Atom Grid Power via Ethernet / Antenna interference / Antenna Selection

[Kurt37]

Hi there,

Sorry if I am opening up a thready which already exists. But I couldn't find an appropriate answer.

Because of various restrictions I am bound to use power via Ethernet. Which cable/make can you recommend without suffering lowvoltage?
Kind regards
Patrick

[PaulSS]

I have a ‘flat’ CAT 6 cable to my ATOM station. I can’t remember the make but it was quite generic and is 15m long. The Pi seems happy (no brown outs) so I don’t think that distance is a problem.

[exfirepro]

Hi Patrick,

What sort of distance are you talking about? Are you running the cable mainly outside or inside?

As it happens I spent most of yesterday researching POE for another ATOM station owner. As far as I can determine, most POE systems (running around 48 volts) seem to be good for up to about 100 metres through 'normal' CAT 5 or CAT 6 cable. I was looking in particular at the likes of the TP-LINK TL-PoE150S PoE Injector with this splitter...  https://www.amazon.co.uk/DSLRKIT-Active-Splitter-Ethernet-Raspberry/dp/B01H37XQP8  which is already configured for use with the Raspberry Pi, but if in doubt look for ones specifically marked as good at this range (or enquire of the buyer before ordering).

If the cable is predominantly outside, I would look for CAT 5E or CAT 6 cable specifically marketed as being for outdoor use (or direct burial).

Hope this helps

Best Regards

Peter

[steveu]

If the cable is predominantly outside, I would look for CAT 5E or CAT 6 cable specifically marketed as being for outdoor use (or direct burial).

I've used this for a security camera:

https://www.amazon.co.uk/gp/product/B009U810UW/

[Kurt37]

Thanks. We are talking about max 30m, I bought the mentioned injector and splitter and test run was good. Is there anither way to test for undervoltage than looking on the remote access data reports page?

And one other question: the station will be on the same mast as a radio frequency antenna. The antennas will be approx 50cm away from the antennas, same height  Will that matter?

Kind regards,
Patrick

[exfirepro]

Hi Patrick,

Most POE injectors seem to quote a feed distance of up to 100m - so voltage should be fine at 30m.

Not sure if there’s an easier way to check for throttling on the ATOM, except just to watch the red Power LED. We’d need to ask Lee.

When you say ‘the station will be on the same mast as a radio frequency antenna’, do you mean a VHF Comms antenna on the aviation band? Although it’s never a good idea to run two systems that close, it’s pretty much what I’m forced to do in my flexwing and I seem to get away with it, so you should too - as long as the RF transmitter isn’t UHF or high power. Do you know the frequency and (approximate) transmit power?

Alternatively, you could try mounting the ATOM antennas a bit lower down on the mast, which should help.

Best Regards

Peter

[Kurt37]

Affirm a VHF antenna, frequency is 131.300. I unfortunately don't know the power.

Kind regards
Patrick

[exfirepro]

Hi Patrick,

In that case, it 'should' be OK. It's very unlikely that the PilotAware antennas will have any effect on the VHF one (unless you mount them right alongside it, when physical blocking could be an issue), but I would advise spacing the antennas as far apart as possible - perhaps by using a cross bar to mount them away from the VHF antenna, or mounting them off the pole in a 'T' or 'Y' format.

I use this type of mount from Screwfix https://www.screwfix.com/p/labgear-l-cranked-aerial-mast-535mm/21470 with the mounting bracket fitted onto the end of the longer section. This gives a good extended 'L' mount. (Not sure if Screwfix trade in Germany, but you will be able to find something similar). If you then carefully cut / file an oval hole for the coax to exit near the mast end of the tube (not too big or you will weaken the tube and carefully smooth the edges), you can slip the coax and antenna connector down inside the tube (the bottom antenna mount is a good fit into the Labgear tube, but it's worth sealing it with a wipe of silicone) and attach it using a good quality 25mm stainless steel screw clamp like these... ( https://www.amazon.co.uk/gp/product/B06XFJRHTL ) overlapping the joint. Once tightened carefully, this provides a rock-solid fix.

You can then fit the antennas to the main pole by 'rounding' the wall mounting plates to better fit the pole and attaching them using two large stainless steel hose clamps round the pole - one above and one below the tubes. This allows you to fit all 3 ATOM antennas together in a 'Y' layout using 2 clamps, though if concerned about stability I'm sure you can come up with an alternative fixing method.

If you have to make a choice on antenna positioning, prioritise keeping the P3i and Flarm antennas apart - the 1090 one isn't critical.

Let us know how it all goes.

Best Regards

Peter

[Kurt37]

Thanks a lot, will report when job done.


One more question:

I bought a Flarm ogn antenna, actually I bought two.
https://h5.de.aliexpress.com/item/32772798538.html

I will it use a Flarm antenna, but I was also thinking to use it as a PAW antenna. Would that make sense? Is there any benefit compared to the original PAW antenna?

Kind regards,

Patrick

[exfirepro]

Hi Patrick,

It might well ‘work’ for P3i, but I can see 3 potential issues:-

First, you’d need to check that it’s a good match RF wise at the slightly different frequency (I would guess probably OK but you need to check the antenna specification or use an SWR meter designed for use on the correct 869.525 MHz frequency.

Second, some of the high-gain Chinese antennas are designed specifically for receive, and (IIRC) present a short circuit to a transmitted signal. (I would need to check this point).

Third, I don’t know whether the rules in Germany are any different to the UK, but over here we are limited to a maximum Effective Radiated Power (ERP) of 500 milliwatts in our part of the 869MHz band. We get away with using the ‘standard’ 7dBi antennas as they more or less balance out losses in the transmission system (coax, connectors, etc.), but using a 15dBi gain antenna - even if it proves a good match - could push the output above this limit. That is of course assuming the 15dBi rating is accurate.

So what I am saying is, it may well ‘work’ for P3i, but you would need to check these factors to ensure it works satisfactorily and legally.

It does look like it will be a useful antenna for FLARM reception though.

Best Regards

Peter

[Kurt37]

Hi Peter,

I requested the technical details for the antenna. (Might also be interested for other ogn-r builders, without intending to interfere with the original recommended spec by pilotaware).
 https://ibb.co/c6GSfs3


RE #1: It states the frequency at 868mhz ith a bandwidth of 7mhz. So it should be okay for 869.525mhz, or?

RE#2: I just switched the original PAW antenna with this one at my home test Station Meppen1, fired up my Rosetta and it received an uplink signal from the above mentioned antenna and station. So I guess there is no short circuit for sending. Please confirm that testing method is a valid way of checking?

RE3#: Same legal regulations here in Germany.

Kind Regards,

Patrick

[exfirepro]

Hi Patrick,

Thanks for the feedback. Not seeing the image though.

Hi Peter,

I requested the technical details for the antenna. (Might also be interested for other ogn-r builders, without intending to interfere with the original recommended spec by pilotaware).

RE #1: It states the frequency at 868mhz ith a bandwidth of 7mhz. So it should be okay for 869.525mhz, or?

869.525MHz is well within that reported bandwidth so match should be fine.

RE#2: I just switched the original PAW antenna with this one at my home test Station Meppen1, fired up my Rosetta and it received an uplink signal from the above mentioned antenna and station. So I guess there is no short circuit for sending. Please confirm that testing method is a valid way of checking?

I wouldn’t recommend that as a test method for high power transmitters, but it seems to have worked fine in this case (PAW is low power, so much less risk of damaging / destroying the output stage), all good.

RE3#: Same legal regulations here in Germany.

OK, so with a power output of about 250mW (IIRC) at the Bridge Socket, we are OK with using gain antennas up to about 6 or 7dBi for Ground Stations - taking into account losses in coax feeders and connectors (connector loss is usually estimated at about 1dB per connector). If this antenna is ‘truly’ 12dBi, you might therefore exceed the ERP unless your system losses are unusually high (for example unusually long coax length or poor quality coax) but antenna gain figures are notoriously unreliable (higher quoted gain generally equals increased sales). I would say definitely worth giving it a ‘trial’ for a reasonable period to see what sort of range it gives, just don’t publicise the fact and if you start getting complaints from neighbours about interference to other systems in the same band (highly unlikely) be prepared to swap it for a lower gain one 

Best Regards

Peter