I bought this cheap wireless relay just to mess about with and to maybe link to a door entry system.
There were no instructions with the relay and I was wondering whether stretching the coil out partially (or even completely) would increase the range of its reception.
Any thoughts?
Tim
That one is for the US market and is illegal to use in the UK.
Wiki suggests otherwise. It?s a 433 MHz device.
The device may be, the listing wasn't ...
Yes, it will intercept more of the signal.
Electrically it is probably a half wave, so you might find it beneficial to add a few cm once the inductance it reduced.
You can always experiment. propogation is an exact science, but your surroundings are not.
AB From the well pummelled keyboard of Archibald Tarquin Blenkinsopp Esq
Ah, just drilled down further into the listing. Looks like it?s a 315 MHz not 433 like I thought.
What are the chances of getting my collar felt? ;-)
Tim
Slim to none but there are plenty of legal ones about.
Having said that, there are instances of remotes operating on 433.9xx being ?jammed? inadvertently by other, legal, users of nearby frequencies.
The receivers in these things aren?t wonderful- some are regen types rather than superhets.
While such key fobs, along with things like remote temp sensors for weather displays etc, are legal, they aren?t a ?protected service?. So, if a local licensed user of the band causes you problems, tough.
zero. Its very short range. You wont make it better by extending the aerial either
The ebay description says
"Specification:
Brand new
Max load current: 10A
Operating voltage: DC12V
Suitable battery for handsender: Button Battery
Working frequency: 315MHz"
What frequency is it on and indeed how much power. Brian
Its probably on a band already in use by something else so its more than likely going to be interference. I remember the old portable phones you could buy which used fm at 49Mhz, you could just listen on most cheap scanners as indeed did credit card fraudsters. Brian
There are only spot frequencies available in that band. Its a ham radio band, that part often used for the output of the Repeater network.
Brian
Absoutely nil I should think.
Agreed. I don't think it is particularly an inductance by design, it is coiled for compactness; by extending it, as ATB suggests, you intercept more signal.
There you are probably wrong. It looks like an inductance tuned to
315Mhz to me
Oh, and antenna theory does not suggest that 'extending it will net you more signal' *necessarily*.
The EFFECTIVE size of an antenna is not its physical size
315MHz, a coil used as an aerial? Very high impedance both ends and the coil frequency would be lower I'm pretty certain. My 2M tuned circuits had smaller coils..
The coil has no directors, so the longer it is, the more signal, up to the point where swr/ impedance mismatches cause attenuation.
As I said, suck it and see. The coil can be reinstated with the aid of a drill or bit of dowel.
Whether the coil is resonant, a quarter or a half wave isn't really going to matter if practically a bigger signal is noted after stretching the coil a bit.
AB From the well pummelled keyboard of Archibald Tarquin Blenkinsopp Esq
You would be with all those Megawatts :-)
The harmonics could cook the turkey as well if it were left in the microwave :-(
AB From the well pummelled keyboard of Archibald Tarquin Blenkinsopp Esq
This is what 4NEC2 is for. Have an idea, test it.
newshound brought next idea :
It also would become more vertically polarised, than the as supplied coil.
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