Sunday, 30 March 2014

I have spent some time this weekend converting my website to better use cascading style sheets (CSS). I have always been an advocate of substance over style though it cannot be denied that a great looking website is a pleasure to browse. Whilst I am aware that my website admin credentials are firmly in the "amateur" category, I am keen to improve my skills and aspire to the professionalism of sites such as wikipedia. I am not totally new to the concepts of what makes a good website, and I am not a fan of sites with large images that take a long time to load and unnecessary video \ animation. I know my limitations, however, and it has been quite tricky getting to grips with CSS. Was it worth it? Well, after reading books such as The Zen of CSS Design by Dave Shea and Molly E. Holzschlag (and its accompanying website I fully understand the benefits of separating style from substance and would respond with a definite "Yes". It's easy to pass judgement when navigating amateur websites, but those of us who understand the benefits of CSS  shouldn't look down on those amateur sites that still use lots of animation and take an age to load. Everyone has to start somewhere, and whilst I could be embarassed by some of my first web offerings, I am not - it's all part of the joy of publishing online...

Friday, 28 March 2014

Offering Assistance to RAYNET

I hear a lot of opinions about RAYNET from within the UK amateur radio community, some praising and some dismissing its existence. One thing is for sure - unless you get involved and give it a try, how are you ever going to know whether you like it? I never thought that I would enjoy being a member of RAYNET, and yet here I am finding myself starting a second year as the Group Controller for Gwent RAYNET group. This is a friendly group of people who always welcome newcomers. The annual subscription for RAYNET is very reasonable at under £10, and new visitors can come along to see if they're interested first before joining. On Wednesday evening I enjoyed getting together some 2m and 70cm equipment to help out with a RAYNET Zone 7 exercise. I was asked to help out because a local spot near Chepstow provides a good operating location (it's quite high up with good views over South-West England) and allows those of us living in South Wales to offer whatever help we can in relaying messages. What I enjoy most about this kind of thing is that it focuses the mind and provides the motivation to get all the equipment charged up and ready to go. These events aren't always 100% successful, but that doesn't matter - the more we practice the better we get. So I would encourage anyone who is the in the habit of criticising RAYNET to come along to a local group and see what goes on. You never know, you might like it!

Sunday, 16 March 2014

Impedances in parallel

Today I have furthered my knowledge of impedance and have put the following page live on my website:

Impedances in Parallel

My incentive for getting to grips with impedance, reactance etc is to have a really good understanding of filter circuits. I would like to be able to approach the design of a filter from a mathematical standpoint, and then to compare this to reality. It is that aspect (theory vs practical) that I most enjoy about the hobby of electronics and amateur radio. Filters are important building blocks in the world of transceiver design and amateur radio!

Until next time, Chris.

Saturday, 15 March 2014

Impedances in series

I've often struggled to get to grips with a.c. circuit calculations involving resistance, capacitance and inductance. There is quite a lot of tricky mathematical jargon here - vector sums, phasors,  polar notation, angular velocity etc etc.

I decided to tackle this head on today and improve my understanding! First of all I learnt about the reactance of inductors and capacitors, which is given units of Ohms. If inductors and capacitors are 'pure reactance, and do not dissipate energy', how can they have a property measured in Ohms? Well I deal with this in my mind by remembering that current does flow back and forth through the inductors and capacitors, and energy flows into and out of these passive components. So reactance is a convenient way of dealing with working out what the magnitude of this current is. It does not mean that the inductor or capacity has some kind of resistive quality.

The next thing I learnt is that the resistance of a resistor can be treated as a 'real' quantity, and the reactance of an inductor or capacitor can be thought of as an 'imaginary' quantity. You can add real quantities, and you can add imaginary quantities together, but you cannot add a real quantity to an imaginary one.

The final thing I learnt is that resistors, capacitors and inductors can all be thought of as having an impedance, and an impedance has a real and imaginary part. For resistors the imaginary part is zero, and for capacitors and inductors the real part is zero. Inductors have a positive imaginary value and capacitors have a negative imaginary value.

Whilst all of this was fresh in my mind I quickly put together the following web page concerned with an electrical circuit with impedances connected in series.

Impedances in Series

I hope that my understanding is correct , and thank you once again for reading!

Thursday, 13 March 2014

Low-pass RC Filters

Today I've been learning about low-pass RC filters. I now know that at a certain frequency known as the cut off frequency the output voltage falls to 1 / (2^0.5) or 0.707 times the input voltage. I also know that at this frequecy the phase shift is 45 degrees. I've also learnt that at an output voltage that is 50% of the input, the phase shift is 60 degrees. I've put together a new page with my findings on my website, a link to which is given below.

Thanks once again for reading! Chris

Tuesday, 11 March 2014

Electrical Wire data, AWG, SWG, ECW

Have just updated the "wire" page on my web site to improve layout. This page gives the diameters of American Wire Gauge or "AWG" and Standard Wire Gauge or "SWG" in common electrical usage. It also gives "turns per inch" starting point data for enameled copper wire (ECW). Find it here:

Slowly getting to grips with Blogger...

OK, so now I realise that there are some things that you can do on the PC that you can't do on the android tablet blogger app, and one of them is that you can switch between "compose" and "HTML" views as you compose your blog entry. Whilst on the PC I took the time to correct the timezone also. Now I notice in the top right of the android compose window three icons, one of which depicts a chain (for a link) so I will go ahead and try to drop a YouTube link below:


Ok, so that seems to work, but doesn't quite give the flexibility of switching to html. I have set my blog to be moderated for now until I get the hang of this!