GM4ULS ham radio station

a QRM-free zone!

Trying out ‘long path’.

Posted by gm4uls on June 11, 2012

My curiosity was whetted by a recent conversation with an Australian operator (via Echolink), who said he had had many HF QSOs with stations in Britain, beaming ‘long path over the North Pole’. Apparently that’s what they said. Now, looking at a Great Circle map, it’s obvious to see that beaming directly over the Pole from here will take your signals on the shortest great circle path available to the North Island of New Zealand, missing great circle to VK by about 45 degrees. Did ‘long path’ therefore mean something other than what I thought it must? I asked around.

No, according to everyone I asked, the simple answer to this simple question was that ‘long path’ was 180 degrees away from the apparent shortest great circle path. So heaven knows what these other ops were talking about.

So today I decided that as I was awake early I would go on 20m (something I don’t often do – ‘Kilowatt Alley’ usually holds few delights for me) and beam directly away from VK and put out a call. My first CQ was answered by a faint signal from a VK7. Wondering whether I was simply working him off the back of the beam I swung it round to the short path and called him again – nothing doing. Back to the long path heading and his signals started coming up again, good enough for a QSO. I then worked a couple of other stations in VK3 and VK6, both lovely strong signals. So basically, after several years of not even trying, I have now worked the Antipodes by long path.

Anyhow, right after the third VK contact I said I would soon be off for my breakfast. I put out another call and was called by an American station, so I swung the beam West. What happened next was that N2KPB (as he explained later) ‘spotted’ me on a dx cluster, so I had a sudden pile-up of American stations after me, plus one in Colombia.

So I started the day with two unusual happenings – firstly my first long path QSOs (as far as I know), and secondly the rare occurrence of being on the receiving end of a pile-up. I thought, “This is worth blogging!” What an exciting life I lead, eh?

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9 Responses to “Trying out ‘long path’.”

  1. ke2yk said

    Reblogged this on Ham Radio – Ham Events – Ham Reviews – Ham Links – Ham News.

  2. Hans said

    At least you have a choice… not much I can do with just a few dipoles!

    • gm4uls said

      Hi Hans. I was just the same until two years ago – never had anything directional on HF, and the only antenna I had at this location was my trusty doublet with the bent leg! So until I got my MA5B, which is just about the shortest 5-band beam you can buy, the idea of being able to direct my signals was foreign to me. I must say it’s actually very interesting. Peaking a signal gives a lot of insights into paths. Anyhow, I have just ‘discovered’ long path, and the main thing that this goes to prove is that after thirty years I’m still finding things out about radio.

  3. John Rowlands said

    I like the blog!

    You’re being open and honest about the experience. A lot of hams aren’t and are hard headed about it all. Lord knows why, but there are a lot of operators out there who haven’t figured out long path at all and can regularly be heard trying to argue it’s something else with operators who work LP daily.

    If you listen from sunrise to a couple of hours later, it becomes very obvious that signals come, peak, then go from the Pacific. You will hear very few stations from that part of the world later in the day. Follow the cluster reports, and you can see the LP become available to points east of you as sunrise takes place there.

    The other giveaway for simple antenna ops like me (deltas are the most complex thing I have!) is that you can’t generally be putting a 59+ signal into the other side of the world with unamplified power, often QRP levels, unless an interesting propagation mode is giving you a helping hand; this is the beauty of long path, where signals are believed to refract in a critical manner such that they do not return to earth until they emerge with few losses and often enhanced levels due to focussing at the other end.

    Long path from the UK appears to take signals down the Atlantic, out over Antarctica and across the ‘radio antipodeal point’, which from very many QSOs I’ve had and plotted, seems to lie about 450 miles (from memory), SW of New Zealand’s South Island.

    There is plenty of scope for more complex paths than a direct line, but if you point an antenna roughly SW in the UK, the guy in VK/ZL land will be pointing his antenna roughly SE, so if there is any skewing, it gets unskewed to yield an effective straight line!

    Also listen out for a mix of long and short paths that’s occasionally heard simultaneously! A very brief delay of a few ms exists on the two signals, sounding like a mild echo.

    If all this sounds like I’m trying to spell it out as gospel, I’m not. There are very complex things art work, and there are plenty of less simplistic theories and even experiments on how that signal gets to the other side of the world quite so well.

    • gm4uls said

      Thanks for this comment. Yes, I’ve heard of the echo phenomenon but never actually witnessed it. Now that I’m studying again my mornings are no longer free, so it is likely to be late spring 2013 before I try out the long path again.

      One thing I have found is that in Amateur radio there is always something one hasn’t tried, and it’s always worth talking/writing about. And then there’s stuff that people forget, like resolving sideband with two AM receivers, but that’s another story…

      Paul

  4. johnres said

    Long Path Tool can work good for such issues!

  5. Nigel Holmes said

    Long Path (LP) propagation between western Europe & VK/ZL is generally feasible 0600-1000 UT. BBC WS on 7150 used to put in a stonking LP signal to SE Australia around 06 UT. Radio Australia b’casts to New Zealand on 100-118° azimuths were strongly received in Europe on 9, 11 & 15 MHz via LP around 0600-0900 UT.

    In 2013 Radio Australia tested MFSK16 & MFSK32 on 11 MHz on 090° azimuth and the right-hand edge of the beam galloped into Europe. Reports & recordings can be found on youtube.

    Moxon in “HF Antennas for All Locations” gives examples of SSB contacts b/n UK & SE Australia with < 5W using Long Path propagation on 14 MHz.

    The Beam Wireless service/Empire Chain terminal in Melbourne (tx: Fiskville; rx: Rockbank) used 11 MHz and a bi-directional, high-gain (low TOA) aerial to achieve high circuit availability across 24 hours simply by selecting SP or LP.

    Kraus recounts using a W8JK array to locate trans-global LP/SP ccts. by rotating the bi-directional aerial & pinging the path with a couple of dits & listening for his signal returning via LP. When he heard his signal he would call & work stations easily all the way around the circuit. Kraus mentions he found the best results on 21 MHz using this technique.

    • gm4uls said

      Thanks for the comment to this old blog post. Since I posted it, I have worked LP on a few more occasions, and more than once heard my own voice coming back.

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