Dry Weather - How's Your Station Ground?

We're undergoing another sunny, dry summer in the UK.  Unsurprisingly, we're all very happy about that!

But there are problems associated with dry weather, and one revealed itself in an unexpected way.

Are your grounding points moist enough?  Image: W8JI

A few weeks ago, I threw together a simple crystal set for the kids. The primary coil uses the station ground, connected by crocodile clip. It worked a treat until, a few days ago, it went completely dead.

Having re-soldered all the connections, it was still dead.

Hmm.  I wondered whether the ground system had dried up in the hot weather.  So, I dumped a copious amount of water in the ground at the earthing point.  Within a few minutes, the crystal set was working again!

So, it pays to keep your station grounding moist in hot weather, especially if you live somewhere like the UK, where we don't expect it to ever be that dry!

2m Slim Jim Antenna - One Year On.

A year or so ago, I built a copper tube Slim Jim antenna for 2m.  This was for general coverage of the local area, and I hoped it would be as good as people claim.

Boy, is this a superb antenna!  Not only is it super-strong mechanically, it's a superb 2m antenna that costs just a few dollars to put together.  Quite why anyone would pay for a piece of wire encased in some glitzy-labelled fibreglass tube is beyond me, when something like this is a real joy to make and a pleasure to use.

Even though the antenna base is only at 3m we are, admittedly, at an elevated QTH (100m amsl), and have a clear shot across the sea to the Isle of Man and Ireland.   Nevertheless, this provides a truer picture of the potential of the Slim Jim, rather than telling you how much an urban setting is robbing your waves of energy!

Matching wise, a good quality VHF or wide-coverage HF/VHF SWR meter lets you see how the SWR changes by sliding the coax tails up and down.  Eventually, you find a 'sweet spot', and solder them on.  I don't recommend using pipe clips - they either rust or become loose.  Solder and then amalgamating tape is best.

When soldering, blast the copper, which should be rigorously cleaned with wire wool first, with some gas blowtorch heat for a minute or so to get it really hot, then melt some solder onto the proper spot.  If you prepare pre-soldered coax tails, you'll find the copper tube momentarily retains enough heat to melt the coax solder and make a good connection without much or any further application of the blowtorch that otherwise tends to also melt the coax plastic!

Detail of the mounting found to work best by far.

Mouting the Slim Jim is a little fiddly.  I eventually used plastic snap-over pipe clips screwed to a back panel of pressure-treated timber (e.g. 1.5" x 1.5")  A very short section of plastic or varnished bamboo cane is inserted between the bottom of the antenna and a short copper tube below (which is merely a mechanical stabiliser)  Just using a longer length of bamboo or plastic leads to a weaker mount.

Superrefraction of the Isle of Man hills.  Expect very good VHF conditions when this happens!

With just 5W out, my little copper tube creation easily and consistently opens and gives a very good output signal on repeaters at 50 miles.  When there is some superrefraction ongoing, that extends the coverage substantially.

So, ignore the bun fights about just exactly how much gain a Slim Jim has, and relative to what radiator that is.  Practical experience shows this antenna does indeed provide very low angles of radiation, converting a lowly handheld into a regionally-capable transceiver.

As usual, the advice is: go build!

One Hour...

...is how long RadCom survived before being put in the recycling bin this month.

Yet again, I ask myself: why?

Lightning Protection Where it Don't Much Storm.

Storms are very rare over these here parts of Wales.  So rare, that one tends to establish a ham shack without too much thought for lightning protection, other than pulling the feeds out when rarely needed.

But, this spring and early summer has seen a fair number of storms already, when there may be several years between storms otherwise.

Not good for transceivers...

So far, with the feed lines out, I've not had any problems, even though there have been a number of very close strikes.  But it's clear that, if you are establishing a new station, or renewing some feed lines, it's worth grabbing some surge protectors and fixing a single point ground box on your property. 

With surge protection units only costing about $25, it's a real false economy not to bother with lightning protection - even if those storms only very rarely come by...

2014 Digifest Test - Trench Thinking

This weekend it's the digimode fest test, if you pardon the rough terminology.

Surprised to see not an awful lot of activity.  More surprising was the entrenched use of 'obvious' modes like PSK-31/63 and, occasionally, 125.  I heard only one station - one - using Hellschreiber, and nobody using the QSB-robust ROS mode. 

There are, of course, plenty of other digimodes that are available, many of which cut through QSB like a knife through butter.  For some strange reason, nobody is using them.  Why?  Why struggle with 80% loss of intelligibility with PSK sometimes, when ROS or FHSS ROS would come through smelling of roses?  It's a mystery.  But there's clearly a large body of hams out there with closed minds when it comes to which digimodes to use.

How very odd!

7QNL - DXpeditioning as it should be.

12m hasn't exactly been buzzing recently.  In fact, other than occasional bursts of activity into Latin America, it's been pretty dead.

So, it was a bit of a surprise to hear any signal on 12m this morning during a quick coffee break.  More of a surprise was that it was emanating from the rare DX entity of Malawi!

Thanks, no doubt, to the lack of interest in 12m due to its current deadness, I was able to get a call in with little trouble, and banked on 'up 5' in the '5 to 10 up' range as likely to get 7QNL's attention.  Equipment in both directions was modest - vertical dipoles and loops in Malawi, and a simple 3-ele LFA Yagi this end. 

We managed a decent 55 both ways.

What struck me as very nice about this DXpedition team is their down-to-earthiness and lack of machismo.  Unlike so many teams from the US and UK, 7QNL has gone out with modest equipment and has deployed by far the most sensible antennas - verticals.  In the shape of loops and dipoles, the verticals are both simple, cheap, lightweight and effective.  Getting a signal over an effectively all-land path to the EU from Malawi is no mean feat, highlighting the success of - and wisdom in - choosing these antennas.

So, a big thanks to 7QNL for showing that DXpeditions don't have to be mega-buck affairs, and reminding the less well-informed that horizontal HF beams are rarely a sensible, or very effective choice for such activity, particularly if you are operating from or near the seashore.