433 Sensors fail to update tellstick.net but ok on zwave box

Moderator: Telldus

PetriK
Posts: 33
Joined: Fri Mar 17, 2023 9:45 am

Re: 433 Sensors fail to update tellstick.net but ok on zwave

Post by PetriK »

Yes, some have wider spectrum, but i have not checked that by being close of each sensor so also the signal strenght can have an impact what we see. Is it possible that the strenght we see is actually reflecting burst lenght more than actually bandwith ?

The official center of frequency is 433.92 but still frequencies can be all over the place as: "receiver is a super-regenerative TRF reciver with only a single LC network to define its operating frequency, and it has the characteristic that it will lock onto the strongest signal it sees within +-5Mhz of its nominal frequency" - assuming Telldus is using TRF. As I have two Telldus.net units next to each other I can see the blue light to blink on both but only one can detect the protocol - for the other its perhaps "garbaged" so much that signal can not be categorized to any known protocol and therefore its not accepted ? This is just an assumption as I dont know enough how firmware works.
etompau
Posts: 2405
Joined: Fri Mar 17, 2023 9:45 am
Location: Skåne

Re: 433 Sensors fail to update tellstick.net but ok on zwave

Post by etompau »

I assume that the Net has the same receiver part as the 433-section of a ZNet, then it's a Maxim 7030 chip with a crystal controlled PLL section, no free-running LC circuits.
tronde
Posts: 625
Joined: Fri Mar 17, 2023 9:45 am

Re: 433 Sensors fail to update tellstick.net but ok on zwave

Post by tronde »

I know some of my sensors are transmitting over a much wider spectrum than others, but it can also be as you say that something that looks like a wide spectrum can be related to signal strenght. You will get a better indication of the spectrum if you look at the spectrum window in the program than what you can see in the water fall.

I don't think they use a superregenerative receiver. They are more or less usless if you have many transmitters. The Maxim 7030 has a crystal controlled PLL, yes, but it does also have a crystal filter for IF and LC on the input. Only Telldus can tell what they have done in detail.

I find it interesting that the frequency range for receiving singnals follow the transmitting frequency. This is an indication for a very narrow filter for the receiver and that it is some kind of circuitry shared between the transmitter and the receiver. The observed differences in transmitting frequency is no strange. 434.04 (as in mine Net) is only 1.00028 times 433.92. That equals 280ppm. Not a good value for a crystal, but no surprise either.

I calibrated my receiver to the transmitting frequency of two known broadcast transmitters, but that is no exact science. If wrong, I assume my value is to high, rather than too low as most crystals should be within 100ppm.
Post Reply