Honeymoon..

Posted on 2011-05-27 by James

So it has been over a month since I have had a chance to write about something radio related and I’d like to think I have a good reason: wedding. Julie and I were in the last stages of organizing our wedding day this past May 7th and so I had little time to play radio.

I did manage to make it out to the April general meeting of the OVMRC which was nice as always. When talking about the difficulties I have encountered using an old radio (FT-101EE) I was pleasantly surprised when Bob (VA3QV) offered to lend me a radio to test with (with the potential of an out-right purchase). I really can’t wait to take advantage of this extremely generous offer (Thanks Bob!). Perhaps when I arrive home from the month-long honeymoon I will make it a priority to cross paths with Bob 😉

It will be nice to have a modern radio to test with (and to enjoy) – it is tough to tell whether you are doing something wrong with your station unless you have a second unit to compare your results to.

My objective of constructing a magnetic loop still remains – I have an air-core capacitor I can test a design with .. so that will be up and coming too.

Truthfully, I’d love to get out camping in the backwoods with my 4×4 and make some contacts from camp.

Well .. back to the beach of Ko Tao (Thailand) for now. Will have more soon (I hope).

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Montreal Hamfest

Posted on 2011-04-13 by James

I am looking forward to the Montreal Hamfest – I hope that I can find some components there (variable capacitor, inductors, etc). With any luck, I can also find a noise blanking circuit for the FT-101E there (at a reasonable price). If anyone reading this wanted to car-pool, just fire off an email my way and we can work out the details.

Cheers for now!

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A better way …

Posted on 2011-03-30 by James

I am sure there is a better way. That better way may just happen to be a magnetic loop antenna.

I was reviewing some old physics text books that I have and I began to contemplate the usefulness of the magnetic component of the oh-so-familiar electromagnetic waves which we use to radiate our radio signals. As it turns out, there are many examples of well designed magnetic loops which behave much as traditional antennas, but with a substantially smaller foot-print. Oh and it should be mostly immune to sources of electrical noise! That is a considerable bonus considering I live in an extremely noisy (electrical) environment.

So now I need a plan.

The theory of operation is quite simple: feed the loop at point “A” and tune the resulting resonant circuit at the opposite side of the structure with a variable capacitor. Building the loop will be trivial at most. It is the sourcing of a capacitor and an antenna analyzer that will be my downfall.

If you are reading this and know where I can get my paws on a variable capacitor (air, vacuum, ceramic) for less than $40 by all means, let me know. The capacitor should be in the range of 5-250pf (or so) with a voltage handling of -at least- 5kV. Yeah, 5kV. I could live with less, however, best engineering practices always require one to design with 50% margin – and in this case, a 5kV capacitor would allow 100W of power. I don’t think I would use 100W as my interests lie in weak-signal modes, however, I personally over-engineer by a margin best measured in logarithmic units.

The next piece of equipment is an antenna analyzer. Yes I realize that I could tune and everything using an SWR meter and an RF source, however, an antenna analyzer is soooo much faster and lets face it – without one, I doubt I would bother with this project.

If I am unable to source a cheap variable capacitor which will handle 5kV, I may break-down and try to fabricate one by hand. The principle is quite simple really – a trip to the local scrap metal shops should yield most of the components. After that, its some seat-time with a dremel tool and many replacement cutting wheels. I’d prefer -not- to have to make a variable capacitor however.

There it is. My plan.

If you can help in any way, please do not hesitate to leave a comment here, or contact me via email or through the Ottawa Valley Mobile Radio Club.

Thanks as always for reading!
73,
James

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JT65 Operation

Posted on 2011-03-29 by James

Over the past week or so, I have been casually putting together an operator’s guide to JT65-HF communications. The beauty of this mode is that with only a few watts and a simple (as in random wire) antenna, one can make distant contacts which are otherwise impossible.

The guide is designed for use at the OVMRC club station, however, the same principles will apply to any operator’s station. For example, the core requirements are the same as for PSK-31 so if you are able to use that mode, JT65-HF will be just an operating extension.

Without any further adieu, the guide can be accessed by clicking on the following link: JT65_Operator_Guide.pdf

Hopefully, the material which I present is useful to someone out there – I believe that JT65 is a great mode and should be explored by more hams. Hopefully this makes it more accessible.

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