End-fed at 80m - the WSPR test

I've been playing with end-fed wires for the first time in years these past few days. Not so much because I expect stellar performance, but because I want a simple, easy-to-erect, reasonably effective multiband antenna for International Marconi Day.

Sunset approaches for the EFHW on 80m.

 

To be clear, by end-fed wire, I mean a 49:1 unun connected to a wire half a wavelength long at the lowest frequency to be used and, therefore, not a half wavelength on any other band, contrary to the general 'EFHW' name.

I bought this to speed-up tests before Marconi Day. A very well-made unit.

 

The unun's at the base of a 9m fibreglass pole, with roughly 8.5m of vertical wire, and the rest of the ~20m wire sloping down to ~3.5m above ground via some light rope. You can also call it a sort of inverted-L antenna. As the counterpoise is said to be the coax shield, I guess it's important to say my coax was about 2m to a QRP matchbox, and a further 1m to the WSPrlite transmitter. No other RF grounding was implemented.

The match through a QRP matchbox, optimised for the WSPR frequency.

The environment is agricultural soil, damp, completely clear of buildings and overhead wires; an open-field, 'big skies' type of place.

I don't expect to operate on 80m very much during IMD, but it may be useful for some inter-G QSOs. So I set the wire up on that band just before sunset last night, and set it to run on WSPR at 200mW.

How did it go? Well, you need to read the whole post, not just the first bits. You also need to know that obtaining up-to-date, reliable information about antennas in use at other stations is not as easy as it should be (no, you can't just rely on information entered on WSPRnet 13 years ago - and that goes for my own entry!)

Sunset-to-sunrise spots, 80m, 13-14/04/2023.

Firstly, most 80m antennas out there in WSPRland seem to be compromise set-ups and, therefore, not especially efficient. This is usually a product of space limitations. Against these - what we may call 'typical' - 80m antennas, the EFHW did OK. Here's my antenna compared to M0GUC, apparently a shortened 160m dipole, for example:

Distances achieved, 80m.

 

Simultaneous spots, all distances, 80m.

Comparison with EI4ACB, which may be an end-fed long wire with a good view of the sea to his east, produced similar results, though with less difference between stations:

Where the news isn't so great is when we select the two best stations on 80m WSPR, and compare with those. Again, I don't know for sure what antenna is being used by either of these stations - operators can often change their setups from what is described on WSPRnet.

So, 'good' station number one is G3VAO, which WSPRnet says is a dipole of some sort:

The difference in distances achieved increases through the night, but it's not an enormous difference overall. Where it all breaks down is in consideration of the received signal strengths:

A 17.33dB difference! And not in my antenna's favour. It's a disappointing result, for sure. If we add that much to 200mW, G3VAO is effectively putting out 19.3 Watts. 

Good station number two is G8MIA, who seems to be using a trapped 80/30m dipole from a fairly open landscape. Again, the difference in distances achieved is not very great:

But the simultaneous received strengths is large, at just under 15dB. Adding that to 200mW means G8MIA was, in comparison, effectively sending 18.7 Watts.

I've changed my initial conclusion about this antenna, at least so far as the bands down to 40m are concerned. A 40m inverted V, or a sloping dipole, is fairly short at only ~20m overall. This is easily and, arguably more easily erected than the inverted-L, and may even be more effective for short-medium haul contacts. For 80 and 160m, the inverted-L may have the advantage in terms of ease of installation, if not necessarily performance.

Inverted-L: will it do for Marconi Day?

With much warmer, if still rather variable weather in the air now, attention is turning to peparations for International Marconi Day on April 22nd.

I don't have a van or a property from which to operate at the site of Marconi's Carnarvon VLF station, so equipment rationalisation is critical - not least because I have to carry it part-way up a north Wales mountainside!

Marconi's trans-oceanic VLF inverted-L, as it was between 1914~1919 (callsign: 'MUU')

 

I thought I might try an inverted-L antenna; this is very much in the spirit of the old trans-oceanic station, as it was arranged as just such an antenna. For a few years, Marconi and his engineers claimed the inverted-L was a 'directional antenna'. My recent PDF-based, 197-page, richly illustrated book about the station looks in detail at how this claim came to be believed. You can buy a copy for £9.99, wherever you happen to be, here. You also get a free Google Earth-based plot of features identified during fieldwork in 2022.

Anyhow, up went the 9m pole in a field free of cows, and a ~21.3m wire run up and away from it as a sloping inverted-L. The end of the wire ended up a couple of metres above ground. The wind was up at about 40 knots, so the matching traces I obtained tend to be somewhat noisy on occasion.

The 9:1 unun feeding the wire was hooked up to a very simple QRP tuner; if this will handle things, anything will. I crocodile-clipped a ~5m radial wire and tested things both with and without it.

So, here are the results. At 40m, the wire is too close to a half wave, and tuning is consequently too sharp, unless one is only using digital spot-fequencies. It will need shortening or lengthening in practice; I'll have to experiment some other day. The best match frequency can be shifted either way. Green with counterpoise, orange without:

 Next, 30m. Pink with counterpoise, orange without:

Now the bread-and-butter band of 20m; green with counterpoise, red without. Some minor re-matching would be necessary in changing from digital to the higher reaches of the SSB portion and vice versa; it is a wide band, after all:

Next, 17m, where the counterpoise has essentially no effect and the matching near-perfect across this very narrow band:

 

15m next, where the counterpoise becomes much more useful. Red with, purple without counterpoise. Despite being a wide band, the matching is such that re-matching with frequency changes is unlikely to be necessary:

At 12m, a very narrow band, things are very good, the counterpoise (green) making a very small difference to without (red):

Finally, at 10m, a rather expansive band. The 5m counterpoise didn't allow effective matching, so I uncoupled it, leaving only around 75cm attached. This only had the effect of shifting the frequency downwards - though this would be a very useful feature for rapid re-matching, without fiddling with the matchbox, if shifting from the SSB portion of the band to digital:

And for reference, here's the full HF sweep without the matching box attached. Dips at 5.1, 11.1, 18.1, 32.6 and 39MHz.  The 60m band should be very usable, but I didn't test it on this occasion:

End-fed wire and 1/4 wave vertical shoot-out

A long time ago, when I started out in ham radio, I bought an EARCHI end-fed wire antenna. It was very cheap and very simple but, with a ~10m wire attached and run up a 10m fishing pole, it gave me access to 40m for the first time. I still remember well a nice QSO with someone on a boat in mid-Atlantic on 40m with it. 

But, over time, I moved on to delta loops, though I never did have an especially good antenna for 40m after that.

The joys of operating radio in a field full of young cows!

 

Anyhow, someone mentioned end-fed wires on Mastodon recently, so I thought I might get the EARCHI wire out again this evening and briefly run it on 200mW WSPR against a 14MHz monoband 1/4 wave vertical for that band.

The antennas were placed about 1.5 wavelength apart on wet agricultural soil (the water's essentially at the surface), though I suppose more spacing might have been better; I have young cattle in the field at the moment, so one has to be ready to single-handedly defend a small, not a large area if they get too boisterous!

The 8.45m end-fed wire (the length I already had attached to it a long time ago) was matched-up with a very simple QRP matchbox, achieving 1.1:1. The 1/4 wave has pretty much the same SWR, though of course without a matchbox.

How did they compare?  Turns out, pretty well - especially considering that the end fed wire can be multibanded with a suitable matchbox. Whilst the 1/4 wave achieved a marginally better geographical reach, the difference wasn't very large. Curiously, the 1/4 wave reached a number of far-eastern stations at up to about 9dB above the detection limit, whereas the end-fed didn't get there at all. That was probably down to differences in elevation pattern.

Here's the plot of where the signals got to. MW6PYS is the end-fed wire, MW1CFN the 1/4 wave vertical monobander:

Next, the distances achieved:

The simultaneous spots across all received distances; only a 1dB difference in favour of the 1/4 wave vertical:

Out at DX distances, beyond 5400km, the difference is still pretty small at only 1.7dB. But remember, out in the far east, the end-fed failed to get there at all, so there are no comparisons to be made in those cases.

The end-fed wire, as I have it arranged, will fit onto a 9m fishing pole whilst keeping somewhat above ground. The advantage of a 9m pole is that it fits into a plastic clothes line screw, whereas a 10m pole doesn't (unless you cut the bottom plastic end cap collar off, which is often difficult to do without damaging the pole). 9m poles are also curiously far less wind-prone than a 10m pole (try it; you'll see what I mean!)

I will be trying the end-fed wire on 22nd April, when I'll be operating at Marconi's Carnarvon VLF station of old, as GB1GLC (details here). It will be much easier to match one wire for different bands than carry a load of monoband wires and have to remove and fix them to poles all day long!

Leave me alone!