Re: [linrad] compiling/linking Linrad's C-source code...etc

[w3sz <w3sz@xxxxxxxxxxxxxxx]

Hi, Peter and All,

----- Original Message Follows -----
> Hi Roger,
> 
> 1:
> 
> Indeed, I did install RH8 + last update 2.4.20-13.8.
> But no nasm : " bash : nasm : command not found ".
> Searching all dirs ( might be it was not in root ? ) : no,
>  no nasm wherever.

I believe you must select it as an option to install it when
you are doing the initial install.  If you do not install it
by selecting it then, you will not find it on the system. 
So if you did not select it initially, your result "command
not found" is expected.

NASM is on CD #3 of the RedHat Linux 8.0 installation disk
set as:
nasm-0.98.34-1.i386.rpm.  So it is there to install if only
you select it.  If you can't find it then RedHat has the
RPM's for nasm on its website as well.


> Roger, may I please abuse this opportunity ?
> Why don't I see separate I and Q audio outputs on your DC
> frontend circuit diagram on Your site ?

Because at the time I wrote the FAQ I was not using I/Q
mixing and thus had only 45 KHz or so bandwidth.  Remember
that I/Q mixing is only needed at the very end just before
the soundcard.  So now I use conventional TUF-1H mixer to
get from 144 MHz to 2.5 MHZ for Leif's hardware, and Leif's
hardware provides the I/Q mixing to give me approx 90 KHZ
bandwidth.

> I do need them for the Delta card don't I ?
> If I want to enjoy the 90 KHz spectrum width .
> I do.

Yes, but I/Q is needed only at the very last mixer before
the soundcard.

> 3:
> 
> I understand that You use Leif's WSE 2500.
> Does this make a significant difference compared to direct
> conversion ( if properly designed and not overloaded ) 
> from 144 MHz to audio ?

Leif is a better person to answer this than I, even under
the best of circumstances.  And here it is 2300 and I am
soon due back at work.  So my answer is even poorer.

First of all, Leif implemented nice I/Q mixer, which I
didn't have.

Second, my initial design was not direct conversion.  I used
conversion from 144 to 40 MHz in one version and from 144
MHZ to 10.7 MHZ in another version, and then down to audio
in both versions.  The only direct conversion I have done is
using "The Time Machine".

Third, Leif knows what he is doing.  I pretty much don't
know what I am doing.  So any theoretical advantages of one
approach over another are outweighed by the fact that the
contest is really Leif's design vs Roger's design, and I
don't stand a chance on that one ;)

But to answer your question.  I think it is very much more
difficult to design a properly functioning direct conversion
receiver at 144 MHz that to do a multiple conversion design.
 Leif has some webpages that cover this.  Practically
speaking, I played around with direct conversion a little
bit without good results.  It was easy to do the multiple
conversion models.

 In which respects ?
> Selectivity ? ( sure.. )
> IP3/dyn. range ? ( questionable ? )
> Total system noise / noise floor  ? ( doesn't multiple
> conversions add noise compared to DC ? ).
> What is the net profit of WSE 2500 above appropiate direct
> conversion ?

I never achieved sufficiently working direct conversion to
say...


> 
> I studied Leif's papers on the WSE system's four modules .
> I am fascinated by the stuff but I am still a bit confused
> with regard to above paragraph.
> Please, any help is welcome.

I am not an RF Engineer, but I know that there is a reason
there are many, many multiple conversion receivers out there
and very few direct conversion designs.  I think direct
conversion could be done, but I want to learn to walk before
I try to run, and I also want to learn from those who have
gone before, and follow the path they have found successful.
 If you want to experiment, I would REALLY like to see a
design for a working H-mode mixer at 144 MHz, much more than
I'd like to see a direct-conversion receiver design
[hint..hint].

> 
> It is not a bargain, though I do understand fully that it
> must be costly for a very limited production .
> In Holland the WSE 2500 will amount to ~USD 730.
> Is it worth the money already now ( as separate WSE 2500 )
> or does it reward only in the chain 144/70/10.7/2.5 ?
> I guess You could have made comparisons between separate
> WSE 2500  yes/no ?

Value is different to each of us.  I am hearing better with
the homebrew front end I have coupled to Leif's WSE2500 and
then the Delta44 and Linrad than I have ever heard with any
other receiver / receive system on 144 MHz eme.  And to me,
that is value to the nth degree.  It is beyond dollars, to
me it is priceless ;)

I have not yet had the advantage of the Leif Chain of
modules, but I hope to use it when they are available.

I feel that I had a major advance when I added the WSE2500
to my homebrew system.  I have great confidence that adding
the remaining modules will enhance my receive system even
more.

> 
> Who else does use the separate WSE 2500 ?

I think that Kohjin, who is surely reading this, is also
using the WSE2500.  THink of it as a very high quality final
IF that provides I/Q mixing.  That is how I am using it.

I sent this to the list as I think you asked very
interesting and pertinent questions that will interest
others.  Even though my answers may not be very good, they
will stimulate further discussion ;)


73,
Roger Rehr
W3SZ
FN20ah
http://www.qsl.net/w3sz




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