16 Sept 2013

In hospital -bleed on the brain

At the weekend I was rushed into Addenbrookes hospital with excruciating headaches and punch drunk legs. After CAT and MRI scan they have confirmed it was a bleed on the brian from a blood vessel in the cerebellum which is being dispersed with drugs and can be treated. Service and care has been excellent at NHS Cambridge. We are lucky to have a world class hospital so close to us.

13 Sept 2013

Optical forward scatter and frequency?

Perhaps some of my readers can help me - what optical frequency is likely to be best for forward scatter off air molecules and dust particles? My tests to date have been over non line-of sight paths up to about 9km at 481THz (red light), but IR should work in daylight with filtered PIN diodes on RX, but I don't know whether infra-red frequencies scatter more easily or worse than red light?  With red light, the RX can easily be de-sensitised by bright sunlight, and this should be (?) less of an issue with filtered IR detectors, I think.

As the atmosphere scatters blue light very well (giving it a blue colour) one might expect IR to scatter less well than shorter wavelengths like visible red or ultra-violet? See http://en.wikipedia.org/wiki/Atmosphere_of_Earth .

On 472kHz again this evening and future plans

In the next few days I need to buy some more wire and coax to continue my antenna experiments. The first thing I shall be trying is the larger "in the air" TX loop for the LF and MF bands - probably 136kHz , 472kHz and 1.8MHz coverage. The lower part of the loop can be several strands of PVC covered wire or coax in parallel to reduce resistive losses but the "up in the air" part will have to be 1mm diameter to avoid sag and being visible to the neighbours. I think I should be able to increase the loop area by 50% and reduce the wire losses by about 50%, so there should be a useful increase in ERP. This could be some weeks away though.

In the meantime I am continuing to TX and RX on 472kHz WSPR with the odd shape loop I currently have running along the garden fence and back along the surface of the lawn. It works, but as I said yesterday, it is some dB below what I can achieve in my small back garden whilst maintaining low visual impact to avoid neighbour issues.

After confirming the performance with the larger loop in the coming weeks, I shall try a short Marconi vertical to compare results - better omni coverage expected, but may not be as effective as the loop in the best directions?

After that, I shall probably be returning to 481THz and infra-red frequencies for more over the horizon scatter tests. I particularly want to try some IR scatter tests in daylight as I find going out on dark nights unpleasant.

World's oldest photographs

As I have come down with a bug of some sort, feeling light-headed and with a headache, I've been sleeping a lot today and not doing too much. My 472kHz WSPR has been running periodically.

Sitting here this afternoon, I chanced on this interesting YouTube video showing the world's earliest photos. Fascinating to look at - see http://www.youtube.com/watch?v=3LkaFCa29mQ .

You may also like The World's 10 Most Mysterious Photos - see http://www.youtube.com/watch?v=E7Cd5FWMusE.

12 Sept 2013

472kHz (630m) WSPR experiment results

Comparing the loop in the air against the simple earth electrode (EE) antenna across the garden these are the results. Remember the loop could be improved by making it larger, using thicker wire and mounting it more fully vertical.

G4KPX - about 6dB better on loop
G6AVK - little difference
PA3ABK/2 - 1-3dB better on loop
G8HUH - little difference
M0PPP - copied on loop, no copy on EE
G3WCB - just copied on EE, no copy on loop

Conclusions?  Well the loop, as it currently is arranged, is a bit better than the EE antenna by a few dB, in some directions, but not amazingly so. Will try a loop up in the air more in the coming weeks and we'll compare results again.

TXing tonight with a 472kHz "in the air" loop

As the next stage in my experiments from the new QTH at LF and MF, this afternoon I converted my earth-electrode antenna into a complete "in the air" loop by removing the earth connections and joining the wires with a length of wire along the grass. The DC resistance of the loop is 0.9ohms and the enclosed area somewhere around 60-100 sq m although the loop is far from vertical and the bottom wire actually runs along the grass rather than up in the air. The measured loop current is around 0.9A and tuning very sharp with around 1.7nF in series and matched with a 3C90 step down transformer. According to my calculations of radiation resistance, the ERP should be in the 20-40mW region, considerably greater than with the earth-electrode antenna.
630m WSPR spots of G3XBM so far this evening
My first report this evening was from PA3ABK/2  at -28dB S/N but I am hopeful of a few more 472kHz spots tonight. I expect that the results with the loop will be better than with the earth-electrode system, but the loop can be further improved by raising the upper wire (bigger vertical enclosed loop area) and thickening up the lower wire to reduce resistive losses further.

I am doing things one step at a time so I can assess the difference.

UPDATE 1800z:  M0PPP has spotted me several times this evening but had failed to copy me in the last 2 weeks, so this is encouraging. Also reports from G8HUH and G6AVK.

10 Sept 2013

More 10m WSPR

With the weather miserable here today - I just managed to cut the grass before the rain set in - I went on 10m WSPR mid-afternoon to see what was doing. With 2W I got a couple of reports from 4X1RF at 3519km at -3 and 0dB S/N, which is VERY strong, but nothing else so far.

This evening, I hope to be WSPRing on 472kHz again (using the original earth-electrode arrangement still) whilst we entertain my brother and his wife. They are coming to stay for a few days. I shall be checking results periodically using my iPod Touch monitoring the WSPRnet database in between drinks and eating dinner.

POSTSCRIPT: I was just about to QSY away from 10m when I noticed I had spotted K3NAL at 5930km. At the time of writing, I seem to be the only European station copying him. Maybe I shall stay on 10m a little longer this afternoon, or perhaps try 10m PSK31 for some QSOs. 10m is another "magic band". Less so at the peak of the cycle but often open to distant places when not expected and definitely under-used in the quiet solar years.  

9 Sept 2013

472kHz - 7 unique WSPR reports so far on earth-electrode antenna

Although not working as well as I had hoped, my very simple earth-electrode antenna is getting WSPR reports. As of this evening, I have been spotted by 7 unique stations so far. Results remind me of my first efforts on 500kHz with a simple wire down the garden some years back. My ERP then was in the uW range and this may well be the sort of ERP I am actually using now currently. A better antenna IS a must!

First 10m spot from the new QTH + more on 20m

Today I ran WSPR on 10m to see what propagation was like. Although European stations further south were catching N-S openings trans-equatorial openings and even VK6, it was harder going from here in the UK and I only managed 1 spot with 2W and that was from 4X1RF - thank you.

Back on 20m it was a different story where I had a huge number of reports from places including KL7L in Alaska,  with just 500mW to the Par EF-10/20/40 antenna. 20m is always a good bet, although not one of my usual favourite bands.

As the autumn progresses I hope 10m will come back to life again. Conditions should be excellent in October and November with still decent sunspot numbers and of course the big CQWW DX contests to add to the activity levels. By autumn next year things will certainly be on the slide down to the next minimum, but the slope down is gradual and conditions can remain decent for several more years yet.

I really must get the full transceiver version of my 10m WISPY WSPR rig boxed up so I can free up the FT817 to do other things.

8 Sept 2013

Earth-electrode antenna for 472kHz in the new garden - not too brilliant

After trying a number of different orientations of earth-electrode pairs in my garden, I have come to the conclusion that this antenna structure does not work very well here in the new QTH. I am a little surprised as the earth-electrode antenna worked well just 350m away at the old QTH. Whatever orientation I try I seem to be always in the -22 to -28dB S/N region with G6AVK 78km away.

Why is it not so good? Well, the most likely answer is that the effective distance between the far and near ground rod electrodes is smaller, even with a similar physical separation. This could be because of buried water pipes and utilities criss-crossing the garden, although I wasn't aware of any, or different soil/rock conditions, although the chalk layer is about as far down here as at the old QTH and the soil is a similar alkaline sort. The fact that the 8.97kHz earth-mode results were so poor last week rather hinted at a problem that was not present at the old QTH.
I haven't quite exhausted every layout possible in  my strange shaped back garden, so there are more things to try with earth-electrodes, but it is looking like I shall have to erect a short Marconi or a fully in the air loop antenna to get better ERP on 472kHz. On my previous tests at the old QTH, a full in the air loop with 1mm diameter wire and an enclosed area of around 80m sq was around 8dB better than the earth-electrode antenna, but far more critical to tune and match because of the hi-Q. If my earth-electrode antenna is several dB down on the performance of the same structure at the old QTH then I could be expecting >10dB improvement or even more.

Half the fun is the testing and finding out what does and does not work.  The coming week we have visitors staying, so not too much time to experiment. I shall have to stick to WSPRing on 20 and 10m.

Portuguese Lesser Chirpy 10m transceiver

CT5JZX version of the Lesser Chirpy transceiver for 10m CW
In an email from CT5JZX, Pedro tells me he has made a version of my Lesser Chirpy 10m QRP CW transceiver. He has already received some beacons with it - he only has a crystal in the beacon part of the band at present - and hopes to TX with it soon when he has some other crystals. He has made a neat job of it in the plastic casing.

It is some time since I fired mine up and currently it is in a box in the loft after my recent QTH move.

VK on 20m WSPR this morning

5 VK (Australian) spots in the very first transmission slot
Whilst waiting for the bathwater to fill, I went on 20m WSPR this morning with the Par 40/20/10 end-fed antenna to see what was about. To my amazement I got no less than 4 VK reports (Australia) in the first transmission plus a lot of other reports too. The little antenna down the garden is certainly working just fine.

7 Sept 2013

2m contest this weekend

After several PSK31 QSOs on 20m, I returned to 2m SSB to see what was doing in the contest running this weekend. First impressions are there are far fewer stations active than last Tuesday evening in the UKAC contest. I have worked a few stations using 5W and the halo but so far only JO01, JO02 and IO92 squares i.e. not that far away.

.....me thinks it is time to QSY to 472kHz WSPR and watch the TV, HI.

First PSK31 QSO from new QTH

E74DO in his shack
After a little while on WSPR I decided to try PSK31 on 20m running 2W to the Par antenna. I replied to a CQ from E74DO and got a 599 report. PSK31 is not a mode I too much like, but it does work when the band is busy and with QRP.

A little later (1646z) I had a nice PSK31 QSO with Svan TF3FIN in Reykavik on 20m.

HF antenna erected at new QTH

This afternoon, I strung out my Par 40/20/10 horizontal end-fed HF antenna for 40, 20 and 10m from the base of my V2000 vertical to a tall branch of the silver birch tree at the end of my garden. Being a bungalow, the height is nothing great at around 4m above ground average. Match is excellent on 10m and 20m but the end wants trimming a few cm to improve the match on 40m.

I have just started WSPR beaconing at 1W on 20m to see how it performs and on the first transmission was spotted by N6RFM, LA6TPA, LA9JO and 4X1RF with reasonable reports. So, initial results look OK.

This now means I have the following TX capability from the new QTH:

(1) 630m - earth-electrode antenna
(2) 40, 20 and 10m HF - Par 40/20/10 antenna
(3) 6, 2 and 70cm - VHF/UHF V2000 vertical
(4) 2m - horizontal halo antenna
(5) 481THz optical - 110mm lens TX

All these antennas are unobtrusive and neighbour friendly. Now let me see how soon I can achieve QRP DXCC from this new QTH.

Experimenting will mean these antennas will come and go.

6 Sept 2013

472kHz - next steps

Ok, so after several more hours I am still getting WSPR spots from just G4KPX and G6AVK. Clearly the ERP with the present earth-electrode set-up in the new garden is in the low uW region only.

I'm going to try to string up a full wire loop for TX and see how this performs. I have a couple of options: (1) a thickish wire loop along the fence made from coax cable about 10m x 2m, or (2) a 1mm diameter PVC coated wire loop with a larger enclosed area. The former would be totally hidden and, because of the higher Q, may perform as well as the larger loop with thinner wire. The former is worth trying as it would be a very "stealth" antenna, totally invisible to neighbours ....and the XYL.

472kHz experiments continued

In my narrower, but wider, garden, I am still trying to work out the best layout for an earth-electrode antenna for 472kHz.

Today I started by trying to find out about the ground connections at the house end, measuring the resistance between various radiators and the mains ground to see which ones had a direct copper connection to a good ground. The answer is none! All the radiators seem to be connected with plastic pipes in the roof. The only direct "copper to ground" connections found in my water system were in the airing cupboard, the kitchen taps and the utility room taps.

The other tests (ongoing) are to a different remote ground further up the side of the garden, further from the shack but not further from the house. I am trying to see if this gives, effectively, a longer earth-electrode baseline between ground points.

So far this evening, with the (perhaps) slightly longer baseline, I am getting consistent reports from G6AVK (78km) but no-one else yet. As best I can judge, reports are very similar to those with the earlier grounding arrangements.  PA3ABK is a very strong signal at -6dB S/N.

5 Sept 2013

First 8.976kHz VLF earth-mode tests from the new QTH

This evening, I did a couple of tests on 8.976kHz earth-mode from the new QTH with my 5W beacon TX. Initially I used the far earth rod about 12m from the house paired with a mains ground and set out on my travels with my loop to my usual first test site just outside the village. This is a car park for the Devil's Dyke walk. Unfortunately the car park has been invaded by gypsies, so I decided to move on to my next test site in the village of Reach (2km). Nothing at all was copied of my beacon.

Then I returned home and used the mysterious copper rod that goes into the ground just outside my shack as the local ground and still keeping the ground rod 12m away as the "far" electrode. I think this may have at one time been an oil pipe from a central heating oil tank. I have no idea where it goes. This earth-electrode pair has launched my 472kHz WSPR signal which has been copied in Belgium and Holland, but results have been disappointing, so I was not expecting much on 8.976kHz.

Rather than travel 2km, I parked outside my old QTH about 0.35km away in the village. My 8.976kHz signals were copied, but not very strongly. I suspect that this was true earth-mode without any real assistance from utilities as I do not believe either ground rod at the TX end is coupled to utilities grounds or copper pipes going into the road.
Weak signals over a 0.35km path

Path tested this evening plotted with Google Earth
Conclusions so far are that both for VLF earth-mode work and for 472 and 136kHz radiated work I need to much improve the earth-electrode arrangement in my garden to get credible results. I need to do some sort of mapping of the garden to see where would result in a good solid connection to copper water pipes going into the road (probably at the outside copper tap) and the best place to locate the "far" electrode as far away from the house (and other houses) and buried pipes as possible.

Loop preamp

After some thought I'm almost certain now to buy a Wellbrook RX loop for use on 136 and 472kHz receive. This loop will also be useful for a number of other applications such as 160m and 80m monitoring and possibly some VLF work.

The ALA1530LF looks perfect for the task being able to cover 20kHz to 30MHz with excellent IP2 and IP3 performance. One concern is that a receiver is being hit with signals from right across the spectrum: although the loop preamp itself will not fall over, the receiver after it might. So, I think a small, high dynamic range tuned preamp with a few dB of gain may be needed ahead of the receiver.  The additional gain may be needed as many HF rigs have poor LF and VLF sensitivity.

A simple preamp is easy to design for either 136 and 472kHz bands. Something along these lines (see below) should be suitable for 472kHz reception. I'm not actually sure that the ceramic filter will be needed: just the single hi-Q tuned circuit on the input may be enough to protect the subsequent RX from being blasted with everything.

Bitsbox - excellent service yet again

A couple of days ago I realised I needed a few tools to help me: a "helping hands" clip to hold PCBs and breadboards whilst soldering, a desoldering tool, some trimming tools, more solder, switches etc. So, I placed an order with Bitsbox, a small UK supplier I've used before. The order was easy to place, a Paypal payment was accepted and the order received very quickly indeed with a low fixed price for delivery by first class post. They have a good range of parts in stock and their service has always been first class. I can highly recommend Bitsbox if you need a few bits for your amateur radio hobby.

3 Sept 2013

2m UKAC this evening with QRP and a halo

Stations worked on 2m SSB with 5W and halo tonight
After 90 minutes of 2m contesting this evening I decided to QSY to 472kHz WSPR even though there was another hour to go.  The contest was my first from the new QTH running 5W into the 2m halo on the roof. In all I managed 12 QSOs with the best DX GW4FZN/P near Bala at 272km. Best DX heard was G4PPT/M in IO70 near Penzance, Cornwall.

The RSGB UK Activity Contests are every Tuesday evening on different VHF/UHF bands each week of the month. Great fun for an hour or so and well supported.

Early morning 6m Es opening

After breakfast I checked 6m beacons this morning at around 0730z and was surprised to hear IW3FZQ/B and YU1EO/B coming through marginally. I then went on to work YL3IQ in KO17OD square at 599 each way on 5W CW at 0736z. Conditions on 6m are still good at times, and surprisingly at such an early time so late in the sporadic-E season. Currently WSPRing on 6m but only UK spots this lunchtime.

2 Sept 2013

3 countries now on 472kHz WSPR with short earth-electrode antenna

Limited success this evening on 472kHz with the earth-electrode antenna with the copper pipe grounding at the house end. Reports from G8HUH, OR7T and PA3ABK/2 this evening, but I am left feeling that results are still some 6-10dB down on at the last QTH. The system is far from optimised yet though.

Tomorrow evening I will have a go at the 2m UKAC contest with the halo but hope to try some different antenna arrangements on 472kHz later in the week. So far 6 unique station reports on 472kHz WSPR in 6 different QTH locator squares. I do feel that a better antenna is needed, somehow!

VHF tropo (non ducting) history

Whilst trying to locate an up-to-date list of VHF 2m beacons I am likely to be able to copy here on a halo, I chanced upon a site with a history of non-ducting tropo (NDT) going back to the work by Marconi in the 1920s and 1930s. See http://www.quercus.demon.co.uk/thistory.html. Interesting reading.

2m halo added to VHF/UHF antennas

This morning, whilst waiting for the Virgin Media installers to arrive, I added the 2m halo to the mast supporting my V2000 6/2/70cms vertical, allowing me horizontal 2m operation again. The picture shows the antenna on the gable end of the bungalow.
V2000 and 2m halo antenna installed
I have also been trying a different ground point for the 472kHz earth-electrode system at the house end. I shall have to wait until this evening to try this. Current into the loop is higher, so I hope performance will be a bit better.

The second picture was the sunset last night as seen from the shack window. It was beautiful.

GB3VHF on the halo

1 Sept 2013

Removing earth rods?

At my old QTH I have 3 solid copper earth rods driven in about 0.8m into the soil. Does anyone have any recommendations on how to remove these please? They are pretty solidly embedded in the soil but it would be good to be able to reuse these at the new QTH as solid copper earth rods are not cheap.

Initial results on 472kHz at the new QTH

Well, I have been WSPR beaconing over a period of about 24 hours at the new QTH on 472kHz. Actual operating time has been just a few hours this evening and last night plus a little bit this morning. Based on the (limited) reports received - just from G6AVK (78km), G3WCB (101km) and G4KPX (14km) and no-one else despite quite a bit of activity - I think the earth electrode antenna is some dB down compared with results "down the hill" at the old location.  On RX, the noise level here is lower using the earth electrode antenna but that may also suggest less efficiency - less signals and less noise being picked up. Having said that, I have spotted stations never seen before (I think) such as G3WCB and have spotted a couple of PA stations.
The QRP operating kit in the shack
The reasons for the poorer performance could be the shorter baseline or the directionality is such that my usual reporters are getting a weaker signal. It may also be due to the use of the mains earth at the shack end and not the copper central heating piping: some of my central heating piping here is plastic, so grounding to the radiator in the shack does not guarantee a good low loss ground! At the old QTH all the central heating pipes were copper and the copper extended into the road.  I need to do a test with a fairly local station to see how signals compare such as G4HJW although I am not sure Bernie is still on 472kHz currently.

So, conclusions so far? Mixed and a little disappointing, but it is early days and lots to try still.