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.

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.

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.

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.

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...

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.