Friday, November 27, 2009

This Thanksgiving Season remember the Amateur's Code

CONSIDERATE...never knowingly operates in such a way as to lessen the pleasure of others.

LOYAL...offers loyalty, encouragement and support to other amateurs, local clubs, and the American Radio Relay League, through which Amateur Radio in the United States is represented nationally and internationally.

PROGRESSIVE...with knowledge abreast of science, a well-built and efficient station and operation above reproach.

FRIENDLY...slow and patient operating when requested; friendly advice and counsel to the beginner; kindly assistance, cooperation and consideration for the interests of others. These are the hallmarks of the amateur spirit. is an avocation, never interfering with duties owed to family, job, school or community.

PATRIOTIC...station and skill always ready for service to country and community.

--The original Amateur's Code was written by Paul M. Segal, W9EEA, in 1928

Thursday, November 19, 2009

A Sourthen Resource - Cherry Blosom Intertie Repeater System

If you find yourself traveling south from Atlanta to Savanna, you might to tune into the Cherry Blosom Intertie Repeater System. A very friendly and very useful resource for the HAM traveler equipped with only a only 2m FM mobile radio.

Personally I was able to access this resource from atop 2 of Atlanta's Metro Peaks (Lost Mt & Pine Mt). I tuned into the network at Forsyth (147.315 no tone). It is the furthest north repeater in the intertie family and covers Monroe and parts of Butts and Henry Counties. From the metro peaks I was able to bring the repeaters with ease at only 5 watts and my standard 5/8 comet mounted on my Jeep. Next time, I'll try a HT with an aftermarket long duckie antenna, no guarantee but the mobile worked so well, I'm optimistic.

Here is a link to their excellent site. In the very near future, I will be updating my North Georgia 2m Repeater list to includes this fine addition.

73 ki4SGU

PS. I'm told there are more repeaters on the network, but are linked only temporarily (during nets, etc), and regrettably I do not have the locations or the frequencies.

Monday, November 16, 2009

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)


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)

Friday, November 13, 2009

Confused by all of the new digital modes when hearing them??

If you have been the HF band lately listening in the digital portions, you will know that there are some very strange noises there. Some are more well known like the inviting sounds of CW, or the sweet double tones of PSK31. Others, like the difference flavors of RTTY or the numerous alphabet-soup of OLIVIA modes are harder to identify by ear alone. Just when it seems darkest, there is a solution right there on the programs you are already probably using.
- The solution is RSID

The Reed-Solomon ID (RSID) is a short 16-tone MFSK transmission which identifies the mode in use. The RSID transmission is about 180Hz wide and lasts for just less than two seconds. -- Reed-Solomon IDs - This idea was originally developed by Patrick Lindecker /f6CTE. -- You should enable RSID when using an 'exotic' mode such as Olivia so that users of programs with RSID support know what mode you are using. Your digital decoder program will then reconfigure itself to support that mode, not everybody uses this yet, but at least, now you know.

There are two ways to enable RSID (DM780 + FLdigi):
  1.   In Program Options select Modes + Ids and check the option to show the RSID button in the transmit toolbar,
  2. Add the tag anywhere in the text being sent.

73 de ki4SGU

Wednesday, November 11, 2009

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

Tuesday, November 10, 2009


Many of you may have already heard me talk about my plans to launch a group build on the local repeaters. The DIXIE PIXIE now has its own BLOGSPOT, please feel free to drop by and stay informed on its progress.

Sunday, November 8, 2009

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.

Friday, November 6, 2009

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.

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)

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

Thursday, November 5, 2009

More on my RAINBOWS in the Dark Series...

More on my RAINBOWS in the Dark Series... I am continuing to have a blast on WSPR

I was mentioned in g4ILO Julian's fine blog "WSPRing all night on 40" for a UK WSPR contact.

Other note worthy contacts were New Zealand and Australia.

Here is a LINK to complete log of 40m contacts @20w.

Of late, I've read some comments about the true worth of WSPR, in my humble opinion this is one hot mode, and is very valid and relevant. WSPR will probably bring-in and retain lots of new technically oriented blood into the hobby, as well as re-energize old timers, specially the QRPer and HOMEbrewers - And that is really a good thing. We need more true HAMs (Builders, HomeBrewers) not more "CBers with a GENERAL CLASS license that can't build, can't solder, do not know code" in a word "appliance operators". -- The WSPR software adds a dimension that was missing from traditional low power building projects, it collects and presents the performance data in an objective and easy to compare form.

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