Decoding Digital Ham Radio Without A Radio

Einstein once define radio this way;

"You see, [the] wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? And radio operates exactly the same way: you send signals here, they receive them there. The only difference is that there is no cat."

Here is your your chance to do Einstein one better, no radio either!

• Stuck in the Hotel room with no radio, because the airlines won't let you travel with your TS940?
• Would you like to practice copying CW with Cyrillic alphabet but your QTH doesn't pull in Russian stations in the solar lull?
• Test your new QRPp rig to see if you can be heard in Washington DC, or in the Netherlands.
  
• Or how about, trying out Olivia or RTTY from your office during those brain numbing conference calls when you would prefer to listen to static?

Then check out Alex /oz9AEC excellently produced YOUTUBE  video on how use a WEB accessible Software Defined Radio (SDR) and your headphone and/or your favorite digiMODE software. The video demonstrates FLdigi (my favorite too), but DM780, or digiPAN, or anything would work too.

click here LINK

Nice Job Alex! Here is a link to the WEB SDR ORG

Signal to Noise Ratio - Rainbows in the Dark

In analog and digital communications, signal-to-noise ratio, often written S/N or SNR, is a measure of signal strength relative to background noise. The ratio is usually measured in decibels (dB). If the incoming signal strength in microvolts is Vs, and the noise level, also in microvolts, is Vn, then the signal-to-noise ratio, S/N, in decibels is given by the formula;

S/N = 20 log10(Vs/Vn)

If Vs = Vn, then S/N = 0. In this situation, the signal normally borders on unreadable, because the noise level severely competes with it. In digital communications, this will probably cause a reduction in data speed because of frequent errors that require the source (transmitting) computer or terminal to resend some packets of data. If Vs is less than Vn, then S/N is negative. In this type of situation, reliable communication is generally not possible unless steps are taken to increase the signal level and/or decrease the noise level at the destination (receiving) computer or terminal.

And this was the world we lived in for most of time, but recently (last 40 years) even HAMs can communicate under the noise. As you may know if you have been following my blogs here, I have been smitten by WSPR and chalk up -30db contacts. PRIMER

Here are my findings to date (with the equipment at hand)

Mode Min SNR
CW@20WPM +3db (machine decoded by MFJ-461)
CW@20WPM +1db (machine decoded by fldigi or CWget)
HFpacket (300baud) +1db
RTTY45 -5db
CW@20WPM -7db (other claim like less, like -13db*)
PSK63 -7db
FELDHell -7db
PSK31 -10db
Olivia 64/2000 -13db
Olivia 16/500 -14db
WSPR -30db (maybe less)

NOTE: * some talk of minimum detectable signal (MDS), but I mean where one can actually decode it, not just hear it.

I prepared some files with simulated noise so I could judge for myself, now you can click on the links and judge for yourselves.

(I left them as .wav files because they sounded better, and are SMALLER than the .mp3 files)

Signal to Noise Ratio Files 091115 // CW string of 'ki4SGU em73ox' // CLICK TO LISTEN

1. Postive 9
2. Postive 7
3. Postive 5
4. Postive 3
5. SNR of 0 (Zero)
6. Negative 3
7. Negative 5
8. Negative 7
9. Negative 9

So here is the deal, if you are using WSPR (and you should be by now), and you make contact with me, drop an email and lets sched up a real QSO using some digital mode CW, PSK31 or Olivia and see if my estimates are right, or just full of hot air. 73 ki4SGU

More on WSPR ... Rainbows in the dark.

I'm continuing to enjoy WSPR -- Last night in a series of propagation studies I have been undertaking from ki4SGU studios, I explored the world of 80m internationally. A thought normally unheard of in these sunspot starved days.





I could not believe that Germany and Italy could be so easy worked on a low band. Studying the SNR data closely, I further believe that working these locations with traditional digital modes (PSK31, RTTY) would be easy, as would also CW but few try, hence few succeed.


(Click on Images to Expand)



Please pause and notice in this image that the Canadian HAM [ve6OG] is engaged in a WSPR QSO with a trans-Pacific station also on 80m.





Here are a few of the QSL cards that were sent electronically to me from Italians HAMs.












... a copy of my electronic log from the WSPR site;

Timestamp Call MHz SNR Drft Grid Report RGrid Km Az
2009-10-30 04:34 KI4SGU 3.594104 -10 1 EM73 NN6RF CM87uw 377 289
2009-10-30 04:16 KI4SGU 3.594090 -4 0 EM73 WA7KGX CN85 3484 304
2009-10-30 03:54 KI4SGU 3.594109 -23 0 EM73 IQ3AZ JN65qq 8003 47
2009-10-30 03:36 KI4SGU 3.594095 -16 0 EM73 KE0CO CN87tl 3476 308
2009-10-30 03:36 KI4SGU 3.594097 -27 0 EM73 G0DJA IO93if 6699 43
2009-10-30 02:34 KI4SGU 3.594093 -21 0 EM73 DL2NI JN48ul 7612 45
2009-10-30 01:54 KI4SGU 3.594099 +6 0 EM73 WB2LMV FN21ts 1314 42
2009-10-30 01:14 KI4SGU 3.594097 -12 0 EM73 VE6OG DO33fn 3164 324
2009-10-30 01:14 KI4SGU 3.594098 -20 0 EM73 AB3DI FM19ma 951 47
2009-10-30 01:14 KI4SGU 3.594095 -13 0 EM73 KC2RXS FN32bj 1391 41



Thereby proving that 80m is a TRUE world band, and that patience, persistence and curiosity are a healthy substitute for sunspots, as well as a welcome respite from the endless regional "ache & pains rag-chews" so common with US hams on the lower bands.

Then finally is an image from later this morning as the propagation faded, imaged captured remotely from work (a nice use of multi-tasking during those rather boring corporate conference calls -- And here you should wonder, How really boring these must be for a guy that likes to "listen to static" mind to wonder off into the ether. Numbingly Boring! - But I digress).

Have HAMs just grown lazy? ... Please quit waiting for the good propagation next year, HAM radio is about doing, action, and making waves. Please get on the air, on any mode tonight - And make your own Rainbows in the Dark.

Pssst.... Do want to know a secret? - Try WSPR!

Last night in a bought of radio depression, I was motivated enough to try WSPR -- as I wasn't too motivated to do anything else -- the band conditions were dismal. I had held off on trying WSPR being loyal to PROPNET a similar venture that uses PSK31. I never do well in those Coke/PEPSI or BETAMAX/VHS sort of questions.... Well PROPNET is equal to BETAMAX, it is better in every way, but you guess it!, WSPR is more popular and hence the better choice. The idea of internet cross tabulating propagation reports is way cool, and more so when the whole world tunes in.. For a quick thrill on 30 watts or less try WSPR.

-- WSPR stands for Weak Signal Propagation Reporter, but it's pronounced "Whisper" - quite an appropriate name as it is all about sending and receiving signals that are barely audible. DOWNLOAD

The software is written by Joe Taylor, K1JT, a Nobel Prize-winning Princeton physicist. It was first released in April 2008. It uses a transmission mode called MEPT-JT. The "JT" stands for Joe Taylor, while MEPT stands for Manned Experimental Propagation Transmitter.

Consequentially, a very interesting interview with Dr. Taylor, k1JT can be found in this month's CQ Magazine - A link provided here.

OK I have decided to launch myself into the blogosphere. I have created this blog in an effort to be able to document the various points of interested that I am interested in, mostly Ham Radio, but I'm sure from time to time I will have other thoughts, however fleeting the may be.

I'm still new to the blog spot interface, so please forgive me if I commit any formatting sins.