Observations from Scotland        Silk Purses and Sow's Ears            28/05/2008

Some people are lucky enough to have decent sized gardens. Others might live on a farm or in the countryside, but for many of us, myself included, we have what are euphemistically called 'postage-stamp' back gardens.  To be fair, living on a street corner as I do, I have a decent sized (but useless from a radio point of view) front garden while my back garden can best be described as 'half a postage stamp' being a small triangular affair.  The longest dimension of the back garden is 13M

Chez SXX with my back 'garden' outlined in blue.

The photo above was taken from Google Earth today and shows the full extent of out vast  'estate'... the red X and the small triangle at the back plus the 'extensive' front garden. At least, it IS extensive compared to some of the newer housing in the area.

The front garden is quite good and pleasant, at least our dog thinks so,  but of course its no good for aerials.  The back 'garden' is at least half the size of a postage stamp but despite this, I manage to have two endfed wires plus an 'extended Fishing-pole aerial of SM0VPO's design. Don't tell my neighbours, but there is a decent lot of radials under their patio and back garden (the garden to the North of mine) which also extends under my own grass. This was done while they were on holiday in Tenerife. I used an edging spade to cut narrow tracks across their grass, fed in some wires.. prodded into place with a forked stick, then stomped the grass back into place.  Lots of 'Miracle Gro' plant food plus nightly watering made sure the evidence was well hidden by the time they came home.  The radials are commoned to an 8 foot grounding rod driven into our heavy clay soil and the rods and radials are also bonded to the communal cast-iron wastewater system.

The fishing-pole vertical was made to this design Extended fishing-pole aerial  and is mounted on an 8 foot length of  scaffolding pole (thick walled) driven in and 'postcreted' in place with 4 feet sticking out of the surface (in the middle of a flower bed!).  So, to recap, in the back garden is a ground system, a fishing-pole vertical and two endfed wires.

On the back wall of the house, outside the shack window is a small cranked pole carrying my digital TV aerial and a DIY 2M slim-jim.  The Slim-Jim is made from 300R feeder stuffed inside some PVC sink-waste and a top cap glued on to keep the WX out.  This works very well and on a good day, I have even copied AO7 on it.  The TV aerial feeds my PC via a cheap digital TV to USB doodah.

In the attic, things are a bit more 'busy'.  I have a discone for airband and vhf/uhf monitoring plus a pair of home made aerials for 2M and 70Cms.   The 2M one has been trashed and rebuilt enough times for me to justify calling it home-made. The only original parts are the boom and the two connection boxes.  It's a ZL special yagi.    The 70Cms aerial is a K5OE designed quagi. K5OE quagi and is made of copper wire, scrap wood and thin soft ally wire. It can be flimsy because it never sees weather or big fat crows! Both are placed on a Yaesu azimuth rotator and pitched up at 25 degrees  (and not 15 as some people advocate) to give me good satellite coverage.

Also in the attic is an electrically shortened 20/80M dipole, this one bent into a U shape to fit the available space. Shortly this will be joined by my super-dooper small transmitting loop, an HF loop that's technically too big to be called a 'mag-loop' but will cover several HF bands. It is 1.9M square and made from 15MM copper water-pipe with soldered elbows and uses a motor-driven vacuum capacitor and is transformer fed from the co-ax..

While purists will throw their hands up in horror at having all those aerial systems in such close proximity etc etc, all I can say in my defence is that they work.  You have to make the best of what you have and if that's a poky little garden and a half decent attic, well that just has to do.  Better to use some sort of compromise aerials than just give up and take up stamp collecting, plane spotting or monopoly.  In short, just go do it. For HF, the mag-loop and its derivatives (like my oversized loop) can provide good efficiency on 20M and above and tolerable performance on 40 & 80M.  After all, a base-loaded vertical (even with radials) of the sorts sold in radio comics with all manner of inflated performance claims rarely manages an actual efficiency measured in double figures, and especially on the lower frequency bands.  A well-made loop CAN compete.

As to the short verticals that 'need no radials'... err, that's just marketing hype.  Strangely enough, many radio amateurs seem to buy the hype.  An RF 'circuit' with no return path... now that's a bit like getting Pea and Ham soup from a Chicken! Rather like the guy I overheard recently in a rag-chew QSO who didn't want any ground current with his vertical aerial 'because that was *wasted power*'.  The mind positively boggles.

One nice thing about loops is that they don't need a ground connection. Sure, they are affected by ground proximity but stick one on a nice high pole and they can surprise and amaze you. They have certainly grabbed my attention after some early failures in my DIY skills.  While a small loop can't compete with a decent wire aerial or beam, they will get you on the air from a 'bijou' (he means you can't swing a cat in it... LA2QAA) location.

 Ayewell, I might have less than perfect aerials, but I have a pretty good ground system, especially for my 'compromise' vertical. Our back garden can best be described as wet clay soil.  Sandra hates it (she likes gardening) but for me, it's manna from heaven. Of course those buried wires, victorian cast-iron pipework and a nice ground stake driven into soaking wet clay soil all help me along. On old maps of our area, there is a burn/stream. It must be in a culvert of some sort because it passes through what serves as our back garden and pops up again in the local cricket club. Although I've never actually seen where the watercourse is actually routed, I KNOW it's there. The maps were made a LONG time ago before our 100 year old house was built.  With grounding, every little helps! 

Oh, and I don't have any connection to the mains ground in the shack.  The electricity supply ground is extremely noisy in many areas. I use an isolating transformer to feed the shack and all the equipment is grounded to a heavy copper braid that connects the equipment by the shortest route possible and is also bonded to the transformer case.  The mains live and neutral go to the transformer input and no mains ground is connected.  All the crackles and bangs I used to hear previously mysteriously disappear using this arrangement.  If you do use a transformer, it MUST be a true isolating type of adequate rating to run all the equipment.  My ground braid goes out through the wall at floor level through an 8mm diameter hole, straight down the wall and is bonded to a huge cast-iron wastewater drain buried in wet clay soil.  If you do use a separate ground, be aware that any sockets should be blanked off so you cannot get a local to mains ground short. In the event of a fault, (either in your home or your neighbour's) you could have a LOT of current flow through such an arrangement.  Installations using PME (Permanent Multiple Earthing) may require different arrangements. If any readers have experience of PME grounding arrangements in a radio shack, I'd like to hear their views.

mailto:allan_gm1sxx@hotmail.com