Primarily for general aviation discussion, but other aviation topics are also welcome.
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User avatar
By lobstaboy
#1845928
For reception it is that simple. Any antenna design, whatever its shape or material, that's 'short' in wavelength terms will not hoover up as much signal as a full size one.
Fancy design will enable it to work well enough over a broad frequency range and fit inside a small box without compromising the transmitter, sure, but that's not what I was talking about.
Of course the sophistication of the electronics is important too, but if there's no signal for it to work with then that's irrelevant.

My point isn't sufficient to claim an overall performance advantage one way or the other, but coupled with @reubeno 's observations I think it's interesting.
Actually I think it all boils down to whether or not philosophically you'd rather see other people most effectively, or have others see you well. Seems to me PAW is good at the first.
gaznav liked this
By Straight Level
#1845937
gaznav wrote:@lobstaboy

The antennae in SkyEcho are much more complex than the simple end-fed monopole PAW antenna for ADS-B (the shorter one of the 2) - hence the SkyEcho can fit their’s inside the small case. They use a meander line inverted F design from what I can see inside my SkyEcho:

So it may not be quite as cut and dry as you describe :thumleft:


An interesting point of the SE2 design is where the batteries have been positioned.
You can't see from the photo but the two batteries are placed on the rear of and are almost the full length of the PCB.
Li-Ion batteries have a steel case and therefore must (?) block a significant azimuthal arc affecting TX and RX performance in that arc.

Something like :-
@gaznav could you take a photo of the other side showing the relative position of the batteries and the antennas?
It would be very interesting to see the antenna radiation plot of this setup.

Image
gaznav liked this
By Crash one
#1845961
So SE2 performance is compromised in favour of a compact unit, onboard battery, no sticky out bits.
Or is that stating the bleeding obvious?
User avatar
By Cub
FLYER Club Member  FLYER Club Member
#1845962
Crash one wrote:So SE2 performance is compromised in favour of a compact unit, onboard battery, no sticky out bits.
Or is that stating the bleeding obvious?


I don’t believe the performance is compromised at all. The performance is based upon a requirement for short range air/air detection and conspicuity in accordance with a technical specification detailed in CAP 1391. The product achieves this. Surely it would only be ‘compromised’ if it didn’t achieve the requirement?
By Crash one
#1845964
If it makes you feel better, replace compromised with reduced.
Whatever the “spec” was that was indeed met, PAW seems to have exceeded it by more than SE2.
In fact I didn’t suggest that the requirement was compromised, just the actual performance.
User avatar
By Dave W
FLYER Club Member  FLYER Club Member
#1845965
Everything in engineering is a compromise; the question really should be "Does it do the job?"

And SE2 does the job.

Could it be done better? Yes, of course - but not at the same price point and level of convenience.
Flyin'Dutch', Miscellaneous, ls8pilot and 3 others liked this
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By Flyin'Dutch'
FLYER Club Member  FLYER Club Member
#1845974
Some of those praising PAW in the last few posts seem to have missed this snippet:

I had planned to try SkyEcho and PilotAware together on two seperate devices last weekend, but unfortunately when I got the Rosetta out of the bag, the 869.5MHz antenna had broken off from the SMA connector. It was quite a busy flight, so it would have been a good test.


:roll:

The PAW we have in one of our aeroplanes has been out of action for 6 months as the power plug receptacle has broken.
gaznav liked this
By Crash one
#1845981
Ok you can break PAW more easily!
Pardon me for having an opinion!
User avatar
By lobstaboy
#1845993
Miscellaneous wrote:
Crash one wrote:Whatever the “spec” was that was indeed met, PAW seems to have exceeded it by more than SE2.

Really, with two external aerials and no internal power supply? You don't think that's also a compromise (by design)? :?


Yes of course it's a compromise.
Horses for courses. SE2 is better as a carry on device that lives in your flight bag because it has internal batteries and no sticky out bits. PAW performs better (maybe) because of its sticky out antennas and is better permanently mounted in the aircraft.
Hand held radios have sticky out antennas I notice - there must be a reason for that, no?
User avatar
By Miscellaneous
#1845997
@lobstaboy unlike @Crash one I am not criticising either product for their designed in compromises and highlighting the perceived 'costs' of those compromises. :wink: I am merely stating those compromises. Fact is compromises are not the same for everyone. :thumright:

Everything is compromise and on reflection I think as an engineer (?) C1 knows that. Which makes his attack on the SE2 nothing other than another attempt at discrediting it. :(
User avatar
By lobstaboy
#1845998
Cub wrote:
Crash one wrote:So SE2 performance is compromised in favour of a compact unit, onboard battery, no sticky out bits.
Or is that stating the bleeding obvious?


I don’t believe the performance is compromised at all. The performance is based upon a requirement for short range air/air detection and conspicuity in accordance with a technical specification detailed in CAP 1391. The product achieves this. Surely it would only be ‘compromised’ if it didn’t achieve the requirement?


I can't find a performance requirement in CAP1391. Can you tell me where it is please?
(I'm being serious - I really don't think there is one!)

Edit to add: ftaod I mean a statement along the lines of "the device, when mounted in the aircraft according to the manufacturer's instructions, shall be capable of receiving and decoding an adsb signal from a similarly equipped aircraft at a range of Xkms."
In other words something that defines how well the device needs to work in the real world.
I speak as an engineer.
terryws liked this
By Crash one
#1846044
So we’ve stirred up the bees nest then.
First @Miscellaneous Where did I criticise SE2?
I said PAW exceeded the spec, and as an engineer I’ve built things to a spec, to do something specific.
Sometimes one design does it better than another.
We used to work on the principle.
You can have it better, quicker or cheaper, pick any two.
Bearing in mind that, I believe? PAW was on the market before SE2, so as a design spec, PAW was then the current design spec, or standard. ADSB was not yet flavour of the month which it seems to have become since.
Also if the “fag packet” design is so important why are several people saying they would like an external antenna socket?
PAW Rosetta is exactly that, unscrew two antennae and drop it in the shirt pocket!
User avatar
By Cub
FLYER Club Member  FLYER Club Member
#1846050
lobstaboy wrote:
Cub wrote:
Crash one wrote:So SE2 performance is compromised in favour of a compact unit, onboard battery, no sticky out bits.
Or is that stating the bleeding obvious?


I don’t believe the performance is compromised at all. The performance is based upon a requirement for short range air/air detection and conspicuity in accordance with a technical specification detailed in CAP 1391. The product achieves this. Surely it would only be ‘compromised’ if it didn’t achieve the requirement?


I can't find a performance requirement in CAP1391. Can you tell me where it is please?
(I'm being serious - I really don't think there is one!)

Edit to add: ftaod I mean a statement along the lines of "the device, when mounted in the aircraft according to the manufacturer's instructions, shall be capable of receiving and decoding an adsb signal from a similarly equipped aircraft at a range of Xkms."
In other words something that defines how well the device needs to work in the real world.
I speak as an engineer.


I don’t believe I said that a performance requirement was mentioned in CAP 1391 but rather that the device was manufactured in accordance to the technical specification detailed in the CAP.
User avatar
By lobstaboy
#1846056
Cub wrote:
Crash one wrote:So SE2 performance is compromised in favour of a compact unit, onboard battery, no sticky out bits.
Or is that stating the bleeding obvious?


I don’t believe the performance is compromised at all. The performance is based upon a requirement for short range air/air detection and conspicuity in accordance with a technical specification detailed in CAP 1391. The product achieves this. Surely it would only be ‘compromised’ if it didn’t achieve the requirement?


That is what you said @Cub in response to @Crash one saying the performance of SE2 is a compromise to allow it to fit in a small box with internal power.
"The performance is based on a requirement... ...in CAP1391". But there is no performance requirement in CAP1391 - lots of other technical requirements, yes.
So clearly you agree that it is perfectly possible for PAW to do what it does better than SE2, in a performance sense.

I am not critical of SE2 at all. It meets a requirement for EC and is very convenient. It's designers have done a good job. But they chose to make different compromises to the designers of PAW.
And, as pointed out before, we have no test data on either in terms of their performance. I totally discount the vector diagrams and the anecdotal review of the Flyer article - they just aren't technically sound.
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