QRP & a NAP - Baby Carriage Portable

This weekend, the sun finally poked out so baby Isabella and I were out for a walk. As babies do, she took a nap (we were at a noisy ball field, so a long walk around the back end of park was a lot quieter for both of us.) Also on the back of the All Terrain Baby Carriage was my FT-817 and a MFJ-1899T with a counterpoise.

The MFJ-1899T, is is a fascinating mini-antenna for on-the-spot HF'ing. It is made by Waters and Stanton of the UK and imported to the US by MFJ Enterprises, I got mine at HRO.

This multiband rig is similar to a miniature Outbacker, with band taps along its lower helical winding section, a jumper lead for selecting bands (wander wand), and a top mounted pull-up whip. The base is fitted with a BNC connector to mate with the FT-817’s front socket.

The MFJ-1899T “Walkabout” antenna covers 80 through 2 meters in a single “break apart and carry anywhere” package. Fully extended, it measures 63 inches in height. Retracted and separated, the helical base section is 12 inches long and the pull-up whip is 7 inches long. Adding a BNC-to-PL-259 plus a right angle PL-259 adapter and connecting it to the stronger SO-239 socket of the FT-817 relieves strain. That same idea also works for adapting the MFJ “Walkabout” to other transceivers (FT-857). But dial it down the output below the antenna’s limit of 25 watts.

It is the counterpoise, that is the key to making this little antenna perform. -- The instruction sheet suggests it need not be 1/4 wave long. In fact, the info sheet suggests using the formula 180/F(in MHz) = Length (in feet) of the counterpoise. I use a 16ft section for 40m & 20m and seems to work well enough, I used stainless steel cable covered in Teflon available at HOME DEPOT.

Isabella, slept for a little over an hour and half. When she awoke, we walked back to where the rest of the family was enjoying the ball games. She was rested and I was very happy to have worked a few stations on 20m QRP.


NOTE: I also listened for k4ESA on 10m, but did not hear anybody local, just lots and lots of South American stations calling, 10m is working well in the afternoon.

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)

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.

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

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

Electrons on Parade

Treat yourself to this 1942 factory promo for RCA vacuum tubes. The short 18 minute video shows how they made metal-can octal base tubes.

A truly fascinating video of how incredibly complex and automated the manufacturing process was even during WWII. Electronics as an industry has lost something of its mystic with vacuum tubes becoming more and more rare, and America as nation, has truly lost something of its brains in the lost of minds like this that built these incredible factory machines.

http://www.youtube.com/watch?v=QCksgN7kiv4

Many tubes are only available now from places like China and Russia. I think I will begin to catalog and cross reference these to make them more available to other radio amateurs, who like me would like a cheap and simple access to these treasures.

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)

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.