This summer's 6m arrangements.

For this summer, my arrangement for 6m is this 3-ele OWL from Innovantennas.  A very good match, actually a little better than the published data, even though it was built for rear, vertical mounting and that I've got it in centre-mounted, horizontal configuration!  The telescopic aluminium mast is a homebrewed, three-section unit, which cost me about £50.

Low deployment during initial matching.

 

With a clear site and ground reflections, I should realise good total gain. So my QRP input of about 5W should see it rise to something closer to a few tens of Watts.  Regardless of the exact figures, it will do well when 6m propagation is running, and I will at least see whether it's worth spending money on a 100W rig for 6m next year. My expectation is that it won't be.

This is the final matching curve at full deployed height of about 5m. Adding a layer of NATO Green spray paint to better blend in with the countryside environment made no difference at all to the matching. It's below 1.2:1 for the whole SSB and FT8 portion of 6m:

Yagi matching.

Last night, I set about getting a 3-element, OWL Yagi from Innovantennas (50MHz) up in the air, simply to get it matched-up properly; sadly, this is not a location for permanent installations (I'm already very fed-up of this and putting the house for sale next week, after only a few months here).

The antenna was designed for rear-mounting, but I decided to try it horizontally for inland-based operation (vertical is infinitely better at the coast).

5-ele version of the 50MHz OWL from Innovantennas. Sturdy, just not very practical for /p; the rear mount of the 3, let alone the 5-ele, also places large, impractical leverage stresses on the boom.

 

The matching using the published element dimensions didn't work out too well, in either horizontal or vertical orientation. Although the lowest point in the curve was broadly in the correct place (~50.25MHz), the SWR at that point was about 1.48:1 when horizontally-mounted. Not the end of the world, but we can do better than that when, at the SSB and FT8 calling frequencies, the SWR was over 1.5:1.

My antenna initially exhibited this type of fairly high-SWR matching, showing the element lengths weren't right.

I didn't think the recommended reflector dimension was long enough; it was essentially the same length as the radiator loop. I increased this by about 2cm per side, and immediately, the matching improved to about 1.38:1. 

I then tried increasing the length of the director elements by about 1cm each side. Again, this had the desired result, bringing the matching to 1.18:1 from 50.150 to 50.320 MHz - SSB and digital portions now perfect!  I'm sure I could bring it a bit lower, but it isn't really necessary.

So, good matching for the OWL antenna, with not too much fuss. I can't say I'm overly-impressed by the antenna in general, though. I don't like having to jam a screwdriver into a hole as the designed way of tightening a through-boom element nut!  The quality of the build instructions is also quite poor, with a very hurried, error-prone feel to it all. Quite disappointed, overall, but it was cheap enough (£89). With the director and reflector removed from the boom, and the outer elements of the radiating loop also, it does fit without too much fuss in a typical family hatchback.

I'm currently building a Moxon to replace this antenna for /p use. In fairness, the Moxon will likely work out about the same price as the Yagi, all things considered, and it also a bit of a transportation nuisance!

Computers always catch you out in the end!

Remember when I had a small number of trolling comments a few weeks ago?  None of them made it past approval, and so none were published.

It now seems that GM4DHJ - or possibly a person falsely claiming to be this operator - has very recently entered some details somewhere on Google, which have propagated back to the comments made earlier.

Unpublished comments, sporting an alleged link back to GM4DHJ (accessed 22/04/2022)

 

I can't tell if this really is the operator identified, or an impostor. But maybe the real GM4DHJ can shed some light on which is the case?  All attempts to find contact details for him proved fruitless, so no comment could be sought prior to publication.

DigiLink Nano - on the Pi.

As followers will know, I'm very much of the 'if it works, don't change it' school of thought when it comes to which equipment I use for radio (and everything else!)

I'm not impressed by new things, simply by virtue of them being new. Instead, I stick with things that have a proven track record. 

In that vein, I've stuck with my ZLP digital interface for about ten years by now. I carried one in my /p box, and use one at home. They are very good, very low-noise units that have stood the test of time under heavy, daily use. What's more, the old-style Digimaster I have can run two rigs, so there's no need to switch connections around when I want to use 2m digimodes after a spell of HF, for example.

Smaller, lighter and lower-noise things are all highly desirable for all /p operators!

A couple of years ago, after just about everyone except Tigertronics (which have a poor noise value, according to many reviews), had ditched on-panel volume controls, I got fed-up with ZLP and chose a DigiLink Nano for home use. That, also, has no on-board controls, but that is the way of things now, and so I decided a change was justified, and the much smaller size a big benefit.

This proved to be very successful - easy to install, tiny, and yet has the same, very low noise levels as the ZLP (as I carefully examined here). I never looked back, and slowly came round to correcting my view that on-panel volume controls were necessary; in fact, they are not, and whilst they do afford a quicker way to adjust things than via software, they must also add a little noise to the circuit.

Last night, I decided to check-out the DigiLink Nano with my Raspberry Pi 4B. Now, things are usually simple with the Pi, but not always. As it happens, it was literally just a case of plugging the Nano into the Pi, and connecting the line to the FT-818 (you can choose which interface you want, included in the price of the Nano).

 

The only difference with the Nano over the ZLP is that you have to set the volume output on the software of both Pi and Windows machines to near, or at their maximum in order to be able to both operate at normal power settings of maybe 5-10W or so, and be able to reduce the power on WSJT-X and the like to much lower levels when needed.

When I initially tried middle-of-the-road sound settings, all worked well, except when I reduced the TX (volume) on the digimode software to just 1W, when the audio output was then not enough to keep the line triggered, so it would stop transmitting or stutter. Setting all to maximum resolves this issue, without problem.

The mic can now remain connected, housed where the ZLP interface was!

 

So the Nano allowed me to vacate the space dedicated in my small box to the old ZLP interface, and use it instead to house the microphone when, previously, the mic had to be disconnected and put in my backpack. I use a 1m audio cable extender to both allow the rig to be a bit further from the computer, and also allow me to disconnect the rig from the extender, rather than directly from the Nano's own audio port, which runs the risk of premature failure. 

Disclosure: I have no connection (pardon the pun!) to either ZLP or Digilink, other than as a paying customer for their products.

What did YOU do on World Amateur Radio Day?

I set-off yesterday afternoon to do a spot of 15m portable from the lakside. Though conditions turned out to be fairly poor, I had one extremely exciting and unexpected contact - with a 6 year old boy and his father!

15m from the lake on WARD.

 

I came across the boy, who was busy saying 'hello' from a distance, with an outstretched hand. I gave him a big thumbs up. He asked what I was doing. I told him I was sending signals to the other side of the world; would he like to see the radio?  'Oh yes!', came an excited reply. His father was nodding his thanks for being kind.

I opened the silver box. He was amazed. I showed him the simple wire we use to send the signals. 'Can you turn it up to two...million?', he stuttered. 'Sure', I said. 'I can turn it up a little bit more than that, even'. 'Waaaw', came the incredulous response.

I then got rewarded for my effort by being shown a series of toy metal cars he was carrying in his pockets. 

Maybe one day, he'll remember the meeting, and try radio for himself?  Let's hope so.

Amazing 6m TEP

I wasn't at the rig when this remarkable 50MHz FT8 signal, at an amazing -5dB SNR, was received (on a mere sloping delta cut for 30m!) from ZS6NJ at 9369km today, which rather overlooks the other, 6 minutes earlier reception of TT8SN, at 4903km.

Seems to have got social media pundits quite excited. 

Wow!

Intermediate licensee challenges laws of physics.

I'm always surprised that so many people seem not to realise that using a horizontal antenna next to sea water, whilst hardly unlikley to produce good results, is nevertheless going to produce vastly reduced performance compared to using a vertical. At least insofar as our usual quarry - good DX - is concerned.

This 1952 graphic (based on real measuerements, not models), and any number of modern versions, is all people like 2W0YMS need to absorb. It's not difficult. Fields depicted over perfect ground (i.e.similar to seawater).

 

So I idly commented on the latest 'holiday-style' DXpedition that were merrily using a horizontal dipole, on Twitter yesterday.

I was a bit surprised to find a fellow Welsh amateur pipe-up with a rather odd - and wholly pointless - response, which clearly indicates his belief that the horizontal vs. vertical assertion is wrong. Oh, and that I appear to buy antennas "off the shelf" (I invariably build my own antennas, and never bought a vertical HF antenna):

 

Well, it takes all sorts. Even ones who are not particularly adept at punctuation, or being a bit circumspect about what they commit to the public sphere.

For those who are more interested in learning than being pointlessly abusive online when your argument is fundamentally incorrect, you can try this site by the Royal Signals ARS, as but one of very many you will find online and in books.

Given the choice between people like the late Les Moxon, G6XN, and an upstart like 2W0YMS, I know which one I will take notice of. Maybe a copy of the ARRL Antenna Book and/or HF Antennas for All Locations for you next Christmas, Mark?  You might just learn something and even go try it out for yourself. 

Going underground with 2m FM!

A meeting of interests over past weeks meant that I had to build a moderately-directional antenna for 2m FM, to be used with a Baofeng UV-5R III handheld.

The interest is in trying to add some evidence to the expected existence of a shaft, roughly 70 feet (21m) deep, that was dug to assist the driving of a drainage adit for the mighty Penrhyn slate quarry, for many decades the largest slate quarry in the world. It was also the site of what remains the longest-ever dispute in British industrial history, a strike lasting between 1900 and 1903.

Penrhyn old quarry, ca. 1970s, before work stopped and water flooded the lower levels.

 

Penrhyn old quarry today. Image: RCAHMW.

Started around 1849, the adit is 1.9km long, with a fall (slope) over that distance of only 3.7 feet (1.1m). It was driven by Mormons who had previously worked in the coal mines of South Wales. They took 2 and a half years to complete their amazing work, and then left Wales for Salt Lake City in Utah, a focus of Mormon culture.

A remarkable (and long!) feat of human effort - and a fascinating journey through time and slate beds!

 

The direction of drill holes, when surveyed fully and plotted out, provides compelling evidence for the existence of shafts - which were expected to be necessary in the contract for the works - in that there are slate arches from which the direction of driving the adit goes off in opposing directions. 

Shoving a mobile phone camera above one of the arches showed some, but not especially clear evidence of a void above one of the arches. So I thought that, in order to conclude several months of work down there, I'd try using VHF handhelds to see if the signal received on the surface might vary when a transmission underground passed under the putative shaft.

Arch number 9, steel-lined and potentially problematic for 2m radio!

 

Unfortunately, the best and most easily surface-located position of a shaft has a steel-lined ('tubbed') roof. This, its concave form, and its radius, means that it is almost perfectly suited to bounce any signal sent from within the arch right back to where it came from, and attenuating anything getting through!

Luckily, another proposed shaft location has a slate arch, so this will likely be much better to try, albeit more difficult to locate on the surface to position a receive antenna. We'll see if it works in a few days' time.

Easton and Amos (1859) water pressure engine, using only a head of water as an energy source, to pump water from levels 137 feet below. This emptied its water into the drainage adit.

 

Due to size, weight and robustness considerations (underground activity is very harsh on any equipment taken in), I opted for a 20mm PVC tube-based Moxon. Moxons are a bit fiddly to make, but not too bad.

There are a lot of plans online for this antenna. Sadly, a number of them haven't paid attention to what they were doing, with all sorts of wrong measurements, some not making mathematical sense, written-up for all to be confused!

Simple, a bit fiddly to make, but cheap and effective!

 

I went back to basics, and used an online calculator. This proved accurate when using enamelled hard-drawn copper wire of about 1.2mm diameter. If you use plastic-coated stranded wire, your measurements may well work out differently due to velocity factor variations.

So, if you want to save some time, and you are looking for FM-range 2m operation in Britain, then here are the measurements that worked:

Long arms for radiator and director, two of each per element = 318mm

Short connectors between element centre junction boxes and handle junction box = 80mm

Radiating element, total single wire length needed = 91.2cm - cut this in half for the dipole elements.

Reflecting element, single wire length needed = 99.6cm.

I made small loops in the ends of each wire so that a thin cable tie could be used to secure and adjust the radiator-director separation. This was 22mm in my case - a bit of trial and error is likely to be needed for each build with this dimension, which is why cable ties are so useful.

 

Very pleasing outcome, plotted by the RigExpert AA230 Zoom analyser.

After a bit of messing-about making sure it was all fairly symmetrical, and winding an air common-mode choke, the analyser saw below 1.2:1 SWR across the FM part of 2m, and below 1.3:1 for the entire 2m band, with a real impedance of ~43 Ohms, and an imaginary component of +2.1 Ohms at 145.500MHz.