Thursday, 17 May 2018

£3499.95

This blog started out, as its header says, to highlight the fact that ham radio does not need to involve huge amounts of money in order to enjoy the hobby and enjoy it effectively.

It also started out to challenge the way things are done, who represents us (if anyone), and promote a more dynamic response to the problems facing modern radio.

I often criticise RadCom, the RSGB monthly magazine, for promoting an elitist vision of the hobby through its reviewing of high-end equipment.

I've written for magazines for about 25 years.  It's clear that 'reviews' are useful and interesting to the reader.  But they are also highly-prized, free advertising for the manufacturer, if not the shops selling them.  There is usually associated advertising set close to the pages containing the 'review' in most magazines.  After all, magazines cannot exist without advertising.  Indeed, they are better perceived as advertising publications, with some articles thrown in between. Facebook's free services in exchange for serving up advertising is not as modern a model as people imagine!

Despite this understanding of advertising, I'm genuinely disheartened, yet again, to find this month's RadCom reviewing a transceiver costing just short of £3500. 

There is a lot of soul-searching that is endlessly repeated about the lack of newcomers and youngsters in the hobby.  With the promotion of products like this through 'reviews', it is hardly surprising that the hobby appears out of reach to so many.

The problems facing the working age population today in the UK are many.  Lack of remotely affordable housing (typical homes for sale now going for between 7 and 10 times average incomes - even the deposits are unaffordable.)  Half the working population in expensive, insecure rented accommodation.  Jobs are insecure, short term, zero hours and/or not very well paid.

With all these problems, £3500 for a hobby radio is, well, obscene.  I can only imagine that, for the immediate future, radio manufacturers are trying to cash-in on those post-war generations that are in or about to reach retirement age.  A bit like expensive 'luxury' ocean cruising holidays came out of nowhere as the population turned white-haired en-masse and looked for ways to enjoy the pensions they 'paid for all their lives' (except, they didn't; pensions of today are paid for from the current working population.  Nobody expected people to have a 50:50 chance of reaching 100 years old and being in retirement for 40 years or more). 

It would be wrong to say that RadCom never reviews the cheap end of the market.  But it does seem, no doubt driven by the money to be made out of expensive equipment, compared to little or nothing from cheap Chinese or other products, not to cover them as much as it could.

There are things like the micro-BITX transceiver costing only $109 as a part-built kit.  I haven't noticed a 3-page review of this yet.  Then again, the small Indian cooperative that makes this unit doesn't advertise in RadCom.  Could there be a link?

In fact, in my view, it would be much better to increase membership fees slightly to cover the cost of a magazine that is not so heavily reliant upon advertising.  Sure, let's have some adverts, but let's also see a much greater focus on just how many effective transceivers and antennas can be made out of everyday materials at very low cost.









LED Montor RFI: the biggest ham radio mystery?

A while ago, I wrote about my troubles with a 21" LG computer monitor (no TV reception circuitry), which produced copious amounts of interference to all bands up to at least 50MHz.

The best solution I came up with was to wind a 10m VGA cable on a wide PVC former to make a choke.  This worked to a degree, but the bands were still simply nowhere near as quiet as they were without the monitor.

I quickly decided to discontinue the use of the £100 monitor as unsuitable for radio station purposes.

During and since those days, I've read the various discussions and blogs about screen RFI.  In fact, given LED screens' popularity in 'NASA-style' ham stations, and that there are so many hams out there, it is a genuine mystery as to why there is not much more discussion about the problem.  I think a lot of it may be to do with the fact that so many people live in RFI-infested areas already.

A search for videos, perhaps to see someone showing RFI on their monitor, yielded no results.

I found a strong element of capacitive coupling with my screen's RFI.  If I brought my hand closer to the screen, or just simply stood in front of it, rather than behind, it would produce much stronger RFI.  I don't know of a potential solution to that problem.  Grounding the screen also provides a handy path for the monitor-generated RFI, which similarly increases in strength.

Most people who claimed to have resolved RFI from screens clearly hadn't.  They had simply added chokes or other measures that only moved the RFI in frequency and maybe reduced its level somewhat, thinking this 'fixed the problem'.  There's a big difference between reducing RFI and eliminating it, especially if you are interested in weak signal work.

When RFI moves in frequency, it doesn't do so to such a degree that it falls magically outside the ham bands.  It just appears in other parts of the band.  So you might find the FT8 section of 20m free of RFI, but parts of the SSB portion displaying very strong birdies.  You can often simulate the 'fixing' of RFI from screens just by changing the resolution.  You may find your WSPR portion nice and free of noise at lower resolution, only to find the RFI is now down at CW parts.

Things that do NOT reduce RFI are:

(1) The PSU. Powering the LED screen from 12V batteries yields the same RFI.
(2) Screening cables.
(3) Grounding the screen and/or cables
(4) Using HDMI instead of VGA cables

Things I found that do reduce the RFI, but not by remotely enough to return to no-screen, RFI-free conditions:

(1) Connecting a random wire to a grounding point on the screen (e.g. connector chassis), causing the chassis to detune slightly. With a laptop screen (HP), I find this detuning is effectively enough to call it a complete fix.
(2) Different positions and distances of screen from transceiver.

(3) Not having your body close to the screen.
(4) Taking cables away from the screen at right angles as far as possible.
(5) An air-wound choke of around 20cm diameter (VGA only; HDMI cables are generally too short for this).

It seems that LED screens, more especially more modern ones, produce high RFI levels across the board.  It doesn't much matter which one you buy.  I've tried our home TV, a four year-old Samsung LED unit, and it also produces the same noise, although at a significantly lower level than the LG, despite being physically larger.

I also found the same capacitive coupling RFI effect with a Nexus 7 tablet connected to a charger.  Whilst it produces no detectable RFI when simply sitting there on a desk, it produces a low but detectable (by ear) change in noise levels when I place my hand near the screen. 

If you have any ideas or example of fixes that actually work and eliminate RFI altogether, then I and many other people would like to hear from you!






 

Wednesday, 16 May 2018

"Your Delta sure is low"

If there's one thing I enjoy, it's proving prejudiced people wrong.  Not in an angry sort of way, but with evidence, plain and simple.

During QSOs with folk, almost invariably from America, it is a frequent irritation to hear the dismissive assertion that my delta loop, which has its base (its inbuilt 'radials') at 'only' 1.8m above local ground, is "way too low" for it to be effective.  Apparently, I should be raising the base to '30 feet' (the US has yet to drag itself out of Imperial measurements).

Well, there is plenty written on this blog to show that is simply a failure to take all factors, including the highly unusual ground, into account in reaching a conclusion. Most of them think that only 'big' antennas and amplifiers are what makes ham radio work.  That, of course, from the country that generates nearly three times more carbon dioxide per capita than the UK.

So the latest poke in the eye to my more machoistic American bretheren is this: the past 24 hours of reception reports for party balloon WSPR station, ZL1RS.  It's sending just 10mW.


My "way too low" delta is one of only two stations in Europe (I am not a Brexit supporter!) that is receiving ZL1RS, at a fairly good -24dB SNR.  Even more satisfying is that there are no reception reports from America at all.  And there are some very good stations there, some with directional antennas.  
Beaming America...
So for those of you who are just stuck in a trench about antennas and how high they should be, please remember: it depends on ground characteristics, both near and far field, and having a low noise floor.  After all, how many stations have an old copper mine underneath their antennas?

On an associated note, the now fairly constant balloon transmitter launches provides interesting WSPR tracking. But use of amateur radio from any airborne vehicle is not permitted in the UK. 

This is quite odd, because it seems to be perfectly legal in many countries.  The safety risk for those balloons that fly above most aviation traffic seems to be negligible, and I'm not aware of any incidents reported about small balloons conflicting with aircraft.  It seems to be a legal conflict between licensing ham radio and licensing aviation radio that causes the problem for balloon-borne WSPR in the UK.  Rather perversely, we can, with prior notification to the CAA, launch balloons, but not balloons with transmitters!  Even as a holder of a CAA pilot's radio licence, I still can't launch a WSPR beacon into the air.  How silly!




Tuesday, 15 May 2018

Crossing to Alaska.

KL7L is a station that I always think is in a very interesting place in terms of HF propagation. 

Overnight, I ran WSPR at 14MHz, using 1W from the vertical delta loop. 

This is the plot of all the spots from 19:38UT 14/05/2018 to 07:50UT 15/05/2018:

The appearance and very sharp peak of signal at around 06:30UT is quite interesting. It is exquisitely linked to sunset at KL7L.  Here's the picture as my signal peaks at 06:36UT in Alaska:


And as the strong peak falls away at 06:44UT, less than a quarter of an hour later:


I've been thinking a fair bit about the likely propagation path for this event.  My transmitter has been in daylight for some hours at 06:30UT, although it's clear from the overall signals received here that the D layer is not yet strongly formed.  In fact, we are just before the point where DX signals vanish and local signals come to dominate.

At the same time, it's the sunset period in Alaska, and the D layer will be weakening rapidly.  At the moment, during the depths of solar minimum, the Lyman alpha radiation is fairly low, too. 

Is there a component of long path propagation?  I'm not sure.  The duration of the peak signal is similar in length to that seen in UK-VK long path propagation, roughly 20 - 30 minutes.  If it was just D layer weakening, then perhaps the peak signal might last considerably longer, given that KL7L evenings are now constant and quite strong twilight.

Any thoughts?  Please post a comment!


Sunday, 13 May 2018

HF Propagation predictions - is there any point?

Most of us have too little time to waste.  As a result, fine people, many with impeccable qualifications, attempt to make the most of our precious time by issuing propagation predictions.

But are these predictions relevant to a world where digimodes provide effective operation way beyond the noise level?

On the ITU-based prediction sites out there on the internet, you can choosea 'SNR' (signal-to-noise ratio) output.  But this effectively has a cut-off of 0dB SNR.  I regularly operate JT65A down into the lower minus 20s dB, WSPR down to around -30dB, sometimes deeper, and FT8 down to around -25dB.  Even CW 'by ear' gets us down to around -18dB.

To underline the argument, -30dB SNR is a signal one thousand times weaker than the noise level (as specified for the rather odd, ham radio way of doing things, a 2500Hz bandwidth - see here for a useful explanation).

So what is the point of continuing to use 0dB as a lower marker, with its implication that there is no point in operating when the prediction yields that result?  I have started to think, perhaps wrongly, that predictors aren't keeping up with digimode developments, and are continuing to issue predictions for the SSB operator. 

Steve Nichols' blogsite currently has a similar sort of prediction.  It, like Gwyn Williams' predictions for May 2018 (see RadCom), strongly suggests that there is nothing much to be found at 12m, even at very moderate distances.

This isn't the reality.  My logbook has perhaps a couple of hundred 12m FT8 QSOs so far for May, with especially good days on the weekend of 12-13th May out to Bolivia (at +01 dB) and ZP9 (+9dB).  OK, I'm not using a dipole with a (unrealistic) 0dBi gain, but perhaps that itself is too restrictive a model.  You can alter antenna and noise settings with online models.  But printed monthly summary forecasts are pretty much fixed.

Even if dipoles for 24MHz had been in operation at both ends, and we take the ZP9 signal as an example, there was still around 30dB 'spare' for a potential QSO, at around the limiting SNR of -25dB, with FT8.  JT65 or JT9 could have offered even deeper plunges into the noise.

Now, to be fair to both men, their predictions make specific assumptions on mode of propagation and gain of antennas at both ends.  So it would be unjust to say that their predictions are wrong simply because a good day of multi-Es hops in fact allowed working distant regions for hours on end using a 3-element Yagi.

And there's the rub.  Is there any point in presenting predictions based solely on F-layer propagation when the summer months are well known to bring Es conditions, for example? 

There is also the fact that ham operators are quite sheep-like in their conduct.  The majority follow the DX cluster or predictions like those under discussion.  Even if the intention is not to say 'don't bother operating when the prediction is simply a blank line', the effect will tend to be that operators will receive and act on the prediction in precisely that way.  You only have to see what happens on 12m to prove that.  Take an empty band.  Call CQ and get a random response.  Announce it on the cluster.  Within seconds, the band will be full of signals.  Hams are simply waiting for others to do the work for them, when it comes to probing empty bands.

Another criticism I have is that propagation can, and often is, very different from various regions of the UK, further limiting the usefulness of predictions.  A station in southern England will often have very different conditions to those in the north of Scotland, or, indeed, in the north of Wales.

Overall, even where the predictions might be generally correct for their given set of assumptions, they are very rarely, in my experience, particularly reliable indicators of which regions of the planet can and will be working each other in practice.

That is why I never even bother looking at predictions.  If I did, I would miss out on a lot of QSOs for thinking it would be a waste of time in trying.

Friday, 11 May 2018

Spanish Burst!

Nothing particularly new, but a very nice example of 50MHz propagation brought about by a substantial cold front passage this tea time.

6m propagation very tightly linked to the passing cold front.

All stations received here in North Wales were from EA land, with the odd CT thrown in for good measure.  Signals came, peaked and passed in step with the front's passing.  Peak signals on FT8 were topping around +15dB S/N.

EA-festival!

Thursday, 10 May 2018

More Pi?

I was waiting for the postman to arrive with excitement this morning.  He was bringing me a new Raspberry Pi - my latest ham radio fascination!

A wonderful aspect of the Pi - apart from its tiny physical size and low cost - is the fact that it boots up from an SD card, where all the software and data is held.

The Pi 3B+.  Much faster but still fits in Model 2 cases (if you use one).

This meant that, having only just downloaded the latest NOOBS package a couple of days ago, getting the Pi 3B+ going was simply a matter of removing the SD card from the Model 2 and sticking it in the card slot of the new unit.

I was glad, at this point, to see that the Model 2 SD socket, which had a relatively high failure rate in its spring-loaded card capture mechanism, has been abandoned in favour of a friction-only unit.  Very much better!  The Model 3B+ also comes with in-built WiFi connectivity, so there is no need for a USB dongle any more, at least if you have strong signal coverage around the house.  That's one USB port freed up, too!

Booting is, of course, pretty quick, and the WSJT-X software already downloaded earlier this week was sitting there on the SD card, needing only a click to start it up.  If only a Windows OS and files could be transferred across so easily!

Since posting about WSPR reception with the Model 2, I have progressed to using my ZLP data interface on the Pi, allowing transmission.  The Model 2 handled all this with no need for driver installation or complexities like that.  It was just slightly slow, in that the Pi took a second or so to activate the rig.  But not so slow as to cause problems.

Where the Model 2 couldn't work very well was with the very fast turnaround mode, FT8.  It took several seconds to decode everything, which made having a QSO impossible.

With the Model 3B+, and the 'Decode' menu item selected on 'Fast', FT8 works very well indeed.  If it's set to 'Deep' decoding, it's then too slow for QSOs.

Usefully, the Model 3B+ is fast enough to both handle digimodes and internet browsing at the same time, something the Model 2 couldn't really do at all.  It also looks like it is fairly good at keeping accurate time; most signals were within a small fraction of a second.  I think that, with an internet connection, the Pi keeps itself regularly time-updated, though I need to look into this a bit more.

Overall, I feel the latest Pi is broadly equal in performance to my 1-year old HP laptop - at a tenth of the price!  It can also be easily deployed in my field shack, where there is only a 12V DC supply - much better than stepping up to 19V for a laptop.  All I need now is a 7" LCD screen for it, although even my spare LG monitor will work off 12V DC, sparing some cash for this month!

To give you a flavour, here's a 1.5 minute video of how it looks in practice (at 28MHz!).  CPU use with FT8 running is only about 13%, and the CPU runs at only a warm, not hot temperature: