Delta Loop Matching - D'oh!

Recent posts have been all about trying to fathom out a series of problems that sprung from nowhere with my delta loop for 15m.

The delta has worked through hurricane winds for more than six years, worked global DX, and never complained a jot.

I started the investigations when I could hear the received signals breaking up intermittently, revealing a problem somewhere.

Having eliminated the audio from the rig as the problem, it was time to follow the coax!

Throughout this story, the rig itself - an FT-450 - and two standard SWR meters all reported perfect happiness at 1:1.15.

My SARK-110 analayser, though, had other ideas.  It showed a good curve from time to time, but had lots of noise.  The noise initially appeared to be down to the MCX connector, but eventully proved to be fine.

Anyhow, to cut a long story short, I found plenty of problems when I started to dig:

(1) badly corroded coax, which I replaced.
(2) a somewhat damp 4:1 balun, though it was only condensation and in fact, seems to work fine
(3) a supplied patch lead from the SARK to the outside world was defective and lost continuity.
(4) a metal fatigue fracture had developed in the antenna's hard-drawn wire, which was simply cut away and a new join made.


The fifth and final problem I discovered, when I just couldn't get the impedance and SWR curves to make any sense despite all the renovation work, was sorted out at past midnight last night!

It turned out that the 4:1 balun was the wrong step-down for the delta, which is corner fed for mechanical simplicity in the 15m antenna's case.  Bypassing the 4:1 with a pair of crocodile clipped leads and connected to a 2:1 yielded the perfect curves for both.

So, I guess the take-home messages are:

(1) a good SWR at an analogue meter can fool you into false security if the impedance is wrong at the antenna
(2) an analyser, or certainly the SARK, can reveal problems that otherwise you would either not know about, or not find out about until they might pose a risk to your rig. 
(3) it seems you can always trust a SARK analyser
(4) RG58/U is not a good coax to use (well, we all start somewhere!) and may have such losses even in 15m-runs that it can mask mismatch problems.

SWR Anomaly! (revised)

Yesterday, I reported on the problems of corroded coax, and a successful fix.

Well, sort of!  Whilst connected to a standard SWR meter, or when using the rig's own internal SWR monitor, all was well in the world of the antenna match.

But, on connecting my trusty SARK-110 analyser to the antenna, I just couldn't get a stable reading.  One minute it was showing a nice curve with low SWR, the next, it was showing a steady SWR of 5 or more.  There was no such instability at the old-fashioned SWR meter or rig.  The key to the problem was that the curve would often shown the hints of a good curve, but with horrendous noise spikes all over it.

This took me a while to sort out, because the strange MCX connector on the SARK never fills me (or some others) with confidence; I do wish it was something more robust-looking, even though it does seem quite well secured to the circuit board.

The problem got more and more unclear as days went by.  One moment it would report a nice curve in the middle of the band and the next, some senseless curve that took off towards 26MHz.

Mightily cheesed-off this lunchtime, I disconnected the delta and connected an alternative feed line to it.  This resulted in the SARK reporting an open circuit!  I was certain both feed lines were perfect.  This had to mean something to do with the SARK was at fault.

Eventually, with a multimeter, I checked the continuity of all the connectors and cable hitched-up to the analyser, to discover the real source of the problem: an intermittent break in the SMA patch lead supplied with the SARK-110.  In case I had really lost track of what I was doing by now, I hooked the whole analyser system up to a dummy load and you can see the result below:

The impedance (red) going somewhere odd, whilst the SWR is up in the sky!

A new patch lead is on its way from RS Components...

Corroded Coax!

The 15m band has been quite active for DX lately, which is very welcome.

But, on listening around, the received signals were intermittently loud, then quiet, then loud.

Something was wrong!

I checked the external speakers in case the connection there was bad.  The problem persisted with the internal speaker. 

The coax braid on the old RG58U has turned to green dust!

I then checked the other bands.  They were fine.  Probably not the rig's audio circuitry, then.

Finally, I switched out my 15m delta to listen on 15m using my 20m delta.  Perfect audio!

Aha!  Must be the coax. A wiggle on the cable seemed to confirm this. After 6 years out in the harsh coastal environment here, the old RG58U had corroded to a nice green powder from the PL259 connecting to the antenna to a length of about 6 inches (150mm) from it.

So, out came the cutters, and the RG58, only ever used in my early days, is in the bin.  The new RG8-X is hanging out the wall, waiting for a calmer day for replacement!

Electric Fence RFI - The OFCOM View

Ever since I've operated at this QTH, there has been 'clicking' RFI from electric fences in the area.  As a farming and equine community, it's to be expected.

For all those years, the RFI has been sufficiently low level not to cause a problem and a simple press of the noise blanker button eliminates it completely.

Electric fences are very eaay to install now, and often tend to be permanent.

But recently, a new fence has gone up to contain a new group of horses.  The RFI under certain weather conditions is severe, hitting over S9 in roughly one second pulses.  Whilst the noise blanker continues to get rid of it most of the time, if a JT signal is present, for example, the noise blanker can let the RFI through.

OK, so this is not the worst RFI problem ever encountered.  That much I grant you.  The irritation comes from the fact that it is still RFI, and RFI that can easily be eliminated altogether if only the farmer paid attention to the wiring and insulation quality of his installation.  After all, if it's producing RFI, the fence won't be as effective as it would be if it was radio quiet.

So, I decided that I'd call OFCOM.  As usual, they were very quick to respond.

When I called them back this morning, they said there was nothing they would be doing, because it was "not sufficiently persistent" and I "can work around the interference".  He said I should speak to the farmer, even though I'd told him that he was more likely to put up more bad fences in retaliation to an approach (farmers here are used to having things their own way and not being concerned about others) than try to fix the existing one.  I underlined the futility of approaching an uncooperative farmer by saying that, without any backup to the complaint from the law or OFCOM interest, I'd simply be told to get lost,and the consequent contempt for amateur radio that would foster.

The assertion by OFCOM that electric fences are "not persistent" in that they "won't be there for very long" is a very odd and entirely ignorant one.  Cheap, easy to install and designed in very consumer-friendly ways these days, electric fences around here are a permanent means of containing animals, with the added benefit of taking just minutes to reconfigure in another part of the field.

So, whilst I reluctantly agree with OFCOM that I can work around the RFI, if not altogether successfully, the harsh reality is that those of us operating from the countyside, and which is often very radio quiet, can't expect any protection under the law - or at least from those charged with upholding it.

Transparency? Not at the RSGB! (Updated 14/02/2017)

For the past year or so, I've been asking the RSGB to publish full details of the General Manager's pay packet.

This started with questions about the former GM, Graham Coomber's remuneration.  A reply from the society, justifying the pay, claimed Coomber was in early in the mornings answering e-mails, and out late at night and the weekends in meetings.

Of course, running a big society, even if it is a hobby society, does carry many responsibilities and there is a fair amount of work to get through.

The central question, though, is this: does being a GM of a hobby society, paid for almost exclusively by its members' subscriptions, justify a salary of, well - there's the rub - we don't know how much he's paid!

What we can say from statutory accouting rules is that for some time, the salary has been "more than £60,000".  According to this 2013 post, and allowing for the fact that inflation has been essentially flat-lining since, that takes Steve Thomas's known salary into the top 5% of UK earners.  Quite a pay packet!


Don't get me wrong.  I don't mind someone earning a good salary for a hard day's work.  But without full transparency, you can't have full accountability.  If a poll of RSGB members were conducted with them knowing the full salary, then perhaps they might approve.  Or not.

Given we, the members, pay for the GM's salary, I think he should waive his right to a hidden salary, and publish it with each accounts.  There is absolutely nothing, other than his consent, that stands in the way of that happening.

Graham Coomber and his merry men weren't willing to make this disclosure when I asked a couple of times.

Now, with a new man - Steve Thomas - at the reins, it's a great shame that he, too, seems perfectly happy to keep the exact amount of money we pay him secret.  I've asked him directly, even advising him that silence would be taken as unwillingness to disclose - and there's been no reply (unlike over other matters, which he's always replied to.)

So I was very disappointed to see this 'keeping mum' continue at RadCom.

I sent in a letter in the same kind of vein as this post, highlighting that, even at the cut-off point of £60,000 for a full declaration, this was over 2.5 times the salary of a time-served NHS nurse, who I think most people would agree put in a very hard day's work.

That the letter was not published might be simply down to the volume of letters received.  Or, as I tend to think, it might indicate that the RSGB continues to be unwilling to make the full salary known, especially when emotively - but accurately - compared to our treasured nurses.  A month later, RadCom is still failing to publish the letter.  I doubt it ever will publish it.


Having recently rejoined the society precisely because I felt Steve Thomas was a more practical, out-there-in-the-field sort of man, I now feel rather hoodwinked.

Mr. Thomas has shown no sign yet of accepting the validity of my argument, and the membership don't yet seem to be adding any pressure.  That's probably because most RSGB members don't take an active interest, but simply pay their dues "for the magazine".  That's a standard response whenever you start talking about the RSGB with fellow hams. Update: Last week (of the 6th February 2017), Steve Thomas stated that he published his remuneration in line with accounting rules.  In other words, he rejects the argument that he should state his full salary to the members.

Mind you, looking at the half-yearly accounts for the RSGB this month, which reveals a deficit of over £13,000 (up substantially on the 2015 figure), one might hope that pressure will start to build.  Why are we paying full commercial pay rates for a hobby society's GM when income is falling, and we know there are membership and thus money troubles straight ahead?

Whilst the RSGB itself is not a UK registered charity, the Radio Communications Foundation (RCF), which has a contact address at the RSGB HQ, is.  The RCF is legally distinct from the RSGB, and the GM of the RSGB has no role, or at least one that needs to be declared, in the RCF, although at least one other staff member (given as Marilyn Slade on 19/9/2016) of the RSGB is directly involved in both organisations. But, all the same, the two bodies are clearly initmately interwoven, so who could argue with the kind of arguments contained in this report on senior officer pay, and that it ought to apply to member-funded hobby societies, too?  The word 'trust' is important, I think...

In respect of the deficit, I think the RSGB is beginning to show panic.  It latched on to one year as being a cash cow by selling more books.  A summer-only voucher scheme has now been extended in order to lever some more dosh out of members' pockets.   It seems from the accounts that the tired, repeated content of many of these books isn't persuading many to reach into those pockets.

The worry I have now is that the RSGB has become blinkered and lost for ideas on how to keep its bottom line healthy, and I'm not persuaded that a "roughly break-even" final accounts, as the RSGB again says it expects, will actually transpire.  The whole idea, indeed, of a 'break-even' seems fatally flawed when we know the post-war Baby Boomers are reaching the end of their lives, and following generations aren't taking an interest in radio.  A cash crisis in the near future is really the only realistic expectation from this situation.

And, to cap it all, as I have boringly and repeatedly pointed out, the failed venture that is the National Radio Centre - otherwise known as a luxuriously-appointed club station for a handful of RSGB bigwigs, increasingly continues to cost the RSGB dearly - over £18,000 this year and up £1000 over last year, and apparently without taking depreciation of assets into account.

How much money the NRC makes for the RSGB is unknown, at least beyond the RSGB office, because there is no specific entry for that.  But it's probably nowhere near enough to break even, let alone make a surplus.

The claim that the NRC has inspired "many" new entrants into the hobby has, to my knowledge, never been proven with real numbers.  If it is true, then the RSGB also seems never to have gone on to show us how many of those "inspired" by the NRC have translated into new society members.  We can only realistically expect it is a tiny number, entirely unworthy of the money spent at the NRC.

Hurricane-Proofing a Vertical Delta Loop

Regular readers - if there are any - will know of my passion for the vertical delta loop.

Quiet in receive, and a top performer from this elevated site overlooking the Irish Sea, it's a long-term success that I will never abandon.

The only problem with an elevated site near the sea is the very high winds we experience.  From October to early March, Atlantic storms are frequently blasting us with 65mph gusts.  But 45 - 50mph can (and do!) occur at any time of the year.

For five years, I've simply held my delta loop up with a standard fishing/squid/roach pole of very thin glass fibre, guyed with one set of Dyneema 2mm rope at the bottom of the fifth section (i.e. at about 4m above ground.)  The pole is 8m tall overall, with the top two sections removed.  The base/radial wire of the loop is at about 1.8m over ground.  This has worked well, requiring the antenna to be retracted only for a few hours when the very worst winds are passing.

The wind wasn't very strong - just 30mph - for the video below, but you can just about see the top wobbling about in the wind, which is what I've been trying to get rid of recently.

But, as the fishing pole stands out in sun, rain and lots of wind, the glass fibre does weaken at maybe 2% per year.  The amount of bending that the pole undergoes in a 50mph wind is quite remarkable, and yet it does so for years without snapping.

When these poles snap, it's because a small crack has developed on the top of one segment, on the side to the lee of the prevailing wind.  With further wind, the crack quickly develops into a rip, and the support fails.  

With my current pole reaching old age, I decided I'd attach a second set of guys at the 6m point (i.e. the bottom of the 7th section), so that rope, and not the pole, takes the brunt of the bending forces.

Just about visible: the new set of guys at the upper end of the loop support, doing their job in a 45mph wind at the time of this photo.

I don't use special guying rings, just the best quality UV-resistant cable ties I can find.  The price of ties has gone up markedly recently, and so buying a proprietary set of rings is more attractive now.  Or, you can always machine your own from nylon or a suitably UV-resistant material.

The result has been to reduce the bending of the top four sections to essentially little more than a quiver in even a force 9 gale.  The very worst winds haven't yet arrived, but I think I'll be happy to let the antenna fly in a 65mph wind.  [UPDATE: it has now survived 66mph gales with ease]

This is the view from the delta's base in gusts of about 45mph with the new guys:
This system is a lot easier to go to sleep with during a severe storm than something just a tad more expensive trying to brave the same weather:

I just hope we don't see a repeat of January 2014, when we saw 109mph one day!