Re: Help on creating an intermittent beacon transmission using HackRF
Hi David!
I'd be very lazy: just pad your pre-recorded signal with zeros, and play it on loop with
the file source.
Padding of files is easy, and essentially free in terms of storage space if your file
system supports sparse files (and if you're on linux, yes, it almost certainly does).
#!/bin/bash
# or #!/bin/zsh, whatever you prefer
# Calculate the number of bytes a 10 minute long sample file has:
reals_per_complex=2 # complex has real and an imaginary part
bytes_per_real=4# for float or int32
sample_rate_hz=$(( 8* 10**6 )) # 8 MS/s
duration_s=$(( 10 * 60 )) # 10 Minutes
filesize=$(( reals_per_complex * bytes_per_real * sample_rate_hz * duration_s ))
# resize your recording to the calculated length
# This only works because on any computer architecture I can think of, numbers
consisting
# solely of zero-valued octets are zeros, numerically
fallocate --length ${filesize} yourrecording.cfile
Best,
Marcus
On 07.02.24 17:09, David Barnhart wrote:
Hi all: I teach a course at USC on satellite ground communications that is a lab-based
class.
I would like to setup an intermittent transmission using a recorded beacon that we have
used before (in cfile format) to have them practice “catching signals” using lab Spectrum
Analyzers and SDRSharp tools in the lab. I can get the beacon transmitting continuously
with its recorded waveform, however am not familiar enough to figure what block structure
to use to only intermittently transmit this signal every 10 or 20 seconds. Might there
be some easy way to do this? Am using osmocom to transmit via bench top HackRF in closed
lab room, with a cfile recording.
Thanks so much! Dave
Research Professor &
Director, Space Engineering Research Center
Department of Astronautical Engineering and Information Sciences Institute
https://www.isi.edu/centers-serc/
USC E-mail: dbarn...@usc.edu
Re: Help on creating an intermittent beacon transmission using HackRF
> > Another possibility is to write your own source block which reads and stores > the samples in memory, then outputs them at a specified time until the > whole buffer is transmitted, then sleeps for a while and repeats. If you > need to control actual transmission time more precisely it can be done > using timestamps at the start of the samples. It also depends on how long > your transmission is (whether you can store all samples in a memory buffer > or need to read and output chunks of it at a time). > Sorry, only now I realized you specified using the HackRF, so please ignore the comment about timestamps. Adrian
Re: Help on creating an intermittent beacon transmission using HackRF
On Wednesday, 7 February 2024 21:03:11 EET Daniel Estévez wrote: > > Hi David, > > One possible solution would be to make a flowgraph that plays the file > once. Then make a bash script that loops, calling the flowgraph and then > sleeping for some time. > > Best, > Daniel. > Another possibility is to write your own source block which reads and stores the samples in memory, then outputs them at a specified time until the whole buffer is transmitted, then sleeps for a while and repeats. If you need to control actual transmission time more precisely it can be done using timestamps at the start of the samples. It also depends on how long your transmission is (whether you can store all samples in a memory buffer or need to read and output chunks of it at a time). Adrian
Re: Help on creating an intermittent beacon transmission using HackRF
On 07/02/2024 17:09, David Barnhart wrote: Hi all: I teach a course at USC on satellite ground communications that is a lab-based class. I would like to setup an intermittent transmission using a recorded beacon that we have used before (in cfile format) to have them practice “catching signals” using lab Spectrum Analyzers and SDRSharp tools in the lab. I can get the beacon transmitting continuously with its recorded waveform, however am not familiar enough to figure what block structure to use to only intermittently transmit this signal every 10 or 20 seconds. Might there be some easy way to do this? Am using osmocom to transmit via bench top HackRF in closed lab room, with a cfile recording. Hi David, One possible solution would be to make a flowgraph that plays the file once. Then make a bash script that loops, calling the flowgraph and then sleeping for some time. Best, Daniel. OpenPGP_signature.asc Description: OpenPGP digital signature
