AmateurRadio.com

Here are a couple links to the PRELIMINARY 2014 NJQRP Skeeter Hunt results:

Scoreboard:

https://docs.google.com/spreadsheets/d/1odmnlTAnQST7FgsEnsItHaT_ZO0e8yZpzLqxcsyGRkY/edit#gid=1768430587

Soapbox:

http://www.qsl.net/w2lj/index%20page%207

I state again - these are preliminary results!  The deadline for submitting summaries is this coming Saturday evening at Midnight, as we roll into Sunday EDT.

I am hoping that by publishing these preliminary results, more participants will send in their log summaries, sending all the results askew and making more work for me - seriously!  The more log summaries, the better! It would be wonderful if everyone who participated, sent in a log summary. I know that's a long shot, but hey, I can hope - can't I?

72 de Larry W2LJ
QRP - When you care to send the very least!
Larry Makoski, W2LJ, is a regular contributor to AmateurRadio.com and writes from New Jersey, USA. Contact him at [email protected].

This afternoon I tried 80m WSPR with the “compromise” antenna (V2000  + 2m halo with strapped feeders) with some success. On 80m I copied M0BLP and PA0WMR although there were very few stations active. I was not copied by anyone. I was going to try 160m but decided there was too little activity.

Later I used 40m and 20m with the Par end-fed.  On 40m, just one transmission resulted in 10 spots in 7 countries. The next transmission resulted in not a single report, probably because I was sitting on the frequency of a very strong station who was TXing at the time?

I later returned to 10m, and spotted EA5CYA (1376km) and LZ1OI (2145km) by Es around teatime. The Spanish station was pretty strong but the LZ was much weaker.

Roger Lapthorn, G3XBM, is a regular contributor to AmateurRadio.com and writes from Cambridge, England.

Thanks and kudos to Jim W4QO (QRP HOFer, I might add!) for posting this link to the NoGA QRP e-mail reflector yesterday.  I never saw these kits, or this provider before, but they look neat and affordable.

http://www.breadboardradio.com/breadboardradio/Products.html

Of course, W2LJ is not connected with the above provider, in any way. Just attempting to do my bit to keep kit building healthy and vibrant! Who knows? One of them just might fulfill a need, or strike your fancy.

72 de Larry W2LJ
QRP - When you care to send the very least!
Larry Makoski, W2LJ, is a regular contributor to AmateurRadio.com and writes from New Jersey, USA. Contact him at [email protected].

The Norwegian-language “The road to the international radio amateur license” came off the press this June. It is based on the RGSB International Amateur Radio Examination Manual from 2006, which RSGB graciously allowed us to use.

But the translation has been adapted on several topics. One example is the chapter on propagation due to the need in our country for more emphasis on propagation in polar regions and in mountainous terrain. Another is a completely new chapter on digital signal processing.


I got involved quite late in the project for this new chapter. The importance of digital signal processing in amateur radio has just kept on increasing as variable digital filters, adaptive noise reduction filters, adaptive notch filters, digital demodulation, and software defined receivers are everywhere.

The entire book project was handled by the Bergen group of the Assocation of Radio Amateurs in Norway. In fact it was done in order to celebrate their 90 year anniversary. The editor has been Frode Igland, LA6VQ.

My efforts resulted in a completely new chapter which was written during the first few months of this year. It was finalized with valuable input from the editor after a process of sending the manuscript back and forth lots of times. It was a fun project, where the challenge was to convey complex ideas with a minimum of equations.

The chapter has these headings:

1. Applications of digital signal processing 
2. Discrete values
3. Quantization – digitization of amplitude
4. Sampling – digitization of time
• Aliasing
• Nyquist frequency
• Reconstruction filters
• The time domain
5. The frequency domain
• The Fourier transform
• The Fast Fourier Transform (FFT)
6. Digital Filters

• Moving average as an example of an FIR filter
• IIR filter equivalent of a low pass RC-filter
• IIR filter equivalent of a high pass CR-filter
7. Example of a software defined receiver with spectral display

Sverre Holm, LA3ZA, is a regular contributor to AmateurRadio.com and writes from Norway. Contact him at [email protected].

We’ve talked a lot about the various Software Defined Radio (SDR) USB dongles that have popped up over the last couple of years. I own several and have often played around with them. They suffer a bit of a flaw in the fact that they connect directly to the computer via USB which isn’t ideal because my computer room isn’t the ideal RF environment.

The advantage of the XiOne is that it has the capability of connecting to your home network allowing you to use a computer/tablet/phone that network to operate it. You can locate it away from RF interference sources and either use the XiOne’s Wi-Fi or run ethernet to connect it back to your router. Very cool. That’s why I think the XiOne’s Indigogo campaign from a German company called XiVero is worth looking at.

As of this writing, they still have 35 out of 100 of their specially priced (US$139) slots left. If you’re interested, might be worth a look. If they can get enough funding momentum, this looks to possibly be a very popular little receiver.

Matt Thomas, W1MST, is the managing editor of AmateurRadio.com. Contact him at [email protected].

Researching suitable LEDs for our lightwave project forced me, once again, to the bottom of the learning curve. Like the variety of photodiodes being used in simple lightwave systems, there were a myriad of LEDs experimentally lighting up the skies both in the UK and in the U.S.

It seemed that the present flavor-of-the-day in terms of LEDs was the Luxeon III, a 3W / 1.4A device being produced by Phillips.....or rather.....was being produced. Apparently our new found interest in lightwave communications had been coincidental with the retirement of this popular LED and all stock had been depleted! Although still available in some wavelengths, there were none in the desired 'deep red' portion of the spectrum that we had chosen for our system.

Courtesy: http://www.luxeonstar.com/luxeon-rebel-leds

All was not lost however as a 'replacement', largely untested by the lightwave community, spec'd-out at a lower power but with a somewhat more efficient design. The new device was the Luxeon 'Red Rebel' and rated at 700ma. ....apparently no slouch at all.




I had also been watching the various offerings available on e-bay which provided a number of tantalizingly inexpensive options. Many of the LEDs from China appeared to offer good promise and may well be good performers, but most appeared to be lower-quality knock-offs of the name-brand models.

These higher-powered LEDs, on close examination, usually contained two or more separate LED die behind the lens. A single light source is required to achieve maximum focusing / lens illumination efficiency and although tempting, should probably be avoided. 'Safe' names to look for include Philips, Osram and Luminus and often, bargains can be found on e-bay when NOS is being disposed of.

Like most 'power' LEDs, the Rebel needs to be mounted on a heatsink otherwise catastrophic destruction would be immediate. The usual method of heatsinking is to attach the LED (by solder or adhesive) to a copper star-shaped interface which is then fastened to a small heatsink.







Courtesy: http://www.luxeonstar.com

The interfaces can be purchased separately but soldering the LED can be challenging without overheating it. They can also be fastened with JB Weld and enough pressure to ensure a firm bond without damaging the LED. An easier alternative is to procure the LED already mounted on the interface as shown here.








Once adequately heat-sunk, voltage can be applied to the LED after taking measures to limit the current to safe levels. Although these LEDs are very small, they emit an exceptionally bright light and must be treated with care. The Rebel is shown here, shortly after first applying voltage. The current in this test was just 100ma. Although they are rated at 700ma, I have run this one up to 1A without failure but it is normally run at the rated current.

Luxeon Red Rebel at 100ma.

The next task was to tackle the 'antenna' which, in a lightwave system, is the lens. Many of the UK amateurs were having good results with inexpensive 4"-5" magnifiers mounted inside ABS or PVC tubing. The remainder, and those in the U.S., were using plastic Fresnel lenses mounted in homebuilt plywood boxes of various designs. Clint's (KA7OEI) website contains a vast amount of valuable hands-on info describing the latter and we chose to go via that route.

Like the large variety of both photodiode and LED selections, fresnels were no different. Once again there was a lot of information to digest while learning about the various types. Eventually, John, Markus and myself each purchased two plastic fresnel lenses from 3DLens in Taiwan. One would be used in the receiver box while the other was for the transmitter. These were 26cm square lenses, model A260.

Unfortunately I no longer see these particular lenses being offered....hopefully it is only a momentary depletion of stock. There are many different sizes and types of fresnels out there....some if them perfect for this type of use and others not so good, so think carefully before buying anything and know what you are getting. Studying Clint's pages regarding fresnels will help immensely.

Things to pay attention to are the focal length and groove 'pitch'. For a typical 10"-12" lens, look for something around 10-12" focal length, otherwise the mounting enclosure will get too deep and awkward to handle. Front surface 'groove pitch' should not be too fine...something around .5mm is good but our finer (.2mm) seemed to work well also.

Now that the LED had been mounted and the fresnel lenses were in hand, the next task would involve the focusing mechanism and alignment. Thankfully John had devised a smart method for mounting and adjusting focus a few weeks earlier, when we were still working on receivers.....
Steve McDonald, VE7SL, is a regular contributor to AmateurRadio.com and writes from British Columbia, Canada. Contact him at [email protected].