||No-Name, NF 0.5 dB
||Analog Devices AD8561AN
|Microcontroller / Board
||Atmel AT91SAM7X256 / Olimex
|Tap into tuner output.
||A slot was cut into the
back side of the box, and a tree-pin socket was glued with epoxy onto
the tuner. The three pins were conected to I+, GND, and I- (or Q+, GND,
||Box looks more fancy.
|Disable main processor
after it has configured the tuner.
||A switch was connected to
the reset pin of the JTAG interface on the main PCB. After start-up,
the switch is used to hold the main processor permanently in reset. The
switch was mounted using the hole for the optical audio out socket,
wheich was removed.
||1. Power supply to the LNB
is switched off.
2. The analog gain control input to the tuner is switched off (very low gain).
3. Box looks even more fancy.
|Supply power to the LNB
||Unsolder transistor Q3.
This transistor is used in the network that controls the 14 V / 18 V
power supply regulator. Removing Q3 lets the control voltage go high
permanently because of a pull-up resistor.
|Generate a suitable gain
control signal for the tuner.
||A 100 kOhm trim pot was
connected to +5V via a 2.2 kOhm resistor, and to ground at the other
end. The centre pin is conected to the gain control inpot of the tuner.
The trim pot now allows to adjust the gain.
|udp_rx.c||UDP receiver software. Compile
||Utility for entropy
extraction using AES, with on-line test of input data. Compile like
udp_rxwrites raw data to standard output, and that
testractpipes from standard input to standard output.
udp_rx | dd bs=1024 count=20480 of=sample_raw.bin
testractutility checks the quality of input on-line data by calculating the byte entropy for each input block of 4096 bytes. It aborts when the calculated entropy is below a threshold given on the command line (2nd argument). Note that the byte entropy is somewhat underestimated due to the small sample size of 4096 bytes. The data are compressed using AES as described above. The number of bytes taken from each AES output block is also specified on the command line (1st argument).
testract 12 7.8 <sample_raw.bin >sample_cooked.bin
udp_rx | testract 12 7.8 | dd bs=1024 count=1048576 of=cooked.bin
1048576+0 records in
1048576+0 records out
1073741824 bytes transferred in 466.669 secs (2300863 bytes/sec)
||raw data, generated as described
||data of sample_raw.bin after