What would take out 2.4 and 5.8 at the same time?

Loopdreams · July 04, 2017, 01:23:01 PM

Intersecting ley lines. Try wandering around the spot with a twig.

Brucey · July 04, 2017, 02:51:18 PM

Have you done the sums to see if it's the fresnel zone your breaking? Just a thought as you said it doesn't happen if flying higher over the same spot

FPVSteve · July 04, 2017, 04:08:32 PM

Quote from: Brucey on July 04, 2017, 02:51:18 PM
Have you done the sums to see if it's the fresnel zone your breaking? Just a thought as you said it doesn't happen if flying higher over the same spot

I haven't, no - I did think it could be the close proximity of myself to the car, but it is just weird that it happens on 2 different frequencies at the same time - plus the 2.4 dropping so low to trigger a telemetry warning so close in I figured that it had to be some kind of local interference.

I'll sit a bit away next time and see if it still does it. I've sat inside the car before and flown out much further with no issues though so not sure.

Guess I'll never know really, just wondered if anyone had any theories about what it could be - I can fly through it as I say but yea.. I see it all the time at that point in space.

krikey · July 04, 2017, 04:28:09 PM

Here's my two additional penneth. The church (St. Oswalds) is out on a limb, down a long track from Luddington. From what I can make out, theres a farm/buildings on the corner or Garthorpe Road and Carr Lane. if you drew a line between those two buildings, that's almost where your plane would be at 250-400m from the road which you launch from.

Alternatively draw a line from the middle of Luddington through the church and its almost the same line. If the church has a Yagi/directional antenna and either of the other locations provides a WiFi signal across that land, it could affect your 2.4 and 5.8? As others have mentioned, try flying out to the North West and see if the same happens.

Edit for clarification: As the Church is out on a limb it may accept a WiFi signal from either Luddington or The building on the corner.

krikey · July 04, 2017, 04:46:36 PM

...and to add to my outlandish theory, there is a directional antenna on the top of the School at Luddington too, which seems to point between the houses and has a clear view of the church from what I can see.

https://www.google.co.uk/maps/@53.6432109,-0.7478646,3a,75y,275.09h,76.06t/data=!3m6!1e1!3m4!1shfIsdlDghOvVwtSWjAKHHg!2e0!7i13312!8i6656

FPVSteve · July 04, 2017, 05:02:55 PM

Good catch krikey, I've never noticed that antenna before (never really looked, I think I'll have a gander tonight while I walk the dog).

The school providing the church with WiFi would make sense actually because the parish council is tightly interwoven with the school / village hall here, and it would certainly explain why the signal is so localised if it is directional towards the East from the school to the church .. and into the field behind it.

Interestingly enough there's a point from my launch point where the signal gets terrible on my quad as well if I fly from it towards the church (which is 400m from my launch point). It would be in the same cone of signal.

So they must be using dual-band for it to affect both my frequencies. Would they transmit with a directional antenna though? Surely it would make more sense to have a high-gain receiver antenna on the church pointing towards the school, instead of the school transmitting to the church?

krikey · July 04, 2017, 05:12:28 PM

I guess it depends on what (if anything) the school are providing to the community and also how focussed the beam is. For the school to provide WiFi to the village, a 180 degree beam would be needed I think which might not fit in with my wild idea!

It's also possible that as I've found things that support such a theory, it's just as likely to be debunked by people who can identify what type of antenna is on the school roof (and indeed if it is an antenna), or even a quick call to the school to ask if they provide WiFi to the Church :)

Edit: if the school are indeed providing this, I suspect that it would need to be official as it would potentially affect other home Wifi, so maybe OFCOM would have records?

g4uvz · July 04, 2017, 06:09:04 PM

In the video we see drop outs into noise on 5.8GHz ..from a pure radio point of view this would indicate a reduced signal arriving at the ground station This could be due to:-
1 The on board battery masking the signal back to the ground station
2 The car getting in the way of the signal path
3 Fresnel Zone issues

The reduction of 2.4 GHz telemetry which is being transmitted from the airframe at a lower level than the 2.4GHz control signal could equally be explained by the above.

The wireless router explanation, I don't believe holds water, as this the router would have to be close to the ground station and the chances of 2.4 AND 5.8 being effected at the same time by an external source are extremely unlikely.

So I would suggest mounting the 5.8GHz antenna in the bottom of the plane where nothing can get in the way of a line of sight signal back to the ground station.
Similarly ensure that the telemetry antenna is similarly placed ..well away from other servo wiring etc

FPVSteve · July 04, 2017, 06:12:44 PM

No idea ... to be honest I would have thought that if it was an antenna it'd be higher up, but then again I've used inter-building IR/laser-links for networking before which are below gutter-level so nothing would surprise me.

I also can't see why the church would need wifi really .. it rarely opens and when it does it's for jumble sales, tea mornings etc.

I think I'll just fly and expect the deadzone.

FPVSteve · July 04, 2017, 06:15:48 PM

Quote from: g4uvz on July 04, 2017, 06:09:04 PM
In the video we see drop outs into noise on 5.8GHz ..from a pure radio point of view this would indicate a reduced signal arriving at the ground station This could be due to:-
1 The on board battery masking the signal back to the ground station
2 The car getting in the way of the signal path
3 Fresnel Zone issues

The reduction of 2.4 GHz telemetry which is being transmitted from the airframe at a lower level than the 2.4GHz control signal could equally be explained by the above.

The wireless router explanation, I don't believe holds water, as this the router would have to be close to the ground station and the chances of 2.4 AND 5.8 being effected at the same time by an external source are extremely unlikely.

So I would suggest mounting the 5.8GHz antenna in the bottom of the plane where nothing can get in the way of a line of sight signal back to the ground station.
Similarly ensure that the telemetry antenna is similarly placed ..well away from other servo wiring etc

Well, the VTXs are mounted on the wing (skywalker) and the underside of the fuselage (mini talon) away from any other components (especially the Skywalker)

The FrSky receivers I use are diversity ones, D8RII+ with the antennas in a V shape, plus I have a 5dBi antenna on my transmitter. They should definitely not only be reaching 300m before I get telemetry warnings ... but maybe that's because the onboard transmission is being blocked when the plane tries to send the RSSI back to me? It is only in that specific place and I have never failsafed - so maybe it can receive fine, but not transmit telemetry back to me due to the interference?

Does anyone know how many mw the FrSky D8RII+ transmits telemetry back at? Or am I mistaken in how the RSSI works?

Dillwhacker · July 04, 2017, 08:12:41 PM

I don't get this...
Are we suggesting that the WiFi is so strong that it disables the VTX on the plane as it passes over?
Stops it from transmitting?
How could that happen?

FPVSteve · July 04, 2017, 08:35:03 PM

Some WiFi routers use 5.8GHz so if it's a strong enough directional signal it could swamp the VTX if the plane is within the RF cone.

krikey · July 04, 2017, 09:26:31 PM

Quote from: Dillwhacker on July 04, 2017, 08:12:41 PM
I don't get this...
Are we suggesting that the WiFi is so strong that it disables the VTX on the plane as it passes over?
Stops it from transmitting?
How could that happen?

Presumably if a relatively low powered VTx transmitting on 5.8Ghz enters another cone of transmission also on 5.8Ghz but is much more powerful, would this not interfere with the VTxs own transmission? I'm thinking laymans terms here which might be very wrong, but if a small wake from a boat crosses a larger wake on the ocean, doesn't the small wake get corrupted/distorted by the time it exits the other side?

Dillwhacker · July 04, 2017, 10:52:15 PM

No, radio waves don't 'mix' like that. Broadcast radio FM signals don't corrupt each other.
If the goggles and the wifi are fixed, then the wifi signal into the goggles is fixed.
If the plane's signal is too weak to overcome the wifi interference at 400 metres, it shouldn't matter whether the plane is North or South , the planes signal strength will be the same.
And why is it OK further out?
Beats me...
(?)

English Turbines · July 05, 2017, 08:52:39 AM

It could be a WiFi link Steve, as I said, simply fly the same distance and height in the opposite direction to test the theory....Some of those (directional) WiFi routers use 5ghz in order to get the Bandwidth higher. The giveaway would be a similar directional receive antenna at the other end, so maybe drive over to the Church for a look to see if you can see any antennas and, where they are pointing?. These type of routers are very directional.

You were flying at 70mtrs, so what happens if you go a little higher?....It could just be the Freznel zone in both cases. As for the beeping FRSky TX Module you are using, try setting the Ducky at 90 degrees to the TX Module, that should make it work better for you. Remember, the telemetry downlink is not as powerful as the control uplink.

:vulture: