Antennas

@inq Check this out, Swiss Guy is big on LORA

Posted by: @zander

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@inq Check this out, Swiss Guy is big on LORA

I finished the range testing using just the wires.  It's good enough for what I need, but I will be trying out some of the directional versions he showed.

I'm experimenting with a new SBC (for me) Orange Pi Zero 2W.  It has an external WiFi/Bluetooth antenna about 60mm long.  I'll be attaching a LoRa module to it and it has an antenna 81.9 mm long (915MHz).  What should my minimum spacing and/or orientation be between these two antenna?

Thanks.

VBR,

Inq

@inq I think your WiFi may be 5gHz. Keep in mind that means more data, but more easily stopped by water and other obstructions

A 5GHz wave has a length of about 6 cm (2.36 inches), while a 2.4 GHz wave has a length of about 12.5 cm (4.92 inches).

915mHz is 78mm or 3 1/16 but that is the middle of the range of 902 to 928 so a few mm one way or the other is no big deal.

Hi @inq, 

Simplistically, the aerials should be as far as possible, apart from each other, to minimise interactions. I suspect rules of thumb of around a wavelength minimum, which would be around 35 cm, might be suggested.

If this sounds tricky, and you need both to be active, consider changing WiFi to horizontal, assuming Lora is vertical. Of course, this implies the WiFi transceiver it talks to may also need to change to horizontal, and so on.  This might just be bending one of the aerials on your WiFi router? Most routers now have 2 or more antenna to spead the signal around. Remember, when the aerial is horizontal, the signal goes in a direction perpendicular to aerial .. sort of broadside on.

In practice, local signals tend to bounce around, and providing signal strength is high, you can bend most of the rules. That applies to WiFi in many cases, but less with Lora, except during development when they are next to each other on the same table.

Perhaps, the most important criteria will be locating your Lora antenna for the maximum range, which may naturally move it away from the WiFi?

Best wishes, Dave

@davee 

Thank you Dave.  I was hoping them being perpendicular to each other might keep me from having to separate them by some large length (aka... 35 cm).  Since this (as the server) is headless, I can put it anywhere, even next to the router.  Optimally, I'd like to print a 3D case that is only big enough to hold the Pi-Zero, LoRa card and two antennas.  ~ 85mm x 35mm x 10mm would just about cover it... except if 90 degree antennas are need, 35mm will go up to 65mm.  That's doable.  

Hi @inq,

  Suggest you try to build in some antenna adjustments, if possible. Things rarely go 100% to text book predictions ... perhaps the aerials can't read the books, so they don't realise? 🤔 

I wondered if the Lora aerial would be better outside, whilst the WiFi and module stays inside? Not a major difference from your plan; just a short cable going from inside to outside. Of course, it might all be happy indoors, depending on the materials (brick, etc.) that the signals battle with. Remember, at least for 2.4G WiFi, water will absorb the signal, so rain, etc., can change the signal strength.

Best wishes, Dave

Posted by: @davee

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I wondered if the Lora aerial would be better outside

I'm sure it'd be better, but my early experiments left one on my desk and the other got nearly 1000 meters a with a large hill in-between.  Bill's video said he had his inside a chest freezer, in an underground basement and he still got reception in his neighborhood.

Hi @inq,

   I agree, Bill's communication from inside a freezer was remarkable.

   At best, radio signals are only semi-predictable. I still remember many people using indoor aerials for (analogue black and white) TV, and ending up walking the aerial around the room, desperately trying to get enough signal to stop the snowy picture rolling, etc., and then cursing when someone moved, and it all fell apart again. 

With digital systems, the radio signals are just as unpredictable, but the signal is either 'sufficient' or 'effectively non-existent'. There are no 'snowy' pictures or 'hissy' radio programmes.

Hence, I tend to suggest looking for a solution that has 'signal to spare', rather than 'just enough', in the expectation that 'just enough' means 'just enough until the moment it can be a real pain, when it will be just NOT enough'.

I'll leave you to decide your best course of action ... my limited experience (of radio signals in general) is that signals inside a building are a lot weaker and more unpredictable than with an outside aerial.

Best wishes, Dave

@davee Wow, my experience was so much different. My parent's home was in the west end of Hamilton, Ont, so we got all the US networks and all the Canadian networks as well as a couple of non-network channels, all on a set of rabbit ears. I did use some foil to fine tune them, but once set up no further adjustment was ever needed. I was into SW radio at the time and had an 80M long piece of 300ohm twin lead cut in the right places so I could have an 80, 40, and 20-meter antenna running from the back of my dad's house across the alley to a neighbour's garage. I listened to stations from all over the world and even listened to the dying cosmonaut that officially was never put into orbit before Gargarin. I have always found antennas to be very predictable and so do countless individuals as well as governments. Science and physics always work, at least on this continent.

EDIT: I just noticed both the US and TO are about 30 miles away as the crow flies, isn't the channel 30 miles? You should have been able to get dozens of signals from all those EU countries. OR, is PAL somehow different in terms of reception? I never thought so, but now I wonder.

Hi Ron @zander,

   I was thinking back to the earlier 1960s ... At that time, there were two channels in the UK ... BBC and ITV, and ITV was a comparatively recent addition, dating to the end of the 1950s for most areas, albeit most people didn't have a TV until after 1960. BBC had frequencies roughly in the range 50-80MHz and ITV nearer 200MHz. You can figure out, a BBC half-wave dipole was not something for the living room!

For colour, the transmission frequencies moved to 'UHF' .. roughly 450-900MHz, and the line standard from 10 (-ish?) kHz to 15,625 Hz.

Colour TV in UK didn't really come in before 1969, when BBC1 and ITV started to transmit colour. BBC2 did colour transmissions before that, but only had programs for a very small number of (by necessity, wealthy) viewers.

It is possible, some people near the South coast could have received signals from France, etc. but I never met anyone who tried, let alone succeeded. In the UK, and probably North Europe, TV transmissions were apparently 'controlled' in the range, presumably by tweaking the transmitting aerials to 'adjust' their ERP in each direction, so that the overlap from different sites was limited, and hence frequencies could be 'reused'.

Occasionally, there would be advisory messages (and patterning on the tv) because the weather conditions were causing TV transmissions from Europe to skip across to the UK, and interfere with the local transmissions. That was unusual, not the norm.

Of course, Dxing & amateur radio was a different world, where long distance communication helped by the ionosphere, etc. was the norm, and for enthusiasts, aerials, etc. literally took on a different dimension. According to the relevant magazine, there were a few TV Dxers around, albeit I never met one.

Best wishes, Dave

I should say, I am not disputing physics, etc, regarding aerials. However, the full analysis of an aerial, combined with its feed system mounting brackets, and other stuff around, is fiendish. This particularly applies as the frequency goes up.

For say 160m - 1.8 MHz top-band, if I recall, the odd few cm of wire as a connector is almost irrelevant .. at 2 GHz, the same piece of wire is longer than a half-wave dipole. I haven't played with Lora, but at 915MHz, I would guess it would tend more towards the 'a millimetre makes a difference' scene.

In addition, at the higher frequencies, most insulators start playing games, as the frequencies overlap those of molecular motions, mainly vibrations, that can make the insulator 'lossy'. And even the smallest bits of conductors increasingly look like unintended inductors, to say nothing of skin effect and so on.

Hence, I tend to go for schemes that allow adjustments, etc, in the hope of working round the unexpected. If they are not needed on some occasion, hopefully little is lost.

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Also, in the Dover-Calais region, I think the distance is just over 20 miles, but that is a 'pinch point'. For most of the South Coast it is further apart.

@davee 

I find these more historic, non-technical flash-backs in a different country real interesting!   Thanks.

@davee 

Ah nostalgia and simpler days - I remember Dad and I (5 or 6 years old) built our first color TV around 1967 https://www.worldradiohistory.com/Archive-Catalogs/Allied-Catalogs/Heathkit-1969.pdf - I remember being in charge of segregating resistors by color code.  Surely they were organized when they came, but when Dad gave them to me, they were all in one big pile.  I guess he needed to give me something "important" to do! 😊 

I also remember how a 25" color TV was huge and something no one else had in the neighborhood. 

VBR,

Inq

@inq The local non network TV station in my home town had color cameras before there was any network color TV. They only broadcast in color a few hours a day and I never saw it since nobody I knew had the money to buy one of those early color tv's in the early 50's. My recollection is I saw B&W TV at a friends house in the early 50s and my Dad got one soon after.

A Scot invented B&W TV and Colour TV, John Logie Baird.

Hi @inq,

   Fascinating to hear your experience.

   During 1969-71, I was still at school in my early teens (school in UK parlance does not include 18+ college), but had contrived a part-time job at a local radio/tv shop, which included setting up the convergence on new colour TVs, which on some models was dreadful as they came out the box. One evening, I even swapped the tube on a 25" set. I can't imagine how that would go down with health and safety now!

So 4 or so years later than your Dad, I too had a go at building a Colour TV ... not from Heathkit, but based on a circuit published in the UK 'Camms comic' Practical Television, with the authors arranging the sale of PCBs they had designed. It was after colour TVs had become fairly commonplace, and I regret to say not a complete success, though pictures and sound were resolved. However, it was a great learning exercise, and very useful for one of the questions in my Uni Finals papers, which I answered without even prior revision!

Nostalgia indeed!

Best wishes, Dave