RE: [Discuss-gnuradio] Unable to tune Tx or Rx with XCVR2450 on USRP2

[Ian Holland]

Hi Matt

Additional to below:
I tried to resume normal testing with A as Rx and D as Tx. Now, it seems
I have an offset of about 2 MHz using internal clocks and running
usrp2_fft.py on A, when I transmit a BPSK signal from D. Moreover, I am
unable to tune D for the low (2.4 GHz) band anymore. In fact, when I
just tried again I don't even seem to be able to detect any received
signal even in the high band, and even though it appears to lock on D.

Regards

Ian.



Hi Matt

I have completed the probing as you suggested. The results are in the
following table. Please note that the voltages did not seem to be stable
when I tried reprobing in some cases. An example of this is for R45,
where I give two sets of results for Combo D. Also, please note the
following expanded definitions for comments in the table.

Triangle = The wave looked more like a triangular wave, never really
settling on a fixed high or low level.
Square50 = The wave looked approximately square, with equal time in
low/high states.
Square33 = The wave looked approximately square, with approx. 1/3 time
in the high state, and 2/3 time in the low state.


Results for probing R45:
Combo | U2#  | XCVR# | Set freq? | Vh (mV) | Vlow (mV) | f (MHz) |
Comment
------------------------------------------------------------------------
---
A     | 933  | 990   | YES       | 16      | -12.8     | 100     |
Triangle
B     | 933  | 988   | NO        | 19.6    | -16       | 100.184 |
Triangle
C     | 1159 | 990   | YES       | 20.8    | -19.2     | 100     |
Triangle
D(1st)| 1159 | 988   | YES       | 21.2    | -20       | 100.125 |
Triangle
D(2nd)| 1159 | 988   | YES       | 12      | -15.6     | 99.83(?)|
Triangle

Results for probing R56:
Combo | U2#  | XCVR# | Set freq? | Vh (mV) | Vlow (mV) | f (MHz) |
Comment
------------------------------------------------------------------------
---
A     | 933  | 990   | YES       | 16      | -7.6      | 33.3    |
Square33
B     | 933  | 988   | NO        | 15.2    | -6        | 33.3    |
Square33
C     | 1159 | 990   | YES       | 15.2    | -6.8      | 33.3    |
Square33
D     | 1159 | 988   | YES       | 12      | -11.6     | 49.969  |
Square50

I guess, the difference in the R56 for case D (the only case for which
XCVR 988 was able to set the frequency) may shed some light??? Anyway,
hopefully from these results you will be able to determine which card is
suspected to have the problem.

Thanks

Ian.


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