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Sunday, June 3, 2018
Understanding Antenna Directivity -- Help from Canada
I am in the process of repairing my beloved 17 meter fishing-pole Moxon. It was taken out of service by the last Nor'easter of the winter. This repair has caused me to review the theory behind antenna directivity. I find there is a lot of "hand waving" in the explanations of how directivity happens: "You put a reflector element next to the antenna. And it REFLECTS!" You are left wondering how that reflection happens.
The Royal Canadian Air Force made a video that does a pretty good job of explaining how the reflector reflects. See above. Thanks Canada!
While we are talking about antennas, I wanted to alert readers to a really nice antenna modeling program that is available for free. It is called 4nec2. You can find it here:
http://www.qsl.net/4nec2/ There is a bit of a learning curve, and I am still climbing it, but I can see how this software would be very useful. It has an optimization feature that runs the antenna through many versions and tells you how to optimize for F/B, gain, SWR, or whatever you want to prioritize.
I have discovered that my Moxon was resonant below the 17 meter band. In other words, the antenna elements were too big. About 3.6% too big according to my calculations. This may be the result of my using insulated wire for the antenna elements. Apparently the MOXGEN software assumes the use of uninsulated wire. I'm thinking that an easy way to deal with this would be to use the frequency 3.6% above my target frequency and then use the dimensions given my the MOXGEN program. Any thoughts on this plan?
What a shame that Cebik's web sites have all disappeared.
Labels:
antennas,
Moxon,
propagation,
software
Friday, June 1, 2018
INTERVIEW: Bob Crane Talks to Jack Purdum W8TEE at FDIM. Definition of "Homebrew."
Jack Purdum has been making enormous contributions to the radio art. His background with digital technology has opened many doors for homebrewers, especially through his books on the use of the Arduino microcontroller. I think his new "JackAl board" is really going to shake things up. I was glad that our correspondent in Ohio, Bob Crane W8SX, caught up with Jack and interviewed him for soldersmoke:
But I have one small disagreement with Jack. It has to do with the definition of "homebrew." Jack seems to define true homebrew as "designing and building your own rig from scratch." My problem is with the "designing" part. By this definition, those intrepid heroes of days-gone- by who saw a schematic in QST, ripped apart some old broadcast radios, and used the parts to build a 50 watt CW transmitter with a regen receiver were not true homebrewers. I would maintain that they were. I agree with Jack that kit building is a bit different, and of course designing the rig yourself earns you the coveted "designer" designation. But for me, if you start with a schematic and an article, gather the parts and build the thing yourself, that is a homebrew project and you are a homebrewer. After all, even the designers are very often making use of standard blocks of circuitry (Colpitts oscillators, common emitter amplifiers, power supply circuits, etc.)
I think we will have to turn to our lexicon expert Steve Silverman for a ruling.
In any case, thanks to Bob Crane and to Jack Purdum.
Labels:
Arduino,
Crane-Bob,
Hamfests and Flea Markets,
homebrew hero
Wednesday, May 30, 2018
Hans Summers and his QCX -- G0UPL Cracks the Code on Si5351A Quadrature
Pete, Brad WA8WDQ and I were recently e-mailing about our admiration for what Hans G0UPL has achieved with his QCX rig. I cc'd Hans -- we got this nice and very informative e-mail. Be sure to click on the link provided by Hans, and from there go to the link to his FDIM proceedings article. I think that article is a real masterpiece -- there is a lot of very valuable information in there. For a long time, getting quadrature output from the Si5351 seemed like an impossible dream. But Hans has obviously figured out how to do this, opening the door to much better and simpler single-signal phasing receivers. Thanks Hans!
Hi all
Thanks for the nice feedback on the QCX and the FDIM conference proceedings a article, which I have published on QRP Labs web page along with other Dayton trip miscellany. See
My seminar presentation audio was recorded by Ham Radio Workbench podcast and they will be publishing it on 5th June.
The QCX kit has indeed been unbelievably popular, almost 5,000 kits have been sold since the launch on 21st August. It seems to have itched an itch that needed itching, in the QRP world. Sales continue to be strong and I'm currently preparing another batch of 1000 more.
I'm very proud of my 90-degree quadrature Si5351A and it helped me towards my low cost, high performance target for QCX. Abandoning the 74AC74 saves a part, reduces cost, reduces complexity, reduces board area (and hence more cost) and even seems to provide better performance (higher unwanted sideband rejection when using the Si5351A in quadrature mode). Getting the Si5351A to do this is one of those things which look easy afterwards. But at the time, and faced with SiLabs un-useful documentation, it took an awful lot of headscratching, trial and error!
73 Hans G0UPL
Labels:
Hamfests and Flea Markets,
Kits,
Phasing Rigs,
SDR,
Si5351,
Summers-Hans
Monday, May 28, 2018
VK2BLQ's Beautiful uBITX in a Wooden Box
Now that, my friends, is a BEAUTIFUL uBITX. Stephen VK2BLQ put that one together. Peter VK2TPM helped him get the KD8CEC software into his Raduino (Stephen had trouble getting it to compile on his Raspberry Pi).
For me there is good news and bad news here. The bad news is that I can no longer tell people that mine is the only "wooden box" rig that they will ever work. The good news is that I am no longer alone.
Sunday, May 27, 2018
INTERVIEW: Four Days in May 2018 -- G0UPL Hans Summers talks to Bob Crane
Once again, our correspondent Bob Crane W8SX has gone to the Four Days in May event and has sent back some really great inteviews with those who made presentations there.
First on the list was Hans Summers G0UPL. Hans is a justifiably famous Homebrew Hero, and a member of the QRP Hall of Fame. The latest of his many contributions to the hobby is his amazing QCX transceiver. Like the BITX rigs, the QCX refutes the idea that hams need to spend kilobucks to get on the air with a decent rig. Priced at around $50, the QCX offers excellent performance. And it comes with built in test gear: the signal generator you need to align the rig COMES IN THE RIG! FB Hans.
I think it was Pete who noted that the price range for rigs like the QCX, the BITX, and the uBITX is in the $50 to $110 dollar range, meaning that "One hundred bucks is the new three thousand bucks." We owe a lot gratitude to Hans and Farhan for this very positive paradigm shift.
Listen here for Bob Crane's 2018 FDIM interview with Hans:
http://soldersmoke.com/G0UPL-18.mp3
We all also owe a debt of gratitude to the QRP ARCI folks who did all the hard work that goes into organizing Four Days in May. Special thanks to QRP ARCI Preston Douglas WJ2V, and to FDIM Chair Norm Schklar WA4ZXV. FDIM is one of the most important events on the Homebrew/QRP calendar.
More info on the QCX (and order yours) here: https://qrp-labs.com/qcx.html
Labels:
Farhan,
Hamfests and Flea Markets,
Summers-Hans
Thursday, May 24, 2018
An Epic Evening on 40 Meters
I had a good night on 40 meters last night. The Radio Gods were obviously with me.
First I called CQ and VP2EIH on Anguilla responded. Nice to start with a whiff of DX.
Then Jason W5IPA called in and said he wanted to try out his uBITX! See the pictures below. FB!
Then I got a call from K5WDW on Hilton Head Island -- Dexter runs Collins gear from an ocean-front shack (see above). Check out his QRZ page.
Then WA4PUB called in. Dave has been on the air since 1948 and was a student of legendary ham and radio astronomer John Kraus. Dave has directional antennas on 40 -- when he switched the pattern he went from LOUD to barely detectable. FB. Check out Dave's homebrew rig below.
Finally Gary W7DO joined us. He has a big 4 Square on 40 that also has some really impressive directional properties. See below for a look at his 80 meter 4 Square.
TRGH
WA$PUB |
W7DO 80 meter 4 Square |
Labels:
40 meters,
antennas,
Collins -- A. Frederick,
K5WDW,
Kraus -- John,
radio astronomy,
uBITX
Monday, May 21, 2018
BITX Night on 7277: First N6ORS and then Canadian BITX Builders
I was about an hour late for the Eastern time zone meet-up at 7 pm local on 7277 kHz Sunday night (my wife and I watch 60 Minutes at that hour). but I figured I could work some guys if I got on at 8 pm. Sure enough, I was called by Keith N6ORS on his MIN-X rig. I was on my QRO DIGI-TIA. It was great to catch up with Keith.
Then I got a call from VE3THR. Last year I'd talked to Tom when he was using his BITX40. This time he was on with his uBITX. FB. Tom's club in Barrie, Ontario is obviously melting a lot of solder and having a lot of fun. Here are some pictures of their rigs.
Then I got a call from VE3THR. Last year I'd talked to Tom when he was using his BITX40. This time he was on with his uBITX. FB. Tom's club in Barrie, Ontario is obviously melting a lot of solder and having a lot of fun. Here are some pictures of their rigs.
Labels:
BITX40Module,
Canada,
uBITX
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