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Re: [Discuss-gnuradio] Default antenna with RFX2400


From: Paul M. Bendixen
Subject: Re: [Discuss-gnuradio] Default antenna with RFX2400
Date: Tue, 13 Dec 2011 13:59:35 +0100



2011/12/13 Josh Blum <address@hidden>


On 12/12/2011 08:25 PM, Phone Naing MYINT wrote:
> Hi,
>
> TX is clear, defaulted to TX/RX. RX default to direct conversion, what does it mean?

RFX2400 is a direct conversion receiver *and* a direct conversion
transmitter. What the docs really should say:

1) When you tune the transmit chain, the default behaviour is to tune
the LO away from the desired center frequency.

2) When you tune the receive chain, the default behavior is to tune the
LO as close as possible to the desired center frequency.

You can of course, override this behavior:
http://files.ettus.com/uhd_docs/manual/html/general.html#tuning-notes

I would personally reccomend you to use this (and scrap GRC) as soon as possible.
The RFX2400 board has some problems selecting a center frequency far enough off, and you might run into trouble if you are using a digital modulation (You can see some of my earlier posts on this)

 


 For receive, using TX/RX or RX2 provides same performance?
>

TXRX vs RX2 is just a simple switch. You must pick what is most useful
for your application (full vs half duplex). Obviously, for a
receive-only application, either antenna option is good.


If you use the TX/RX as a receiver, you will notice a small attenuation (~2dB) compared to using RX2.
Also remark, that the attenuation between TX/RX when transmitting and RX2 is ~65 dB.

-josh

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Best Paul

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