SM5BSZ Linux PC Radio

 

Leif Wrote:


The Linux dsp radio I have been working with for quite some time now has reached a state where it could be used for real communication. The program has no adaptivity, the user is still responsible for tuning and in case of two channels
polarisation adjustment.

The program and some demo files can be downloaded at
http://ham.te.hik.se/homepage/sm5bsz/linuxdsp/linroot.htm
Note this is just a very early and incomplete package with
most probably a lot of bugs in it, but I hope it is enough
to start playing with.
 
This program is very flexible and should work with more or
less any sound board. In the future I hope someone will put
a radio A/D plus decimation chip on a board so one can
feed 0 to 200MHz directly to the computer only having a
band selecting filter between the antenna and the A/D.

In the meantime when radio A/D is not available for the PC
computer conventional sound boards do a pretty good job.

I am contemplating some hardware to make it easier to
interface ham bands to the PC.

One alternative is the 10MHz radio. A small low cost
board to which you feed 10MHz and which fits the
computer.

Another alternative is a small board to which the user
has to provide his own local oscillator at 4 times the
desired frequency. In this case the user also has to provide
a selective preamplifier.

The boards I think of would be zero IF boards so one
10MHz input will produce 2 audio signals. With a
Soundblaster the bandwidth would be 35 to 40kHz
for a single antenna. With a more expensive sound board
such as Delta 44 two 10MHz boards would provide about
90kHz each for two antennas (X-yagis)

I do not want to produce the synthetiser for a LO to
convert from 144 to 10MHz. The frequency 10MHz
can be derived from a standard computer oscillator at
40 MHz (Is there anyone knowing if there may be a
sideband noise problem with these small and cheap
units ?) For 10.7 an oscillator at 42.8MHz would be
required. For a small project I do not want to order
X-tals at non standard frequencies.
Other alternatives are 7.5MHz, 8.33333MHz, or
12.5MHz.

Boards like this have to be made in a minimum quantity
of at least 100 units. I understand most hams want
something that is a complete radio but not having that
choice I just wonder how great the interest might be
in the simple unit I contemplate.

73

Leif / SM5BSZ


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