Antenna Location & GPS Input

[GeoffreyC]

Try 'hanging' the antenna 'upside down' by attaching it to the plastic pitot pipe to the left of its present location with a cable tie (doesn't need to be pulled too tight). That will move it far enough away from the front strut to be effectively 'out in the clear' and will give much less screening to the right. The antenna will work fine upside down and that location should not cause any problems this far forward in the pod.

Thanks for the idea Peter, I will try that.

I'm having to move the Aware slightly further backward as I've spent today fitting a Trig transponder to my flexwing and ended up with the Trig control box mounted under the base tube exactly where the Aware was.  Unfortunately the lead on the ADSB antenna that I shortened may now be too short and I'll have to buy a new one - grr.

Geoffrey

[Paul_Sengupta]

http://www.ebay.co.uk/itm/5dBi-5-dbi-Digital-Freeview-DVB-T-TV-HDTV-Booster-Portable-Digital-Antenna-Aeria/272109699956

[GeoffreyC]

Try 'hanging' the antenna 'upside down' by attaching it to the plastic pitot pipe to the left of its present location with a cable tie (doesn't need to be pulled too tight). That will move it far enough away from the front strut to be effectively 'out in the clear' and will give much less screening to the right. The antenna will work fine upside down and that location should not cause any problems this far forward in the pod.

I followed your suggestion and hung the P3I antenna off the pitot pipe.  I didn't need a cable tie, just looped the cable over the pitot pipe,  but found that the antenna hung down and was going to collide with the front forks.   So I affixed a sticky pad to the inside of the pod and cable tied the bottom end of the antenna to that pad.

See attached photo.

I could see another PAW equipped plane 4Km away, and they could pickup my PAW signal as well, so its working in this position,  but they did appear and disappear a couple of times as they flew away from me (their PAW is in a Skyranger on the dashboard) so maybe something is sub-optimal as I'd have expected more than 4Km range?

Geoffrey

[Bill Maxwell]

The crew in the other aircraft may well have their bodies attentuate the signal as they flew away from you, given that they or at least their upper torso and heads would then have been between the dash-mounted PAW and your receiving antenna?

[GeoffreyC]

The crew in the other aircraft may well have their bodies attentuate the signal as they flew away from you, given that they or at least their upper torso and heads would then have been between the dash-mounted PAW and your receiving antenna?

Yes fair comment, that could have been a factor.   I was interested in what others experience of range on the P3I is.  Seem to recall it is up to 30km straight line of sight, reduced as you say by obstructions.

Geoffrey

[Ian Melville]

I have seen so few P3i in flight, so difficult to judge what is the norm with my installation. With the antenna mounted internally on the rear cockpit bulkhead of a PA17 (fabric) I have bee seeing 20km, occasionally more. Worst case would be head on, but I don't recall any contacts in that direction.

[Robski]

I have a fabric aircraft question related to mounting the antennas inside the fabric skin.

What is the screening capability of such fabric(s)?

I am mainly considering how the low power of the P3I transmissions, and the miniscule signal strength of the GPS signals cope with Ceconite (and similar) fabric. Such coverings are applied and then UV protected by the application of the silver (aluminium powder mixed in the dope) coats that render the fabric completely opaque: NO light gets through properly applied Ceconite AT ALL.
I would guess that would definitely screen GPS transmissions, and could conceivably attenuate P3I transmissions.

I am sure that it has been mentioned before that certain (domestic and industrial) window coatings are metallic and quite effectively screen low power transmissions. This makes me wonder what methods the newer fabric coverings (Poly Fibre, Oratex etc) use for UV protection and how opaque to radio signals they are.

[exfirepro]

Rob,

My only personal experience with fabric covered aircraft and PAW has been with SkyRangers and similar, where I have noticed no negative effects attributable to the fabric. I would be interested to hear from other users though. Do you know which aircraft types use Ceconite coatings?

Regards

Peter

[Robski]

Do you know which aircraft types use Ceconite coatings?

AFAIK pretty well every older fabric covered type you can think of that isn't still using linen!

Evans VP1s (had one), Piper Cubs (and variants), Luscombes (where they have fabric wings), Stolp Starduster (I'm restoring one) and associated Acrodusters, Acrosports etc, Pitts Specials, Taylor Titch & Mono etc, Druine Turbulent,  Steen Skybolt, Jodels, Austers, Aviat Husky...

To name very few...

Ceconite is a DuPont trade name (I think - my partner in restoration crime does the fabric work). There are other , similar heat and/or dope shrunk coverings (including linen) but pretty well all of then use an aluminium powder in dope coating as UV protection for the fabric.

Ever wondered why airships and many WW1 era aircraft were silver?

[Paul_Sengupta]

I would suggest trying it and reporting back! 

As for windows, yes, the Pilkington K type glass seems to shield GPS signals quite well. When we were doing some 3G trials for a mobile operator, their office windows were coated in something metallic, and we had to open all the windows to let a mobile signal in, despite the base station being sited in their grounds with antennas pointed directly towards the building! 

[T67M]

The tests we've done recently on modern glass-fronted buildings suggest that the glass provides 30-40dB of isolation across a wide frequency band, certainly above 400MHz. 30dB means that only 0.1% of the signal gets through - 40sB means 0.01%.

[exfirepro]

That's pretty serious attenuation Mike!

It will be interesting to get some feedback from users of PAW in fabric covered aircraft. I must admit I wasn't aware of 'Ceconite' and had assumed fabric coverings to be low to no attenuation at the frequencies we are using (excepting the screening effect of metal tubing framework of course).

All feedback gratefully received.

Regards

Peter

[Ian Melville]

It's something I have been wondering about for a few weeks now, but uncertain of how to test scientifically. I fly a Ceconite covered rag and steel tube aircraft, but also restoring a Wooden aircraft with a lot of ply skins covered in Ceconite. I was looking to mount as many antennae in that aircraft out of sight.

I could get hold of a section of fabric that has been removed but lack a Field Strength Meter, so any test would be subjective. Could T67M run tests against a supplied fabric panel?

[Paul_Sengupta]

Glass itself has a low attenuation, around 1dB at 10GHz, depending on thickness. Adding the IR shielding metal film makes it a lot worse!

[tnowak]

I am no expert, but wouldn't the tiny particles of silver (something) in the Randolph dope be non-conductive? Or, if conductive, at least not touching adjacent "silver" particles to create a an overall screening effect?
Or, to put it another way, I wouldn't have thought the Randolph silver dope would act like a thin sheet of aluminium foil under the topcoat.
Perhaps someone can try measuring the resistance of the applied silver dope?
I may be able to do this in a month or so's time when I get to that stage of my fuselage recover project. Yes, I am using the traditional Ceconite process.
Tony