Crossing the Atlantic on 2m

This (May 2016's) QST features a really interesting article about an attempt in 2014 to get a 2m 'first' by getting a signal across the Atlantic from Newfoundland to Europe.

The set-up was quite heavy-end: a 43-element ladder Yagi of horizontal polarisation with a claimed ERP of about 150kW from a 750W input (I make it more like 182kW.)

A 40-something element 2m ladder Yagi isn't beyond modest means, but it's a little bit of effort - and perhaps not ideally polarised.

Even with that power level, and some persistent working by the intrepid team, they failed to bag the Brendan Prize, because the brief signal they did manage to get across the Pond was due to reflections from the ISS.

That ought to be the subject of a prize in itself!

Resting on the shoulders of giants like the Newfoundland team, I set to thinking about ways in which the chances of success might be improved.

The one obvious way to increase the chances of anything happening is to make an attempt more often.  Operating at the power levels they were, and effectively out on a field trip, the team had only a narrow period during which they made the attempt.  So, someone sitting at home in the same location, perhaps with much more modest equipment but, crucially, able to try every day, might well succeed - eventually.

The other problem I identified was the timing of the attempt.   Es is loosely associated with other summer phenomena such as Polar Mesospheric Summer Echoes and noctilucent cloud.  All these phenomena are strongly influenced and modulated by atmospheric gravity waves.

So, from an analysis of Es statistics at VHF, and from knowledge of seasonal changes in the upper atmosphere, the Newfoundland team, in operating during the first days of July, had already reduced their chances of success.  That's because the phenomena that could help them get their signal across the Pond reach a very strong, sharp peak in mid-June.  The upper atmosphere is exquisitely sensitive to changes brought about by the progress of the Earth's orbit, and it would be a mistake, perhaps as the Newfoundland team might have done, to dismiss a couple of weeks as unimportant to the chances of success in this difficult endeavour.

Then I turned to the gain of the antennas in use.  I can't model a 43-element Yagi in the ARRL HF Terrain Assessment software, but I can compare equivalent 8-element Yagis, relative to their differing terrain profiles.

For Newfoundland, a near-clifftop location makes modelling easy - a fairly sharp drop to the ocean from about 60 feet or so.  I also modelled by own chances by using my existing terrain profile out towards North America.  I know that at least 7dBi is available to add to the antenna's own gain from my terrain.

This is the result for the 8-element Yagis, remembering that the Newfoundland team calculated a gain of 26dBi for their 43-element ladder Yagi:

Blue: my ground gain (8-ele at 145MHz), against Newfoundland (red), also 8 ele.

Interestingly, the 8 element Yagi comes in at 23dBi, 3dB lower than the 43-element ladder Yagi.  So the feeling that more frequent attempts through the season might bring a success, even with a much more common-or-garden antenna, might well be reinforced by this result.

This is even more the case when you look at the gain at very low angles, up to about 2.5 degrees above the horizon.  There is a very big gain difference of about 8dB that has to be made up in Newfoundland, compared to my location, at those very low angles.  Even then, it's not clear that a bigger antenna would actually result in significantly more gain at those angles.  Unfortunately, I can't test it out due to the software's limitations.

But it does seem that a somewhat bigger Yagi, and especially if it were vertically polarised, and located at my QTH, might in fact have a pretty good chance of success in getting a signal across the Pond on 2m. I'm now thinking about a 20-odd element Bruce Array, which is very easy and cheap to make, especially at VHF.  A much shorter version on 6m that I built some years ago proved to be extremely effective.

It's so encouraging, I think I might well try it.  I'll be able to try regularly with no more effort that switching the rig on.  OK, I don't have 750W to pump into the antenna, but the old addage of 'if the propagation's running, the signal will make it, regardless of power', remains largely true.  Even so, running about 40W into a commercially-available 22-element Yagi still yields a respectable 1.7kW, which I'm pretty sure is overkill for the task in hand, conditions allowing.

So, with HF being pretty dead these days, the summer HF lull about to enter full swing, and plenty of sunshine, what better project than getting a huge 2m wire antenna made-up and having a go with the JT modes?  The more of us who try, the more the chance someone will get just the right conditions - provided it's not another ISS bounce!