Learning about 433 MHz radios - how?

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Squonk42
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Re: Learning about 433 MHz radios - how?

Post by Squonk42 » Fri Mar 17, 2017 11:07 pm

Search for the ARRL (American Radio Relay League) Handbook in PDF.

Another good source for understanding modern RF transceivers can be found in some Semtech RF chip datasheets, such as the SX1232 (http://www.semtech.com/images/datasheet ... df#page=18, look at section 3).

turboscrew
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Re: Learning about 433 MHz radios - how?

Post by turboscrew » Sat Mar 18, 2017 12:31 pm

THANKS!

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Re: Learning about 433 MHz radios - how?

Post by turboscrew » Sun Mar 19, 2017 1:19 am

SX1232 looks quite similar to the RFM69.

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Squonk42
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Re: Learning about 433 MHz radios - how?

Post by Squonk42 » Sun Mar 19, 2017 3:58 pm

It looks like RFM69s are just (legal?) repackaged SX1231H chips:
https://lowpowerlab.com/forum/rf-range- ... es-or-not/

They copied a large part of Semtech's datasheet, that's why it looks very similar.

But the section 3 in the Semtech datasheet is really nice to understand how a modern RF transceiver really works by following the data path.

turboscrew
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Re: Learning about 433 MHz radios - how?

Post by turboscrew » Mon Mar 20, 2017 6:50 pm

There are some differencies in the chips too.
Like SX1231H has restriction Fdev + (BR/2) <= 250 kHz, but for RFM69 it must be less than 500kHz
Also for SX1231H:
Note
no constraint applies to the modulation index of the transmitter, but the frequency deviation must be set between
600 Hz and 200 kHz
and for RFM69 the frequency deviation must exceed 600 Hz.

But the SX1231H data sheet seems to have descriptions that are not there in RFM69 data sheet. :)

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Squonk42
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Re: Learning about 433 MHz radios - how?

Post by Squonk42 » Mon Mar 20, 2017 9:34 pm

turboscrew wrote:There are some differencies in the chips too.
Like SX1231H has restriction Fdev + (BR/2) <= 250 kHz, but for RFM69 it must be less than 500kHz
Also for SX1231H:
Note
no constraint applies to the modulation index of the transmitter, but the frequency deviation must be set between
600 Hz and 200 kHz
and for RFM69 the frequency deviation must exceed 600 Hz.

But the SX1231H data sheet seems to have descriptions that are not there in RFM69 data sheet. :)
Where did you get these figures for the SX1231H?

When looking into the latest official datasheet from Semtech (Rev 1 - Oct 2011, http://www.semtech.com/images/datasheet/sx1231h.pdf), I get this in section 3.3.3:
To ensure a proper modulation, the following limit applies:
FDEV + BR / 2 ≤ 500kHz

Note no constraint applies to the modulation index of the transmitter, but the frequency deviation must exceed 600 Hz.
This perfectly matches the description on RFM69 datasheet, and I don't see these figures anywhere else.

turboscrew
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Re: Learning about 433 MHz radios - how?

Post by turboscrew » Tue Mar 21, 2017 12:11 am

Squonk42 wrote:
turboscrew wrote:There are some differencies in the chips too.
Like SX1231H has restriction Fdev + (BR/2) <= 250 kHz, but for RFM69 it must be less than 500kHz
Also for SX1231H:
Note
no constraint applies to the modulation index of the transmitter, but the frequency deviation must be set between
600 Hz and 200 kHz
and for RFM69 the frequency deviation must exceed 600 Hz.

But the SX1231H data sheet seems to have descriptions that are not there in RFM69 data sheet. :)
Where did you get these figures for the SX1231H?

When looking into the latest official datasheet from Semtech (Rev 1 - Oct 2011, http://www.semtech.com/images/datasheet/sx1231h.pdf), I get this in section 3.3.3:
To ensure a proper modulation, the following limit applies:
FDEV + BR / 2 ≤ 500kHz

Note no constraint applies to the modulation index of the transmitter, but the frequency deviation must exceed 600 Hz.
This perfectly matches the description on RFM69 datasheet, and I don't see these figures anywhere else.
I got those from the earlier link.
3.4.3. FSK Modulation

Aahh, they were data sheets for SX1232!

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Squonk42
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Re: Learning about 433 MHz radios - how?

Post by Squonk42 » Tue Mar 21, 2017 5:51 am

Ok, sorry for the confusion, the SX1232 is the one I am most familiar with, and the original intend was not'to compare it to the RFM69 in particular.

BTW, it looks like other RFM chips are also re-packaged Semtech chips, but those seems to be "accepted" copies, as Semtech is listing Hoperf (RFM69 manufacturer) as one of their FSK parners:
http://www.semtech.com/wireless-rf/wireless-solutions/

turboscrew
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Re: Learning about 433 MHz radios - how?

Post by turboscrew » Tue Mar 21, 2017 9:31 am

Squonk42 wrote:Ok, sorry for the confusion, the SX1232 is the one I am most familiar with, and the original intend was not'to compare it to the RFM69 in particular.
I'm sorry too. I could have read...
BTW, it looks like other RFM chips are also re-packaged Semtech chips, but those seems to be "accepted" copies, as Semtech is listing Hoperf (RFM69 manufacturer) as one of their FSK parners:
http://www.semtech.com/wireless-rf/wireless-solutions/
Yes. It was made quite clear in the link to the discussion. I think Hoperf is a licensee...?

And I have made progress just by reading the RFM69 data sheets and googling. Going through then 3rd time now...
A bit tough when you don't have any radio tech background. Just little something from basic electronics.

turboscrew
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Re: Learning about 433 MHz radios - how?

Post by turboscrew » Tue Mar 21, 2017 9:45 am

BTW, if someone else is interested, just found this:
http://edge.rit.edu/edge/P09141/public/FSK.pdf

And another one - especially for RFM69 (and maybe for SX1231H too):
https://lowpowerlab.com/forum/rf-range- ... ith-rfm69/

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