TV tuner cards loaded but cannot tune

TV tuner cards loaded but cannot tune

I have installed two separate PCI tv tuner cards in my HP Proliant N40L microserver running Ubuntu 12.04.2 LTS. Both cards are successfully recognized and registered as DVB-T cards
Attempting to use DVB utilities (scan, w_scan) or other software (TVHeadend) returns no signal. There are no errors messages in dmesg (see below). One of the cards has successfully been used in a Windows PC plugged into the same antenna cable, so I feel confident that the hardware and signal are fine.
What are the next steps to troubleshoot this issue?
[   10.500910] DVB: registering adapter 0 frontend 0 (Realtek DVB-T RTL2832)...
[   10.503616] input: IR-receiver inside an USB DVB receiver as /devices/pci0000:00/0000:00:04.0/0000:03:00.0/0000:04:00.2/usb4/4-1/input/input2
[   10.503795] dvb-usb: schedule remote query interval to 287 msecs.
[   10.503802] dvb-usb: USB DVB-T Device successfully initialized and connected.
[   10.503833] dvb-usb: found a 'USB DVB-T Device' in warm state.
[   10.503844] dvb-usb: will pass the complete MPEG2 transport stream to the software demuxer.
[   10.507107] DVB: registering new adapter (USB DVB-T Device)
[   10.529997] RTL2832U usb_init_bulk_setting : USB2.0 HIGH SPEED (480Mb/s)
[   10.765649] RTL2832U check_tuner_type : FC0012 tuner on board...
[   10.875461] cx25840 3-0044: loaded v4l-cx23885-avcore-01.fw firmware (16382 bytes)
[   10.907187] tuner 1-0061: Tuner -1 found with type(s) Radio TV.
[   10.925702] xc4000 1-0061: creating new instance
[   10.926262] xc4000: Device not found at addr 0x61 (0xffff)
[   10.926366] xc4000 1-0061: destroying instance
[   10.926529] cx23885[0]: registered device video0 [v4l2]
[   10.926620] cx23885[0]: registered device vbi0
[   10.926827] cx23885[0]: registered ALSA audio device
[   10.930850] tuner 1-0061: Tuner has no way to set tv freq
[   10.942820] cx23885_dvb_register() allocating 1 frontend(s)
[   10.942824] cx23885[0]: cx23885 based dvb card
[   10.962568] xc4000 2-0061: creating new instance
[   10.963291] xc4000: Successfully identified at address 0x61
[   10.963293] xc4000: Firmware has not been loaded previously
[   10.971195] DVB: registering new adapter (cx23885[0])
[   10.971203] DVB: registering adapter 2 frontend 0 (Zarlink ZL10353 DVB-T)...
[   10.971857] cx23885_dev_checkrevision() Hardware revision = 0xa4
[   10.971865] cx23885[0]/0: found at 0000:02:00.0, rev: 3, irq: 18, latency: 0, mmio: 0xfe600000
[   11.332565] DVB: registering adapter 1 frontend 0 (Realtek DVB-T RTL2832)...
[   11.334180] input: IR-receiver inside an USB DVB receiver as     /devices/pci0000:00/0000:00:04.0/0000:03:00.0/0000:04:00.2/usb4/4-2/input/input3
[   11.334319] dvb-usb: schedule remote query interval to 287 msecs.
[   11.334324] dvb-usb: USB DVB-T Device successfully initialized and connected.
[   11.334357] dvb-usb: found a 'USB DVB-T Device' in warm state.
[   11.334371] dvb-usb: will pass the complete MPEG2 transport stream to the software demuxer.
[   11.336039] DVB: registering new adapter (USB DVB-T Device)
[   11.355161] RTL2832U usb_init_bulk_setting : USB2.0 HIGH SPEED (480Mb/s)
[   11.596933] RTL2832U check_tuner_type : FC0012 tuner on board...
[   12.163908] DVB: registering adapter 3 frontend 0 (Realtek DVB-T RTL2832)...
[   12.16