Message passing test

Dear sir
I want to implement a feedback system for example
attached feedbackmessageoassing.pdf attached. Its output is zero. No
thing comes for output.
I tested message passing in different ways. No clear output comes. For
the
above feedback system nothing comes out.
Please help me. How to implement such a feedback syste.
Thanks
Neil

Ads-b uses a 1 MHz pulse position modulation scheme

Is this possible to create on gnu ?

Is it the data rate that makes the spectrum wide ? 7 MHz ?

Also thinking about a b200 usrp looks nice

Andrew vk4tec

Sent from my iPhone

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Hi Neil,

yes, this can’t work; you can only multiply two numbers if there are
two numbers (factors). Which will never be the case, since there has
not been a multiplication before the first factor.

Message passing can’t make an flowgraph that has a synchronous path
(“normal” sample flow) asynchronous. What you most probably want is to
receive the message with a block that e.g. sets the factor in a
multiply_const block.

Hope I could help a little,
Marcus

On 29.01.2014 13:15, MHMND Herath wrote:

mailing list [email protected]
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

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Hi Andrew,

just a quick heads-up: I nearly missed your message because it was
hidden in another thread, since you seem to have hit reply and changed
subject and text; however, my mail client recognized the In-Reply-To
header, and sorted you in - please directly write mails unless you
actually mean to reply.

So now for your question

Ads-b uses a 1 MHz pulse position modulation scheme
On 30.01.2014 01:22, Andrew R. wrote:
Ads-b uses a 1 MHz pulse position modulation scheme

Is this possible to create on gnu ?
GNU Radio is only a software radio framework. Basically you can do
anything with it that can be done in baseband signal of a sample rate
that your ADC/DAC and mixers (and analog filters, amps and so on)
support.
With gr-air-modes there is a comfortable receiver implemented in GNU
Radio, and as a not-to-rough simplification you can transmit
everything with a software radio that you can receive with one.

Is it the data rate that makes the spectrum wide ? 7 MHz ?
Ok, I don’t really understand your question, could you please elaborate?
Reception of ADB-S works quite well with a 4MHz sampling bandwidth,
but I’m not quite sure on the technical requirements of ADB-S
transmission.

The actual bandwidth of PPM systems of course depends on pulse shape
and pulse frequency.

Hope I was able to help a little,
Marcus
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Basically, yes, but that’s communication theory. I’d refer you to
Kammeyer – Nachrichtenübertragung, but that’s a German book. I guess
Proakis would be a fine source, too, but I don’t have his book at hand
right now.

Anyway, ADB-S should define the pulse shape. Best look into Nick’s
gr-airmodes code for matched filtering; the matched filter directly
gives you the transmission filter. (But that’s even more signal theory)

Greetings,
Marcus

On 30.01.2014 10:44, Andrew R. wrote:

[email protected] To: “Andrew R.” [email protected]
unless you actually mean to reply.
on) support. With gr-air-modes there is a comfortable receiver

The actual bandwidth of PPM systems of course depends on pulse
shape and pulse frequency.

Hope I was able to help a little, Marcus

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When you demodulate ads-b it becomes just square waves

Sent from my iPhone

Thanks Marcus

Pulse shape and repetition frequency determine bandwidth then ?

Square is the worst - gausian is better ?

  • Andrew -

----- Original Message -----
From: “Marcus Müller” [email protected]
To: “Andrew R.” [email protected]
Cc: [email protected]
Sent: Thursday, January 30, 2014 5:27 PM
Subject: Re: Modulation question

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Ah yes you’re right; I’ve just taken a look myself, and gr-air-modes
uses a moving average as a matched filter, which implies a rectangular
shape. So your pulse bandwidth is the same as system bandwidth.

On 30.01.2014 11:11, Andrew R. wrote:

book at hand right now.

Pulse shape and repetition frequency determine bandwidth then
Sent: Thursday, January 30, 2014 5:27 PM Subject: Re:

a comfortable receiver implemented in GNU Radio, and as a

The actual bandwidth of PPM systems of course depends on
pulse shape and pulse frequency.

Hope I was able to help a little, Marcus
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