statemachine said...
take the device to a communications shop,the type that services two way radios and such.Get them to hook it up to their service monitor.They should be able to get the info you want.Bry.
There is something to be said about doing it yourself.
FYI)
I ran a few tests this weekend, just to show how effective the 455kHz filter is... even with a square wave input which BTW isn't really the ideal type of signal to be feeding a filter. They like sine waves much better.
The Input frequency was a 3.3V square wave that varied from 455kHz to 435kHz.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Beau Schwabe
IC Layout Engineer
Parallax, Inc.
In these Photos I'm actually generating 27.145MHz and 26.690MHz and feeding them into the 455kHz filter.... In the first image the signal is the RAW result. In the second Image the signal uses a simple resistor/capacitor filter.
The last image shows both the 27.145MHz and 26.690MHz without the 455kHz filter.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 11/10/2008 7:08:45 AM GMT
So now I have a basic understanding that a 455kHz signal comes out of the 455kHz filter's output when certain RF frequencies are present on the filter's input.
And "a simple resistor/capacitor filter" can be used after that to give a more defined signal to work with.
Your images show this.
Here's what I think I understand:
The transmitter sends a 27.145MHz signal. The signal is modulated to represent the desired digital bits being sent.
The receiver's antenna picks up many frequency signals. All these signals are "mixed" with the 26.690MHz oscillation and fed into the 455kHz filter.
If the 27.145MHz signal was present, the 455kHz filter will output a 455kHz signal, otherwise it won't.
But I'm still struggling to understand something.
The original 27.145Mhz signal was modulated.
Are those modulations also in the 455kHz signal coming out of the filter?
Is the 455kHz just used to indicate the presence of a 27.145MHz, or does its output contain the transmitted data?
Where is the transmitted data?
I probably need to read more about modulating RF signals.
Ion
The modulation is preserved by the filter. The filtered and amplified intermediate frequency signal then has to be demodulated. A useful book with all this stuff in it is the ARRL Handbook for Radio Amateurs.
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
Comments
That IS one way to go. Thanks
Ion
Post Edited (ionymous) : 11/9/2008 2:33:00 PM GMT
There is something to be said about doing it yourself.
FYI)
I ran a few tests this weekend, just to show how effective the 455kHz filter is... even with a square wave input which BTW isn't really the ideal type of signal to be feeding a filter. They like sine waves much better.
The Input frequency was a 3.3V square wave that varied from 455kHz to 435kHz.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe
IC Layout Engineer
Parallax, Inc.
In these Photos I'm actually generating 27.145MHz and 26.690MHz and feeding them into the 455kHz filter.... In the first image the signal is the RAW result. In the second Image the signal uses a simple resistor/capacitor filter.
The last image shows both the 27.145MHz and 26.690MHz without the 455kHz filter.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 11/10/2008 7:08:45 AM GMT
Thanks for sharing your investigation.
So now I have a basic understanding that a 455kHz signal comes out of the 455kHz filter's output when certain RF frequencies are present on the filter's input.
And "a simple resistor/capacitor filter" can be used after that to give a more defined signal to work with.
Your images show this.
Here's what I think I understand:
The transmitter sends a 27.145MHz signal. The signal is modulated to represent the desired digital bits being sent.
The receiver's antenna picks up many frequency signals. All these signals are "mixed" with the 26.690MHz oscillation and fed into the 455kHz filter.
If the 27.145MHz signal was present, the 455kHz filter will output a 455kHz signal, otherwise it won't.
But I'm still struggling to understand something.
The original 27.145Mhz signal was modulated.
Are those modulations also in the 455kHz signal coming out of the filter?
Is the 455kHz just used to indicate the presence of a 27.145MHz, or does its output contain the transmitted data?
Where is the transmitted data?
I probably need to read more about modulating RF signals.
Ion
Leon
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle