DX-maps - a prediction

Interesting conditions? Post DX alerts here. Please use this forum for DX alerts ONLY!
Post Reply
daveB
Posts: 1170
Joined: 07 Oct 2014 16:49

DX-maps - a prediction

Post by daveB » 16 Apr 2018 19:51

I predict that DX-maps is going to become next to useless for sporadic E openings.

I hope I'm wrong but I make this prediction because of the sudden popularity of a new weak signal mode FT8. This allows "QSOs" (if you call an exchange of call-sign, report and locator square by two computers, a QSO) down into the noise. As a result the operators are reporting weak tropo scatter, or maybe it is even aircraft scatter, beyond around 400 km as SpE. So just now we have the following five stations most recently logging:

2018-04-16 18:01 DK8NE (JO50AL) 50.313.0 FT8 G1BTF (JO01CM) LoTW 697 km Sp-E (88MHz) FT8 -18 dB 1112 Hz CQ
2018-04-16 17:56 M0PNN (IO82TS) 50.313.0 FT8 PE1LJS (JO22OI) ____ 514 km Sp-E (111MHz) FT8 -18 dB 2130 Hz CQ
2018-04-16 17:53 DK8NE (JO50AL) 50.313.0 FT8 G0MBL (JO01QH) LoTW 614 km Sp-E (97MHz) FT8 -19 dB 1601 Hz CQ
2018-04-16 17:40 SM0NKZ (JO99IQ) 50.313.0 FT8 IW4AOT (JN54QK) LoTW 1765 km Sp-E (52MHz) FT8 -14 dB 1546 Hz CQ
2018-04-16 17:39 DK8NE (JO50AL) 50.313.0 FT8 IW4AOT (JN54QK) LoTW 678 km Sp-E (90MHz) FT8 -11 dB 1573 Hz CQ

Because of the short distance, isn't it more likely that lines 2 and 3 are tropo. The operator wouldn't know the propagation mode as the signal is so weak. If I read the explanation correctly -18 dB is 8dB above the noise floor in a 2.5 kHz bandwidth.

This is getting annoying :D
2018-04-16 18:32 M0PNN (IO82TS) 50.313.0 FT8 PE1LJS (JO22OI) 514 km Sp-E (111MHz) FT8 -17 dB 2239 Hz CQ
2018-04-16 18:16 M0PNN (IO82TS) 50.313.0 FT8 PE1LJS (JO22OI) 514 km Sp-E (111MHz) FT8 -15 dB 2245 Hz CQ

Somebody send the following link to the operator: http://www.uksmg.org/content/tropo.htm Goodness knows what DX maps will look like if the predicted tropo lift appears.

Are there any other resources? Reading the explanation on the G7IZU Live MUF site I would expect the same issue to arise as it says "when propagation is reported" the MUF at the mid point is shown "as calculated by the Live MUF application". From that I take it that a 500 km contact mis-reported as SpE will generate a much higher MUF figure at 250 km, than a 1500 km contact.

FMList visual logbook is probably the most reliable. Any thoughts?

David
SDRPlay, AirSpyMini, RTL dongles, SB920s, Yamaha TX930. 5 ele compact yagi on rotator at 18ft agl. FM5 facing east, FM5 facing south, FM3 facing NE, OIRT dipole, 3-ele Moxon vertical facing east.

satnipper
Posts: 884
Joined: 03 Oct 2014 12:58
Location: Western Europe

Re: DX-maps - a prediction

Post by satnipper » 16 Apr 2018 22:47

You got it the wrong way round. DXmaps is useless when there is no real Sp E due to the mode being misrepresented. Most FT8 contacts on 6m will be tropo enhancement or F layer related. When there is real Sp E then the real logs will swamp the MGM ones.

User avatar
John Faulkner, Skegness
Posts: 4834
Joined: 19 Sep 2014 15:55
Location: Skegness, Lincolnshire. JO03dd
Contact:

Re: DX-maps - a prediction

Post by John Faulkner, Skegness » 17 Apr 2018 01:03

This is getting irritating for me too. I thought DK8NE in particular would have got the modes correct by now, but obviously not and I don't expect this will change in a hurry either.

I would like to give JT8 a go myself for Es, *if* I could only get my SB2000 interface to talk to to my IC7000. It just isn't playing ball. The plan was to have WSPR running so as to act as early band 2 Es alerts.

User avatar
John Faulkner, Skegness
Posts: 4834
Joined: 19 Sep 2014 15:55
Location: Skegness, Lincolnshire. JO03dd
Contact:

Re: DX-maps - a prediction

Post by John Faulkner, Skegness » 18 Apr 2018 09:58

There's a turn-up. Either DK8NE reads this forum, or somebody has contacted him and pointed out the error of his ways. Today marks the first day I have seen him reporting tropo or aircraft scatter, etc. as tropo and not Es.

User avatar
Reggieman
Posts: 4
Joined: 15 Apr 2018 19:11

Re: DX-maps - a prediction

Post by Reggieman » 19 Apr 2018 13:16

I know less than nothing at a purely technical level, I have in the past used it as an indicator come 10:30 am in summer months to see
if there will be much on 11meters for Sporadic E. It serves its purpose there but you seem to be very advanced with the
predictions etc. I thought tropo was only good for 200-300 miles-ish ? (but maybe that is only 10/11meters)

Out of pure interests sake whenever I have spoke to Holland from UK I always assumed that was tropo. It seems very hard to contact
via F2 layer (probably impossible as you are going over the top of them) with a decent low angle radiation antenna. And never get them on any "ground wave" or close to earth 0 degree radiation as it gets absorbed/attenuated by buildings/land/earth. Sporadic E would appear impossible as well unless you have a really high angle take off spur.

Holland is close but still an elusive DX target on 11m. I have spoke only once or twice, glad I made it through though.
All nice and cosy with the signals.

satnipper
Posts: 884
Joined: 03 Oct 2014 12:58
Location: Western Europe

Re: DX-maps - a prediction

Post by satnipper » 19 Apr 2018 14:56

You get increased range with frequency with trops and Sp E. Tropo of over 1000 km is not unusual with a good opening on Band II and 2m.

The Netherlands is generally too close to the populated parts of England for Sp E where the minimum range is 600-700 km. I have worked NW Scotland from London on 6m but that was quite unusual.

Your best bet to work PA on 10/11m is back-scatter and I have worked one or two Dutch guys on 10m from London that way. A bit of power is required though...

Stuart

User avatar
John Faulkner, Skegness
Posts: 4834
Joined: 19 Sep 2014 15:55
Location: Skegness, Lincolnshire. JO03dd
Contact:

Re: DX-maps - a prediction

Post by John Faulkner, Skegness » 19 Apr 2018 17:09

The lines can be blurred when we look at the various propagation modes.

Some of it is relatively straight-forward, as with Es, or F2, but it's not difficult to confuse troposcatter and aircraft scatter.

There's ionoscatter too, which potentially blurs the lines even more. The old Grunten transmitter on band 1 used to propagate at carrier level to me virtually all the time when I lived in Nottinghamshire. Now which mode would that be? Probably ionoscatter as troposcatter tends to cut off around 800 km, though I have twice heard troposcatter stations on band 2 from over 900 km. I was on high ground on both occasions.

Post Reply

Return to “DX Alerts”