AmateurRadio.com

Website moved to a new server…seems all ok to me. This new server will give me more space and flexibilty as well as being far faster than the previous one.

update: A couple of issues need ironing out but these won’t be done for a bit. But things are back on the air at least.

Alex Hill, G7KSE, is a regular contributor to AmateurRadio.com and writes from Cumbria, UK. Contact him at [email protected].

Now it seemed that up until just a few years ago, most amateur lightwave work had been done using lasers. The UK boys, as well as others, were now using LEDs, whose technology had made huge strides in recent years. The 'non- coherence' of LED light, unlike lasers, offered a distinct advantage when used for communications. Fading and signal dropout during periods of poor visibility were significantly reduced with the non-coherent LEDs when compared with laser light's 'all or nothing' characteristics.



Courtesy: KA7OEI As well, the thought of using lasers was somewhat scary in view of the growing amount of negative publicity from frequent reports of irresponsible use....combined with the fact that my path to VE7CA had to cross Vancouver International Airport!



Shining just a low-powered laser across this region was not something that I felt even remotely comfortable about doing. I felt much better about the project the more I learnt about LED's and of the good results being had by other experimenters.


Another exceptionally good source of valuable information (and probably the best on the Internet) is the 'optical' page site of Clint Turner, KA7OEI. Clint is an exceptionally gifted engineer-experimenter and is extremely generous in sharing his knowledge with others. As our local project developed over the course of many weeks, we exchanged several e-mails. My numerous questions would always result in very long detailed answers...and precise explanations for the reasons behind the answer or suggestions.

Clint Turner, KA7OEI

Just name any radio-related activity and Clint seems to be not only involved in it but has excelled in it. His willingness to share with others is just another example of why our hobby is so enjoyable!


While still deciding on receiver / transmitter designs, I built a small audio tone generator that would be needed, no matter what type of transmitter was eventually built. The plan was to have some method of making our signals stand out when searching for them in the noise. A distinctive two-tone FSK alert tone was decided upon as it could easily be built using a pair of 555's or a single 556. The final module allowed for three separate modes...an FSK 'beacon' mode, a keyed 'CW' mode and a short 'dash' mode (less annoying than the 'alert' tones).



Modulator mounted on TX

Here is a recording of the FSK 'beacon' mode in action.



Courtesy: http://electronic-projects.50webs.com/p1.htm

The base tone was set at about 600Hz since we preferred the lower tone for CW work.
No doubt there are other methods of building the FSK alert module but the 556 is simple and worked well.

For very weak-signal CW work, likely involving slow-speed (QRSS) modes in future 'non-line-of-sight' (NLOS) 'cloudbounce' trials, something with a bit more accuracy such as a crystal oscillator divided-down to audio frequencies would be better. Such a system would be very stable and provide a more precise modulation frequency... necessary for the narrow bandwidth viewing windows required for Argo or similar DSP audio viewers.

With the tone generator taken care of, the receiver was next on the list.
Steve McDonald, VE7SL, is a regular contributor to AmateurRadio.com and writes from British Columbia, Canada. Contact him at [email protected].

In an attempt to establish my ERP on 472kHz, I have crunched some numbers. I think it is error free, but no doubt someone will soon tell me!

With a 1:46 step up toroid, I am measuring the DC volts rectified across a 470 ohm secondary load resistor using a small 50uA meter in series with 240k ohms (120k twice) and a series silicon diode. This circuit is straight out of the “LF Today” book available from the RSGB bookshop.

DC current = 30uA
DC voltage across 470ohm secondary load  = 0.6 + (240 x 10E3 x 30 x 10E-6)  = 7.8V
DC voltage (rms) across 470 ohm = 7.8/1.414 = 5.52Vrms
I secondary = 5.52 * 10E3/470 = 11.7mA
I primary =  46 * Is = 46 * 11.7mA = 0.54A

Rrad = 160 * pi^^2 * Heff^^2/lambda^^2 = 160 * 3.14 * 3.14 * 2 *2/(630 * 630) =0.0159 ohms

P(erp) = I^^2 * R = 0.54* 0.54 * 0.0159 W = 4.6mW

My original guesstimate of 5mW ERP is not far out!

Clearly getting the antenna much higher would help enormously as ERP is proportional to Heff^^2. All one can really be sure of is the order of magnitude. I am running low milliwatts.

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

I like listening to the podcast of Ham Nation – which is both in video format and audio format – during my commute to the office.  Every other week they have a segment with user supplied videos.

Burke Jones, NØHYD, is a regular contributor to AmateurRadio.com and writes from Kansas, USA. Contact him at [email protected].

I like listening to the podcast of Ham Nation – which is both in video format and audio format – during my commute to the office.  Every other week they have a segment with user supplied videos.

Burke Jones, NØHYD, is a regular contributor to AmateurRadio.com and writes from Kansas, USA. Contact him at [email protected].

So long for now, sort of!

I have decided to ask Matt W1MST, the Editor at AmateurRadio.com to end the mirroring of this blog there.  I know this may appear to be kind of sudden, but actually, this has been a decision that I have been trying to discern since this past Easter.

The content of this blog is mostly about QRP and CW as you all know. So actually, I do cater to a rather small niche in the Amateur Radio world, and the things of which I write are not of interest to everyone – or even a large portion of everyone.  In addition, I have also been known to throw in random posts here and there that are of a religious or political nature, when the mood strikes me.  And I also regale my readers with my wacky sense of humor now and then.  They say that writers should write about what they know best, and that’s what I try to do – and at this stage of my life, I’m not going to change that.

That’s fine for people who actually come to w2lj.blogspot.com looking for that kind of thing.  They know what they’re in for when they walk through my door. But to be foisted upon folks coming to a “general interest” Amateur Radio site?  I think maybe not so much.

So, AmateurRadio.com readers, if you like my ramblings – please feel free to come to w2lj.blogspot.com at anytime, 24/7/365.  The door is always open and you’ll always be welcome. And per chance, should you not like what you see there – you’re always free to “change the channel”.

My thanks to Matt W1MST and AmateurRadio.com for the continued support over the past few years. Matt has been a most gracious host, ever since he asked my permission to mirror this blog over there. Certainly, the service he offers to the Amateur Radio community is a treasure. I will continue to keep the link to AmateurRadio.com active and open in my blog roll.  I hope you’ll feel free to bounce back and forth between us.

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].