5 Mar 2013
Double or single peak for cycle 24?
At the moment the jury is still out on this. We've seen activity slide since the peak around Nov 2011 but there may be signs that the trend is upwards again leading to a second peak as has happened in a few recent sunspot cycles. This NASA video gives some insight into the thinking.
More analysis with Spectrum Lab software
Spectran is a very easy package to use but it has its limitations when analysing weak audio signals. A more powerful package is DL4YHF's Spectrum Laboratory which is an extremely powerful piece of software. The problem is that if I've not used it for months it takes me hours to remember how to drive it. A secret is to store ".usr" configuration files so one can go back instantly to a set of settings e.g. a given frequency to analyse with a specified bandpass filter and bandwidth.
Anyway, to cut a long story, this evening I set up some config files to allow me to look again at the recordings of my 8.9775kHz VLF earth-mode signals made during recent drive around tests locally. Although the original analysis was done at 180mHz bandwidth I can now replay the recordings and look in bandwidths down to 34mHz. What happens then is that signals present but too weak to see now appear above the noise floor as a faint line. The net result is that the signals can be detected in some of the "in between" locations that were not apparent from the 180mHz (wider!) bandwidth analysis.
I intend to use Spectrum Laboratory and narrow bandwidths for the over-the-horizon 481THz optical tests if Spectran proves not up to the job. However, when bandwidths are very narrow there is a time-lag before the trace appears on the screen. This is less than ideal when trying to align weak optical signals with beamwidths measured in a degree or less. What is needed is an accurate beam heading and then allow the trace to build on the screen. I don't have enough experience yet to know how much beamwidth spread a cloud or free space dust scattered optical signal gets. When looking for G4HJW's signal over the horizon in clear skies last year the alignment was quite critical, but his signal was audible in headphones so the optics could be peaked by ear before analysing with Spectran or Spectrum Lab. I had more luck with my own QRSS3 signal over the horizon on a shorter path, managing to align by eye on visible landmarks enough to see the trace on the PC and then peak it.
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| Faint line at 8.9775kHz visible at greater range (43mHz bandwidth) |
I intend to use Spectrum Laboratory and narrow bandwidths for the over-the-horizon 481THz optical tests if Spectran proves not up to the job. However, when bandwidths are very narrow there is a time-lag before the trace appears on the screen. This is less than ideal when trying to align weak optical signals with beamwidths measured in a degree or less. What is needed is an accurate beam heading and then allow the trace to build on the screen. I don't have enough experience yet to know how much beamwidth spread a cloud or free space dust scattered optical signal gets. When looking for G4HJW's signal over the horizon in clear skies last year the alignment was quite critical, but his signal was audible in headphones so the optics could be peaked by ear before analysing with Spectran or Spectrum Lab. I had more luck with my own QRSS3 signal over the horizon on a shorter path, managing to align by eye on visible landmarks enough to see the trace on the PC and then peak it.
Mobile 8.977kHz VLF loop tests started
Today I started to do my tests on 8.977kHz using my 5W earth mode transmitter at home but using a mobile loop antenna on the car connected to my PC via a tuned preamp. The idea is to be able to drive around and measure signal levels with Spectran software whilst actually on the move.
The loop was mounted behind the car in such a way that it would detect any ground propagated signals. The loop is about 10cm off the ground.
A drive test to Swaffham Bulbeck was carried out and signals were detected more or less continuously out to 3.5km from home before they disappeared in the noise. Bandwidth used was 0.18Hz with a continuous carrier. Although coverage was as I anticipated, signal levels were not as great as when the loop was actually laid directly on the ground. At one of my usual test sites 3.5km out in the fens there was no copy with this loop arrangement yet there was a decent signal copied with the loop on the ground a few days earlier. I need to do some direct comparisons between the loop on the ground, the loop mobile mounted 10cm above the ground and with the E-field probe on the car roof. Initial indications are that the difference between the EFP and the mobile loop is probably no more that 5-6dB.
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| 30t 80cm loop mounted behind the car |
A drive test to Swaffham Bulbeck was carried out and signals were detected more or less continuously out to 3.5km from home before they disappeared in the noise. Bandwidth used was 0.18Hz with a continuous carrier. Although coverage was as I anticipated, signal levels were not as great as when the loop was actually laid directly on the ground. At one of my usual test sites 3.5km out in the fens there was no copy with this loop arrangement yet there was a decent signal copied with the loop on the ground a few days earlier. I need to do some direct comparisons between the loop on the ground, the loop mobile mounted 10cm above the ground and with the E-field probe on the car roof. Initial indications are that the difference between the EFP and the mobile loop is probably no more that 5-6dB.
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| Signal received with Spectran and the mobile loop |
Revised UK Frequency Allocation Chart
From the OFCOM email newsletter today:
My understanding is therefore that below 8.3kHz the UK administration "does not care" what happens as long as interference to allocated services is avoided. This is my interpretation and not a legal statement.
The table shows frequencies below 8.3kHz are unallocated in the UK but there are some footnotes in the ITU frequency allocation table that require administrations to ensure no harmful interference to services above 9kHz and to notify other administrations about research below 9kHz.UK Frequency Allocation TableOfcom has published a revised UK Frequency Allocation Table. This details how various frequency bands are used in the UK, and which bodies are responsible for planning and managing them – including frequencies assigned to individual users or installations at particular locations. It also shows the internationally agreed spectrum allocations of the International Telecommunication Union.
My understanding is therefore that below 8.3kHz the UK administration "does not care" what happens as long as interference to allocated services is avoided. This is my interpretation and not a legal statement.
2 Mar 2013
VLF earth-mode mystery deepens
This afternoon I did a larger coverage test with 5W 8.977kHz earth-mode, driving in several directions locally in the car with the roof mag-mounted E-field probe RX antenna and with a PC in the car monitoring the signal. I drove for several kilometres in different directions recording where the signal could, and could not, be copied. The best reception distance with the E-field probe was 3.2km.
The map shows the results. Yellow shows where I drove and red shows where there was signal present and recorded on Spectran. I have recordings of the whole trip which I will more carefully analyse later.
The interesting thing is that the signal could be copied in 4 local villages (Burwell, Reach, Exning and Swaffham Prior) but there was almost zero coverage once outside of these villages. This is NOT the case when looking with a magnetic loop RX antenna, where the signal can be copied more extensively in the rural areas at even greater distances.
It would appear that the E-field signal needs to be strong above ground to be copied with the EFP and this only happens where there are buildings i.e. in the villages. It suggests I'm detecting the signal from cables or pipes in houses.In more rural areas the signal is weaker above ground and not detected, at least not with 5W TX.
The map shows the results. Yellow shows where I drove and red shows where there was signal present and recorded on Spectran. I have recordings of the whole trip which I will more carefully analyse later.
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| 5W 8.977kHz earth-mode coverage using EFP RX antenna |
It would appear that the E-field signal needs to be strong above ground to be copied with the EFP and this only happens where there are buildings i.e. in the villages. It suggests I'm detecting the signal from cables or pipes in houses.In more rural areas the signal is weaker above ground and not detected, at least not with 5W TX.
1 Mar 2013
Mobile on 8.97kHz VLF
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| Route taken from A to F (about 4km) |
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| Signal strength on 4km run between 2 villages |
What I am detecting (I think) is the local E-field from the VLF signal in the ground, no doubt aided by local utilities. What puzzles me is why there is NO copy in between the 2 villages when there are, I think, pipes and cables in the road.
In the coming days this test is worth repeating locally in other directions and further afield. Fascinating to think a 5W VLF signal injected into the ground can be copied on a 19 inch whip on the car roof like this.
28 Feb 2013
Another approach to 472kHz WSPR
An old work colleague Richard G4KPX has been doing more experiments with indoor loop antennas. Recently he has been using an indoor loop for 472kHz with an ERP of around 1mW. I just checked the WSPR database and see he has achieved some amazingly good results with 49 unique spots with best report from Sweden at over 1300km! Well done Richard.
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| G4KPX's WSPR results over 500km with just an indoor loop TX antenna |
Optical NLOS test - next time pack everything!
This evening I set off to my Landwade location where I hoped to check the non line-of-sight (NLOS) signal level from my 481THz, red LED, QRSS3 beacon TXing from home. This time I'd carefully aligned the TX and adjusted the RX optical alignment in daylight, so everything should have been spot on.
Then I realised I'd left a vital lead at home that allowed me to connect the optical RX to the laptop. Next time I need a checklist as it is a 10 mile round trip to the test site.
Instead, I tried to copy the signal using the optical RX fed into my iPod Touch with SpectrumView software, but the bandwidth was too wide to allow me to find the weak signal. I hope to repeat the test in the next week (with the laptop and Spectran set to 0.34Hz bandwidth), but this time with EVERYTHING packed for the test.
I was very annoyed with myself for forgetting this audio lead as it prevented a meaningful test being done. I also need to find a different NLOS test site that is less far to drive to but still at about the same distance (3.6km).
The limitations of my cheap tripod are also apparent: I need a much sturdier one that has a compass attached and much smoother pan and tilt.
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| 481THz RX with iPod Touch 4g running SpectrumView |
Instead, I tried to copy the signal using the optical RX fed into my iPod Touch with SpectrumView software, but the bandwidth was too wide to allow me to find the weak signal. I hope to repeat the test in the next week (with the laptop and Spectran set to 0.34Hz bandwidth), but this time with EVERYTHING packed for the test.
I was very annoyed with myself for forgetting this audio lead as it prevented a meaningful test being done. I also need to find a different NLOS test site that is less far to drive to but still at about the same distance (3.6km).
The limitations of my cheap tripod are also apparent: I need a much sturdier one that has a compass attached and much smoother pan and tilt.
8.97kHz earth-mode tests with mag-mounted E-field probe
Today I started some tests at 8.97kHz with my mag-mounted E-field probe (EFP) on the car roof. As usual, the transmitter was my 5W QRSS3 beacon feeding the 20m spaced earth-electrode antenna in the garden.
The logical starting point was to drive to my usual "strong" test site 1.6km from home and compare signal levels on the usual 80cm square RX loop with that on the EFP. For reasons I have yet to understand the signal was NOT copied, even on the loop! What I did see was what looked like an FSK telemetry signal, possibly from overhead power lines close to 8.97kHz. I've never seen this before. Anyone know what it is?
I then drove to my new QTH (due to be occupied in about 4-5 months time) which is 0.4km from the TX and sat in the car in the drive with the iPod Touch 4g running SpectrumView software connected to the EFP. The antenna was a short 19 inch whip. Signals were copied quite well (see photo showing "3" from my callsign). The bandwidth on SpectrumView cannot be narrowed enough to optimally receive QRSS3 and results would be better with the PC set to 0.34Hz bandwidth.
Tomorrow I'll have to find out why I couldn't see my earth-mode signal at the usual test site on either antenna. I'm also going to do some /M reception at 8.97kHz using the E-field probe and laptop with Spectran set to 0.34Hz or 0.17Hz bandwidth. With a continuous signal I'll be able to log the signal level as I drive around the village and nearby.
The logical starting point was to drive to my usual "strong" test site 1.6km from home and compare signal levels on the usual 80cm square RX loop with that on the EFP. For reasons I have yet to understand the signal was NOT copied, even on the loop! What I did see was what looked like an FSK telemetry signal, possibly from overhead power lines close to 8.97kHz. I've never seen this before. Anyone know what it is?
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| 8.97kHz 5W earth-mode signal at 0.4km on E-field probe |
Tomorrow I'll have to find out why I couldn't see my earth-mode signal at the usual test site on either antenna. I'm also going to do some /M reception at 8.97kHz using the E-field probe and laptop with Spectran set to 0.34Hz or 0.17Hz bandwidth. With a continuous signal I'll be able to log the signal level as I drive around the village and nearby.
27 Feb 2013
What IS amateur radio?
This is a question I keep asking myself. It clearly means different things to different people, but I am saddened by the trend to cheque book amateur radio.
In its early days the hobby was clearly about experimental radio: making receivers and transmitters that communicated over short distances, with many/most of the parts being hand-made, even down to the variable "condensers". Over the years this has changed for many (most?) amateurs and now one could be forgiven for thinking all that matters is how expensive ones new HF radio or antenna is, so one can boast about how wonderful ones station is to others on HF.
I was struck by the cost of the hobby, for some, again tonight when visiting http://www.bigskyspaces.com/w7gj/vhf.htm and looking at the massive and very expensive antenna farm at W7GI. Now this 144MHz antenna, like many, antenna arrays at this amateur's QTH is aimed at reliable EME operation where large antenna gains help. But what I see is 16 very expensive antennas plus an equally expensive support structure, expensive coax and an expensive mast. This is just one antenna for one band. He has another very big array for 50MHz too, plus no doubt a shack full of expensive radios and linears. The rotator to turn this lot will be a very large device indeed. Yes, successful EME operation needs big antennas and high power, but honestly is this AMATEUR radio still or semi-commercial experimentation?
I can understand why an amateur may want one 100W commercial radio as the "mainstay" radio for the shack, but I see many shacks loaded to the gunnels with very expensive radios that must have cost their owners well over £10k and in some cases well over £20k. It amazes me how much money some amateurs must invest in their hobby. I had a decent job and a decent salary when I worked, but there is no way I, personally, could justify this sort of expense on my hobby. It's a personal view and I do not want to preach to others on how to enjoy their hobby, but I am fascinated that spending lots of money on radios seems to be the norm.
Are any readers prepared to share (in the comments) how much they spend, on average, a year on their hobby? £10, £100, £1000, £10k, £20k? Just for the record, I reckon on about £2 a week (a couple of new HF transceivers over 12 years plus the odd accessory and components). It is possible to really enjoy the hobby and spend less than the cost of a coffee every week.
My question is, what IS amateur radio?
In its early days the hobby was clearly about experimental radio: making receivers and transmitters that communicated over short distances, with many/most of the parts being hand-made, even down to the variable "condensers". Over the years this has changed for many (most?) amateurs and now one could be forgiven for thinking all that matters is how expensive ones new HF radio or antenna is, so one can boast about how wonderful ones station is to others on HF.
I was struck by the cost of the hobby, for some, again tonight when visiting http://www.bigskyspaces.com/w7gj/vhf.htm and looking at the massive and very expensive antenna farm at W7GI. Now this 144MHz antenna, like many, antenna arrays at this amateur's QTH is aimed at reliable EME operation where large antenna gains help. But what I see is 16 very expensive antennas plus an equally expensive support structure, expensive coax and an expensive mast. This is just one antenna for one band. He has another very big array for 50MHz too, plus no doubt a shack full of expensive radios and linears. The rotator to turn this lot will be a very large device indeed. Yes, successful EME operation needs big antennas and high power, but honestly is this AMATEUR radio still or semi-commercial experimentation?
I can understand why an amateur may want one 100W commercial radio as the "mainstay" radio for the shack, but I see many shacks loaded to the gunnels with very expensive radios that must have cost their owners well over £10k and in some cases well over £20k. It amazes me how much money some amateurs must invest in their hobby. I had a decent job and a decent salary when I worked, but there is no way I, personally, could justify this sort of expense on my hobby. It's a personal view and I do not want to preach to others on how to enjoy their hobby, but I am fascinated that spending lots of money on radios seems to be the norm.
Are any readers prepared to share (in the comments) how much they spend, on average, a year on their hobby? £10, £100, £1000, £10k, £20k? Just for the record, I reckon on about £2 a week (a couple of new HF transceivers over 12 years plus the odd accessory and components). It is possible to really enjoy the hobby and spend less than the cost of a coffee every week.
My question is, what IS amateur radio?
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