What is the best orientation of a wireless thermometer's sensor to get the maximum range?
The sensor contains an aerial coil at the top of this photo:
Is the greatest range when the recievering unit is on the side of this coil or along its axis?
I think there may be several things to consider here.
If it's to be used unprotected from the elements outside it should be use the right-way-up so that the drain / air movement holes are at the bottom.
It looks like the aerial 'wire' is folded in half and top loaded so the signal would probably be all over the place but certainly radiating out horizontally (like ripples in a pond) with it the right way up.
So I think the bottom line might be that whilst there may very well be positional 'sweet spots', it might be a difficult thing to predict?
You could do a plot of the signal strengths with a suitable scanner that has a signal strength meter and that covers that frequency (433Mhz?)?
However, if it only transmits every 30 seconds it may take you a while. ;-)
Roomba equipped with LIDAR, a plan of your house and a datalogger connected to both that and the scanner? ;-)
Cheers, T i m
In theory, tx and rx antenna should be in the same orientation for max range.
However, in practice, you may find you need to experiment, especially if there isn't a clear path between the tx and rx.
I find the picture ambiguous. Does the right hand end of the coil of wire go anywhere (such as a trailing wire out of the box) or just stop? Or even join the circuit board somewhere we can't see? And is the white object the wire is wrapped around just plastic or does it have some magnetic material, such as ferrite, in it?
This will make some difference to the answer.
Roger, those remote beasts tend to operate around 433MHz and I suspect that the antenna is a crude helical on a plastic former.
Some of the earlier ones did, I believe, operate on about 418MHz- before the 'harmonisation' rules were introduced. I can't recall when that was- perhaps 10 years back.
True, it doesn't look 'optimised' for 433MHz but it is only a short range beast and a decent antenna like we amateurs would use would be obtrusive. Plus, there are restrictions on ERP etc.
You're quite right about the frequency. It says 433 Mhz on the sensor casing.
I'm not clear. Surely you don't mean, for maximum range, the receiver aerial and the sensor aerial can be either:
(a) in-line with each other (b) side-on with each other.
I can't understand why the aerial wire does a detour down the side of the unit (on the left) and then back up through a pair of grooves cut into the double lip.
Perhaps it's a drip loop to prevent moisture drips entering the space for the electronics but why do all that if the aerial tube coul dhave been positioned inside the double lipping cavity.
I'm not looking for a hobby to while away endless spare hours that I haven't got!
If you have access to a radio scanner, you can probably hear the signal on about 433.92. It will sound like a burst of data- like an old fashioned modem or fax machine.
That bit of the spectrum is allocated to 'unlicensed' devices like you have, also things like radio key fobs for cars etc. It is also one of the amateur radio bands but, fortunately, 'slotted' between frequencies we normally use. Having said that, mutual interference is sometimes a problem, especially to key fobs. Under the rules, the unlicensed devices are unprotected- ie they have to put up with the interference.
If you have an amateur near you, it is possible you may notice the odd 'drop out' of signal if he is active on the relevant band. However, it shouldn't stop the beast working- you will just see the odd delay in updates.
When we had our central heating updated, I avoided an RF thermostat due to the potential problem (I'm a radio amateur). However, I had a similar remote sensor to yours and, other than the odd delay in updates, it was fine.
Pamela, unless you can ensure that your thermostat and receiver emulate black-body isotropic radiators in free space, (and trust me, you can't) just screw it to the wall and forget it.
If the coil really is the arial then to max the range put the axis of the coil to point at the receiver
Yes on3e only has to look at the best places low band mobiles work to see how illogical it all is in a real situation.
The other things to consider are how many other devices are out there probably on the same channel and is there a nasty switch mode power supply nearby chucking out grot all over the spectrum as well. Brian
Hard to say, it so much depends on the reflections and how good the receiver is as well. Brian
i want to comment on your sig line. There is no such thing as Incapacity benefit any more, its ESA and PIP. Brian
Nor is your correspondent. He's confusing polarisation with azimuth.
Bill
A helical a small fraction of a wavelength in diameter?
Bill
You are confusing this with an axial-mode helical antenna, looks like a yagi, but has a continuous helix instead of elements. Typically used for communicating with balloons and spacecraft.
What we are discussing here is a normal-mode helical antenna, typified by the rubber duckie on a handheld. It behaves a whip with a loading coil. The loading coil *is* the whip and will theoretically have a null "end on".
In line might not work as there might be a weak null in the direction parallel to the aerial. I suspect what Brian meant was that if one is horizontal the other should be horizontal rather than vertical.
On reflection, I'm pretty certain the answer to your original question is that the stronger signal is perpendicular to the plane of your original photo.
Wouldn't there theoretically be a signal null along the axis of the coil? I'd have advised the opposite (or the orthogonal, anyway).
Yes, as in a 'rubber duck(y)' helical, as often found on hand held transceivers- more of a loaded whip really.
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