Arduino Forum

Using Arduino => General Electronics => Topic started by: quiddi on Apr 20, 2019, 12:31 pm

Title: RF Signal 40.6835MHz
Post by: quiddi on Apr 20, 2019, 12:31 pm
Hi everybod,

I want to read and send 40.6835MHz signals with an Arduino. Has someone done it before?

My first idea was to buy a send receive kit for 433MHz and switch the crystal to a 40.6835 one on the sending unit. Do you think that's possible? The second problem is then, how to receive the packages.

Any ideas?

Title: Re: RF Signal 40.6835MHz
Post by: jremington on Apr 20, 2019, 04:52 pm
Possible, but it probably won't work.

Why do you want to send on that frequency? Is it legal to do so in your country?
Title: Re: RF Signal 40.6835MHz
Post by: Geek Emeritus on Apr 20, 2019, 06:14 pm
RF circuits use a thing called a tank. a tank passes a certain frequency and eliminates all others. a tank is composed of a coil and a capacitor.

changing the crystal will just move your RF oscillator to a frequency rejected by the tank
Title: Re: RF Signal 40.6835MHz
Post by: Grumpy_Mike on Apr 20, 2019, 09:20 pm
Quote
I want to read and send 40.6835MHz signals with an Arduino. Has someone done it before?
No. That is a really odd frequency.

Quote
My first idea was to buy a send receive kit for 433MHz and switch the crystal to a 40.6835 one on the sending unit. Do you think that's possible?
No. The other component values you will have to use ensures that you will need a total redesign. And some expensive test kit to test it.

Title: Re: RF Signal 40.6835MHz
Post by: slipstick on Apr 20, 2019, 09:35 pm
The only thing I know of operating around that frequency is Radio Control in some countries (including the UK for surface models only). But whatever it is you're doing you're going to need to know a lot more about the RF signal than just the carrier frequency.

Steve
Title: Re: RF Signal 40.6835MHz
Post by: Paul__B on Apr 21, 2019, 01:02 am
In short you need to purchase the ready-built transmitter for that frequency.  This has little or nothing to do with an Arduino but should be self-evident.

Yet another example of  the simple-minded "you can do anything with an Arduino" meme.  Too much time spent on "instructables" perhaps?  :smiley-roll:
Title: Re: RF Signal 40.6835MHz
Post by: MarkT on Apr 21, 2019, 02:22 pm
Hi everybod,

I want to read and send 40.6835MHz signals with an Arduino. Has someone done it before?
Do you mean 40.685MHz garage door opener?   If so get a garage door sender and receiver
and hack into them?
Quote
My first idea was to buy a send receive kit for 433MHz and switch the crystal to a 40.6835 one on the sending unit. Do you think that's possible?
Not in the slightest, completely different band, radio circuits are narrow-band tuned circuits that have a
small amount of frequency flexibility only.  Not to mention the SAW filter.
Quote
The second problem is then, how to receive the packages.

Any ideas?
There's always SDR of course...