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Interferences on cable TV
#1
I have just noticed that controlling my CoCo (KaKu) switch with pilight interferes with the reception of my cable TV. There occur sound and picture noise.
To explain for a non-electronic like me: is that possible and what else could be disturbed?

Unfortunately, I can not test it with the remote control, do not use one.

PS: just tested with pilight 7: there is no error
Terrarium:  RPi Model B Rev 2 / pilight 8.1.2 / stretch
Aquarium: RPi Model B Plus Rev 1.2 / pilight 8.0.6 / jessie
 
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#2
Yes there are interferences.
You use a 433MHz RF Transmitter and OOK (On Off Keying) to modulate the Pulses. The additional Frequencies generated do highly depend on your hardware design, the biggest impact is your GPIO IO driver’s ability on how fast it can switch from ON state to OFF state and vice versa; this depends on length of your IO wires (e.q. The capacity and the inductance load of your wire) and the value of your Pull Up/Pull Down resistors.
The Pulses with durations of 0.2, 0.3, 1.1, and 2.8 mS (will create a lot of harmonics of the 433MHz RF carrier.
Most probably your cable TV provider is utilizing channels 21 or above as they are the closest ones to 433MHz (the Frequency is 308MHz plus 8MHz*channel-nr).
You may be able to reduce the impact by using coax cable with double shields for your TV and by increasing the distance between your pilight devices and your TV/TV cable infrastructure.

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#3
@wo_rasp

Thanks for your detailed explanation.
But is that then related to the restructuring of the software (rewrite / v8)?
That's something I've never noticed before with pilight 6/7 on same hardware.
Terrarium:  RPi Model B Rev 2 / pilight 8.1.2 / stretch
Aquarium: RPi Model B Plus Rev 1.2 / pilight 8.0.6 / jessie
 
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#4
It depends a bit. One main difference is that the number of repeats, e.q. how often is a pulsetrain repeated, differs between the various pilight releases and this has an impact on RF interferences.
There could be present a hidden bug, but it would be speculating from my part if this is the case as I currently use my own code base only.
Time permitting i will move my existing code base on one of my Pi’s to V8 early next year.


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#5
I will observe the matter a little bit more.
The aquarium with about 15 shifts a day it is not tragic.
It would be worse if I change the terrarium to pilight 8.
Since I have 200 to 250 switching operations per day, which could really be disturbing.

I will get a better cable for the TV set in any case.
Terrarium:  RPi Model B Rev 2 / pilight 8.1.2 / stretch
Aquarium: RPi Model B Plus Rev 1.2 / pilight 8.0.6 / jessie
 
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