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Wednesday, 29 August 2012

RF Earth - How about this then?

I've been fiddling around with the RF earth in the shack today; mainly because I was very aware how totally pants the existing arrangement was.

So to start with I have driven three four foot earth rods into the ground just outside the shack window. These rods are soldered together at the top using a piece of old copper pipe - I did the soldering using a blow torch and plumbers solder & flux.

This is fed by a 10mm squared cable into the shack by the shortest route and this in turn is also connected to a piece of copper water pipe. This pipe is not part of any water system but simply used as a distribution bus for the earth:


So in total I have soldered (using the blowtorch method) seven separate connections onto this pipe and secured it underneath the desk using pipe clips. The main earth coming into the shack is the connection you can see on the left hand side and each of the other six points are fed by separate earth cables to the individual pieces of equipment.


This seems like a much more sensible arrangement to me than I had previously and I think this qualifies as a decent RF earth. Cat didn't seem too bothered:

Good though, egh?

Monday, 27 August 2012

Well, This Top Band Twig, Does it Work?

So, Top Band... This piece of wire strung across the garden will never work will it? There's even an inductor in there that's basically connected to air at one end....

Well, I left the TS-590 WSPRing on Top Band last night:

So it certainly seems to be working rather well!

I'm delighted!
 

Sunday, 19 August 2012

Top Band, what happens there then?

Well,

Following some inspiration from my ever patient chum Vince, G0ORC, we built a "sloper" at his QTH for top band. The basic design was inspired from this site here:

http://www.mds975.co.uk/Content/amateur_radio_antennas_02.html

This is the site of Mike, M0MTJ. He has done some fine work on sloper antennas. I sent Mike some email to ask about the inductance being used in his Top Band antenna and he pointed me here:

http://www.k7mem.com/Electronic_Notebook/antennas/shortant.html

Now this is an amazing site including the java based calculators. So assuming that my "sloper" is half a loaded dipole I have done some calculations (this is after the first experiment at the QTH of G0ORC).... and I have come up with this design based on the space available in my back garden.


So, the inductor was wound on a piece of drain pipe which has an outside diameter of 63mm. Using the extremely handy Ring Core Calculator:

http://www.dl5swb.de/html/mini_ring_core_calculator.htm

And using the part for "Air Cores" I calculated that using my drain pipe I would need about 30 turns to create a 42uH inductor. So using some hard drawn copper wire I had here I made the coil.

I got hold of some "flex weave" antenna wire and cut an appropriate length. The coil looks like this in reality:


And this is the ground arrangement; I've driven two earth spikes into the ground which I have soldered an old piece of pipe between. To this I have soldered the outer of the coax feeder and also the end of a wire which I have trailed round the garden at ground level:


The antenna looks like this, although its rather hard to see - its the wire on the left hand side of the picture:


You can see above that the pole is looking rather bent, the co-linear that's on the top could come down as I don't use that for anything now, so I really should try and put up a thicker pole with some less bendy joints! It will do for now I'm sure.

But much to my total disbelief, when I stuck the antenna analyser on the end of this new sloping antenna; this is what I saw:


So it seems by some complete fluke I have managed to create a top band antenna. If it actually hears any signals will be a different matter, but only time will tell.

I also took the beam down again this weekend and have added a plastic owl to the top; his name is Oliver... I'm hoping his presence will reduce the amount of bird droppings on my back sitting area! I also hope it won't deter birds from the garden completely. You can see him on the top of the pole here:



We shall have to see.

Fun though, egh?

Friday, 17 August 2012

Changes at the Top!

Well,

I've not been overly happy with the arrangement to adapt from the top section of my new mast (which is 2" OD box section aluminium) to the 2" OD pole that holds the rotator. This was originally a aluminium plate that had "U" bolts for the pole and some nuts and bolts that fitted through the plate and then through one wall of the top mast section. When the wind picked up there was the risk of:

  1. The whole thing folding back on itself;
  2. The plate twisting.
You can see the original plate in this picture here:


Now, as I was concerned about this before the changes today, I had actually inserted a smaller diameter pole inside the rotator pole which was secured by a bolt that passes right through the rotator clamp. This smaller pole extends through the top rotator stub mast down into the top section box part of the mast itself. This (I was certain) would ensure that the plate didn't fold back on itself in high winds.

So, what I have done today is use a piece of 3" OD aluminium box section to create a kind of sleeve that sits over the rotator stub mast and the top section of the mast itself, this sketch kind of explains what I've made:

And it looks like this in reality:


And this is a close up of the top section of the mast itself where it enters the new sleeve:


And here you can see how I have made larger (looks like using my teeth) holes in one of the walls of the sleeve to access the bolt heads to ensure the pole and the mast top are hard and fast against the side wall:


and this is the underside of the same bolt:


So, all in all, I think this will enable me to sleep better knowing that the antenna isn't about to land on the back of the house!

What do you recon, better egh? Cat's not impressed, seems to like the new radio though:

Monday, 13 August 2012

I've really done it now!

Well,

After the installation of the new antenna system, my HF capabilities have improved significantly. The front to back ratio of the new antenna is excellent and I'm really pleased with the performance.

I've been out this weekend and swapped one of my radios for a newer one, I've treated myself to a FT-DX-5000D, it looks like this:


It's got a free Kenwood towel draped over the top of it right now. So the shack has had a slight modification to one of the shelves, but it's looking like this in the radio area:


The receive performance of this radio is simply outstanding, the noise floor is very low and there seems to be a noticeable improvement over the FT-2000 that I had previously. It's also got a fully DSPd 2nd receiver as well as a 200W output. The radio can also be placed into Class-A mode so that the output is cleaner; in this configuration the maximum output power is 75W which is ideal in digital modes like RTTY for driving my solid state linear.

All in all it's just fantastic!

So that's me done spending for a while, but it looks good, agree?

Saturday, 4 August 2012

It's now Official; I am completely nuts

Well, following a recent street party to celebrate the Queen's Jubilee; a discussion with my neighbours about antennas ensued. The conclusion was that whilst they are somewhat intrigued over what they are for (one neighbour thinks I am a spy), they are not "bothered" by them in the slightest.....

This got me thinking....

The past two days have been spent making some changes here to the antennas; so the first job was to bring down the main HF antenna. If you have been following this blog you may remember the last time this came down, it involved bailing twine and some knots, the details are here:

http://g0mgx.blogspot.co.uk/2011/11/so-how-can-it-possibly-go-wrong.html

So we tried the same trick again (with the ever patient Vince, G0ORC):


Remove the U-bolts holding the mast to the T and K brackets... then start to tip and let the bailing twine out slowly...


And a bit more....


So here is the antenna on the floor:


So now I needed to remove the pole(s) and the T & K brackets holding it all against the house. Once this was complete I could install the new mast. I got this mast from Gary, MM0CUG he's custom made it for me.

The first job was to unpack the box of bits:


The I had to fit a new top bracket and drop a plumb line:


Then I had to mount the base bracket and line it up with the top bracket and plumb line. I cheated a bit here and actually used the mast itself to line the two parts up:


This is the bottom bracket, not securely fixed yet - just look at the brick dust:


So once the mast was in place OK, I then needed to build the new antenna - it's an MA5B from Cushcraft, here are the elements beginning to be assembled:


And the new rotator and boom on the top of the mast whilst tilted over:


Here is the first element on the boom:

And then the whole thing up in the air:


What do you recon? Insane, hugh?