Re: [Discuss-gnuradio] [USRP-users] X310 with SBX120's

[Alexander Levedahl]

Please hit reply all in future.

I am uncertain what the present issue is.

The research cannot happen if the level does not change with the direction of the antenna.  It appears that it is changing with the direction of the antenna, or did I read your email incorrectly.

On Mon, Apr 4, 2016 at 7:31 AM, engineer1357 <address@hidden> wrote:

I put a spectrum analyzer next to the receive antenna  of the X310, and when I point my log-periodic transmitting antenna coming out of same X310 in different directions I get no signal on the spectrum analyzer when the antenna points elsewhere.   I get a strong signal when it's pointing directly at the spectrum analyzer.   During this whole process the X310 5 MHz band receiver antenna doesn't fluctuate at all.  It's a solid strong level the whole time.  I can't do my research if the level doesn't change with the direction of the log-periodic antenna.  I feel I should have bought 3 independent N210's instead of this expensive X310.

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From: Alexander Levedahl
Sent: ‎4/‎3/‎2016 11:23 PM
To: address@hidden
Cc: usrp-users
Subject: Re: [USRP-users] X310 with SBX120's

If I understand correctly, when you are transmitting on one port, you receive on another?

Even when you do not attach antennas, it is possible to transmit and receive.  The signals will be weaker than if you had an antenna. 

You mentioned that you think it is coming in to strong for this to be the case, how do you know it is too strong?

On Sun, Apr 3, 2016 at 8:39 PM, engineer1357 via USRP-users <address@hidden> wrote:

Hi, I have an Ettus X310 with two SBX120 daughtercards inside.  I have been driving it for months with GNURadio, but have been getting a strong signal on the RX2 port (A:0 or B:0) which drowns out the true signal being received from the air.  Is there strong cross talk on these SBX120 daughtercards within the X310.  Seems like there is no insulation between what gets transmitted on the daughtercard and what gets received.  I have no antennas hooked up to the X310 at all.  I have the plastic caps on all the antenna ports but when I transmit on my SBX120 daughtercard A on the TX/RX antenna port (A:0), I receive a strong signal on my second SBX120 daughtercard B on the RX2 port (B:0).
1)  Any ideas why I would be receiving my transmitted signal from SBX120 daughtercard A  on the receive port (B:0) of the second SBX120 daughtercard B with no antennas??   The only thing I can think of is that the pink-ish thin wires that connect the daughtercard to the front-panel are not insulated and being received on the second daughtercard before it even reaches the front-panel.  I'm using the pink-ish thin wires provided with the daughterboards.  The received signal is just too strong for having no antennas attached.
2) When I do have antennas attached I'm using the log-periodic Directional antennas for transmitting, thus, I would expect very little signal on the receive antenna, which is out of view of the Directional antennas, but instead I get a strong transmitted signal received.  This tells me there is something wrong internally.
3) Base on the above problem, of course, I get the same problem when using only one daughterboard (Transmit on A:0, receive on A:0).

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