[Elecraft] P3

[Philippe Trottet]

P 130 is blank on the pdf document !
73's
Philippe A65BI

>>> Kok Chen <chen at mac.com> 16-02-2010 14:16 >>>

On Feb 16, 2010, at 12:39 AM, turnbull wrote:

> When you write the manual for the P3 would you please include a good explanation of the use of waterfall displays.  I have one on my OII but do not fully understand its benefits.   

Spectrograms, such as "waterfalls," make use of your eye-brain system to help find signals that are below the noise level, especially when signals are drifting and don't allow temporal averaging methods.

You can see an example of its use (1971) here:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730010095_1973010095.pdf 

Fig 11-7 on page 130 (although poorly reproduced in the PDF scan) and the text on that page explains its use for discovering very, very weak and very, very DX signals.

In the amateur world, the first use of waterfalls was by Skip KH6TY in his Digipan program, I believe.  Without Digipan and the ease of "waterfall tuning," PSK31 probably would not have become as popular as it is today.  

With the addition of some special filtering, you can make a waterfall see even deeper into the noise when the signal is not drifting. The two figures here

http://homepage.mac.com/chen/w7ay/cocoaModem/UsersManual/mfskManual/mfskManual/dominoex.html#weak 

show the same weak DominoEX signal with 18 FSK carriers.  The top figure is what the weak signal looks like in a simple waterfall, and the figure at the bottom, with the same input SNR, takes advantage of a signal that is not drifting, as explained in the accompanying text.  

In the digital world, you can't work them unless you can *see* them :-).

A good waterfall display will also show a CW signal that you can't hear, and can make "zero beating" a virtually instantaneous effort.  Or zero beating to a synchronous AM carrier, etc etc.

73
Chen, W7AY

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft 
Help: http://mailman.qth.net/mmfaq.htm 
Post: mailto:Elecraft at mailman.qth.net 

This list hosted by: http://www.qsl.net 
Please help support this email list: http://www.qsl.net/donate.html