New WSPRer!

Having a daughter living in Lima, Peru, I was delighted to start hearing OA4DKJ on 14MHz WSPR last night - a DX distance of 9991km.

MW1CFN receiving OA4DKJ, 2019 September 26

I'm hoping Eduardo will stay on WSPR for many years to come!
 

Lima: a great place for radio!

Better late than never. Better never late...

RadCom, the RSGB's monthly magazine (not available in any shops), is, by any standard, a pretty poor offering.

As such, the magazine gets put in the bathroom, where I pick it up and put it down until the next month's pointless text arrives.

This month (October 2019), I was interested to see the EMC section dealing with the 'novel' RFI source that are CCTV camera systems.

Novel, that is, to the RSGB.  I first noticed RFI from a wireless image transmission system around 2009.  I wrote about a later, entirely wired system, in 2014.

So, congratulations to the RSGB for catching up - eventually.

There is something else that struck me as very, very odd in this month's EMC section.  In relation to some work by one operator to minimise RFI, it's implied that a reduction to the point where the 'S' meter does not register a signal is an indication of success.

Well, this would certainly not be acceptable for my WSPR reception.

I can switch on a number of poorer SMPSUs around the house, and they will produce copious amounts of RFI.  The CCTV system I reported on in 2014 is the only one I've seen trigger the 'S' meter.  Typically, SMPSUs will raise the noise floor by several dB without triggering the 'S' meter at all. So use something like an SDR receiver or spectrum analyser to determine the success or otherwise of EMC efforts, so that you get an objective, numerical assessment.

Looking forward already to summer, 2020.

As I've mentioned a few times on this blog, 2m SSB and digimodes is something I would really like to try.

Unfortunately, whilst a mobile 2m FM transceiver can cost less than £100 in the UK, a SSB unit somehow costs a minimum of £685 for the FT-857D - but I don't want HF!  The top-end VHF/UHF rigs don't bear thinking about: £1795 for the new, albeit very nice ICOM IC-9700, for example.

So, I had a look around at various used transceivers with 2m multimode capability.  The FT-857Ds are fairly common on E-bay, but are so sought-after that their used price is not sufficiently below that of a new one.  Ergo, there is no sensible point in buying them.

Eventually, I found a very clean ICOM IC-746 for £495 from a reputable seller specialising in amateur radio.  That was at least £200 below the used price for the same rig from one of the big radio outlets, so I bought it!  It's even being delivered in person by car, so that it won't get thrown around by delivery companies!

The 746 isn't a rig absent of problems, such as a well-known, overheating display screen backlight transistor.  But these are minor things that are either inconsequential, or else easily repaired.  There are plenty of online videos to guide people like me.  My first job will be to add a heat sink to that transistor, so that it helps avoid the problem in the first place.

So, the next step is a decent 2m antenna.  Although they are very easy to build, this time I'm going to buy a Innovantennas 10, maybe 12 element LFA Yagi.  For 2020, it will beam permanently across the Atlantic.

New for 2020: a 10, or maybe 12-ele LFA for 2m DX.

I'm quietly confident that, armed with some terrain analysis and a good antenna, I might be able to break the Brendan challenge. Some people think I'm stupid, and that enormous ladder Yagis and enormous power is needed for this to succeed.

But look at the terrain analysis for my location (100m up, sloping all the way down to the Irish Sea), which is for a notionally low (3m above ground), 8 element Yagi (largest available under the software), not the intended 10/12 antenna I will eventually acquire.  A total gain at extremely low angles of nearly 25dBi!  Gain remains above 14dBi until 8 degrees.

In other words, assuming I can get a good 26dBi out of a slightly larger antenna, a sensible input of 25W from the transceiver magically appears as just under 1kW from the antenna.  If I make the rig sweat at 90W into the antenna, the effective output rises to 36kW!  This is definitely worth pursuing!

Spectacular low-angle gain available, even for a modest, 8-ele Yagi.

Terrain in the direction of the US: an antenna on a 3m pole here is effectively 100m high!

Whilst some think there is too much atmospheric extinction at 2m for low angles to be usable, I have to beg to disagree - based on experience with SO-50 satellite.  My best DX with SO-50 came when I worked a Canadian station using a 5W FM handheld into a 5-ele 2m quad; the satellite was computed to be about a degree above the horizon at that point, not allowing for refraction effects that close to the horizon.  The fact I could clearly hear the other station on 70cm downlink also means that atmospheric extinction is not a barrier to low angle VHF working.

Field-portable market hots up!

Wow!  This soon-to-be-launched QRP rig, which seems to have outstanding mechanical engineering, really has my attention:  https://lab599.com/

Nice!

Non-linearity, straightened out.

Last week, a strange WSPR anomaly was causing some headaches for me.

The problem was that G0CCL, a very useful beacon in Cambridgeshire that switches its output from 1W to 5W at intervals, was receiving strange signal reports in that the 7dB switch from 1W to 5W yielded, at various receivers I selected, a 12.5dB improvement in signal.

This seemed to be odd to me, so I asked the keeper of G0CCL to examine the setup, in case settings had drifted over time.

In the true spirit of ham radio and scientific enquiry, Jonathan Kelly, G2HFR, attached an antenna to his spectrum analyser, and found...a 12.8dB difference between the nominal settings of 1 and 5W!  A person of lesser integrity would have made excuses, failed to respond, or even denied the anomaly.  So, very much credit is due to Jonathan.

Something not quite right.  A supposed 7dB power setting change yields a 12.86dB difference in actual output.  Image courtesy Jonathan Kelly.

The agreement between analysing remote receiver reports and a local spectrum analyser assessment is remarkable - just 0.3dB difference!  I was rather happy with that, and the fact that it pointed to a problem that needed resolving with the drive amplifier of the Raspberry Pi system in use at G0CCL.  Jonathan is going to change it for a log amp with more steps next week, as a result of this finding.

As this had complicated my analysis of seaside and inland stations somewhat, I bought another WSPRlite transmitter, and set off for the beach one, last time this afternoon.  The temperature was hitting the upper 20's Celsius, which was really quite amazing for the end of September.

Warm weather won't last much longer.  At IO73rf, Traeth Llydan, west coast Anglesey.

Now I could compare two identical elevated 1/4 wave verticals with 2 radials, one at home, one at the beach, each putting out 200mW for a couple of hours.  As the tide was high when I began, and the beach slope steeper than when it's lower, I was able to keep the seaside antenna with its feet right at the water's edge throughout, occasionally being washed by waves.

The results are very interesting - and very different from fully inland stations, which are worse than my hilltop, home vertical only a few km from the coast.  My seaside antenna produced about 2dB better reports across all distances and all stations, increasing to 8dB as the distance reached long-haul DX at beyond 6000km or so.  Most eastern US stations were reporting a 5dB better signal from the seaside.

This is broadly comparable to the ~10dB improvement seen from earlier coastal work, although there were no dramatically better signals this time.  Signals to the east (landward) were a maximum of 3dB better but, generally, they were marginally (0.5-1.5dB) weaker from the seaside.

Sadly, I'm reluctant to compare with others' inland stations, because there are too many things that we can't know about them.  Some use rubbish antennas, others are surrounded by buildings, and the significance of these isn't always appreciated by the users.

As with other work, I found a significant number of stations - up to 40% - that heard me from the seaside, but not at all from home.  Those are perhaps more telling and important than the other comparisons.

Another crucial element to examine was the frequency (how often heard) of spots for each station, which is very revealing: the more inland antenna had, on average, only a quarter the number of spots from any given station that the seaside antenna did. 

All distances, all stations = 2dB improvement from the seaside.

Eastern side of US reporting 5dB improvement from the seaside.

8dB improvement from the seaside for far west US receivers.

Tidying up at the beach

During the past 24 hours, I decided to gather more WSPR data by comparing identical (elevated, 1/4 wave vertical, 2 radials) antennas, one located at the seaside, the other at home.  Previous work had tended to compare a mobile whip with a delta loop at home, or used more distant stations for comparison, both approaches having advantages and disadvantages.

'Home' means 100 metres up on a ridge overlooking the sea.  In the direction of the eastern seaboard US, the sea is about 12km distant, and visible.  In the direction of the west coast US, the sea is 7km distant, and visible.

West coast Wales, listening to the US.  My old runaround car has hit a fair few boulders in its travels!

Whilst I had been back-calculating to compensate for power output differences between my own station on the beach and my reference inland station, G0CCL, I had to abandon this method.  That was because there is a very clear and consistent disparity between reception reports at 5W, and those at 1W.  That is probably an effect of the ionosphere and/or noise local to the receivers, and not anything to do with G0CCL.

So, the simplest option was to resort to listening instead.  This also removed the 20 minute delay in propagation changes that occur as a result of the longitude difference between me and G0CCL.

The outcome of the evening listening to the US was a +10dB advantage to the sea side.  The range was +14dB to +4.5dB.

To the east, in the morning, there was a +12.5dB advantage to the sea side antenna.  The range here was +19dB to +10dB.

East coast listening in the morning.

In both cases, there were several stations that were not heard at all by the vertical at home.  In the case of JA9TTT, which was heard at -14dB at the seaside, and not at all back home, the inferred signal enhancement there, based on WSJT-X's detection limit being -34dB, might be as high as 20dB.  I've seen up to 29dB enhancements with other stations in earlier work.

So, I've now run out of time and energy for this work, and will soon ruck out of luck with the very fine weather we have had for most of September.

The basic story is that being at the coast, without actually having to be in the water, typically boosts your performance by roughly 10dB, or a ten-fold increase in signal, with a good number of paths showing enhancement of about 14dB (25 times), and occasional ones nearly 30dB (1000 times).

WSPR - a peculiarity.

Seaside WSPR, 16/09/19, Anglesey west coast.

Just as I was getting ready to do some more analysis on seaside operating with WSPR, I came across an interesting anomaly.

To my simple mind, if one increases the output of a transmitter by 7dB (1W to 5W), then the improvement in signal strength at the receiver might be expected to be of a similar order.

But in using a reference station - G0CCL - with which to compare my own results, I found that increasing the power by 7dB resulted in a quite consistent 13dB improvement at a distant receiver (in this case, US receivers).

G0CCL is operated by quite experienced electronics whizzes, so I doubt that the power outputs are not correctly set or indicated - though it's always possible and I have asked them to check.

If anyone has any ideas, I'd be interested to hear of them under 'comments'.  One idea from elsewhere has been that noise may vary at the receiver.  That may well be true, especially as the overwhelming majority of receivers are in noisy environments where noise may vary substantially.  The proof of this idea must be to select a station like DP0GVN as a receiver in future work.  I noticed that, when I chose TF4M in a remote and RF-quiet part of Iceland, changing the output by 7dB resulted exactly in a 7dB change in received signal strength.