[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: [linrad] Help!

Hello Sigurd,
Thanks for the help.  I used the main.c file provided by Kohjin - JR1EDE, to successfully compile linrad and after editing /etc/ld.so.conf and running ldconfig, I am now successfull in running linrad.
Now I have to figure out how to "use" the program :-)
Very good!
My long term goal is to use linrad to improve my microwave receive capability, 900 MHz thru 10 Gigs, over distances up to 500 Km.
The transverters output is at 144 MHz, and I use a DownEast Microwave converter to bring the second IF frequency down to 28 MHz and a Kenwood TS-690 to bring the signal to baseband.
If I leave the TS-690 filters out my received audio has a bandwidth of 12 KHz.  for this configuration I assume that I should sample at a frequency of about 24 KHz.
The received audio goes from some low frequency X to X+12kHz. To avoid
mirror image signals I assume you have to place the passband at something
like 2 to 14 kHz. To avoid aliasing you should then place the Nyqvist
frequency at say 16kHz which means you should sample at 32 kHz.
There may be some possibiliity of using the TS-690 DSP interface to do better, but I don't yet understand how I might do that.
I have no idea.
Would it be usefull to build a receive interface circuit to generate two "channels" of audio from the TS-690 and feed one into the left soundcard channel and the other into the right soundcard channel?
If you think 12kHz is not enough you can increase the bandwidth this way. You
could get something like 40kHz bandwidth sampling I and Q at 48kHz. With
good anti-alias filters you can get up to about 46kHz bandwidth.
I think 12kHz is enough to get started:-)
Sigurd Kimpel, KJ1K (usaually operate microwave bands as a rover)
I hope you will find the AFC function useful. It should allow you to use
somewhat narrower filters to receive unstable microwave signals.
In case you receive signals for which the functions of Linrad do not
seem optimal, please make a recording (press S) and send an E-mail.
If the file is big I would like you to upload it somewhere, E-mail
attachments over 1 megabyte is a problem here.
I think rain scatter could be one such case.
Leif  /  SM5BSZ