!

Riggers
10-10-14, 16:33 PM
Riggers - this is what i bought from LX Aviation and fitted on my Nynja... i did plan ahead and did this before fitting the fuselage bottom!

Bryan: You're obviously one of those annoyingly-organised guys who thinks ahead & misses all the character-building escapades we 'born-adventurers' love so much: mostly, digging ourselves out of messes of our own making. :-( I'll bet you're even solvent at the end of each month, so you don't even get that frisson every fourth week!

Anyway, nice solution: I assume it's very thin copper, to keep the weight down? I'm interested to see it's round, to suit the blade antenna: I have the spigot-type antenna, & I've read somewhere that I should ONLY use a rectangular ground plane, which I've fabricated from 0.5 mm alloy sheet. It ticks so many boxes, (crew protection, etc), & sits sooooo well, just aft of the flap lever, that I can't currently imagine it anywhere else. It even picks up an existing hole:
11743

Although it's 1.3 m from the transponder, in a straight line, I can't do that, because of the adjacent steel control cables, which I'm advised could cause problems to the signal. The result is that I'll have to go around the houses with the cable, lengthening it & thus reducing transmitted signal strength.

Riggers
11-10-14, 08:22 AM
OK, if the cable length question's too difficult, has anyone any experience of using foil or tape as a ground plane, for a com antenna? The Trig installation manual for the TY91 radio suggests a ground plane of ONE METRE SQUARE: seems an awful lot to me, but hell, what do I know?. There's not that much space in the Nynja fuselage for that, but getting even close will require a substantial piece of alloy sheet, unless there's a tape I could use.

Dumb question (4 or 5, I've lost track): if I used an adhesive wide aluminium foil, for example, the shiny (ie reflective) side would face inwards, away from the antenna, although it would still constitute a thin sheet of aluminium, or copper. What I want is a reflector to the antenna. Are the reflective characteristics a function of the material, (aluminium foil), or the surface finish? If the former, would it work?

There appear to be some possible options out there:

http://www.ebay.co.uk/itm/EMI-Shielding-Self-Adhesive-Copper-Foil-Tape-SHEET-1m-LONG-x-300mm-wide-/271458864186?pt=UK_Sound_Vision_Other&hash=item3f34358c3a

http://www.tapes-direct.co.uk/index.php?main_page=product_info&products_id=1094

http://www.tapes-direct.co.uk/index.php?main_page=product_info&cPath=215_217&products_id=1126

Rick Moss
11-10-14, 10:06 AM
I've had good results with the com antenna grounded to the airframe. A good alternative is to make an effective dipole antenna from a quarter wave whip by simply taking a piece of wire the same length as the antenna whip (68cm?) and attaching it to the antenna ground, and orientating it directly downwards in line with the whip. If your com antenna is mounted on the end of one of the tubes behind the doors at the flap root, that's easily achieved.

Riggers
11-10-14, 10:36 AM
Thanks again, Rick.

Again, according to the Trig manual, I also have to achieve 1 m lateral displacement from the transponder antenna.

Here, I'm losing the will to live, at the moment... :-(

bryannortje
13-10-14, 13:53 PM
1175011749

Riggers - here are some photo's of my Antennae mounting. I have mounted on the rear upper fuzz just behind rear windows. Well away from my Transponder antennae. The ground plane i made up of a very thin sticky copper tape of 50mm width. stuck on the inside of each half of the fuzz mouldings. The copper tape adhesive has conductivity in it so when you stick one piece over the other then you still get continuity. The photo's are viewed from the inside looking up and backwards..... I have Installed the FUNKE OLED Radio and Transponder and have fantastic radio comm's and great transponder signals. I have no intereference and get 5's on any radio check and have not had any requests from any ground station to repeat messages due to poor signal quality or backround noises.

Regarding the transponder ground plane - yes very thin copper, but not as thin as the copper tape. I dont think it has to be square anyway. If it did then they would supply a square groundplane in the first instance. I used some of the copper tape to around the outside just to help stop the edges from lifting. I'll see if i can get a photo of the transponder mounting from inside and out for you to see - even though you have mounted yours already...

Riggers
13-10-14, 14:41 PM
Bryan: thanks very much for the feedback: I'll pore over it tonight.

I haven't fitted anything yet: after a frustrating weekend, I thought I'd better lie down, in a darkened room....

bryannortje
13-10-14, 16:55 PM
Hey Riggers

where are you based as perhaps we could meet up and i could help with some of your dilema's. we flew into Cromer yesterday....

I have some of the copper tape left which would solve ALL your antennae groundplane issues

Riggers
13-10-14, 17:52 PM
Hey Riggers

.... we flew into Cromer yesterday....



Hey, Bryan!

You flew into Cromer?

That's tragic: I'm about 15 mins away, in Central Norfolk, and depending where you came from, you may well have overflown us... Where are you?

i'd like to see your installation & generally chew the fat about the subject - I don't have much of a clue.

Riggers
14-10-14, 17:33 PM
....I have some of the copper tape left which would solve ALL your antennae groundplane issues


Bryan,

how much copper tape have you got left over - enough for me to do all of mine? If so, maybe we could come to some sort of 'arrangement'. If not, where did you buy it what do I ask for?

Phil

Russ_H
14-10-14, 18:44 PM
Slug Barrier Tape (apparently a galvanic reaction between their slime and the copper gives the little blighters a shock)....I get it at my local bits and bobs shop, but I think B&Q sell it

Riggers
17-10-14, 09:10 AM
Slug Barrier Tape ... I think B&Q sell it

Thanks, Russ. I tried the B&Q at Witney, but they didn't stock it. However, I DID find it on Ebay.

In the mean time, I paid a humbling visit to Bryan's airfield yesterday and drooled over G-TORO. The finish and attention to subtle detail on it is quite remarkable. He said he might drop in on me, en route to Cromer: think I'll have to misplace my hangar key, that day...

Coming away from Turweston quite depressed, Bryan provided some consolation by donating his leftover roll of the magic tape - THANKS, BRYAN; look forward to seeing you in Norfolk, soon.

Phil

dave nixon
17-10-14, 18:41 PM
Phil you said Bryan's attention to detail ,I think anyone buying one of you're builds would be getting a very well built plane

Riggers
17-10-14, 20:22 PM
Oh, David, tut, tut, TUT!

Your faith, whilst touching, is misplaced <severe blush>: just ask my inspector. Er, on second thoughts, please don't!

Were he free to speak, doubtless he'd tell you that I'm a fumbling oaf, who TALKS a good build, but can't actually achieve it. Fortunately, I pay him JUST enough to keep schtum.

Now where was I.... oh, yes: "Now, when I worked on Lightnings...."

PS: I'd be REALLY grateful if you could keep all this under your hat: I mean, if it ever got out...

Riggers
26-10-14, 18:54 PM
Decision time: I've fitted the radio antenna midway down the fuselage top:

11781
Inside the skin is a bracket which attaches to frame 39A and also reinforces the skin, so that the fibreglass isn't loaded directly.

The transponder's gone just aft of the flap lever, on the lower surface, achieving the 1m horizontal separation of the antennae:

11782

Inside, Bryan's miracle tape completes the ground plane:

11783

Of course, I always thought it would be easy.....

dave nixon
26-10-14, 19:08 PM
So Phil is the end in sight,keen to see her in the air

Riggers
26-10-14, 19:15 PM
Hi Dave,

Don't get your hopes up: latest estimate is 2016: however, that might slip... :-(

dave nixon
26-10-14, 19:19 PM
The suspense is killing me,I best come over to stay for a bit

Riggers
27-10-14, 09:11 AM
The suspense is killing me,I best come over to stay for a bit

Yes: that would be really useful, especially if you could bring a few tools, Oh, and a large wodge of cash!

dave nixon
27-10-14, 09:28 AM
Like this Phil ,I use it as a coffee table at mo11785

Riggers
27-10-14, 09:48 AM
Like this Phil ,I use it as a coffee table at mo11785

No, no, not THAT much: why, you could buy a new Rotax ignition unit for that much.

Well, ALMOST.

Riggers
31-10-14, 18:50 PM
I spent a disorienting afternoon on my back in the rear fuselage, creating the ground plane for the radio antenna:

11812

That done, I plotted the cable routes for both antennas, using strimmer cable:

11813 11814 11815 11816 11817

The slug tape idea is BRILLIANT - thanks again Bryan!

Tomorrow's task is to mock up the loom connecting the Radio & Transponder boxes to their controllers and the Garmin GPS, then the ancilliaries. I can then bunch the strimmer cables & label each one with its specification, including cable type & end connector, with orientation. So bunched, when it's removed, I can get the dimensions & even give it to the 'Loomerer' to 'make it so'. [Think Jean Luc Picard in Star Trek].

If only Scotty was around to factor in some dilithium crystals... <sigh>

Sounds good in theory, anyway!

VinceG
01-11-14, 01:20 AM
Any idea why this thread was closed?

Terry Viner
01-11-14, 11:02 AM
I didnt think it was closed Vince

Riggers
01-11-14, 11:16 AM
I think it was, Terry.

I submitted the piece about the antennae wiring, and maybe I screwed it, so that it closed, saving the text, but preventing the pictures from working.

"My stuff is so important to everyone, I thought I'd repeat it on the electrics thread". <large portion of tongue in cheek, there>


Phil
Radios R NOT us

dave nixon
01-11-14, 12:01 PM
It wasn't you Phil I tried and it said thread closed ?o

Riggers
01-11-14, 13:02 PM
Dave: par for the course for me: ANYTHING to do with radio goes TU for me.

I'm a one-man Faraday cage...