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Re: [Discuss-gnuradio] RFX400 Tuning & WBX Comparison

From: Matt Ettus
Subject: Re: [Discuss-gnuradio] RFX400 Tuning & WBX Comparison
Date: Wed, 09 Jun 2010 07:43:05 -0700
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20100430 Fedora/3.0.4-2.fc12 Thunderbird/3.0.4

On 06/09/2010 12:12 AM, Andrew Gilbett wrote:

When I ask my RFX400 to tune a frequency for example 438.600MHz I get
the following output.

A: Flex 400 Tx MIMO B
        r.baseband_frequency = 442000000.0
        r.dxc_frequency = -3400000.0
        r.residual_frequency = -0.381469726562
        r.inverted = False

This means that the synthesiser tunes to 442MHz and in the FPGA the
base band signal is frequency translated to -3.4MHz? Thus the output
is on frequency at 438.600MHz.
Have I spelled that out correctly? I am just trying to get a picture
of how the system works to tune all the frequencies that I may throw
at it.

Yes, that is correct.

Also questions about the WBX:
How come the RFX400 is now depreciated in favour of the WBX but the
rest of the RFX series are not and seem to be covered by the WBX
frequency range?

The WBX is better than the RFX400 in every specification, and so we have discontinued the RFX400. Nobody was buying them anymore after the WBX came out.

While the RFX900 and RFX1800 frequency ranges are also covered by the WBX, and the WBX specs are in _most_ cases slightly better, we still sell the RFX900 and RFX1800 because:

- The RFX900 and RFX1800 have as much as 6dB higher power output
- OpenBTS only works with the RFX-series for now.

The connector J101 pictured on the WBX on the image available on the
ettus website; is that so that a SMA connector can be directly
attached to the receiver? Thus eliminating problems relating to cross
talk in the little rf switches on the grand-daughter board.

Yes, you can directly connect the antenna to J101 and bypass the daughterboard. This also bypasses the first LNA. However, there are no problems relating to cross talk.


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