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This was a question I was asked earlier today. Someone thought it was an exotic digital mode. It is not.

GDX means “best DX in the UK” , nothing more.

If you live in the UK it is probably a phrase you know. If you live outside the UK then it may be a phrase you’ve maybe never heard of before or were too embarrassed to ask.

In the same way ODX means “best overall DX”.

UPDATE 1545z:  Just 6m locals and GDX this afternoon. No Es here since CN8LI lunchtime.  May be more teatime?

CN8LI (2113km, Morocco) spotted my 1W ERP twice around 1200z today on 6m. This is the first real DX (Es presumably) today.

G4HBA (189km) is the best GDX so far today. He was spotted at -27dB S/N at 1138z when running 10W with 2Hz Doppler, so maybe some aircraft reflection?

Recent 6m WSPR spots today

Last night my new Win 8.1 Dell PC decided it needed to install updates. I chose to  switch off until restarting this morning. It said “Loading Windows updates. Do not switch off your computer”. Being a good boy, I obeyed and waited as it got to 81% complete …… and waited, and waited, had breakfast, went for a walk, had more breakfast and still it said 81%, please wait. In all it had now been 1 hr 40 minutes!

At this point I was about to ring up that nice Dell man in India when I decided to turn off the PC and try again. THIS time it sailed through 81% and reached 100% complete in no time. PC works fine! What the heck was going on?

10m is my favorite band of all: there is the possibility of local QSOs on 10FM out to 30-40km (at least) even with very modest (CB level) powers to a 1/2 wave vertical. It is good for GDX with suitably equipped stations out to many hundreds of kilometres. F2 and Es propagation allow really long distances.

6m is the “magic band”. It seems to be good for locals and GDX seems to work out pretty well too out to several hundred kilometres, as for 10m. Although F2 is rare except close to good sunspot maxima, Es is there every spring and summer and at other times too, but more rarely. More stations active (e.g. on WSPR – a great DX mode) would indicate more openings, I suspect.

Actually one could do a lot worse than concentrate on WSPR on these 2 bands only. That is what I may do in future. In effect I  am already doing this, but I could better optimise the antennas – maybe a 1/2 wave vertical on 10m and a halo on 6m? My antennas may be compromised but in my present state of health (stroke) they will have to do.

UPDATE 1820z:   All afternoon on 6m it has been just locals G4IKZ, G4KPX and G0LRD only here with no signs of GDX or Es at this QTH. Things on the “magic band” can change quite quickly, so I shall be staying on 6m for the rest of the day. We’ll see.

UPDATE 1830z:  Looking back through the WSPR logs I see G3IGU (172km) near Doncaster was being spotted here at 1254z with only very slight Doppler or warm-up drift (-1Hz).  This may have been tropo or a favorable aircraft again. So there was some GDX around.  I have seen a surprising number of GDX stations now on 6m at decent distances. Theseare all “accidental” spots – no skeds, I just happened to see these stations.

As I write this I see G6AVK (78km) is spotting my 1W ERP at -27dB S/N at 1830z , yet more GDX.

UPDATE 2030z:   Just the locals reporting me. No Es or GDX currently.

UPDATE 2155z:   Still just the locals.  Soon be time to pull the big switch to off.

After a fun day on 10m, I’ve now gone back to 6m and my 1W ERP was immediately spotted on WSPR by locals G0LRD and G4IKZ. On the lookout for more distant 6m stations now by any mode.

UPDATE 1120: G4KPX (14km) is spotting me well on 6m and the first 6m GDX today G4HBA (189km) using 10W from IO93fn square (near Barnsley, Yorkshire) is being spotted here at -25dB S/N with 3Hz Doppler, suggesting aircraft involvement.

LB9YE and I have been exchanging WSPR spots since 0458z this morning. In both directions there is considerable Doppler. On another signal (not currently decoding) there are clear signs of meteor reflections as the signals are strong but in short bursts. I wonder if MS was playing a part in LB9YE’s decodes?

Earier in the night PB0AIC (288km) was decoded STRONGLY at -8dB S/N . At this range I assumes this was early morning tropo or again possibly MS? At the very same time 0404z, G8VDQ (93km) , was decoded strongly at -12dB S/N.

Otherwise all quiet on the Es front.

I do wonder sometimes about Es (SPORADIC E-layer) reflections. Many signals do come into this category with fleeting, often quite localised, strong openings, but many others are anything but sporadic. Are these really Es as we know it or some other propagation?

At 1936z G8VDQ (93km) in IO91um was spotted here at -26dB S/N.  When there are GDX stations they seem to be copied. G8VDQ’s signal had -3Hz Doppler, suggesting aircraft reflection was involved.

UPDATE 1950z:  Es is still in evidence with DK6UG spotting me 4 times (so far) now at around -22/-23dB S/N.

UPDATE 2120z:  Es again; this time  IK1WVQ (1084km)  spotted at -20dB S/N.