Signal to Noise Ratios - Rainbows in the Dark - Part 3

Not all S-Meters are calibrated, mine sure is not. Below you'll find a nice chart for the ideal S-Meter, a standard originally proposed by the Collins Radio Company 50+ years ago and it is now accepted as the de facto industry standard. (The original standard stated S-9 = 50uV, the rest are linear extrapolations)

S-Meter    Signal    dBm  
S-9 +60db  50,000uV  -13
S-9 +50db  15,811uV  -23
S-9 +40db   5,000uV  -33
S-9 +30db   1,581uV  -43
S-9 +20db     500uV  -53
S-9 +10db     158uV  -63
S-9            50uV  -73
S-8            25uV  -79               
S-7          12.5uV  -85     
S-6          6.25uV  -91      
S-5          3.13uV  -97      
S-4          1.56uV  -103      
S-3          0.78uV  -109      
S-2          0.39uV  -115      
S-1          0.20uV  -121      
S-0          0.10uV  -127

The source of this chart is ARRL's QST Magazine DEC2009, Page 45

There many ways to calibrate your S-Meter, but that lies outside of the scope of this blog. For our purposes here relative measurements will more than suffice.  So let say you are on 40 meters, typically the "noise" will be S3, or about -109dBm (your location and radio will vary, but work with me here). If your receiver has an MDS (minimum detectable signal) of -131dBm, it means you’re loosing 22dB of your dynamic range to the noise! (131-109=22dB). In this case, the S-meter is more-or-less giving you an absolute power DIFFERENCE between its MDS and the noise floor, in dB.

You then hear a CW (or any other kind) station calling CQ, and he has a S7 signal. Therefore S7-S3=S4 or 109-85=24db, so a +24db, that is a fairly clean and easy signal to work. Are you with me so far?

In my previous blog Signal to Noise Ratio - Rainbows in the Dark I created files of where I thought certain digital modes could be work under the noise level (SNR).  With some digital modes listening and decoding signals that are much much harder than that. In my previous example file of about a -7db signal, I'm talking about a -109db+7db=116db or one S-Unit under the noise! By now, we have all seen that WSPR can do -27db (maybe less).  In my last blog in this series, I posted that "CW@20WPM could only be done at -7db or better" (this was sure to draw fire from all camps)

I had a few folks tell me that they could do much better, one fellow whom I trust Dick /k2UFT, basically agreed with my -7db level estimates, but wisely suggested that I should re-do the files and embed a secret word with each file. In that way the testers would be blind and could then report what they heard and decoded.

So here is my new challenge, listen to the new files, preferably just once, just like a real QSO copy. Then  please email me (or blog post) the correct secret word embedded in each. Never mind about -3db and above, those are easy, right? -- just focus on -5db and below. Since so many folk were so confidant that could do better than -7db, I have taken the time to create four additional files with even more noisier levels. (HINT: all of the words are 8 char long)

SNRtest_ki4SGU_091116_1_pos9.wav
SNRtest_ki4SGU_091116_2_pos7.wav
SNRtest_ki4SGU_091116_3_pos5.wav
SNRtest_ki4SGU_091116_4_pos3.wav
SNRtest_ki4SGU_091116_5_evn0.wav
SNRtest_ki4SGU_091116_6_neg3.wav
SNRtest_ki4SGU_091116_7_neg5.wav
SNRtest_ki4SGU_091116_8_neg7.wav
SNRtest_ki4SGU_091116_9_neg9.wav
SNRtest_ki4SGU_091116_10_neg11.wav
SNRtest_ki4SGU_091116_11_neg13.wav
SNRtest_ki4SGU_091116_12_neg15.wav

I know, I know... I can hear you thinking out there, "What if you use a computer?", knock yourselves out, FLdigi away and/or any DSP filter you'd like to use, remember just keep it like a real QSO. Also there is no prize for being right or first, so why cheat?

As an update, I also worked with Eric /ab3DI on PSK31 vs WSPR last week, we were not able to validate that a two-way PSK31 QSO can take place @ -10db (so for now this remains a guess-ti-mate)

For those of you that are only on SSB -- What value does this provide you?? WSPR can provide you a baseline, granted for voice SSB the SNRs have better be positive. If you like to check what your link budget is for a given path, simply have your station and the remote station fire up WSPR and let them run for a day or two on the given band and given power. This will reveal the observed SNR between those points (hourly). Please understand, time of day and time of year, WX, and solar activity will all be variables, but at least you'll know that on that day you had that SNR, albeit it will vary over time but if your net is always at the same time of day, chances are the numbers you observed will provide you with a "reasonable" estimate to base further decisions concerning moving your net to a different band or time. Also no need to do just 2 stations at a time, for a regional net have a bunch of the guys try it all at once, the WSPR database will sort out all of the link budgets at once.

Once last idea, if you have a program like VOAprop by g4ILO (an excellent program!) you can use your WSPR data (observed data) to calibrate your other VOA predictions (predicted data), and in the end be able to make better predictions.

73 ki4SGU

PS. This blog series has been mentioned on SOLDERSMOKE PODCAST 118 (QRP & Homebrewers Inspirational Incense)

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

Stone Mountain Hamfest - Extra Extra - Read all about it.

I recently attended the Stone Mountain HAM Fest near Atlanta, GA. This is the area's largest and best featuring lots of vendors and bone-yard tables.

The weather could not have been better, and I was able leisurely walk around slowly eying up lots of great deals on new parts for my JUNK BOX, and I also passed my EXTRA exam, DX here I come! So it is Mr. ki4SGU/AE if you please.

Among the electronics treasures I found, were four variable caps (3x 4-100uF & 1x 75-350uF), all less than $2 ea. I also stocked up on mono audio plugs for the upcoming PIXIE build, and some nifty multi turn 10K pots, and 2 new 10m ham-sticks for a ham-stick dipole for any future LX peditions.


The crowds were fairly large, even folks taking the Hams test numbered more than 40. With the testers and the all star VEC crew made for tight quarters while testing.






For all you Yaesu fans, they will be offering a new APRS & GPS dual band radio, the FT350.

For the Kenwood crowd, they will be offering two new models a new HT (a super new version of their popular Kenwood TH-D7AG Data Communicator) and a new HF (a super new version of the Kenwood TS-570SG). It is all hype now, but the booth guys were bragging about a k3 beater on RX. I was not able to find any pictures to share here, but I did find a video which I saw in person at the Kenwood booth, I found a version it here on YOUTUBE ICOM did not attend this year, but our old faithful friends MFJ and HRO were so busy, I did not fight the crowds to get a peak, or even a new catalog.



I also attended a very folksy and entertaining forum by the author of ARRL's Low Power Communication Guide, The Art and Science of QRP By Richard H. Arland K7SZ.

Ham Radio and Ham Radio Festivals are alive in well here in Georgia.

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

New treasures from the east...

New treasures from the East... have arrived at my home and another season of QRP building will have started in ernest.

If you are a QRP builder (or would like to be), you may have already noticed recently your local Radio Shack doesn't stock the parts you crave. - My secret is eBAY, with Keyword "HONGKONG" -- A paradise where 1/4w resistors are still a only .01$US and most items well under a buck. Happy Hunting

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.

The Emperor Has No Clothes - More on my infatuation with coils.

As you may already know, I have developed a wholesale interested in coils. I have been trying to increase my personal understanding of coils as used for antennas (as baluns) and as they are used in band-pass-filters (ummm, as well ... coils) and all other things of an inductive nature.

After the normal frenzy of Google searches, I was lead to -- "Understanding, Building, and Using Baluns and Ununs" by Jerry Sevick, W2FMI -- This book is presented (ARRL, eham, and everyone else) to be universally touted as the pinnacle and the state of the art for those seeking a deeper understanding and actually building. I ordered it....

20 bucks and a few days later... I wish I could tell that it were true, in short they are all wrong and I would strongly suspect not one of them actually read the book. I found the book to be at best a loosely coupled collection of articles which seems to start in the middle of basic ideas, and seem to trail on and then abruptly end. To the say the book is badly written, I will not say, I'm no English major myself, and I'll leave that to others. What I can and will say is; I did not enjoy it, and I found it to be contradictory, weak and misleading. -- In many cases the author warns the reader of the evils of voltage baluns (probably a true statement), but then extols the superb benefits and divine merits of Ruthroff's work on the same. huh?!

The author constantly refers to the seminal publication of G. Guanella in the Brown Boveri Review in September of 1944 (PDF) but never really takes the time the explain to the modern reader the construction outlined in the article. The article also constantly referred to C. L. Ruthroff August 1959 equally seminal article (PDF) -- I'm sorry, I had missed that one too, as I imagine most modern readers will have (as in 'we were not born yet!?') and my subscription to the BBR is still in the mail. -- I have posted both of the articles above so that you may acquaint yourselves with their genius.

Like the little boy in Hans Christian Andersen's story, "The Emperor’s New Suit". I post this rather negative review at great peril to myself, because HAMs are a funny lot (as in not "ha-ha"), and are very similar to sheep, and do not take kindly to folks having a difference of opinion on something they hold sacrosanct. Flame On QRPers!

As to not become the Andy-Rooney-of-HAM-radio with my Casandra like opinions, I will share with you that I did find a few articles (Free PDF) on the web that are very helpful, and go a long way towards really being helpful.

C. Greene w1CG 2002.pdf (PDF) & C. Greene w1CG QRP 4:1.pdf (PDF)
and R. Bertran vk2DQ 2005 OCF dipole.pdf (PDF superd, must read!!)

I also share with you Jim Brown's J. Brown k9YC APR-2008.pdf (PDF), but with a warning. For it also seems to suffers from Current-vs-Voltage confusion affliction -- For the record the Guanella balun is NOT a voltage balun.

73 ki4SGU

Reading for FUN // SolderSmoke - The Book!

A book by Bill Meara N2CQR/CU2JL/M0HBR the host of the QRP classic podcast SolderSmoke.

I've loved the show from the very beginning, hanging on every story. His stories are wonderful, and not because they are unique, but because they are our stories too. If you like I have been interested in the uber-geek pastime of Ham Radio then chances are you will find that many of Bill's childhood stories will resonant in a eerie sort of way with your own life. I recently picked up SolderSmoke - The Book! from LULU.COM and I'm planing to read it at work during my lunch break, in true SS style.

Also, If you have not had a chance to listen to SolderSmoke but are interested in QRP radio and other subjects of interest like Astronomy, CW & Electronics. Be sure to check out SOLDERSMOKE - The PodCast too. (It is free)

Sun Spots and Atlantic Storms Correlation

In order to comply with the complaining about the low solar numbers quota that every HAMs must comply with as per of FCC rules, Earlier this week while driving I was amusing myself by dreaming about higher solar activity. -- Doesn't everybody?

In this particular day dream, I started to notice that there was an apparent relationship between solar activity chart in my head and the hurricanes I could bring to mind, please remember I'm driving, so my data was more than a little fuzzy. So this PDF is a result of an attempt to do a slightly less fuzzy back-of-an-envelope type of calculation.

I got my Solar Data and chart from the Solar Influences Data Analysis Center - (SIDC) http://sidc.oma.be/sunspot-index-graphics/sidc_graphics.php

and my Storm Data from the National Oceanic and Atmospheric Administration - (NOAA) - http://www.aoml.noaa.gov/general/lib/mgch.html (and a few others)

This seems so obvious that I knew I could not have been the first to notice, so a little google search turned a few references, but the best and cleanest seem to be this wiki entry. Where it names good 'le GATECH as the authors of just such an idea.

http://en.wikinews.org/wiki/Hurricanes_may_be_associated_with_sunspots

OK, so it is not a new idea, but an interesting one all the same. Notice the storms seem to ovoid the peaks (and troughs - except for Betsy). My original idea was that really large US hitting storms would only occur 18 mo ~ 24 mo AFTER the solar peak. This simple chart shows that is not exactly exclusively true. While it is true that storms do seem to follow that pattern, they also seem to happen 18 mo ~ 24 mo BEFORE the solar peak. This needs a little more work before any real conclusions can be made, but there does seem to be a pattern.

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.