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

Re: [linrad] RE: noise blanking/weak signal comparisons


It would be a terrible mistake to say that Linrad provides 'poor' CW weak signal
capability, which is how someone just coming on the scene could interpret your email
to the list.

Linrad EXCELS in weak signal CW copy.

I have used it on 144 MHz EME to copy signals that NOTHING else I have used can copy.
 THis includes the Elecraft K2 with or without DSP-BLaster DSP audio processing, the
FT1000MP with its own DSP or with or without DSP-BLaster, etc.

A test is only good for testing what it is meant to test.  Your comments were based
on a single file from one of my web pages, which was made to give folks an idea of
how Linrad and its noiseblanker stacked up against the SDR-1000, as I had received
many email questions on that.  The files were not meant to give an appraisal of
Linrad's ultimate weak signal handling capability, and were not represented as doing
so.  I have posted many files to the list and my webpages over the years which were
made under very weak signal conditions on 144 MHz using Linrad.  Some of those were
wave files, and some were Linrad "S" files.  Linrad excelled on those files.  Some on
the list have undoubtedly listened to some of them before.

I DID NOT have Linrad optimized for HF weak signal work when I recorded the noise
blanker and related files.  They were recorded just to demonstrate the noise blanker
during a period of time when intense pulse-type noise was present, and then to
compare the SDR-1000 and Linrad again when pulse noise was not present.  Having both
sets of data helps to show how INCREDIBLY GOOD the Linrad noise blanker really is.

I do not have an optimal front end on Linrad for HF work, as I don't have an interest
in HF and don't have the time to play in that sandbox and still do what I AM
interested in ;)
Linrad won't turn a sow's ear into a silk purse, although it comes close to doing so,
and so I will never be able to demonstrate its ultimate abilities on HF, unless
someone else designs / builds the front end and I get a copy of it.  So DO NOT use my
data to decide what Linrad cannot do with weak HF signals.

All I have been writing for the last 2 years plus is how GOOD Linrad is for weak
signal CW work.  So I was quite concerned to see:

> I realize that W3SZ's files would not be enough upon which to make 
> any judgements but I was struck by how poor the weak CW copy was and 
> yet how good was the SSB copy.

which goes against everything I have experienced and said and written over the last 2
years, because it could give others a very unfortunate, wrong impression.  That is
why I write this email to the list.

The files were not recorded in a manner to demonstrate weak signal CW receive
capabilities.  They were hastily recorded with the most simple front end one can
imagine, with less than ideal parameters, in order to get a series of files recorded
with different radios before the interference disappeared.  And they served their
purpose, demonstrating the incredible utility of the Linrad noise blanker, even under
less than ideal conditions and with less than ideal parameter settings.

Linrad is easy to implement and if you already have a computer, not expensive to get
going.  If you are interested in HF you should be able to put together quite a nice
HF front end pretty easily.  If you do so, I can guarantee you will be most amazed in
a very positive way at what Linrad can do.  Don't wait for someone else to do the
benchmarking, do it yourself.  It will be a lot of fun!  And we would love to see
your results.

Have a great weekend, and 

PS  my experience is that Linrad does much better with weak signal CW than it does
with SSB.

Roger Rehr