FW: RE: linrad, spectran,dspfil (W3SZ Sept 29 2002)

[Leif Åsbrink <leif.asbrink@xxxxxxxxxxxxxxxxxxxx]

-----Original Message-----
From: owner-linrad@xxxxxxxxxxxxxxxxxxxxx
[mailto:owner-linrad@xxxxxxxxxxxxxxxxxxxxx]On Behalf Of W3SZ
Sent: Sunday, September 29, 2002 4:14 PM
To: linrad@xxxxxxxxxxxxxxxxxxxxx
Subject: RE: [linrad] linrad, spectran,dspfil


HI, Arie!

You have asked a very interesting question!

I have used Spectran, DSP-Blaster, etc for some years, and I used
HamView before Spectran became available. I've also tried at least half
a dozen other DOS/Windows DSP processing programs.  I've been using
Linrad for a long time.  I have used all of these for EME purposes on
144 MHz, as well as playing with them on HF, etc.  In this location its
often impossible to do 144 MHz EME without DSP processing of some type,
so the situation is different from yours.

For me for this purpose (144 MHz EME) there is NO comparison between
Spectran, DSP Blaster, and the other DOS/Windows programs on the one
hand and Linrad on the other.  Linrad wins Hands Down.  This is however
with my own homebrew receiver front end.  The difference here is not so
overwhelming when I use Linrad attached to the audio output of the
commercial ham transceiver (receiver).

In my opinion when you do post-processing of a commercial rigs's audio
output by any method you are really just chipping away with a needle at
a 1000 km square ice-berg, so to speak.  I know others may disagree, but
if you want to REALLY improve the signal detectability, then you need to
start operating much earlier in the receiver chain.  Its really pretty
easy to build a homebrew receiver front end that, with Linrad,
outperforms the commercial stuff by far.  Mine is very simple (and
cheap) and does a very good job for me.  The cost in parts is less than
that of a new trackball for your computer See:
http://www.qsl.net/w3sz/FAQ.htm#5a and
http://www.qsl.net/w3sz/HBreceiver.gif .

I am sure many of those subscribed to the list could draw up a superior,
but still very simple receiver for these purposes.  And Leif's hardware
will be superb;  I plan to get the units as quickly as they become
available.

If you are interested, there are some pages on my website that discuss
my experiences with all of this.  However, the difference between Linrad
and the other programs in my experience is so great, and I have
discussed them for so long that I figured people were pretty much bored
with / tired of the now nearly 2 year old comparisons (in some cases) so
that I have removed a lot of the material on the comparisons from my web
pages.  See:
http://www.qsl.net/w3sz/linrademe2001.htm
http://www.qsl.net/w3sz/w3szdspnew.htm for a few of the remaining
documents.

Since I wrote those webpages I have become even more impressed with
Linrad, and I don't use the Elecraft K2 or the FT1000 MP either alone or
with the DOS/Windows DSP programs for EME anymore (except for JT44).  I
just use Linrad.  Doing anything else is just like banging my head
against the wall ;)

However, for microwave purposes (1296 and above) I have found that I do
not need Linrad for readability.  I find the same as you;  I can always
pull out of the noise the signal (of anyone who can copy me) with
conventional rigs without outboard DSP, or with the DSP-10 RF version if
I am using that for the IF.  To copy the signal I don't need Linrad.

Having said that, I have found that on the Microwaves being able to see
40 KHz of spectrum with Linrad is VERY helpful, as some guys are WAY off
frequency.  Although I use Rb or GPS locking here, and check my
frequencies vs the beacons, that doesn't help to find the OTHER guy when
he is off frequency.  But seeing him pop up 5 KHz away on Linrad makes
the probability of completing a contact much higher as it removes the
'way off frequency' variable from the equation.  I just point and click
on his Linrad waterfall trace, and copy him, then zerobeat my
transmitter to that frequency, and complete the contact.

I hope that helps.  Feel free to reply / query / etc either via the list
or privately as you feel best.

73,

Roger Rehr
W3SZ   FN20ah
2 Merrymount Road
Reading, PA  19609-1718
http://www.qsl.net/w3sz





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