Cloudy, with a chance of DX – super tropo.

A baby 70cm station is born, ready for action!

EI3KD antennas

2m (11el F9FT) and 70cm (19el F9FT) at EI3KD

Some months ago I added a 432MHz 19el F9FT antenna to the mast (approximately 4.5m a.g.l.), with the help of G4CLA – thanks Pete! My FT857D is capable of 20 Watts output on 70cm, but I did find an old sspa that, with a reduced drive from the rig, bumped it up to a massive 30 Watts! Every decibel counts, right? Anyway, the sspa’s built-in preamp was probably a small improvement over the rig’s front-end. Even with such a small set-up I’ve managed to give away a few points in the RSGB UKAC 70cm contests, and also had a few DX contacts during brief spells of enhancement. I also have a higher power sspa to modify for 432MHz, but that’s another story.

Since added the 70cm antenna I’ve been looking forward to a decent tropo opening, and early February wasn’t going to disappoint! Apologies for the length of the blog that follows, but it was an exceptional tropo opening…

Worked and heard maps 8-12 Feb 2015

144MHz worked and heard, 8-12 Feb 2015

144MHz worked and heard, 8-12 Feb 2015

432MHz worked and heard, 8-12 Feb 2015

432MHz worked and heard, 8-12 Feb 2015

The forecast looked good…

At the start of February, the F5LEN and Hepburn tropo forecasts were hinting of some approaching good conditions, under a large anticyclone. This was a good sign, because winter anticyclones can provide exceptional long-distance propagation. At this time of year, in northern latitudes, the sun is too low in the sky to heat land significantly; consequently there is less likelihood of heated air rising and disturbing mid-tropospheric subsidence inversion(s) that will be forming under any high-pressure system. It is these temperature inversions that form ducts along which VHF radio signals propagate, so the less disturbed they are, the better! There’s a clue in the name of this type of inversion too: the air mass under an anticyclone is gradually descending (that’s why the pressure is high at the surface, because the air is “pressing down”), so the inversion is usually at its highest altitude when the anticyclone is newly-formed, as this one was going to be. A higher altitude inversion can mean longer distances, not least because it’s less likely to be disrupted by mountain ranges.

Now, there’s no guarantee of getting an opening just because an anticyclone is nearby, even if it does contain one or more high-altitude inversions – there’s still a large element of luck involved in being able to couple into any ducts that are formed. But, the scene was set…

Sunday 8th February

Hepburn tropo 08/02/15

Hepburn tropo forecast for 08/02/15 06z.

Synoptic chart 08/02/15

Synoptic chart 08/02/15

The only major enhancement noted here on the 8th was that the GB3NGI (IO65, 372km) and GB3ANG (IO86, 618km) beacons were extremely loud, and ED1ZAG ( IN53, 973km) was also audible at about 559. However, more stations were worked during the RSGB AFS 70cm contest than is usually possible, with a quite a few contacts around 600km – not bad with 30 Watts… This all tied in nicely with the propagation forecast.

Monday 9th February

Hepburn tropo 09/02/15

Hepburn tropo forecast for 08/02/15 06z.

Synoptic chart 08/02/15

Synoptic chart 09/02/15

The high pressure system hadn’t moved too far since yesterday, and likewise conditions didn’t change much. Activity was quite low, but I had a nice random contact on 2m SSB with John GM4WJA (IO87, 714km) – that’s normally quite a difficult path, so things are definitely looking up. A 2m test with Clive GM4VVX (IO78, 720km) failed, so conditions weren’t good from here to the far north of Scotland even though the Hepburn forecast says it should have been ok – that could have been the first sign that the system contained selective ducting.

Tuesday 10th February

Hepburn tropo 09/02/15

Hepburn tropo forecast for 10/02/15 06z.

Synoptic chart 10/02/15

Synoptic chart 10/02/15

Ok, this looked more interesting. The anticyclone had moved a little to the east and tropo was forecast right across to southern Scandinavia; looking good for the Tuesday NAC 70cm contest? Actually, the F5LEN forecast (which unfortunately I don’t have archived) was even more optimistic, also showing possible propagation into central Europe.

The first signs appeared here early in the morning, around 07z, when the ON0VHF (JO20, 905km) and PI7CIS (JO22, 857km) beacons appeared at reasonable strength on 2m but apart from that the bands seemed entirely devoid of activity! Things looked up around mid-morning when stations in central and northern England reported contacts into Denmark and Germany on 2m, shortly followed by similar enhancements on 70cm.

At 12:12z I checked the beacons again and discovered HB9HB (JN37, 1231km) on 2m was extremely strong – a great sign that a strong high-altitude duct was present. At around the same time the ON0VHF (JO20, 905km) beacon was 579 on 70cm. I could see via the ON4KST chat that Matej, OK1TEH (JO70) had just contacted Dave G4ASR (IO81) on 70cm and 2m, and that was getting close to IO51…

Matej, OK1TEH (JO70, 1596km), suggested that I should listen for him on 2m – When I checked, I found I could hear his CW, but there was too much local interference here to make a contact feasible. Instead, we decided to try on 70cm, with the old adage “nothing ventured, nothing gained”. As soon as I tuned to 432.210MHz I thought I could hear something, and the signal kept coming up until Matej’s CW was easy copy! I tried to reply on CW but Matej could only see a trace of my signal (he has 600W compared to my 30W) so we switched to JT65B and, unbelievably, quickly completed a very fine contact. Much to my regret I didn’t have the audio file auto-save in WSJT turned on, but here’s the sent and decoded text:

122800 Transmitting: JT65B OK1TEH EI3KD IO51
122900 10 -15 0.1 -13 2 * EI3KD OK1TEH JO70 1 10
123100 11 -19 0.3 -24 3 # EI3KD OK1TEH JO70 OOO 1 10
123200 Transmitting: JT65B RO (Shorthand)
123300 10 -18 -28 3 RRR
123400 Transmitting: JT65B 73 (Shorthand)
123500 10 -20 -30 4 73

At the end of the JT65B QSO, signals were strong enough that we could complete a CW contact too. I didn’t have the audio recorder running the complete time, but here’s a snippet of Matej finishing with me on 70cm, followed, at a later time, by a much weaker cq after Matej had dropped in qsb:

OK1TEH end of EI3KD 70cm cw QSO (right-click here to save)
OK1TEH cq 70cm cw (right-click here to save)

Once that contact was complete it was “game on”… It was obvious that, although the bands appeared quiet, there was a strong elevated duct across the entire width of the anticyclone. Conditions improved as the afternoon progressed, with a few more in the log, including fine CW contacts on 2m with Matej, OK1TEH, Milan, OK7GU (JN69, 1532km) and Andy, SP3IYM (JO82, 1714km).

10th Feb afternoon qsos

DateTimeCallLocBandModeDistance (km)
10/02/201515:59OK1TEHJO70FD 2mCW1590

At 18:57z, the Sportovni Radioklub, OK1KAD (JO60, 1480km) appeared on 432.220MHz at a booming 59 on ssb. Their location is at 1224m a.s.l., and was right within the duct. I forgot to have the recorder running for our qso, which is a shame because Jiri couldn’t stop laughing (!), but I did record his signal a little later. Oh, by the way, Jiri was running 5 Watts!

OK1KAD on 70cm ssb (right-click to download)

70cm was improving all the time, and I managed to get a few more stations in the log including fantastic contacts with David, OK1RK (JO70, 1619km) and Milan, OK7GU (JN69, 1526km). Once again I’m thankful for their perseverance with my QRP 70cm signal, which they managed to dig out of the noise. I made a recording of the CW qso with Milan, which we made using alternating 1-minute periods – you can hear I had no trouble copying him!

OK7GU on 70cm cw (right-click here to download)

10th Feb early evening qsos

DateUTCCallLocBandModeDistance (km)

Conditions were changing as the evening progressed, with the path from here gradually drifting northwards. Luckily the RSGB/NAC contest band for this evening was 70cm, resulting in a lot of activity and happy UHF operators… I didn’t hear too many stations but did get a few nice ones in the log, including OZ7KJ (JO46, 1225km) and OZ9KY (JO45, 1256km), both on 70cm. OZ9KY was very loud:

OZ9KY JO45vx 70cm tropo (right-click to download)

10th Feb late evening QSOs

DateUTCCallLocBandModeDistance (km)

Wednesday 11th February

Hepburn tropo forecast map not available
Synoptic chart 11/02/15

Synoptic chart 11/02/15

A quick tune around after turning the radio on immediately proved there were still exceptional conditions to the east, I had been hearing the beacon OK0EA (JO70, 1667km) on 432.468MHz yesterday, but this morning both it and OK0EP (JO80, 1786km) on 432,886MHz were exceptionally good signals:

OK0EA 70cm tropo (right-click to download)
OK0EP 70cm tropo (right click to download)

On 2m I found Andy, SP3IYM (JO82, 1714km) calling CQ and we had a great SSB contact to follow on from our CW qso yesterday:

SP3IYM on 2m ssb tropo (right-click to download)

This was followed shortly after by a JT65A qso with Andrzej, SQ1FYB (JO73, 1569km), his signals were peaking at -18dBjt here with quite a lot of fading – not quite enough for an SSB contact but still good.

082906 Transmitting: JT65A SQ1FYB EI3KD IO51
082800 0 -33 8.9 -16 39
083000 2 -21 -0.6 16 3 * EI3KD SQ1FYB JO73 1 10
083106 Transmitting: JT65A SQ1FYB EI3KD IO51 OOO
083200 10 -18 14 4 RO
083301 Transmitting: JT65A RRR (Shorthand)
083200 10 -18 14 4 RO
083400 10 -20 15 4 73
083501 Transmitting: JT65A 73 (Shorthand)

On 70cm, at about 09:30z I heard OZ5KM (JO45, 1260km) at 59 on SSB, but couldn’t raise him at all – I suspected I had a problem and later discovered the small sspa I had after the rig had died, so there was no power going out at all. That was a real shame, because I also heard OE2CAL (JN67, 1594km) on 432.200MHz at around the same time, working into the U.K., having also just heard him a few minutes earlier on 2m!

I wasn’t at the radio for the rest of the morning, but came back mid-afternoon (having got 70cm qrv again with just the barefoot rig) to find conditions still good to the east. At about 16:45z I tried to contact Przemek, SQ2SAT (JO83, 1769km) on 2m SSB but, unfortunately, the path wasn’t quite good enough for him to hear my confirmation report, so the qso wasn’t complete:

SQ2SAT 2m SSB tropo (right-click to download)

However, just after trying with Przemek, I got a huge surprise, with Marek SP4MPB (KO03, 1939km) calling in with a fantastic signal over such an amazing tropo distance:

SP4MPB 2m CW tropo (right-click to download)

I have to say, I was beginning to wonder when this exceptional tropo was going to end, but as the day progressed it was obviously beginning to drift away too far north and east to be accessible from here. However, there was one last sting in the tail, with the SK1UHF (JO97, 1796km) beacon appearing on 432.403MHz at around 19:30z, getting louder (with deep qsb) as the evening went on:

SK1UHF 70cm tropo (right-click to download)

With this in mind, Kjell SM7GVF (JO77, 1570km) spent some time calling in my direction on 70cm. I could hear him pretty well between periods of deep fading but the path wasn’t good enough for him to hear my 20 Watts, until we finally struck lucky:

SM7GVF 70cm cw tropo (right-click to download)
SK7MHH 70cm tropo

At about the same time, the SK7MHH (JO86, 1684km) beacon was audible on 432.440MHz, which rounded off a fabulous 3-day period of VHF/UHF DX!

11th Feb qsos

DateUTCCallLocBandModeDistance (km)

6 thoughts on “Cloudy, with a chance of DX – super tropo.

  1. Przemek

    TNX Mark for the audio file with our no completed QSO. A very little beat for succes… J Hope we do it again in right time. At this time it was to late for ssb. Duct mooved to the east. Any way thanks for try again. Best 73!

  2. Alan G0XBV

    Interesting comments, Paul. I recall a very large anticyclone from Jan 1977 I think it was. It had a centre pressure of 1055mb and looked very promising! I was watching it out the window of my school classroom (never been that good at maths anyway :>) and it produced the same looking weather (cold, grey and gloomy). However nada. The air mass collapsed under the weight of the cold air and destroyed any chance of an inversion. So I didn’t have high hopes last week, but it came good :>)


    1. Mark Turner Post author

      Hi Al, I’m not sure who “Paul” is?

      That flat, grey, gloomy looking cloud under an anticyclone is a sure sign of an elevated temperature inversion. It almost certainly supports a “duct”, but there’s no guarantee it’ll be accessible, or that it’ll support one’s frequency of interest… it can be a right tease 😉

      Regards, Mark


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