Hello
I've made a small patch to use Paul's excellent vlfrx-tools with direct
sampling mode on RLT2832 DVB-T dongles. This is a nice cheap option for a
remote VLF/LF/MF receiver, just keep in mind that this has only 8 bits
of resolution, so don't expect a lot of dynamic range, watch the input
amplitude (with vtscope for example) and use some frontend filtering.
To use apply the patch to vtrtlsdr.c, and modify the dongle to connect the
input directly to the RL2832 inputs. For the mod google for "direct
sampling mod": i've disconnected all input from the tuner chip, and a used
a modem audio transformer to connect to the balanced I input, but you can
just couple to I+ via a capacitor, and short I- via a capacitor to ground.
You can also use the Q inputs (use -D 2).
Example:
#use 1MHz sample rate (giving 500kHz of rx bandwidth), start at 0Hz
vtrtlsdr -v -v -r 1000000 -F 0 -D 1 @sdr
#send it to spectrum lab (this is only for quick testing, Paul's tools
#might be better suited for some tasks.
vtsl -n 7777 -s -k -vv @sdr
In Spectrum Lab select "audio file & stream analysis" -> "analyze and play
stream/url", use url tcp://1.2.3.4:7777/ and select "Uncompressed with
stream info headers". (where 1.2.3.4 is the IP address of the machine
running vtsl).
The patch also extends the valid sample rates, so that you can use sample
rates >225kHz (226-300k and 901k-2.56M work).
This patch was also sent to Paul, but i think he's battling with some
equipment failures and with the weather right now, so i thought i would
also post it here. Hope it will be useful to someone.
VY 73
Jacek / SQ5BPF
vtrtlsdr.diff
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