USRP2 / RFX2400 choppy transmit

Hi,

I’m seeing what I think is choppy transmission from a USRP2 with and
RFX2400
daughtercard.

I have two USRP2s - one acting as the transmitter and one as the
receiver.
When I transmit a continuous tone, the received samples all look fine,
no
discontinuities. However, if I transmit canned packets, sometimes (
about 1
in 30 ) they come out on the receiving end very choppy - meaning the
power
drops to zero at various points in the packet for various lengths of
time.
It also appears that the amount of time spent at zero power increases
the
transmission time of the packet. (i.e. classic underflow?)

I’m using the tx_samples app in ./gnuradio/usrp2/host/apps to transmit
canned packets and I’ve used both rx_streaming_samples and
usrp2_rx_cfile.py to receive the data:

./gnuradio/usrp2/host/apps/tx_samples -e eth0 -m 36:ab -f 2600000000 -g
21
-i 8 -I …/code/C/tx/tx_samps.dat

./usrp2_rx_cfile.py -m “35:7c” -f 2600000000 -d 20 -g 21 rx_samps.dat

./rx_streaming_samples -m “35:7c” -f 2600000000 -d 20 -o rx_samps.dat

I thought maybe it was a PA settling issue, but I’ve padded to front of
the
packets with tons of zeros with no luck.

Anyone know what’s going on?

Mike