Monthly Archives: May 2008

Tower Update

DSC_3207Last night, we finally fitted the rotator housing and G450 Yaesu Rotator to the tower and tested it out with a small VHF ZL Special which we’ll use for VHF NFD in July (being at 1,000 feet means that we might be able to get away without high-gain antenna arrays, time will tell).

Barry (M0DGQ) is working on designs for a hinged rotator cage which means we will be able to use a 20 foot aluminium pole at ground level. Maybe next year..?

Anyway, we can now claim the record for putting up a 35 foot antenna: 20 seconds with a hydraulic switch :)

Callum

My new vertical(!)

CB AntennaWith a feeling of “if you build it, they will come”, I installed a CB style antenna for the 10m band yesterday evening. I needed to shorten it about half a meter for it to work but I noticed that at 12 feet above the ground, it tunes with a low SWR on both 12m and 10m, although it’s not so good around the 27MHz slot- so it’s not exactly broadband. I was also surprised on the 15m band as it presented less than 2:1 in my shack. Red-herring.. it may present a low SWR, however it’s just a crap aerial on that band. The hobby of designing low SWR antennas goes out the window with the dummy loads.

Anyway, why the hell am I writing this? It’s this; I want to know how to feed a half-wave vertical. Why don’t I need radials? I have a 10m fishing pole and I’ll make one for the 20m band and work it all out myself. I know there’s a coil somewhere..

Oh! .. and in the making of this article, I captured a picture of a fly whilst taking a picture of an antenna. See it here: http://www.m0mcx.co.uk/gallery/picture.php?/692/category/67 

Where’s that Glenlivet?

Ameritron AL811x 800w tuning tips

Ameritron AL-811xDon’t spend your life tuning amps. Do it once with sticky labels and forget!

I’ve recently un-mothballed my Ameritron which has seen good service and delivers 200 watts for 10w drive – ideal for PSK31 and other low-power digital modes. This amp will go further and deliver 400 watts for 30 minutes key-down so it’s ideal for full legal power in the UK.

Anyway, flicking from 80, 40, 30 and 20m during the grey line with the AL811, I’ve discovered that I have never mastered the speedy band switching that some operators appear to have worked out. So I developed my visual system(!) using sticky labels tuned against a 50 ohm dummy load to calculate the fastest (approximate) setting for each band. It works blooming marvelous too!

Since a picture tells a thousand words, I won’t bore you any more. Here’s a close up! http://www.m0mcx.co.uk/pictures/Ameritron_AL-811X.JPG

[Later] – I can’t get 10m to tune. Maybe it’s not an export model? In which case, according to sources on the internet, to convert a non-export model to an export model, one needs to make a mod by cutting a wire. This will enable 12 & 10 meters on the Aux switch. I hate engineering! :)

Cheers, Callum.

 

Ham Radio Realtime Gray Line

Current Gray-Line Position

Courtesy of http://www.fourmilab.ch/, this is the current real-time position of the Gray

Line, as utilised by Ham Radio operators over the world.

For those who don’t know, the”grey line” is a band around the Earth that separates daylight from darkness as the earth rotates.  Propagation along this line can be very efficient.  One reason for this is that the D layer, which absorbs HF signals, disappears rapidly on the sunset side of the grey line, and it has not yet built upon the sunrise side.

Interesting? Well, I’ve spoken to people on the other side of the planet during this 30 minute phenomenon. It certainly gives you a buzz.

[Later: This damned map can takes ages to load.. Grrr]

Cheers.

Proposed Field Day Location

VHF NFD Location

I’m very excited that we appear to have found a new Field Day location in the Cotswold Hills, particularly useful for VHF NFD since it is only a whisker short of 1,000 feet. Of course, this will be spectacular for SSB Field Day as well since we might even make use of the height to secure a few more 10m SSB contacts around the UK and into the continent if we’re lucky.

Tim, James, Terry and I visited the site today to ensure that it is suitable – and at only 40 miles from Solihull it’s not as if we’re stretching the fuel tanks to get there either.

I’ve never operated seriously at such a height so I will be fascinated to know how our performance compares with other years when we used to operate at a local club that sported 450 feet ASL plus a 100 foot mast. I have a feeling the extra 500 feet might prove to be exceptionally useful!

May I thank Tim who drove around one evening for hours with a friend of his, door knocking land owners that happened to live very high up. This land owner shall remain anonymous for the time being. Thank you Sir for assisting our group.

VHF Field Day 2008 M0XXT

VHF Field Day 2008 M0XXT

We’re looking for 1st-class contest operators which a good sense of humour who want a couple of interesting weekends away with our club call; M0XXT. If you are interested in joining our group, please email me your phone number.

Callum, M0MCX.