PilotAware
British Forum => General Discussion => Topic started by: stephenmelody on October 25, 2015, 06:05:27 pm
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Bryannortje and I went out to do some testing today. Mixed bag of results, inbound to Turweston I could only see him whilst in the Circuit (his device on the ground). In the air, we had about 4 miles between us, but this is a bit unverified as at one point Bryan seemed to stop moving on mine, and I stopped moving on his - although I was able to see changing speeds and altitudes of his output, it was stuck on the map.
Aside that, we did notice that after a while, instead of showing the ICAO code, we both started showing our registrations on Skydemon. Neither of us were transmitting ADS-B, only Mode S transponders.
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Hi Stephen
This is cool isnt it, but purely by accident.
PAW stores a single record of information indexed by the ICAO code.
So there is data received from PAW and your mode S, the mode S supplies the flight id,
PAW supplies positional info.
When PAW looks at the record, if it has a flight id, that is used, else the ICAO is used.
Thx
Lee
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Hi all fellow PAWs users.
Yes had a good bit of flying today with Steve. I would point out that while PAW is stationary the hex code is shown and in our cases today they both changed to our Reg numbers once we were moving.
Mixed bag on range and interesting that at some times i was close to Steve in flight and the A/C icon was not red. I suspect that only if we on an actual collision heading it goes red.
During the flight from EGBT to Damyns Hall, Steve asked me to shoot ahead so we could see how far in line of sight he we would see each other. I agree that we saw around 4nm before it appeared he was literally in a hover and he said the same for me.
It is without any doubt in my mind that the mounting position of the current PAWS units is critical and this is compounded with metallic aircraft. I'm fortunate that my Europa is all plastic so others are seeing me long before i see them. ;D Would be nice to do some air to air with another europa to see what sort of range we could get. I will post an image of my PAWS install on a following post
Cheers
Bryan
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Hi Lee, if you keep making accidental features like this, PAW has a great future!! ;D ;D
Following on from Bryan's report, something went funny part way through the flight when I appeared to overtake his stationary aircraft, even though he was pulling away from me in front. Positioning is very important, I had it on top of the coaming on it's side, might be better if the aerial was vertical rather than horizontal - thoughts?
Whilst Bryan was within visual range behind I could see him and the SD alarm wouldn't stop going off, his trace was consistently red, which is good, but bloody annoying if you're flying in formation!!
here's a link to my GPS track, something went very funny around Goff's Oak, which is where we both became static on each other's display. Not sure who's device stopped working as expected but it was very strange. Both of us appeared to be moving on track as expected on our respective SDs, but both of us had stopped moving on the other device (I hope that makes sense). Clicking on Bryan's aircraft on SD would show track heading and speed / altitude, but just not moving on the map.
It's only when I looked at the log I saw the issue. We flew direct so I don't know why it thought I was overhead Harlow, as we definitely didn't overfly that area. I rebooted my device once we realised there was an issue, and I only picked Bryan back up during my flare, even though I could visually see him in the circuit ahead of me.
https://www.logbook.aero/flight/4306jq789a
Would be good to get up and test again with more PAW users!
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Photo of my installation in my Europa.
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After a bit of detective work recently I noticed our Funkwerk Mode S transponder :
a) Transmits the ADS-B records just with no position info (but inc the flight ID (aka Reg) even with no ADS-B out connection, just ordinary mode S. These are picked up by PAW.
b) Does the above even if in STBY mode (which seems to just standby the squawk code emission.
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Having the aerial vertical is essential! Most of the signal goes out in a very flat donut shape with the aerial going through the hole. You want that donut to be horizontal with the hole facing up/down, so the aerial MUST be vertical to get a decent range. The difference will be 10:1 or more.
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I've got the stubby aerial, which means it's difficult to achieve on the coaming, as I can't put the PAW unit completely vertical.
Would something like this work??
http://www.ebay.co.uk/itm/RIGHT-ANGLE-SMA-MALE-TO-SMA-FEMALE-ADAPTOR-CONNECTOR-90-DEGREE-GOLD-LOW-STATIC-/191009295666?hash=item2c790a8d32:g:uzkAAMXQlgtStDf5
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Hi Stephen, can you post a picture of your antenna ?
Im not sure what you are referring to as the 'stubby' antenna.
The antenna must be tuned for 868mhz which means an 8.2cm antenna length for 1/4 wave monopole
Thx
Lee
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https://www.wirelessthings.net/868-915-mhz-small-rubber-duck-antenna
This one.
Because it's got no bend in it, I can't have it vertical.
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https://www.wirelessthings.net/868-915-mhz-small-rubber-duck-antenna
This one.
Because it's got no bend in it, I can't have it vertical.
Gotcha, OK so as mentioned in an earlier post, having it horizontal is not a good plan.
Sounds like the best plan is the 90degree male/female connector.
I am not sure what kind of aerial this is, but I am guessing because it is so short, it is a coiled spring.
not sure of the performance issues with that type of antenna
Thx
Lee
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I'm going to set them up one night this week and test the RSSI (or whatever it is called) with the two different aerial types in master/slave mode.
So considering mine was horizontal and Bryan's was vertical and we got 4nm, that's not too bad then!!
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Would a short cable run between the PA unit and the aerial cause any serious drop in signal strength do you think?
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Or turn the PAW through 90 degrees ;D ;D
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I still wouldn't be able to get it on the coaming due to the slant of the windscreen. I've ordered 2 right angle adapters, I'll get them set up at home and see if there's any loss in using them.
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How about trying the F***M dipole antennas..... They are already tuned and ready to go. You could stick them to the window with a small suction cup. Here is the link, they have both the ADS-B and the 868 Mhz. Disadvantage is the price >:(
http://www.lxavionics.co.uk/collision-warning-systems.htm
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After a bit of detective work recently I noticed our Funkwerk Mode S transponder :
a) Transmits the ADS-B records just with no position info (but inc the flight ID (aka Reg) even with no ADS-B out connection, just ordinary mode S. These are picked up by PAW.
So, why not set your transponder to transmit Extended Squitter and feed a GPS signal? You'll show up with the big boys.
b) Does the above even if in STBY mode (which seems to just standby the squawk code emission.
I think that's an issue with SW version 4.5 or 4.7. You may want to check the service bulletins.
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That's the plan - early days
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Would a short cable run between the PA unit and the aerial cause any serious drop in signal strength do you think?
Not much, but don't see much evidence that testers are using ground planes, which are an essential part of the antenna system. With a remote antenna it would be more important.
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Would a short cable run between the PA unit and the aerial cause any serious drop in signal strength do you think?
Not much, but don't see much evidence that testers are using ground planes, which are an essential part of the antenna system. With a remote antenna it would be more important.
Ground plates for which antenna? I understand it'll help the ADS-B side (but that's not a problem, airborne I can see planes up and down the whole country), would it help the ARF?
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Yes, but there are buts..
I am no radio expert, but did some experimental work with UHF antenna 35 years ago at Tec colledge. The reality is we need a 360 degree globe around our aircraft, which will be difficult to achieve, esp with only one antenna.
Assuming no blanking by aircraft structure. A vertical dipole would be the best option, at the expense of blind spots above and below us.
A whip antenna is in fact half a dipole, and requires a ground plane to make up the other half. There is a high risk that the antenna is not matched to the feed, and will in simple turns sap power from the signal, and possibly cause the TX section to overheat. Both can reduce range.
Ground planes will shape the signal. A horizontal flat plate will deflect the horizontal donut upwards, making you invisible to any RX below the plate. Using arms at 45degrees down improves that, but is still less than ideal.
A dipole in as clear air as possible or two whips, one above and one inverted below the aircraft would give the best coverage. Neither solution would be 'mobile'.
Sorry got to go to work now :-\
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I still wouldn't be able to get it on the coaming due to the slant of the windscreen. I've ordered 2 right angle adapters, I'll get them set up at home and see if there's any loss in using them.
I have the same rubber duck and a right angle connector, and the TX at least is good, the_top_pilot picked me up at > 5nm, although I received nothing. I also aim to test against the supplied big antenna, when time permits.
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I have now tested the WirelessThings short 868 MHz rubber duck against the kit antenna supplied with the ARF. The executive summary is that it is about 12 db down, so it's going in the bin. Detail :-
Master, end fed kit antenna. Slave pigtail fed short rubber duck. Master/slave test 30' apart in the open.
Slave RSSI -034 or -035, Master RSSI -033
Changed slave from small to kit antenna :-
Slave RSSI -023 or -024, Master RSSI -020
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Are the RSSI figure Decibels? I would be surprised if they were.