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SDR: Add option to set local oscillator (LO) offset

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By default it is set to -1 MHz.
This commit is contained in:
Andreas Eversberg
2017-12-04 14:12:11 +01:00
parent c49ee3b2a8
commit 9f901384de
10 changed files with 58 additions and 30 deletions
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10
docs/sdr.html
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@@ -77,9 +77,7 @@ In case of B-Netz, I use the following parameters:
# bnetz --sdr-soapy \
--sdr-tx-gain 50 \
--sdr-rx-gain 30 \
--sdr-bandwidth 5000000 \
--sdr-samplerate 5000000 \
--sdr-tune-args "OFFSET=1000000" \
-s 100000 \
-k 17
@@ -89,10 +87,10 @@ In case of B-Netz, I use the following parameters:
In order to change from analog sound card to SDR, you need <b>--sdr-soapy</b> option.
In my setup I use antennas directly connected to the SDR.
Being about 1-10 meters away, I use the <b>gain</b> as defined above.
The IF filter requires a minimum <b>bandwidth</b> of 5 MHz.
The <b>sample rate</b> must be 5 MHz minimum.
The default <b>bandwidth</b> follows the sample rate, if not specified using <b>--sdr-bandwidth</b>.
Higher sample rate causes more CPU, RAM and USB load.
The local oscillator frequency causes the transmitted signal to be noisy, so I shift it 1 MHz away, using an <b>offset</b>.
The local oscillator frequency causes the transmitted signal to be noisy, so I shift it 1 MHz away, using the default <b>--sdr-lo-offset</b>.
The audio processing rate of 100 KHz (<b>-s 100000</b>) is used to generate two channels: <b>17</b> and 19.
Note that channel 19 is not given here, but will be used automatically.
With B-Netz, the transmitter switches from any voice channel to the paging channel (19) whenever the phone gets paged.
@@ -174,9 +172,7 @@ Because C-Netz uses only odd channel numbers for 10 KHz spacing, we use channel
# cnetz --sdr-soapy \
--sdr-rx-gain 50 \
--sdr-tx-gain 30 \
--sdr-bandwidth 5000000 \
--sdr-samplerate 5000000 \
--sdr-tune-args "OFFSET=1000000" \
-s 100000 \
-k 131 -k 135 \
-C 0,0
@@ -192,7 +188,7 @@ Give PAL 'FUBK' test image on TV channel 21.
# osmotv --sdr-soapy \
--sdr-tx-gain 60 \
--sdr-tune-args "OFFSET=-3000000" \
--sdr-bandwidth 60000000 \
-r 13750000 \
-c 21 \
tx-fubk