On Jan 17, 8:05=A0pm, Jim Stewart <jstew...@jkmicro.com> wrote:
>
> Diversity receive is the usual solution to this
> sort of problem. =A0You might contact the manufacturer
> and see if their protocol can be adapted to it.

Thanks. For now I have simply reduced the sampling rate
by factor of two (quick & dirty solution - simply
discarding every second sample without antialiasing filtering,
but my source is supposed not to contain signals above 12 kHz),
and the resolution to 20 bits.
Now it is possible to send the bitstream via RFM70
with autoacknowledge/retransmission.

The noise level has decreased significantly because
no packets are lost.

wzab wrote:

> My questions are. Is it reasonable to expect, that two RFM70 will work
> correctly
> together at distance of ca. 10 cm?
> How should I allocate the frequency to them?
> I have 83 1MHz channels. At 2mb/s air bitrate each RFM70 occupies
> 2MHz. Should
> it be OK to separate both channels by 4MHz or it is better to assure
> the distance
> of ca. 40 MHz? (But then I'll more significantly spoil the 2.4MHz band
> in my viccinity ;-) ).
> What do you think about it? Any hints are appreciated.

Diversity receive is the usual solution to this
sort of problem.  You might contact the manufacturer
and see if their protocol can be adapted to it.

On Jan 15, 10:27=A0am, wzab <wza...@gmail.com> wrote:
> On Jan 15, 5:45=A0pm, linnix <m...@linnix.info-for.us> wrote:
>
>
>
> > No sure how much you can adjust these modules, but you will have
> > serious interferences with two transmitting at the same time. =A0For
> > higher data rate, you might need higher carrier frequency (i.e. 5GHz).
>
> Hmmm, in fact I'm rather afraid if one module will be able to receive
> the acknowledge, when the another one is transmitting.
> I'm afraid, that the input RF amplifier may get saturated by the
> signal
> sent by the neighbouring module, even though it is tuned to another
> freuency...

Yes, you need some settling delays, which would cut into your data
rate further.  You need to either compress your data or go to the 5GHz
ISM band.

On Jan 15, 5:45=A0pm, linnix <m...@linnix.info-for.us> wrote:

>
> No sure how much you can adjust these modules, but you will have
> serious interferences with two transmitting at the same time. =A0For
> higher data rate, you might need higher carrier frequency (i.e. 5GHz).

Hmmm, in fact I'm rather afraid if one module will be able to receive
the acknowledge, when the another one is transmitting.
I'm afraid, that the input RF amplifier may get saturated by the
signal
sent by the neighbouring module, even though it is tuned to another
freuency...
The big advantage of RFM70 is their good availability and very good
price.
It can be done at 2.4GHz, as Nordic offers nRF24Z1
( http://www.nordicsemi.com/index.cfm?obj=3Dproduct&act=3Ddisplay&pro=3D86 =
)
and AUREL offers the audio links 16b/44.1 kHz
( http://aurelwireless.com/rf-wireless-modules/product-info.asp?id=3D303
http://aurelwireless.com/rf-wireless-modules/product-info.asp?id=3D302 )
working in this band.
Unfortunately I'm not able to buy the nRFZ24Z1 breakout board in
Poland
and AUREL's modules are quite expensive (and you need to solder
wires to the chip pins to extract the signal in a digital I2S form
from them).

On Jan 15, 4:54=A0am, wzab <wza...@gmail.com> wrote:
> Hi,
>
> I've just finished my RFM70 based wireless guitar system
>
> (I hope to publish it soon, but code and documentation needs some
> polishing
> =A0- the system is designed =A0to be very cheap - just CS5343/4 as ADC,
> ATmega88
> =A0and RFM70 in the transmitter, and RFM70 with ATmega32u4 in the
> receiver.
> =A0The system is visible as USB MIDI/audio device so you can connect it
> thorough
> "alsa_in" to "jakcd" in Linux and then to your virtual guitar amp/
> soubd processor
> =A0- e.g. rakarrack or guitarix. Additionally the transmitter contains 4
> switches and
> 4 potentiometers, which are mapped to MIDI controls)
>
> The system works acceptably with 24bit/48kHz without acknowledge/
> retransmission.
> Anyway some packets are dropped and this increases the noise level, so
> probably
> the acknowledge/retransmission will be needed.
> Other users reported that 500 kb/s is achievable with ACK.
>
> I think, that I'll need to use two RFM70 in parallel in the Tx and in
> Rx to provide
> the bandwidth sufficient for may needs (OK. maybe I'll reduce the
> resolution to 20bits,
> which gives 960kb/s).
>
> My questions are. Is it reasonable to expect, that two RFM70 will work
> correctly
> together at distance of ca. 10 cm?
> How should I allocate the frequency to them?
> I have 83 1MHz channels. At 2mb/s air bitrate each RFM70 occupies
> 2MHz. Should
> it be OK to separate both channels by 4MHz or it is better to assure
> the distance
> of ca. 40 MHz? (But then I'll more significantly spoil the 2.4MHz band
> in my viccinity ;-) ).
> What do you think about it? Any hints are appreciated.
> --
> TIA & Regards,
> Wojtek

No sure how much you can adjust these modules, but you will have
serious interferences with two transmitting at the same time.  For
higher data rate, you might need higher carrier frequency (i.e. 5GHz).

Hi,

I've just finished my RFM70 based wireless guitar system

(I hope to publish it soon, but code and documentation needs some
polishing
 - the system is designed  to be very cheap - just CS5343/4 as ADC,
ATmega88
 and RFM70 in the transmitter, and RFM70 with ATmega32u4 in the
receiver.
 The system is visible as USB MIDI/audio device so you can connect it
thorough
"alsa_in" to "jakcd" in Linux and then to your virtual guitar amp/
soubd processor
 - e.g. rakarrack or guitarix. Additionally the transmitter contains 4
switches and
4 potentiometers, which are mapped to MIDI controls)

The system works acceptably with 24bit/48kHz without acknowledge/
retransmission.
Anyway some packets are dropped and this increases the noise level, so
probably
the acknowledge/retransmission will be needed.
Other users reported that 500 kb/s is achievable with ACK.

I think, that I'll need to use two RFM70 in parallel in the Tx and in
Rx to provide
the bandwidth sufficient for may needs (OK. maybe I'll reduce the
resolution to 20bits,
which gives 960kb/s).

My questions are. Is it reasonable to expect, that two RFM70 will work
correctly
together at distance of ca. 10 cm?
How should I allocate the frequency to them?
I have 83 1MHz channels. At 2mb/s air bitrate each RFM70 occupies
2MHz. Should
it be OK to separate both channels by 4MHz or it is better to assure
the distance
of ca. 40 MHz? (But then I'll more significantly spoil the 2.4MHz band
in my viccinity ;-) ).
What do you think about it? Any hints are appreciated.
--
TIA & Regards,
Wojtek