Month: May 2016

DSP and NDBs

The HDD arrived and I have a computer again!

I’m using Spectran to examine the audio output of my IC-7000.

I had good success using my ears alone in identifying weak signals but the waterfall display helps identify the really weak ones. I can also narrow the digital audio filter to 1 or 2 Hz to separate two or more signals on the same (or very similar) frequency.

I’ve picked up a few signals that I would not have known were there (using my ears alone) with this technique. The one thing that is nice is the duration of the waterfall (many seconds) helps me identify the non-DAID (no dash after ID) signals. I know I was moving through the correct frequency on their silent time between IDs. Now I can see the signal before or after I arrive on frequency and can set up correctly to receive them when they transmit.

I’ve noticed some wider bandwidth signals in the middle of the NDB band. They seem to be digital.

… Research …

They are on the correct frequencies for DGPS signals so I’m going to need another software program to decode them. I’m looking at WSJT for this but the learning curve is quite steep.

More later as I figure this out.

EDIT: It looks like Spectrum Lab also can decode DGPS … I have a better grasp of how that program works so I’ll start there.

EDIT 2: I can’t seem to get the terminal section of Spectrum Lab to “see” the signal. Obviously I have done something incorrectly. I loaded DSCcoder and it works great. I’ll keep testing it for a bit to see if it is the software for my situation.

Computers and signals

I’ve dabbled with computers, SDR systems and software for spectrum analysis on my HF radio for a few months (more off than on) and have not really thought too much about these tools. Then the computer decided that the HDD was no longer a HDD and stopped working completely last month.

When this happened I said “Oh well, I don’t use it for too much so it can sit on the shelf for a bit”. This turned out to be the opposite of what I really should have done!

I’m at a point in my NDB hunting career where I have heard most of the signals that are audible on a normal evening. On quiet nights with good propagation I’ll hear more but I feel it’s time for some new strategies.

One is building a loop to null the “loud ones” (it’s on the project list) and another is digital signal processing (DSP).

Weak signal detection using DSP can allow me to “see” the signals that I cannot hear well (or at all). I can also use programs that will decode digital signals or display QRSS (slow speed CW) easily. Recording is also possible with these programs so I don’t have to stay up late every night!

So now I’m at a standstill as my computer is not working. I ordered a new (old PATA style) HDD and it’s on the way. Once here, I’ll rebuild the computer using some backups I have (you have backups don’t you?) and re-install other programs. I should be back up to speed by month end (I hope).