Artificial Ground - You What?

Well,

My chum Vince, G0ORC has been having a spot of bother in his shack. We have concluded that this may be down to RF problems and as his shack is upstairs, there is little point in trying to create an RF earth as by the time the cable gets to the radio the impedence will likely be too high to be of use.

I found this whilst rummaging on the interweb:

http://www.remeeus.eu/english/hamradio/artificial_ground.htm

And it looked like exactly the kind of thing he needed. As I have quite a collection of bits here, I had a rummage and started to make this for him:

The hardest part by far was mounting the tuning capacitor such that it's issolated from the chasis and effectively floating within the circuit.

The inductor was very scientific and involved some detailed calculations; I just found an old silicone tube and wound some wire round it:

We have configured this inside the shack of G0ORC and initial reports are suggesting that this is enabling current to flow out of the shack into a counterpoise that we have constructed.

As a starter for 10 Artificial Ground experiment goes, seems to work OK.

Fun, egh?
 

How Much Power?

Well,

Myself and my chum Vince, G0ORC headed off to the National Hamfest last Friday, following a lot of consideration I was thinking of changing the Linear Amplifier that I have here for HF work. I have been using a Ameritron 600 watt Mosfet linear, with great success, however I was wanting to be able to run UK legal limit RTTY without pushing things to far.

ML&S had a very intersting linear amplifier at the show which just took my fancy, another great re-shuffle in the shack and it's in:

The linear is manufactured by a company called ALPIN:

http://www.alpinamplifier.com

And contains a single 4CX800A tube capable of 1300W SSB and 1000W continuous CW or RTTY work. The amplifier looks (both inside and out) to be a close copy of the ACOM 1000:

http://www.hfpower.com/

I am told that Alpin are ex-employees of ACOM or something like that (I don't actually believe a word of this).

Anyhow, the amp certainly looks the business:

and it's very easy to tune, I have created a chart of the "starter" settings for my setup and you simply rotate the "load" control as instructed on the LCD display and then peak the "tune" control for maximum smoke (RF out).

There is a good review of the amplifier here from RadCom:

http://www.alpinamplifier.com/images/RadCom%20Review.pdf

The review seemed to say the right kind of things....

I've had a dabble in the CQ WW RTTY contest this weekend and have been delighted with my station performance. This is a map output from my log from this weekend, most of the contacts have been on 10M:

you can see that I have worked far and wide and the RTTY station here at G0MGX is clearly working well!

Cat's not been helping much as normal:

Good though, egh?

Your are, you're completely Loopy!!

Well,

Following some interesting reading on Top Band RX antennas, here:

http://www.qsl.net/kc2tx/

I decided I might like to have a go at making one of those.... the main reason being that my experiments with my sloper from here:

http://g0mgx.blogspot.co.uk/2012/08/top-band-what-happens-there-then.html

especially when using it on WSPR, I seem to find that I am being heard by far more stations than are hearing me.... so perhaps a different antenna for receive may help...

So here is this ridiculous concoction:

and as you can see, perhaps not quite as rigid as it needs to be....

but anyhow, it was strapped to a wooden support and connected to the wireless.... result.... local MW broadcast stations significantly weaker on this loop then the sloper, but more interestingly the noise was higher on this antenna than the other.... a total disaster!

So I decided to solder another earth cable onto the existing slopers earthy side and plant some more copper in the garden:

We will have to wait and see if this improves the RX performance...

Here is an interesting image of me in concentration mode:

Cat's weren't much help as normal:

Here the Geddy cat is asleep on my laptop keyboard - not very handy!

Good though, egh?

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?

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!
 

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?

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: