Thursday 20 February 2014

That G-Whip Pro Mobile Antenna Revisited

A while ago, I wrote about my early experiences with the G-Whip Pro Mobile antenna.

I haven't changed my mind about this being a well-made, well-performing antenna at a reasonable price.  But there are a few things that I think make this a less-than-ideal antenna, at least for me.


Much lighter and seconds in switching bands, I'm now using monoband whips.

Firstly, the top section of the antenna, which is removable so as to allow the addition of coils, is prone to bending, apparently being made of brass or similarly soft metal.  This leads to a need, though infrequent, to bend the metal back into shape.  Not a big deal, but rather annoying and it does eventually become a kinked, rather than just bent rod!

Secondly, the need to change coils is a big drawback.  Because you have to remove the whole antenna from the mount to change the coil for a new band, you may as well remove the whole antenna and replace it with a dedicated monoband whip.  This is all the more sensible because, with the G-Whip, you also have to make a record of the top whip adjustments for each band, which don't always work out as expected due to small movements in the magmount position, environment and so on (although that will also happen with other antennas.)

The advantage with the G-Whip is that you need only carry three small band coils, rather than three entirely separate, full antennas in the car. 

The G-Whip is also quite heavy and very stiff for almost all its length; on a magmount, it has enough momentum on a rough track to pull the magnets off the roof, allowing the mount to slide.  OK, if you are going to rough it often to that degree, you'll use a more permanent mount, but even a potholed farm track at slow speed was enough to yank the mount recently. Remember also that a more permanent mount is more likely to be attached to a lower part of the car, such as a towhook or bar, with the consequent loss of about 3dB in gain, according to experienced mobile users.

So, the G-Whip is a good antenna, but I have decided, after a few short months, to ditch it and buy a set of lightweight monoband whips that can simply be screwed off when the band conditions change, and a new band popped back on in seconds.   It eliminates the need to change coils, remember where the spanner is, get the book out to recall the right whip length, struggle with a tape measure and, finally, get back on the air.

Price wise, a monoband whip is just under £40, so multiply that by three and you end up with much the same price as the G-Whip with three coils.




Monday 17 February 2014

Crank-Up Masts - Potential Killers

Many of you will have already read this on QRZ.com.  However, crank-up towers are very common, work very smoothly and apparently safely - until a cable snaps.  Then the sections, and even recoiling wire, can very quickly turn into killing machines.


The only thing between these folks and death is some wire. 

Have a read, and think twice before trying to coax a section free, climbing or otherwise sticking any part of your body anywhere near a crank-up tower; danger is only a few strands of rusty steel away...

"A 52-year-old ham radio operator in Athol lost several fingers and one of his hands Thursday when his amateur radio antenna tower collapsed on him while he was working on it.

Multiple agencies responded to Bearpaw Galindo's home on Caravelle Road after his wife, Gail Perry, phoned 911 and informed a dispatcher the man was hanging 20 feet in the air with his right arm pinned within a telescoping-type tower.


Perry said Galindo was repairing a portion of the 40-foot-tall telescoping tower, when a cable holding it up snapped and caused the top portions of the tower to collapse on his hands.


"I saw his fingers fly off of his right hand," Perry told The Press. "I never want to see something like that again."


According to a press release from the Timberlake Fire Protection District, crews were dispatched to the scene at 11:58 a.m., and proceeded to raise the tower in an effort to free Galindo's arm. After 20 minutes, the man was extricated and lowered to the ground.


Galindo was trapped for a total of 45 minutes.


"I can't say anything better about them," Perry said of the emergency responders. "They were awesome."
Galindo was then transported by Life Flight to Kootenai Health.


Doctors told Perry her husband was in critical condition early Thursday evening. At 3 p.m., Galindo was taken into surgery, where doctors performed a partial amputation on his left hand and a full amputation on the right. Perry said doctors estimated the surgery would last more than four hours.


"They (doctors) said that he will be in the hospital for quite a few days," Perry said.

Sunday 9 February 2014

TO7CC DXpedition - worst ever 20m Reunion signal?

Some blokes have just landed in Reunion, to much fanfare and the usual over-excitement of childish men who want the DX.

Idyllic Reunion, a place where verticals excel.   Image: France Tourism.

Having managed comfortably to bag W1AW/KH6 with just a quarter wave vertical a couple of hours earlier (this being my very windy days antenna), this was no bad propagation day.

I should also point out that I've spoken to Reunion many times, always with a very easy copy despite normally using a simple delta loop or simpler, and have no need to sit for half an hour, waiting to be heard to bag the DX. 

So, why is TO7CC's 20m signal quite so poor?  They were certainly beaming Europe, to which they have a good aspect.  So it wasn't a heading or location issue.  I suspected they may have fallen for the trap of using a horizontal antenna from a seaside location.

I looked up their website, to find this is indeed what they've done for 20m.  Why, is something only they can tell us about.  If they had a quarter wave vertical, two elevated radials and stuck it near the water, it would beat the pants off the Spiderbeam horizontal yagi on DX paths.  Anyone who knows anything about seawater and vertical radiation will tell you that.

2E0EDX would tell you all about basic systems, verticals near the sea, and DX.

In fact, so far as their information lets you work out, they aren't actually at the beach at all, but operating from the grounds of a hotel.  No doubt it's much more convenient, but it's not making the most of the near-perfect ground lapping against the beach. Being 'somewhere near the sea' just isn't good enough; you have to place your antennas at the surf line - I usually place them in the surf - to get the benefit of the seawater.  By the time you're a few metres away from the sea, the effect is already rapidly diminishing.  By the time you're at a hotel, it's lost altogether.

It just seems a lot of people have real difficulty getting to grips with the distinction between absolute gain, and where that gain occurs in the vertical plane.  Either that, or they are suffering from the age-old need to use 'big' antennas.

If you don't believe me, run a model of a three element yagi at 10m (I doubt a DXpedition would get an antenna higher than this in most cases) against a quarter wave next to the sea (you can use 'perfect' ground conditions - it's near enough.)  What can you see?  Yes, the yagi sticks its radiation out somewhere in mid-air, whilst the little vertical, just a 7m tall fishing pole if elevated radials are in use, fills the gap at lower angles.

You can also get some proof from the extremely poor signal on 20m.  Operator, beware!