Monday 30 December 2013

Vacuum Capacitor - From Russia (Via Ukraine) With Love

For a long time, I've been looking out for a decent vacuum capacitor to reliably tune my 20m magnetic loop antenna.

At long last, and just before Christmas, I 'won' an ebay auction for an 'new old stock' vacuum capacitor, sold by stas3105, based in Kiev, Ukraine.

Now, you may feel a bit nervous dealing with Ukraine.  Happily, I can reassure you in that I've only ever had very good service from several Ukrainian sellers.  There seem to more ham operators in Ukraine than any other country on Earth!

Wow!  These Russian capacitors are huge!  They have a very good reputation for quality, according to fellow hams across the EU.


The capacitor, far from being some dodgy second-hand unit, really is in brand-new condition, liberally covered in protective grease and oil.  According to the accompanying leaflet,  it was made in 1990. It set me back a very modest £69, including the necessarily hefty carriage bill, the item being rather delicate.  I obviously managed to get a good price by buying just days before Christmas, when there was less interest than usual in this stuff.  It only took about a week to get here.

I happened to have a lot of tinned copper braid in the junk box, so this was ideal to make the connections, using jubilee clips to secure the braid to the capacitor tips.  It took a few minutes to find the correct tuning for the loop. 

WSPRing across the globe - 5W, 75cm off the ground in the kitchen!

Once tuned-up, the loop ran on WSPR for a few hours at 5W.  Unfortunately, the internet was on the blink most of the time, so only those stations hearing me are recorded for the most part.  Spectacularly, and again it was missed by broadband outage, I heard a signal from ZK1DRP in the Pacific Cook Islands.  That's pretty good going for a tiny magloop working indoors!


Wednesday 25 December 2013

Magnetic Loop Antennas - Why You Should Have One.

Magnetic loops are quite well known in the ham world.  It's just that they aren't all that well-used.

This is very odd, because over the past couple of winters, I've been playing with my own homebrew version, and the results are spectacular.  I would also refer you to the WSPR results of my colleague, Ken Franklin G3JKF, who has some of the most carefully-made loops producing amongst the best signals in the EU on several bands.

Thanks to this nice image by M0UKD, you can see how simple, beautiful and practical a magloop really is. Once you start trying to make one, you will realise they are not as demanding or difficult to tune as many make out.

By 'spectacular', I don't mean 'it will beat the pants off a yagi at 120 feet'.  That's just a silly comparison.

But, if you have ever put up a dipole and been a bit disappointed with the performance and noise levels, then the magnetic loop should be next on your 'to do' list.  Note: not on your 'to buy' list!

The reasons I say a magloop is worthwhile are as follows:

  • Physically small - about 1.25m per side for a 20m version, which you can also tune to the higher bands with a suitably rated capacitor.  
  • Does not need height for proper operation.  A metre or so is enough.
  •  Because of the size, is a (perhaps the only) solution in very high wind areas (like mine!)
  • Won't be recognised as an antenna by most, giving you far less likelihood of neighbour and planning problems (loops for 20m are generally within planning rules, if you live in such an intolerant area.)
  • Magloops can be used very successfully indoors.   Mine gets across the world on 5W WSPR beacon mode, at 0.5m off the kitchen floor.  The difference in signal between a quarter wave vertical with elevated radials out in the wild weather and the loop indoors can be undetectable (WSPR tests.)
  • Magloops are essentially immune from household mains and local noise, allowing effective use in proximity to such sources. 
  • Built from 22mm copper tube, are very cheap to build for the 20m and higher bands.  Even at 80m, with a perimeter of 15m and made of wide 42mm copper tube, the price is hundreds of dollars lower than a commercial loop.
  • Capacitors can be found second hand, homebrewed, or bought.  If you are good with heavy duty soldering and electronics, a comb-type capacitor can be made and the loop tuned by opening and closing the two halves of the loop (which does, admittedly, demand high insulation and construction standards.)  Vacuum capacitors are to be preferred, as they are very reliable and predictable in tuning.
  • Performance is often said to be similar to a dipole, but without the height.  I think this is a fair comparison, though allow for much lower noise and QRM levels from the loop.  I find a horizontal dipole is rubbish next to a magloop (or, in fact, much of any other antenna type.)

There's a lot of stuff written about loops that tends to put people off.  Chief amongst these is talk of very high voltages across the tuning capacitor.  This is really silly, because, whilst it is true there is a high voltage present, this is not something that should scare off those comfortable with basic radio and electronics.

The main thing to contend with is very sharp tuning.  So you need good quality, stable and weatherproof means of installing and adjusting your capacitor.

A loop is, purely and simply, a fairly short perimeter of copper tube - make it as wide as resources and the cost-benefit analysis allows- with either a direct feed using various matching legs, or via a Faraday loop, which is an even shorter bit of wire made into a loop and connected to the coax feed.

Somewhere in the loop, usually the top, you must install a capacitor - either a high voltage butterfly air spaced type, or a vacuum type.  Vacuums are available on e-bay from eastern European or Russian sellers regularly, at prices well below $100.  I've never yet had a problem with sellers from those regions.

The only care you need to take is in making very good connections to the loop and capacitor.  A rush job won't do.  Use wide copper braid or heavy duty cable, and don't mix metals by using stainless steel clamps bonded to copper, which can lead to much lowered efficiency.

Having used all sorts of wire antennas, the magloop is the one that stands out as being a very good performer, immune from heavy winds, can be used indoors with little performance reduction, and can be practically scaled with only modest cost impacts to 80m (or lower!) 


Tuesday 17 December 2013

Hills, Sloping Ground and Cliffs

This winter's surprise has been the finding, mediated by objective WSPR tests, that my simple equipment wire, 80m inverted L, is putting out the strongest signal of any station from the EU on DX paths.  By this, I mean, typically, the path to the US.

Is this self back-patting?  No.  I have tested many antennas, and many are useless.  Horizontal antennas usually fit into this category for this QTH.

A hill by the sea.  The perfect DX location!


What is going on?  There are people across the EU with very capable antennas - a few full-sized quarter wave GPs, half-Ls like mine, and probably infinitely more experience and care behind them than I will ever have!

The answer is both interesting and useful for others to note.  Firstly, this QTH has reasonably steep sloping ground in all directions bar to the NNE.  The slope is 6 degrees for just about all of that horizon, being a bit steeper to the north.  This is without doubt a very important feature in obtaining the best performance from simple wire antennas.  I have noted the same phenomenon with delta loops for 20 and 17, vertical GPs and end-loaded dipoles for 20m.

Secondly, the surroundings of the antenna are clear of any substantial buildings.  Our home is a small Welsh cottage, nestled into the hillside.  There are some electricity supply lines of domestic ratings nearby, but these seem to have little or no effect, apart from a degree of de-tuning if you place an antenna too close!

Lastly, and perhaps of little comfort to others unless you live in South America or Australia, is the very high degree of mineralisation due to the QTH being on top of an old hydrothermal vent, more latterly a copper mine.  It is almost certainly soluble iron, and not other minerals, that is responsible for the excellent ground conditions.  Digging a deep hole for my tower some years ago revealed a thin layer of soil, a thin layer of red clay - which is known to particularly enhance RF ground conditions - and then very friable ground-weathered shale that has dissolved iron slowly flowing around within it.

So, whilst the latter element is probably very rare in coincidence with a radio station, the message about sloping ground and an environment as clear of obstructions as possible is something anyone willing to pack their kit onto even a modest hill, cliff or mountain should be able to benefit from. 

And of course, don't forget to try sticking a quarter wave GP at the surf line, where you will really see some spectacular benefits!


Sunday 15 December 2013

Radcom - December Update

It's in some sense satisfying to see more readers hitting this blog about the time of Radcom's arrival in the post each month.  Perhaps it's a quirk of searches prompted by the magazine.  Or maybe people have come to expect monthly comments upon it!

Either way, it's been interesting to see response to my musings recently on the future of the hobby within the 'letters' pages.  It's been very positive, and there are clearly a minority out there who 'get' what the concern is all about. 

Change you say?  You button-twiddling, buy-it-off-the-shelf imbeciles! 
 
One writer declares quite openly that RadCom is "editorially still the same as it's always been."  Perhaps that's true of the overall content, but at least the current editors are not censoring constructive criticism.

Disappointing in his response was the 'owner' of the GHz section.  The author spends a surprisingly numerous initial sentences claiming he's "noted" my claimed lack of material that would help an ordinary mortal - and not a lifelong RF engineer - into that aspect of radio.  Having done a bit of sounding democratic, he then concludes by saying, unless he gets any suggestions, he'll go his own way with the articles. 

Well, that's fine and dandy, then!

That's rather regrettable - and an inaccurate reflection of reality - because I sent a very polite suggestion as to content last year.  There was no reply.  Apparently, there have been some projects published for beginners.  But those haven't, frankly, been the type of projects this beginner would be able to tackle nor, I suspect, would most others.  I've yet to see hoards of people operating parabolic dishes up the local hill.

And there we go again.  The hobby is a reflection, made worse by its socio-economic make-up, of how society has developed over the past couple of decades.  Dominated by the retired, white middle class, many of whom were not only amateur radio folk, but professional electronics workers, to boot, pontificating on what real men's radio is all about.

It really won't do for the old guard to dig ever-deeper trenches whilst the number of participants in amateur radio falls off a cliff edge.  That is the mentality that dominated the argument for not allowing non-Morse literate users onto the HF bands for what seemed like eternity.  It was always a stupid position, borne of prejudice and selfish interest.  It undoubtedly held the hobby back and lost valuable interest.

And before you get on your soapbox, identifying a group of people - who just happen to be older - as being generally responsible for inertia in the hobby is not equivalent to being ageist. 

But, on the positive side, as the more stubborn and stuck-in-their-ways elders move on to a higher plane, perhaps the message to RSGB HQ that it continues to fail in its recruitment obligations and representation of those who haven't just retired from commercial electronics with a golden goodbye, will become a crescendo. 


Until then, I regret that Graham Coomber's bleating about 'change' and 'corporate identity' and so on will continue to ring hollow - and see our hobby fade into oblivion.




Monday 9 December 2013

80m and the USA: What's up with that?

Over the past couple of weeks, I've started being active on 80m for the winter time.  Using just a simple inverted L with two elevated radials, I've found myself up there with the best of the crowd. 

It's fascinating to run WSPR, a kind of personal beacon mode where unbiased, semi-objective signal reports are sent back to the user via the internet.  WSPR really does let you see how well your antenna is working, and whether that latest tweak made things better - or worse!

That's your American lot!  Not a lot of 80m WSPR interest, stateside.

It's really odd, therefore, that on 80m, there are only a handful - and by that I mean fewer than ten on most nights, active on WSPR from the US.

Why on earth might this be?  There's plenty of antenna design and construction activity, and tens of thousands of hams out there.

In many places, there are oodles of land and low winds to allow the erection of really very good, full-sized 80m antennas.

Sadly, they just don't seem to be there - at least on WSPR.  It's a big gap in our coverage, and it's to be hoped many more users across the US contribute to understanding their own antennas, those of others, and how the signal propagates between them.


Sunday 8 December 2013

Amateur Radio Foundation Licence: Some Thoughts.

Being a girl, my daughter likes talking.  She was lucky enough to have a brief chat with a girlie expedition to Greenland a few weeks ago, and as a result, it spiked her interest in radio. She's only seven years old.



I decided to sign my daughter up to the Foundation Licence course, which in our case, was a very comfortable affair, held each week at kindly MW0SEC's QTH.

It's a long time since I studied for my full licence, so it was interesting to see how the 'new' system of split licence levels works.

In general, the syllabus is pretty easy, and my daughter, with a bit of help from dad, managed to grasp, at least in some sense, what are often very esoteric facts about electronics and radio. True understanding of many things in the syllabus escapes even very old timers, as any read of forum posts on the internet often reveals!

But there are a few major let-downs if, as we might desperately hope is the case, the licensing body and the RSGB want to attract younger members.

One of these is the very heavy-going part on licensing conditions.   Whilst it's allowed to look at the licence conditions for the exam, the wording is so legalesque that it really does make it quite difficult for adults who are not used to looking at formal documents, let alone children.

Whilst it's difficult to say the syllabus is in any particular sense wrong, it could be very much more user-friendly.  The whole thing does still, I regret to say, have a certain aftertaste of years gone by, when non-Morse licensees (called, in that very British way 'Class B' holders) were sneered at as second-class undesirables.

The place where useful change could take place is in the exam.  Here, I think it would be very useful for children sitting the exam to be helped with interpretation of some of the questions (and not answering them) and the whole mechanism of sitting a formal test, which is quite novel - and very daunting - to someone of that age. If those responsible for setting up the system think back long and hard enough, they might recall just how terrifying an exam can be to youngsters.

A review and change is needed, with an emphasis on making the whole thing a further level less stuffy.  I hope that it comes a little bit faster than the glacial pace, far outstripped by the rate of fall in members, at which the RSGB and Ofcom seem to think is appropriate.  As my flying instructor used to say: "if something's not going right, do something about it straight away!"  Quite so...

Thursday 28 November 2013

Ham Web Site of the Day



Hat Tip: K7EK and 4x4 Ham

I dislike unnecessary levels of power.  I committed years ago to never using an amplifier and to always aim at using much less power than the rig's native maximum output for any given mode.

The link below is to a fellow ham's site, who has very usefully put together a routine that allows you to input your normal JT65 output level and typical signal reports.  In return, it gives you a series of lower power levels you could have used to achieve a good copy at the same stations, with only a modest decrease in the reception reports:

 http://www.k7ek.net/viewpage.php?page_id=15


Theoretical, but very useful to remind us that lowering one's output power should always be an admirable aim of any ham.

Wednesday 27 November 2013

80m Inverted L Antenna (updated for 60m)

What to do when the XYL is watching crap TV and the nighttime has stolen the higher bands away?

Yes folks!  It's time to go 80m!  [Update: and now, 60m!]

I first decided to try 20m of equipment wire (read: much cheaper than 'proper' antenna wire, whatever that is!), at the end of an end-fed matchbox made by the Hawaii Emergency Radio Group.  This is a very handy multiband box I bought a long time ago, but really only an adequate arrangement that gets you on the air in some form.

I ran this up to the tower at 10m, then down again to near the ground in a bent end-fed arrangement.  It worked, but the signals, though reaching where everyone else's were getting to, weren't very strong and matching it wasn't as easy as it needed to be.

Down it came!

Following night, after browsing some other clever people's inverted Ls, I decided to fix 10m of wire from the tower to a 10m fishing pole (at 9m high), whereupon the remaining 10m of wire hangs down to the ground where I initially used a 4:1 balun, a single elevated, 20m-long counterpoise and a short copper ground rod (I have exceptional ground) are connected to it.  At just 10m long, this is an 80m antenna that can fit in a fairly small garden without performance compromise.

[UPDATE:I tried two elevated radials, but found the second one made no difference at all as reported by WSPR receiving stations.  So you can certainly spare yourself the space and expense of an additional 20m of wire!  I found through very careful WSPR work during exceptionally stable conditions (13/12/13), that the best radial system is one elevated radial under the top wire, and as many buried radials of about 0.1 lambda or a bit longer as you can accommodate.  The buried radials added a consistent 3dB to the received signal]

My inverted L.  Feed is at bottom left.

Results?  Very good indeed - for DX!  Being predominantly vertical radiation, it's not an antenna for talking to your mates up the road.  In fact, you're unlikely to hear them at all on 80m, but is very good for NVIS at 60m.  Easily up there with the best of the 80m DX WSPRing crowd and, during early December 2013, I was the first and, for a fairly long period during the earlier evening, the only station getting across to the US and VK on 80m.  On 19/12/2013, I was the only one hitting VK7DIK from anywhere in the world on WSPR.

And if you want evidence, here it is, showing VK7BO's receptions of WSPR signals over the 24 hours spanning 17/18 January 2014.  Mine was one of only two being heard from any 80m station in the world:

World-leading 80m performance - from a piece of equipment wire!

So, a definite success.  What's more, both the internal and external transmatch match up the antenna very easily.  Native SWR (at the design band of 80m) is very good indeed - see plot on Update 2. Remember that, even at high SWR, losses with even cheap coax at the lower end of HF are just small fractions of a dB, so no need to worry or install expensive feedlines!

This is how MMANA-GAL thinks the radiation goes out when fed with an exact model of the above-pictured antenna (radial supported 1.3m off the ground - plants or fence posts in the garden achieve this!)  Real-world RF measurements support the pattern:

Not a bad pattern for such a simple antenna.  Red is vertically polarised; blue horizontal.  Gain figures are for my ground, which is exceptionally good and sloping.

So there you go.  Dirt cheap wire off E-bay, and I'm doing the business on 80m!  Now it's your go.  Two 10m fishing poles supported by fence posts are just as good - you do not need a tower!  Or just use one pole and slope the horizontal section; it only has a very small effect on overall gain.  Wind tolerance is about 45mph with my arrangement.  Not an issue if you have trees or a tall house, of course!


Here's the schematic.  Measurements are not critical, as the nature of the antenna necessitates the use of an ATU.  The 20m 'counterpoise' is raised in that fashion to allow a person to pass under the wire.  If you don't need to do this, the wire ought to be roughly 1.5m above ground.  About 90% of the return current is picked up well within 0.1 lambda of the vertical section, which is why the buried return path wires can be this short.

Update:

Having had an unused Notice of Variation for 60m for a couple of years, and with the onset of autumn, I set up the same inverted L and matched it up - which it does easily - for this relatively new band.

I had good results on WSPR, but the real surprise came when I came across 59+15dB signals from all across the UK in the SSB sections of the 60m band.  There's also surprisingly little noise on most nights, making QSOs at short range stable and comfortable.  I made several SSB QSOs using the above antenna, but by now, the horizontal wire slopes to just 6m off the ground at the 'far' end, because of my 12m Yagi's tower usually being deployed at that height.  This makes little difference to the performance.

The 80m inverted L, operating at 60m.  A very useful pattern for this great band.


Modelling the new antenna, I can see why this inverted-L does so well on short skip, and clearly will do well on DX too - a very 'bread loaf' pattern, highly reminiscent of a corner-fed delta loop's pattern.  In short, this is perhaps an antenna perfectly suited to 60m.  Thanks to all on the band who made me so welcome, too!

UPDATE 2 - March 2016.

Having my own SARK-110 analyser now, this is what the inverted-L looks like without an ATU fitted.  That's an extremely good match at 80m!

The SARK-110 plot of the inverted-L at 80m.


A full-HF plot showing the multi-band possibilities of this antenna.  Even though it doesn't look so promising at 60m, the antenna does, in fact, work very well, with easy ATU matching.  An auto-ATU at the antenna base will clearly reduce losses considerably at 60m.


Wednesday 20 November 2013

The Much-Maligned Quarter Wave Vertical

It's that very windy time of year again, when cold air from the north is rushing away to the south. It's a very, very bad time for antennas at the Copper Mountain Station!

Whilst my delta for 20m can put up with gusts up to about 60mph, sometimes the wind does easily exceed this level - up to 85mph -  and sustained winds of 48mph for hours or even days on end are common.

I recently played with a phased, two element vertical system for 20m.  I didn't find it a very practical system, and it was rarely better than my delta loop.

1/4 wave of vertical element, 1/4 wave of radials.  Easy!


So, I cut one antenna out of the equation and left one standing.  A 7 metre fishing pole is ideal for a 20m vertical, being 5.03m or thereabouts in length, thus raising the feed point and radials to a good 1.5m above ground.

I only use two radials because more become a big headache in a family garden, and that my ground is excellent and that two radials are, in fact, more than adequate for a quarter wave vertical!  One radial is more-or-less parallel to the local ground, the other slopes 5 degrees downhill; QST magazine reports this to be the best configuration in terms of gain, though this is marginal, to say the least.

You can get more involved in shorter-than-quarter-lambda radials if you read Les Moxon's 'HF Antennas for All Locations'.  Suffice it to say that quarter-wave radials do, however, work!

KI0WN enjoying the very low angle radiation of a vertical at the beach (keep it very close to the surf!)


The result?  There's certainly more noise on the vertical than the delta, but for all but the very weakest signals from, say, Antarctica, it really isn't a distraction.  Signal levels are, at this QTH, generally stronger on the quarter wave than a large delta.  Indeed, during a test in extremely stable conditions on 20m with VK3QD (long path, December 2013), there was simply no discernible difference down under in the received signal between the two.  Being shorter and thinner, it's infinitely more wind resistant than the delta, uses much cheaper poles as a support, and is very easy to repair if it breaks (although that's largely true for the delta, too!)

If you need any further convincing about the DX potential of verticals, just have a listen to the increasing number of members of the 'Real HF Radio' group, daily down on the beach and challenging or exceeding the boys with big yagis.

It's clear to me that many simple wires, including the 1/4 wave vertical, need an updated assessment, because most of today's texts either don't take account of the powerful digital modes that have come along in the past few years, or just blindly regurgitate tired old texts, sometimes from decades ago, when antennas were largely compared to one another by ear, using either SSB or CW. And inevitably, many of those texts were written by well-seasoned hams, operating large stations and who had long forgotten - or were trying to justify their expenditure by ignoring - what a simpler antenna could in fact achieve.

Books and internet bleating will warn of dire EMC problems if you use verticals to "fire straight into your neighbour's home".  There may be an increased possibility of this, relative to a yagi at 15m, but that isn't really a reasonable comparison.

I have seen very slight interference on the PC monitor when running an antenna close to the house, but it is cured in seconds by winding the signal cable of the monitor around a ferrite sleeve.  That is something you can do in your own and your neighbour's house without prompting a big fall-out, and at almost zero cost.

The pros for the quarter wave vertical are thus:
  • Robust in even hurricane force winds.  Mine was the last man standing in the antenna farm during 85mph storms!
  • Extremely easy and quick to build - three wires of the same, correct length
  • Convenient direct coax feed
  • Collapsible for transporting to beach or field use
  • Low angle radiation; at a beach, very near to the water, you will easily beat a 3-element yagi!
  • Good signal reports
  • Cheap!  Any old wire can be used.
So, rather than condemn a vertical with the tired-old maxim that it "radiates equally poorly in all directions", I think a more considered assessment would be that it is a very practical, cheap and effective omnidirectional antenna, and is an excellent entry point for newcomers.



Sunday 17 November 2013

RSGB Centenary - a PR Opportunity Lost?

Sitting next to my radio this afternoon, I casually glanced at the latest edition of RadCom across the table.  It reminds me in the corner, on the cover, that 2013 has been the centenary year for the RSGB.

Last week, I was delighted to see a really positive spin put on the hobby by the enthusiastic members of the Chorley and District Amateur Radio Society in aid of a nicely-presented BBC news item.

It is a great pity to say that the Chorley lot seem to have gained massively more publicity in a few hours than the RSGB has managed all year.



Sticking 'RSGB centenary' into Google search (17/11/13) brought up the following depressing message:

Your search - rsgb centenary - did not match any news results. 

That really takes some doing in today's news-skimming electronic world.  For sure, I've not seen any ham-related items in the newspapers I read or the radio stations I listen to.  The only result I found in the entire labyrinth of the internet was under "RSGB 100 years", which came up with a solitary item reported in the Redditch Advertiser, a free rag with a circulation of 39,000 according to industry sources.

This is a very clear reminder to the RSGB Central Apparatchik that patting insiders on the back and getting mates of insiders to pat you on the back is not a successful way to bring radio to the masses.

I have no doubt at all that the general public have a latent interest in radio, provided it is presented to them in the right way.  The success of popular science programmes proves that.  Bringing in the Queen's representative in full military regalia is not really what we want to see, and it clearly hasn't been of any interest to the mass media, if Google's results are anything to go by.

So, once more, the RSGB has wasted an entire year by patently failing to launch a successful and highly-visible media campaign.  As a result, it has wasted a good opportunity to attract new interest and new members.  Gold-plated Morse keys and name badges do not - read again - do not attract anyone into the hobby.

Morse alienated potential new members for decades.  In its centenary year, the RSGB promoted itself with, amongst other things, a gold-plated, erm, Morse key (the owner of the key is not related in any way to this article.)


In addition, it continues to try and cover the damaging cracks caused to the society by endlessly presenting the National Radio Centre as a wise use of its members' money.  It wasn't, isn't, and never will be.

One day, the Board Members might just get the message that they are not doing their job properly.  Too much time has been spent trying to persuade the muppets that pay the annual sub that the bad old days have long gone.  They haven't.  For 2013, the all-new Board has miserably failed to present the hobby to the public that have yet to discover amateur radio.  That, my radio friends, is a tragedy when you remind yourself, once more, that the age profile increases in step with each passing year.




Friday 8 November 2013

At Last! Perfecting the Delta Loop

One of the reasons I started this blog was as a personal diary of developments with antennas and other equipment.


For several years now, my bread-and-butter antenna has been the trusty 20m delta loop.  For all that time, it's been an apex-up, coax corner fed unit, using a 4:1 balun at the feedpoint.  At the start, the antenna was much too long - about 23metres - but it worked most of the world anyway, coupled to an ATU.

The revised, almost-perfect delta loop for 20m in a Frank Hurley-inspired night-time image.

Later, I shortened the loop to a lower SWR, and fed it with higher quality RG213 coax, again to a 4:1 balun.  Again, the delta carried on adding DX to the list, reaching 116 entities in a pretty short period.

So, the first take-home message for anyone starting out with a delta loop is: a corner fed delta is easier to put up than one with a feed a quarter wave down from the apex.  It yields low angle radiation but doesn't really need to go up more than 8m at the top. It will also certainly let you work the world with decent signals.

And on that note of being 'only' 8m at the top (or about 2m off the ground), and to answer many, mostly US-based criticisms of this, raising a delta loop too high is a bad, not a good thing.  This is because as the loop rises, it starts sprouting high angle lobes.  High angle lobes allow high angle signals to come in, which negates one of the main benfits of a delta: low noise.  At 20m, these lobes are well-developed when the bottom wire is above about 5m, regardless of ground type.  So keep that bottom wire within 2 to 4m of the ground (it also becomes increasingly complex to rig a delta above this height.)

The only drawback with a corner-fed delta is that its pattern in elevation is very broad because cancellation of the horizontal radiation is not complete. Consequently, it has much the same gain from near the horizon to overhead.  That means closer-in stations coming in at steeper angles can cause excessive QRM.

It is to rid the high angle stuff that necessitates the use of a feed point a quarter wave down from the apex, or 0.08 wave up from the bottom corner if you prefer that.

I decided I would try, at long last, the latter feed arrangement, and used a very lightweight dipole centre attached to 300Ohm twin.  A broken fishing pole holds up the twin at a 90ish degree angle from the antenna, keeping it reasonably balanced, and is led off into a 4:1 current balun outside the shack.  A very short section of RG213 completes the journey to the rig.

So, having braved the cold, cut the delta down to 21.4m, and soldered once more in stiff winds (a propane/butane torch is extremely useful for this, but aim its jet downwind to avoid accidents!),  I put the rig into CW mode and pressed the mic.

Had it worked?

Yes, the delta's now working at an SWR 1:1.2 in the digital and CW sections, rising to 1:1.5 at the upper band edge of 20m.  If I had an analyser to confirm my reasoning, I would say I can afford to trim another 10cm or so off the loop.  But for now, the loop has finally reached the kind of place where it is pretty much perfected with low SWR and very low angle radiation.

So, that is the culmination of years of experience of a delta loop.  The final wire length for resonance is indeed in keeping with online calculators.  Books are not always so accurate...




Tuesday 5 November 2013

Delta Loop Examined

Regular readers (are there any?) will know I am a big fan of delta loops.  These wonderful triangles of wire, easily propped up by just one pole for a vertically polarised version (ideal for my QTH) took me from noisy dipoles and less-than-ideal long wires to working global DX with relative ease.

Sure, it's not a beam, but then, you have to look deeper than that.  You have to look, especially, at the angles of arrival and departure into and from the antenna.  These are important, no matter what someone else has written.

This weekend past, the pole broke on the 20m delta, so I took the opportunity to change from corner fed to 0.08 lambda up from the bottom corner (0.25 lambda down from the apex.)  Before I did that, I ran the corner fed delta against a dipole held aloft at 10m on a tower, using WSPR to eliminate any human bias.

Here, firstly, is the pattern of the dipole at 10m above ground.  Remember that these are my approximate ground conditions on top of an old copper mine; your ground will almost certainly be worse as a result.  Also, my delta base ('radial') wire is at 2m.  A lot of US-based hams comment this is much too low.  But that's wrong, because the pattern develops higher angle lobes much beyond about 4 or 5m (for a 20m loop.)   It's also almost impossible to mount a 20m delta loop with its base at 5m, especially in windy locations and keeping to the non-conductive mast requirement.

Plenty of gain at higher angles, which falls off rapidly as you near the horizon - where good DX is found.
 
Here is the rather odd pattern of a corner-fed delta loop as modelled by MMANA-GAL (others yield the same pattern):

A corner-fed delta worked the world in a very short time for me.  But it can be improved upon.  The 'loaf of bread' elevation pattern is a problem for rejecting higher angle signals.


The result?  The delta loop came in very slightly ahead, by about 0.5dB, of the dipole.  In essence, and because the statistical significance needs to be built up a bit, it's pretty clear the two antennas are neck-and-neck, except that the delta has an almost omnidirectional field against the dipole's distinctly directional two lobes.  This fact was of course taken into account in making comparisons, using only stations within the peak beam of the dipole and delta.

So what?  Well, some people have tall trees, poles, or other supports.  But an awful lot of people don't.  As I've noted previously, getting anything 10m in the air is not the simple operation antenna books and magazine articles endlessly try to make out.  It is an awful lot easier to stick a single fishing pole with a triangle of wire attached to it than even putting up a wire dipole, which needs at least two, strong supports.

For those looking at claims of ground gain from certain aluminium dipoles up on towers or long poles and wondering whether it's a good idea to part with £300, you may want to take stock of the above, equal result.  That, and the roughly £50 it costs to make and install a delta loop.

A test 20m dipole going up to 10m - the expensive way!

So, if you have a fairly clear site and like working interesting DX, it seems to make much more sense to put up a delta than a dipole.  Argue amongst yourselves, or leave a comment!

Next, it was time to take advantage of a calm, starry night and change the delta's feed point.  Off came the cumbersome RG213 and 4:1 balun, on went 300Ohm twin to a dipole centre at 0.08lambda (about 1.72m) up from the corner at which it used to be fed.  Greasing of the conections helps avoid SWR changes during rain.  The old corner was soldered easily together, strung up, and the twin secured.  The twin runs to a 4:1   current balun just outside the shack, from where a short section of RG213 connects it to the ATU or rig 'tuner'.

The new, twin-fed, 0.08lambda-up-from-bottom-corner delta.


The result?  Immediately obvious is the much quieter reception.  That's because the pattern is much more directive in elevation.  Italian stations, notorious for high-power, higher-angle QRM in the UK, have become several 'S' points weaker, entirely in keeping with the modelled pattern.  VK stations, coming in on extremely low chordal long path hops are now about an 'S' point stronger.  An Italian Antarctic station was easy to hear at 55 (58 with preamp), and I got the same 55 report back.  I should also note that, if you can only corner feed, that version managed three previous Antarctic QSOs for me, so it's by no means essential to use this dog-legged feed.

Here is how the pattern looks with the new feed:

The upper elevation angles are now much attenuated, and the low angle gain improved significantly.

What's more, with the twin and 4:1 combination, the delta is matchable, if not the most efficient, on all bands to 6m (15m could not be matched with the previous, corner feed).  But, primarily, the delta is good only on the band for which it is cut, and its second harmonic at 10m, where it has a perfect match.

When I get a chance, I'll run the dipole vs. delta again, see what difference, if any, becomes evident.

Further reading:

Large Loops by ON4UN.
 












Wednesday 30 October 2013

KQ2H-R: Getting Worse.

It's about a month into the excellent 10m propagation conditions that has seen the KQ2H-R in upstate NY creak under the calls coming in.

But the operators attracted there vary enormously from the excellent to the downright inept.

Aye.  Settle down to a cuppa and hold up the world on KQ2H-R.  Nice one!

Sadly, some of the regular worst visitors to KQ2H appear to be from the UK.  Not content with short, polite exchanges than acknowledge the extreme numbers trying to call in, ol' George stations settle down to a nice cup of tea and a moan about the weather.  Inevitably, they are elderly.

KQ2H-R is not a place to thrash out, once again, the arguments about what makes a QSO.  It is simply a very busy place where you call in politely, say hello politely, and then leave quickly.  It's not a place to ask 400 other stations to 'stand by' whilst you take ten minutes to express how strange it is to 'work the UK the long way round'.  We've heard it all before, and we all understand how it works, thanks.

So, as they say in the US, home of KQ2H-R, "MOVE ALONG THERE!"

Wednesday 23 October 2013

The Positive Health Effects of Amateur Radio.

The electromagnetic spectrum is, or at least once used to be, the attention of all sorts of wild claims about adverse health effects.



Ham radio hasn't generally been the victim of widespread antagonism from the general public, at least in the way that mobile phone masts once were.  Strangely, phone mast health concerns appear to have vanished as soon as the operators gained the ability to install towers simply by informing local authorities, rather than asking for their permission.  Evidence, perhaps, that too much democratic influence isn't always a good thing.

But are there any positive health effects from radio, and more specifically, amateur radio? 

I'd argue that there certainly are.

As I've noted in recent blogs, I have been suffering from the intense pain brought about by a prolapsed vertebral disc.  It's not something I'd wish on my worst enemy.  Mercifully, I am now coming through all that nightmare.

But, between the pain, the back exercises and the pills, going on the radio from time to time also had a very positive influence on my recuperation.  Instead of wallowing in pain on my own, I could have nice QSOs with someone far away.  I could look up their QTH on Google and, for example, experience in some small way the wide, open expanse of the central Russian skies.

I don't know how much my pills cost the Welsh NHS over several weeks.  But they didn't come cheap.  It would be very interesting to see whether, for those who have the licence or for those who might like to get one, ham radio could complement treatment for various health problems, most notably those of depression and loneliness, in a cost effective manner.  It would be surprising if it could not.


Saturday 19 October 2013

Things To Do On KQ2H Repeater.

Picture the scene.  KQ2H repeater opens up on 10m.

It's busy.  Very busy.  People are calling in from Latin America, North America, Europe and the Caribbean.

Then, the inevitable happens. Some Brit ops come on to pontificate how others have been calling too much.  Being such experienced folk, they had earlier decided to "let them to it" and not bother with the repeater.

That 2 minute-long exchange took place whilst the repeater was in the aforementioned condition, groaning under the pressure of dozens of people hitting it at the same time.

So, thanks to 2E0UDX and one of his pals who let the world know - and at such length - how terribly fed up they were of people tying-up repeaters. 

On the other hand, congratulations to just about everyone else this afternoon, who kept it short and sweet.



Tuesday 15 October 2013

Mobile Antenna for HF

Yes folks, a rare occasion when I buy an antenna!

I've decided that mobile operating would be rather nice, and a good way to pass the occasional half hour whilst waiting for the kids to come out of school.

But which of the plethora mobile antennas do you buy?  They range from those sold for about £25 with very good reviews to those sold for well over £100, sometimes with not-so-good reviews.

The first impression you'll get of the G-Whip Pro Mobile.  It's a good impression.

Enter, yes, once again, Mr. Geoff Brown, aka G-Whip Antenna Products.  This is a man who knows how to make products and serve the customer as though he matters.

I looked-up Geoff's web site and quite liked the look of his G-Whip Pro Mobile antenna.  It comes with three coils of your chosen band as part of the package, and can be mounted on a tow bar, tow recovery hitch point, or standard mag mounts.  A mag mount on top of the car can be expected to have about 3-4dB better performance than tow bar mounting, also avoiding issues with rear screen heating wires and so on.

For £125, the antenna is not the cheapest, but then you are getting three dedicated antennas in one, so on that score, it's darned good value.  And that's without yet taking a look at the quality of the antenna you get.

The three coils (you can choose your favourite bands.)  Impressions even better...


So, I placed the order and twiddled my thumbs for a couple of days.  I got a test report and SWR curves for each of the coils just before the antenna was delivered.  Then, a sturdy cardboard tube enclosing the antenna which was itself encased within a further plastic carry-case, arrived by next-day delivery.

With just a quick screwing-on of coil and then the adjustable tip assembly, the antenna is ready to go.  With a few minutes spent getting the antenna to resonance (yes, you even get a spanner for the job!), I was down to about 1:1.2 SWR and ready to fire-up.

A few QSOs were had with easy, predictable European stations with excellent reports.  I even had a QSO with a man in south Italy operating /M using the same TS-50S and 50W output as I was, both with 57-8 reports.

A fine-looking, well-performing G-Whip Pro Mobile, as seen on my car!


Stunningly, I heard a strong Indonesian station on 20m, and gave him a call out of curiosity.  No, he didn't get my full call, but clearly asked the mobile station to come back again and eventually said sorry, he had an S-3 noise floor, just where my signal was hovering.  There is no doubt whatsoever that, whilst this mobile antenna is obviously not always going to compete with home stations, it is going to put in a good show and probably beat most of the other mass-produced Chinese whips out there.

I will be updating this post regularly as I spend more time with the antenna.  I only report honestly, so you can judge for yourself whether this is the mobile antenna for you.  Certainly, even at this very early stage, I have nothing but praise for the superb build quality and evidently good performance of the G-Whip Pro Mobile.  By the way, I am only a customer of G-Whip, and have no other links with the business or its owner.

Out and About with the G-Whip Pro Mobile.

Going mobile is really rewarding!  Pull in on a hill, mountainside, or by the sea.  You may think it's a bit of a struggle, but with this antenna, you start to wonder if the QTH antenna is as good as you think!  What's more, you get more on-air time, so more chances to catch interesting DX.

Here is the best indication of the potential of this antenna.  The red lines are direct contacts; the yellow is to KQ2H-R, with green then from the repeater to the station contacted.  The QSO with OA6 is quite rare, and shows the usefulness of being able to be on air when otherwise you would lose out.  The bias to the west is exclusively down to operating during mid-to-late afternoon in late autumn.  What isn't shown on this spherical map is the 54 QSO with VK6MV from outside the kids' school on long path on 15/11/2013!

Just a few of the best QSOs over the first month or so...




Saturday 12 October 2013

A 2-Element Vertical Beam for 12m (Cheap Price!)

The 12m band is great for working far eastern countries from here in north Wales.  From early to mid-morning during the spring and autumn propagation periods, all sorts of distant and disparate areas come to life on the PSK screen.

But, I've never had a dedicated 12m antenna, so relied on forcing my 20m delta loop to radiate at a frequency quite unnatural to it.  OK it worked, but the radiation pattern is very distorted and obviously not an ideal way to work.

So, inspired by my friend 2W0MTD doing very well indeed into the east with his homebrew doublet, and the 12m band livening up a lot in autumn 2013, I grabbed two 7m fishing poles (I recommend you use 8m versions) previously destined to be part of a Moxon beam, and cut some wire for a vertical dipole for the 12m band.  A number of thin cable ties keeps the wire snugly attached to the poles.

The 2-element 12m beam looking towards the far east.

I fed the radiator with 300 Ohm twin, led into a homebrew 4:1 current balun outside the shack wall.  With no cutting, this came in at an SWR of about 1.7 at the bottom of the 12m band.  Because I'm using twin feed, the losses due to SWR, which tends to rise as the weather gets drier, are minuscule and utterly inconsequential. I cut the reflector element at about 5% longer.

Pounding (with a bad back!) some half round fence posts into the ground as tried-and-tested supports, I simply cable tied the poles to them, led the twin wire at a decent angle away from the radiator, and retired to the shack.

The result?  Excellent!  A noticeable improvement was that calling CQ almost always brought an immediate reply.  I started working all over Russia, out to the far east and even a QRP station running 5W into a dipole somewhere on the line between European and Asiatic Russia.  The gain is pretty respectable at anything between 6 and 7.4dbi, depending on which ground conditions you use; it's also DX-useful low angle radiation.  This is the only antenna I have which regularly yields better (objective, JT65A-based) outgoing signal reports than incoming.

Standing behind the reflector, the RF meter reads zero, showing excellent F/B.

I took out the homebrew RF meter to get a fell for the radiation pattern.  Remarkably, this extremely sensitive meter, even at its maximum setting, gave a zero reading directly behind the reflector.  The model suggests there ought to be a reasonable amount of radiation, as the F/B is computed to be a modest -6dB or so.  In reality, the F/B appears to be more like 10-12dB.

Here's the pattern for the vertical beam as computed for extremely good ground, bottom of the antenna at about 40cm off the ground.  The -3dB beamwidth is, for a manually-steerable beam, a usefully-wide 120 degrees.

How MMANA-GAL computes the 2-element 12m beam.  The F/B is, in reality, much better than this.
I've modelled the antenna spun 90 degrees to one side, as a horizontal beam at half a wavelength up (about 6m.)  The gain below 10 degrees is in fact better for the vertical, even though the horizontal has a better peak gain of 11.7dBi, but which doesn't occur until 27 degrees.

So, the vertical is better at rejecting higher angle signals, having a peak gain of 7.6dBi at 12 degrees, and this was evident in on-air tests.  By a combination of grey line working and this modest beam, I've managed to log several African stations in the space of just a few days, after a long period of being a bit tough in the southerly direction.  Given the sparcity of African stations, that's pretty good going!

I've added three more fence posts to enable the reflector to be moved around the radiator (at a separation of about 2m), making a manually-steerable beam. I'm now using 40mm drain pipe clips as an easy way to locate and relocate the reflector, but I did need to rotary-tool sand away the ring on the base of the screw butt-end of the fibreglass pole to make it all go smoothly.

An unexpected bonus is that this beam works more than decently on 10m as well, allowing nice contacts into KQ2H-R when the propagation is running.  

Happy vertical radiating!


Friday 4 October 2013

Going HF Mobile, G-Whip Style.

Yes folks, I've finally decided to go HF mobile.  Having recently acquired a new car and pondered on the comment by a colleague that "radio's more fun when out and about", I sat down to view my options online.


I am by no means an antenna expert; that much is clear.  I also have little time at the moment to learn about coils, measure their characteristics, and build a successful antenna.

Towbar and tow hook mounts are available, but magmount atop the car makes for significantly better performance, essentially doubling the signal strength.  Image: G-Whip.


In short, I've decided to buy an antenna!  This is a very rare event indeed for me, as I've previously only bought a 10m and 20m end fed from Geoff Brown, AKA G-Whip.

Anyone who's bought from Geoff will know the clear benefit of doing so: personal, prompt and polite customer service, coupled to very high quality products, usually of military standard.  This is despite being a very busy man who essentially hand-builds every product he offers.

I've not yet received the antenna, but the magmount and rig are all sorted out, ready for the off.  It all feels a bit like the CB days of old, but better!

As soon as I get out and about, and especially park at the seaside, I'll let you know whether or not the £125 I parted with for Geoff's Pro Mobile antenna was a good investment.  Quite what parents waiting outside school will make of it will be equally interesting!

Wednesday 2 October 2013

High Geomagnetic Activity - Does it Affect Human Health?

I woke up this morning, with usual renewed excitement about what DX might be coming in.

Although I could hear a couple of VK stations, they were quite weak, and the band was clearly wiped-out by geomagnetic activity.  A visit to NOAA's space weather site confirmed a G2 storm had been underway overnight.
Neuropathic pain such as sciatica is tremendously distressing and debilitating.  Does the Sun make it worse?

Now, I suffer from very severe sciatica.  I take GABA inhibitors to block the intense pain that otherwise renders me a crippled man of 44 years.  Until I took the GABA inhibitors, I couldn't sleep, which sent me on a road to hell.

So, for a couple of weeks, I have slept with no pain at all using these miraculous drugs, more usually prescribed for epilepsy sufferers.

But, last night, at 02:30UT, I woke up with a pain as though I hadn't taken the pills.  I checked I had taken the correct ones, and I had.  With a combination of drugs, I eventually drifted off to sleep, and the morning brought renewed positivity.

Could this be a warning that a higher dose of painkillers might be needed?  (warning: do not exceed your prescribed dose)


Now, was the fact I had pain this morning related to the G2 storm, which commenced just after midnight and so coincided with the onset of my pain?  Correlation, of course, does not prove causation; I'm well aware of that.

However, a search this morning on the internet revealed a surprising number of peer-reviewed papers on the negative effects of enhanced geomagnetic activity on human health.  Some of the statistical probabilities recorded clearly indicated more work was necessary.  Others were much more robust.

So it seems that not only can the Sun's tantrums wipe out our beloved HF bands, but can also make life a misery (or worse) for humans too.  I find that fascinating because I had never before heard anyone mention such a possible link despite a lifetime in science, and for the mechanism behind the effects.

Postscript.

For those looking for evidence that ham radio is bad for human health, the above is nothing to do with that topic; it's about entirely natural, solar-induced effects. Current conclusions on ham radio are that the low powers used do not represent a health hazard to humans.  The UK has a very low power maximum of 400W, compared to 1kW or more in other countries.  Most UK hams use 100W or less.

Sunday 29 September 2013

RSGB - Thank You.

Like many hams, this op often has a few gripes with the RSGB.  As a society, it's right the RSGB receives reasonable comment and listens to it.  In the past, that certainly wasn't always the case.

Recently, I have been trying to get a club station set up at my local primary school, which I'm glad to say has embraced the idea with enthusiasm.  Practicalities may get in the way and it may never happen, but at least we'll get a few field days at school events, if nothing else.

Slowly, the RSGB is whetting the appatite of the young.  It - and its members - all need to do much more of this.

So, in pursuit of some support and encouragement from the RSGB, I e-mailed them to ask if they would be kind enough to provide some publicity material.

Sure enough, the response was immediate and enthusiastic.  Some days later, I received a fairly large package of materials, most of which is attractive and useful.  The very uninspiring centenary poster, however, is pretty rubbish!

So, a genuine, sincere and big thanks to those at the RSGB who provided the material so readily.  Keep it up.  Publicity, especially amongst kids and now without the benefit of GB4FUN, is nothing short of essential.  I hope the RSGB remembers and acts upon that more in the future. If it does not, there will be no RSGB.

Friday 27 September 2013

Amateur Radio Revolution?

Tune up to the macho 20m band and all its manly bravado, and you'll soon hear things like "running 1.2kW into a 5 by 5 stacked 5 element array" or some such idiotic nonsense.

If you have the money and obsessive qualities to turn your hobby into a way of life, that's all fine.

For the rest of us, there's a recession bordering on depression going on, and life is hard.

JT65 (or JT9): the way to easy DX with simple equipment.

Of late, I've really taken to the digimodes.  It's never as satisfying as actually talking to someone, but if offers a nice way to keep on operating when the kids are asleep, and shouting down the mic is out of the question.

So digimodes really ought to be the way in which we attract new entrants into the hobby.  And, boy, do we need them!  The attraction of computers and radios linked together is clear.

But the real point of my ramblings tonight are this: with digimodes able to happily work with signals down to -28 or lower, anyone with the ability to attach a matched wire to a transceiver can now operate global DX on low power.

For example, I've a folded 'pyramid', originally a WSPT test unit, that is no more than 4m high, and takes up the space of a very, very small garden.  It is fed by twin line to a homebrew 4:1 current balun.  It has a fairly high SWR of about 3, but that is of little importance with twin, as matching losses are miniscule.

Whilst is is not the best antenna in the world in terms of absolute signal, it can get a pretty decent signal out.  Attached to JT65 running on a laptop, it's easily capable of getting a signal across the world with plenty of perseverance and informed operating (grey line, long path, etc.)

So, let's not forget in our discussions about which $3000, 7-element beam might be best put on top of a $10,000, 100 foot tower that none of that is, today, necessary to enjoy global DX.

If we got that message out to youngsters, maybe we wouldn't be seeing the logarithmic decline in the number of people participating in the great hobby of amateur radio.

Tuesday 17 September 2013

MFJ 941E ATU - Replacing That Pesky SWR Light

Its many years ago now since I bought the MFJ-941E matching unit.  MFJ have a very American style of advertising, and reading one of their leaflets sometimes brings to mind a rather dodgy second-hand car salesman's pitch!  The endless use of excited italics to highlight rather unexciting features is also rather quaint.

But that would be to do MFJ a disservice.  The 941E has matched just about anything I have ever thrown at it.  This afternoon, its SWR panel light gave up, giving me a chance to open it up to fix.

These are the very tidy workings inside my MFJ 941E:

Fair play, that's an honest day's work by MFJ for about £140.
 
You can't really find anything to criticise in there, especially mindful of the price.  The 4:1 balun is absolutely tiny, but I always use my homebrewed transformers just outside the shack with balanced line anyway, and never now use the twin input into the MFJ.

Now, back to the SWR panel meter light.  For some utterly unknown reason, MFJ, at least for a time, produced this transmatch using a small incandescent bulb to light it up.  Inevitably, after a couple of years, it blows.  I decided to replace it with some old white LEDs from a broken 6V torch I had just thrown in the bin.  I hastily recovered it, took out the two LEDs, took an educated guess at the correct voltage and current, and added a couple of 90 Ohm resistors in series to bring the nominal 13.8V DC output from the station PSU down to something that didn't turn the LEDs into little heaters!

Two LEDs from an old 6V torch, plus 180 Ohms added resistance give me a nice new SWR meter light for pennies.

I just glued the little circuit board holding the two LEDs to the outside of the panel meter, at the top, keeping the LEDs clear of any plastic and in free air, just in case of any excess heat production.

It works a treat, and I doubt I will ever again have to change the light source for that SWR meter!

Cool blue LED replaces mellow yellow incandescent glow.